Professional Paper 1794–B

U.S. Department of the Interior

U.S. Geological Survey

Status and Trends of Land Change in the Great 

Plains of the United States—1973 to 2000

Status and Trends of Land Change in the 

Great Plains of the United States—

1973 to 2000

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond

Professional Paper 1794–B

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment—visit http://www.usgs.gov/ or call 1–888–ASK–USGS 

(1–888–275–8747). 

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod/.

To order this and other USGS information products, visit http://store.usgs.gov/.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from 

the copyright owner. 

ISSN 1044-9612 (print) 

ISSN 2330-7102 (online) 

http://dx.doi.org/10.3133/pp1794B

Suggested citation:

Taylor, J.L., Acevedo, W., Auch, R.F., and Drummond, M.A., eds., 2015, Status and trends of land change 

in the Great Plains of the United States—1973 to 2000: U.S. Geological Survey Professional Paper 

1794–B, 180 p., http://dx.doi.org/10.3133/pp1794B.

Cover:

Field of sunflowers in Elbert County, Colorado, about 80 km east of Colorado Springs, Colorado. Photograph taken in 

2006.

Inside cover:

Wheat fields, with Sweet Grass Hills in background, in Liberty County, Montana, about 25 km north of Chester, 

Montana, and about 25 km south of Canadian border. Photograph taken in 2005.
iii

Foreword

This Professional Paper is the first multitemporal assessment of late-20th-century land change in 

the conterminous United States across all regions and all land-use and land-cover sectors. The work is the 

culmination of nearly 10 years of research and development by the U.S. Geological Survey, with support from 

the U.S. Environmental Protection Agency and the National Aeronautics and Space Administration, as well 

as university collaborators. It represents the most complete and comprehensive analysis of the rates, types, 

distribution, and drivers of recent changes in land use and land cover. The study bridges the gap between 

coarse-scale continental and global assessments and fine-scale local and regional case studies. 

Land-change studies attempt to explain the “what, where, when, how, and why” of changes to the 

vegetation and to the use of the land. Land-change research is aimed specifically at measuring where 

change is occurring (and where it is not occurring); which land-use and land-cover classes are changing 

(and what they are changing to); how much land is changing (and how fast); and what drivers are 

responsible for the measured changes. The goal is not only to understand the scope of change but also to 

provide the information base necessary to evaluate, predict, and manage the consequences of change.

Like many key issues in climate change and ecosystem functioning, land use and land cover are 

both drivers and indicators of environmental quality. The National Research Council has identified the 

understanding of land-use dynamics as one of the grand challenges for environmental research—no other 

global-change parameter is so tightly intertwined with issues of past, present, and future land-use practices, 

weather patterns, soil and carbon dynamics, ecosystem health and diversity, economic development and 

policy, technology issues, human population size and distribution, and overall human health. People and 

their use of the land are interrelated in complex ways, and the effects of land-use and land-cover change 

can have a huge impact on their quality of life, on the goods and services that they can expect from the 

land, and on the hazards that they may face. Despite these profound consequences, the Intergovernmental 

Panel on Climate Change’s Third Assessment Report has cited the lack of scientific understanding about the 

timing, magnitude, and direction of response of ecological, social, and economic systems to the combined 

effects of climate change and land-use and land-cover change as a key uncertainty in determining societal 

vulnerabilities and predicting both regional and global impacts of climate change.

Prior to this study, only sectorally specific or spatially limited assessments and inventories had been 

conducted to categorize land change in the United States. These efforts often included only certain land-use 

and land-cover classes or ownership categories, or they were conducted over short time intervals only, 

and integrating these various assessments into a comprehensive and consistent national synthesis of land 

change was not possible. The research presented in this Professional Paper has been specifically designed to 

provide the first comprehensive measurement of land-cover change in the conterminous United States. 

Relying on Landsat satellite imagery—the longest continuous and consistent dataset of synoptic Earth 

observations—the authors characterize changes across 11 primary land-use and land-cover classes spanning 

four time periods between 1973 and 2000. For each of these time periods and classes, estimates of change are 

developed for each of 84 distinct ecological regions—or ecoregions—across the conterminous United States.

The results provide useful, if not essential, information for understanding climate change, biodiversity, 

resource management and planning, resource security, and disaster planning. A significant conclusion is 

that no single profile of land-use and land-cover change exists. Numerous different, and often complex, 

interactions between an ecoregion’s socioeconomic drivers and its biological and physical characteristics 

have produced widespread regional and temporal variability in the rates, types, and total extent of land 

change. Among the scientific findings presented are estimates of overall forest decline in response to 

increased rates of disturbance, urbanization, and agricultural intensification. 

This research provides a critical ecoregional to national perspective of U.S. land change in the 

conterminous United States. With the completion of the 1973–2000 assessment, this study lays a foundation 

for understanding the Nation’s land-change dynamics and makes possible a new era for analyzing the 

consequences of land change, as well as for modeling future land changes.

Acting Director, USGS
iv

Preface

U.S. Geological Survey (USGS) Professional Paper 1794–B is the second in a four-volume series on 

the status and trends of the Nation’s land use and land cover, providing an assessment of the rates and 

causes of land-use and land-cover change in the Great Plains of the United States between 1973 and 

2000. Volumes A, C, and D provide similar analyses for the Western United States, the Midwest–South 

Central United States, and the Eastern United States, respectively. The assessments of land-use and 

land-cover trends are conducted on an ecoregion-by-ecoregion basis, and each ecoregion assessment is 

guided by a nationally consistent study design that includes mapping, statistical methods, field studies, 

and analysis. Individual assessments provide a picture of the characteristics of land change occurring in a 

given ecoregion; in combination, they provide a framework for understanding the complex national mosaic 

of change and also the causes and consequences of change. Thus, each volume in this series provides 

a regional assessment of how (and how fast) land use and land cover are changing, and why. The four 

volumes together form the first comprehensive picture of land change across the Nation.

Geographic understanding of land-use and land-cover change is directly relevant to a wide variety 

of stakeholders, including land and resource managers, policymakers, and scientists. The chapters that 

follow present brief summaries of the patterns and rates of land change observed in each ecoregion in the 

Great Plains of the United States, together with field photographs, statistics, and comparisons with other 

assessments. In addition, a synthesis chapter summarizes the scope of land change observed across the 

entire Great Plains of the United States. The studies provide a way of integrating information across the 

landscape, and they form a critical component in the efforts to understand how land use and land cover 

affect important issues such as the provision of ecological goods and services and also the determination 

of risks to, and vulnerabilities of, human communities. Results from this project also are published in 

peer-reviewed journals, and they are further used to produce maps of change and other tools for land 

management, as well as to provide inputs for carbon-cycle modeling and other climate change research.

This report is only one of the products produced by USGS on land-use and land-cover change in the 

United States. Other reports and land-cover statistics are available online at http://landcovertrends.usgs.gov. 

Acknowledgments

The U.S. Environmental Protection Agency’s Office of Research and Development and the National 

Aeronautics and Space Administration provided initial funding to support this project. 

The U.S. Geological Survey’s (USGS) Geographic Analysis and Monitoring Program and Climate and 

Land Use Change Research and Development Program provided long-term support for this research.

Adam Davis (USGS) provided extensive support in the production of figures and tables.

All photographs contained within this Professional Paper were taken by various members of the 

Land Cover Trends research project while conducting field investigations between 1999 and 2010.

Author Affiliations

William Acevedo

Roger F. Auch

Mark S. Brooks

Mark A. Drummond

Beverly A. Friesen

Steven Kambly

Krista A. Karstensen

Carl L. Rich

Kristi L. Sayler

Michael P. Stier

Janis L. Taylor

U.S. Geological Survey

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

U.S. Geological Survey 

Stinger Ghaffarian Technologies
v

Contents

Foreword....................................................................................................................................................... .iii

Preface ...........................................................................................................................................................iv

Acknowledgments........................................................................................................................................iv

Author Affiliations.........................................................................................................................................iv

Regional Synthesis

 Land-Cover Trends in the Great Plains of the United States—1973 to 2000 ............................. 3

By Mark A. Drummond and Roger F. Auch

Western Plains Ecoregions

1. Central Great Plains Ecoregion.....................................................................................................19

By Mark A. Drummond

2. Nebraska Sand Hills Ecoregion.....................................................................................................27

By Janis L. Taylor

3. Northwestern Great Plains Ecoregion......................................................................................... 35

By Kristi L. Sayler

 4. Southwestern Tablelands Ecoregion............................................................................................43

By Carl L. Rich and Mark A. Drummond

 5. Western High Plains Ecoregion.....................................................................................................51

By Mark A. Drummond

Glaciated Plains Ecoregions

 6. Lake Agassiz Plain Ecoregion........................................................................................................61

By Mark S. Brooks

 7. Northern Glaciated Plains Ecoregion...........................................................................................69

By Roger F. Auch

 8. Northwestern Glaciated Plains Ecoregion...................................................................................77

By Janis L. Taylor

 9. Western Corn Belt Plains Ecoregion............................................................................................ 87

By Roger F. Auch

East-Central Plains Ecoregions

 10. Central Irregular Plains Ecoregion............................................................................................... 99

By Krista A. Karstensen

 11. Flint Hills Ecoregion........................................................................................................................107

By Steven Kambly

Southern Plains Ecoregions

 12. Central Oklahoma/Texas Plains Ecoregion................................................................................117

By Michael P. Stier

 13. East Central Texas Plains Ecoregion...........................................................................................125

By Krista A. Karstensen

 14. Edwards Plateau Ecoregion.........................................................................................................133

By Michael P. Stier and Beverly A. Friesen
vi

Conversion Factors

Inch/Pound to SI Multiply by To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.004047 square kilometer (km2

)

square mile (mi2

) 2.590 square kilometer (km2) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C=(°F-32)/1.8

 15. Southern Texas Plains Ecoregion................................................................................................141

By Michael P. Stier

 16. Texas Blackland Prairies Ecoregion............................................................................................149

By Roger F. Auch

 17. Western Gulf Coastal Plain Ecoregion........................................................................................159

By Mark A. Drummond

Appendix 1. Map of Ecoregions in Conterminous United States .......................................................169

Appendix 2. Abbreviations for Ecoregions in the Great Plains of the United States......................172

Appendix 3. Land-Cover Classification System Used in “Status and Trends of Land 

 Change” Study..........................................................................................................................173

Appendix 4. Methodology Used in “Status and Trends of Land Change” Study.............................174
Regional Synthesis1

Land-Cover Trends in the Great Plains of

the United States—1973 to 2000

By Mark A. Drummond and Roger F. Auch

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Introduction

One of the important stories of the Great Plains of the 

United States is the geographic and temporal variability 

of recent land-use and land-cover change, including the 

underlying causes of land conversion. Because it is an 

agricultural region, land use in the Great Plains depends in 

large part on the available natural resources, as well as the 

inherent suitability of the region for crop production and 

rangeland grazing. Areas that have favorable soils and climate 

have had a long history of cultivation, whereas areas that are 

unsuitable for crops often are used for livestock grazing. Given 

a range of conditions and land-use regimes across such a large 

expanse, analysis shows distinct regional characteristics of 

land change that also vary across relatively short time scales, 

as human activities intersect with the environmental setting. 

The prevailing climate and other biological and physical 

factors (for example, precipitation variability, soil quality, 

water availability, and topography) affect in complex ways the 

actions of people and society (for example, public policies, 

regional and global economic opportunities, population and 

demographic change, technological advances, and local cultural 

histories) and, thus, can control the rates and characteristics of 

land-use and land-cover change. 

The Great Plains as a geographic region has been variously 

defined (Rossum and Lavin, 2000). The region generally lies 

between the dense forests of the East and the mountains and 

deserts of the West. The vast, flat-to-rolling plains are used 

primarily for cropland, rangeland, and settlements. Weather 

can be extreme, and drought periodically affects the region. 

Precipitation amounts, which are limited in the western plains 

that sit in the rain shadow of the Rocky Mountains, increase 

toward the east, and temperature has a strong north-south 

gradient. The northeastern and extreme northern parts of the 

Great Plains are glaciated areas that have numerous “prairie 

pothole” wetlands, and they have more cropland than the western 

plains. The western plains primarily are a semiarid shortgrass 

steppe in which both streamside and groundwater irrigation 

from the High Plains (Ogallala) aquifer are important in places. 

Shrubland and forest are more prevalent in the southeastern part 

of the Great Plains where land-use practices and fire suppression 

have encouraged woody encroachment (Engle and others, 

2008). Few large cities are situated in the interior plains, and 

population loss is a concern in numerous communities. Most 

large population centers in the Great Plains are on the fringes of 

the plains, especially in the southeastern part. 

Beyond these broad generalizations, many areas within 

this expansive region have contrasting socioeconomic and 

environmental characteristics that potentially can have different 

effects on their land-use/land-cover trends. Ecoregions—that 

is, areas that are similar in their biotic-, abiotic-, terrestrial-, 

and aquatic-ecosystem components, with humans considered as 

part of the biota (McMahon and others, 2001)—serve as useful 

entities for studying regional land-use/land-cover change, as 

they can encapsulate both the similarities and differences in the 

range of potential land-use/land-cover changes that are likely to 

occur regionally (Gallant and others, 2004).

To understand the rates, types, and causes of land change, 

as well as to aid in assessing the consequences of change, the 

U.S. Geological Survey interpreted and analyzed trends of 

land-use/land-cover change, using the U.S. Environmental 

Protection Agency’s Level III Ecoregions (Omernik, 1987; 

U.S. Environmental Protection Agency, 1999) as the spatial 

stratification. A statistical sampling approach was used, in part, to 

account for the large amount of error that can occur in assessing 

wall-to-wall change for multiple time-steps across large regions 

(Stehman and others, 2005). For the 17 ecoregions in the Great 

Plains of the United States, a set of 10 × 10 km sample blocks 

was randomly selected for each ecoregion from a uniform grid. 

Within each sample block, land use/land cover was mapped, 

and its changes were interpreted, at a 60-m resolution using 

Landsat Multispectral Scanner, Thematic Mapper, and Enhanced 

Thematic Mapper Plus satellite data for five study dates:1973, 

1980, 1986, 1992, and 2000. A detailed explanation of project 

methodology can be found in appendix 4 (see also, Loveland and 

others [2002] and Stehman and others [2003]). The approach 

provides a systematic basis for understanding land-use/landcover change and can aid in managing and planning for future 

human-environmental interaction. 

Regional Synthesis 

The U.S. Geological Survey analyzed land-use/land-cover 

change for 17 ecoregions in the Great Plains of the United 

States as part of a national assessment of land change (fig. 1A). 

For purposes of discussion, the 17 Great Plains ecoregions, 

which cover about 2,231,159 km2

 (861,455 mi2), have been 
4 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

50°

45°

40°

35°

30°

110° 105° 100° 95° 90°

0 200 400 MILES

0 200 400 KILOMETERS

MEXICO

CANADA

A

CGP

NWGP

WCBP

CIP

WHP

NGP

NWGLP

SWT

EP

COTP

STP

NSH

TBP

TBP

LAP

FH

WGCP

WHP

ECTP

Gulf of

Mexico

Ecoregion boundary

State boundary

Land-use/land-cover class

EXPLANATION

Water

Developed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Transitional

Figure 1. A, Map of all 17 ecoregions in Great Plains of United States, showing land-use/land-cover classes from 1992 National Land-Cover 

Database (Vogelmann and others, 2001); note that, for this “Status and Trends of Land Change” study, transitional land-cover class was 

subdivided into mechanically disturbed and nonmechanically disturbed classes. B, Map showing four main Great Plains ecoregion groups, 

modified from U.S. Environmental Protection Agency’s (1997) Level II Ecoregions for Great Plains of United States. Within each ecoregion group, 

individual ecoregions share many similar physical and biological characteristics. C, List of four main Great Plains ecoregion groups depicted in 

figure 1B; also listed are individual ecoregions included in each ecoregion group, as well as ecoregion abbreviations used in figure 1A.
Land-Cover Trends in the Great Plains of the United States—1973 to 2000 5

divided into four main groups, within which the ecoregions 

share many similar physical and biological characteristics: 

the Western Plains Ecoregions, the Glaciated Plains 

Ecoregions, the East-Central Plains Ecoregions, and the 

Southern Plains Ecoregions (fig. 1B). 

Agriculture and grassland/shrubland are the dominant 

land-cover classes in the Great Plains ecoregions (fig. 2). A 

substantial shift between the amount of both agriculture land 

cover, which includes all cropland and related agricultural 

uses except rangeland, and grassland/shrubland land 

cover occurred over the 27-year study period (table 1). 

Agriculture was the dominant land-cover class mapped in 

the 1973, 1980, and 1986 study dates. The total percentage 

of agriculture in the ecoregions increased from 46.0 percent 

in 1973 to 46.4 percent in both 1980 and 1986. Grassland/

shrubland became the dominant land-cover class by 2000 

when it reached its greatest extent of 44.4 percent of 

the ecoregions. Taken together, grassland/shrubland and 

agriculture make up more than 88 percent of all land cover in 

the Great Plains ecoregions (fig. 3). 

The total extent of forest land cover in the ecoregions was 

5.8 percent in 2000, a slight decline from 1973 (5.9 percent). 

The total extent of water land cover in the ecoregions remained 

at 1.8 percent between 1973 and 1992, increasing to 2.1 

percent in 2000. Developed land cover increased steadily in the 

ecoregions, increasing from 1.1 percent in 1973 to 1.5 percent 

in 2000. Wetland land cover was relatively consistent (1.8 

percent, decreasing to 1.6 percent in 2000) through the study 

period (fig. 4), as was barren land cover, which remained at 0.6 

percent. All other land-cover classes remained at or below 0.1 

percent of the ecoregions (table 1). Because the biological and 

physical underpinnings, as well as the socioeconomic factors, 

vary across all the ecoregions, land-use/land-cover change 

Figure 1.—Continued

Western Plains

Glaciated

Plains

East-Central

Plains

Southern

Plains

Western Plains Ecoregions

CGP – Central Great Plains Ecoregion

NSH – Nebraska Sand Hills Ecoregion

NWGP – Northwestern Great Plains Ecoregion

SWT – Southwestern Tablelands Ecoregion

WHP – Western High Plains Ecoregion

Glaciated Plains Ecoregions

LAP – Lake Agassiz Plain Ecoregion

NGP – Northern Glaciated Plains Ecoregion

NWGLP – Northwestern Glaciated Plains Ecoregion

WCBP – Western Corn Belt Plains Ecoregion

East-Central Plains Ecoregions

CIP – Central Irregular Plains Ecoregion

FH – Flint Hills Ecoregion

STP – Southern Texas Plains Ecoregion

TBP – Texas Blackland Prairies Ecoregion

WGCP – Western Gulf Coastal Plain Ecoregion

Southern Plains Ecoregions

COTP – Central Oklahoma/Texas Plains Ecoregion

ECTP – East Central Texas Plains Ecoregion

EP – Edwards Plateau Ecoregion

EXPLANATION B C

in the Great Plains can be further understood by examining 

individual ecoregions.

Overall, an estimated 8.4 percent (186,616 km2) of land 

cover in the Great Plains ecoregions changed at least once 

between 1973 and 2000 (table 2). However, the overall amount 

of change varied substantially across the 17 Great Plains 

ecoregions (fig. 5). The ecoregion that experienced the highest 

amount of change was the Northwestern Glaciated Plains 

Ecoregion, at 14.1 percent, and the ecoregion that experienced 

the lowest amount of change was the Lake Agassiz Plain 

Ecoregion, at 1.5 percent. Both of these ecoregions are part of 

the Glaciated Plains Ecoregions group, which includes areas 

of Wisconsin-age glaciation and former glacial lakes in the 

northern and northeastern parts of the Great Plains. 

Across the Great Plains, the characteristics of land-cover 

change varied from ecoregion to ecoregion, depending on both 

biological and physical factors. For example, the four ecoregions 

that had overall spatial change amounts of less than 5 percent 

have contrasting characteristics that constrain land-cover 

change and enable stability. For example, the Western Corn 

Belt Plains Ecoregion (3.2 percent overall spatial change) and 

the Lake Agassiz Plain Ecoregion (1.5 percent overall spatial 

change) have level topography and glacial-till soils that are well 

suited for intensive cultivation. Conversely, the Nebraska Sand 

Hills Ecoregion (4.0 percent overall spatial change) and the 

Flint Hills Ecoregion (2.2 percent overall spatial change) have 

hilly topography and poor soils, a combination that constrains 

cultivation in favor of rangeland use and grassland maintenance. 

However, both types of characteristics (prime cropland versus 

historical rangeland) resulted in relatively stable land-use 

patterns and low rates of change. 

Ecoregions that have high rates of spatial change tend 

to have lands that are marginal for agriculture. Under adverse 

climatic or economic conditions, 

these marginal lands either cease to be 

viable cropland or are subject to other 

land-change processes. For example, 

fluctuations between grassland/shrubland 

and agriculture in the Northwestern 

Glaciated Plains Ecoregion (14.1 percent 

overall spatial change) and the Western 

High Plains Ecoregion (12.5 percent 

overall spatial change) contributed to 

the high rates of overall spatial change 

as marginal lands were brought into 

and out of production, depending on 

changing commodity prices, farm 

practices, and farm-program incentives. 

Cyclical clearance of mesquite (Prosopis

spp.), juniper (Juniperus spp.), and 

scrub oak (Quercus spp.) for rangeland 

improvement and to enhance water 

availability contributed to the high rates 

of change in four of the ecoregions in 

the Southern Plains Ecoregions group, 

particularly in the Southern Texas Plains 
6 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Table 1. Areal percentages of land-use/land-cover classes in all 17 Great Plains ecoregions for each of five study years 

(1973, 1980, 1986, 1992, 2000) and corresponding margin-of-error values for 85-percent confidence interval (in brackets).

[Percentages are of total area in all Great Plains ecoregions. See appendix 3 for definitions of land-use/land-cover classifications]

Land-use/land-cover class

1973

[margin of error]

(% of area)

1980

[margin of error]

 (% of area)

1986

[margin of error]

 (% of area)

1992 

[margin of error]

 (% of area)

2000

[margin of error]

 (% of area)

Water 1.8 [0.5] 1.8 [0.5] 1.8 [0.5] 1.8 [0.4] 2.1 [0.5]

Developed 1.1 [0.2] 1.2 [0.2] 1.3 [0.3] 1.4 [0.2] 1.5 [0.2]

Mechanically disturbed 0.0 [<0.1] 0.0 [<0.1] 0.0 [<0.1] 0.1 [<0.1] 0.1 [<0.1]

Mining 0.1 [<0.1] 0.1 [<0.1] 0.1 [<0.1] 0.1 [<0.1] 0.1 [<0.1]

Barren 0.6 [0.3] 0.6 [0.3] 0.6 [0.3] 0.6 [0.3] 0.6 [0.3]

Forest 5.9 [0.4] 5.9 [0.4] 5.8 [0.4] 5.8 [0.4] 5.8 [0.4]

Grassland/Shrubland 42.7 [1.6] 42.2 [1.6] 42.1 [1.2] 44.2 [1.6] 44.4 [1.6]

Agriculture 46.0 [1.6] 46.4 [1.6] 46.4 [1.6] 44.2 [1.6] 43.8 [1.6]

Wetland 1.8 [0.2] 1.8 [0.2] 1.8 [0.2] 1.8 [0.2] 1.6 [0.2]

Nonmechanically disturbed 0.1 [>0.1] 0.0 [0.0] 0.0 [0.0] 0.0 [<0.1] 0.0 [<0.1]

Figure 4. Wetland area in Nebraska Sand Hills Ecoregion. 

Wetlands dot many Great Plains ecoregions, providing vital 

habitat for birds and other wildlife. 

Ecoregion (12.0 percent overall spatial change) where woody 

vegetation is removed periodically, often through state-funded 

brush-control programs.

Population changes in smaller cities across the Great 

Plains, and in the Southern Plains Ecoregions group in 

particular, affected the conversion of agriculture and 

grassland/shrubland. For example, in the Texas Blackland 

Prairies Ecoregion (11.1 percent overall spatial change), 

urbanization of former agriculture land made up a large 

component of change. The Western High Plains Ecoregion 

(12.5 percent overall spatial change) has had the most land 

enrolled in the Conservation Reserve Program (CRP) since 

it was enacted by Congress in 1985 to provide economic 

incentive to convert environmentally sensitive cropland from 

agriculture to perennial grassland/shrubland cover. 

Figure 2. Dryland agriculture in Northwestern Great Plains 

Ecoregion.

Figure 3. Livestock grazing in Western Gulf Coastal Plain 

Ecoregion.
Land-Cover Trends in the Great Plains of the United States—1973 to 2000 7

110° 105° 100° 95° 90°

45°

50°

40°

35°

30°

25°

Gulf of

Mexico

MEXICO

CANADA

CGP

NWGP

WCBP

CIP

WHP

WHP

NGP

NWGLP

SWT

EP

COTP

STP

NSH

TBP

LAP

FH

WGCP

ECTP

TBP

0 200 400 MILES

0 200 400 KILOMETERS

Overall Spatial Change

1.5–3.1

3.2–5.4

5.5–8.2

8.3–11.0

11.1–14.1

Figure 5. Map showing overall spatial change, as percent of ecoregion area, for each of 17 Great Plains 

ecoregions over entire study period (1973–2000).
8 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Table 2. Overall spatial change in each Great Plains ecoregion (in square kilometers and as percent of 

ecoregion) for entire study period (1973 to 2000) and corresponding margin-of-error values for 85-percent 

confidence interval (in brackets).

Ecoregion Ecoregion

area (km2

)

Overall spatial change [margin of error]

(km2

) (% of ecoregion)

Western Plains Ecoregions

Western High Plains Ecoregion 288,752 36,094 [6,641] 12.5 [2.3]

Southwestern Tablelands Ecoregion 159,938 14,075 [3,679] 8.8 [2.3]

Central Great Plains Ecoregion 273,189 22,675 [3,825] 8.3 [1.4]

Northwestern Great Plains Ecoregion 346,883 25,669 [6,938] 7.4 [2.0]

Nebraska Sand Hills Ecoregion 60,541 2,422 [908] 4.0 [1.5]

Totals 1,129,304 100,934 [11,293] 8.9 [1.0]

Glaciated Plains Ecoregions

Northwestern Glaciated Plains Ecoregion 160,684 22,656 [3,535] 14.1 [2.2]

Northern Glaciated Plains Ecoregion 141,341 10,459 [1,979] 7.4 [1.4]

Western Corn Belt Plains Ecoregion 216,363 6,924 [1,731] 3.2 [0.8]

Lake Agassiz Plain Ecoregion 40,636 610 [163] 1.5 [0.4]

Totals 559,024 40,649 [4,472] 7.3 [0.8]

East-Central Plains Ecoregions

Central Irregular Plains Ecoregion 122,589 8,949 [2,452] 7.3 [2.0]

Flint Hills Ecoregion 27,911 614 [140] 2.2 [0.5]

Totals 150,500 9,563 [2,408] 6.4 [1.6]

Southern Plains Ecoregions

Central Oklahoma/Texas Plains Ecoregion 103,412 6,722 [1,241] 6.5 [1.2]

East Central Texas Plains Ecoregion 44,076 5,333 [793] 12.1 [1.8]

Southern Texas Plains Ecoregion 54,744 6,569 [1,369] 12.0 [2.5]

Texas Blackland Prairies Ecoregion 50,501 5,606 [1,313] 11.1 [2.6]

Western Gulf Coastal Plain Ecoregion 80,965 8,016 [1,781] 9.9 [2.2]

Edwards Plateau Ecoregion 58,634 3,225 [704] 5.5 [1.2]

Totals 392,333 35,470 [2,311] 9.0 [0.8]

All Great Plains ecoregions 2,231,161 186,616 [10,639] 8.4 [0.5]

Water availability in the Great Plains from streams and 

aquifers, which include the immense High Plains (Ogallala) 

aquifer and also the Missouri and Platte Rivers, enabled the 

expansion of intensive irrigation (fig. 6) and contributed 

to the conversion of grassland/shrubland to agriculture 

(Dennehy and others, 2002). However, water scarcity in 

the Western High Plains Ecoregion, caused in some areas 

by historically high rates of water use, also constrained 

expansion (fig. 7). Climate variability played a role as 

well, and changes in precipitation patterns resulted in both 

wetland conversion and lake expansion in the Northern 

Glaciated Plains Ecoregion (7.4 percent overall spatial 

change). 

Changes throughout the entire 27-year study period resulted 

in net increases in grassland/shrubland, developed, water, mining, and mechanically disturbed land-cover classes (table 3; fig. 

8). Grassland/shrubland also experienced the greatest amount 

of gross change, followed closely by agriculture (table 4). Net 

change in land cover is a measure of the end result of conversions 

associated with each land-cover class, whereas gross changes 

indicate the total area of change (table 4), which can be much 

larger than the net change (for example, timber-harvest cycles 

and also the cyclic transitions between agriculture and grassland/

shrubland). In addition, expansions in some locations often are 

counteracted by declines in others; the unidirectional, relatively 

permanent conversion to developed land is a notable exception.
Land-Cover Trends in the Great Plains of the United States—1973 to 2000 9

Figure 6. Irrigation of cropland in Central Great Plains Ecoregion.

 Figure 7. Open rangeland in Western High Plains Ecoregion.

Land-use/land-cover class Net change [margin of error] (km2

)

1973–1980 1980–1986 1986–1992 1992–2000

Water –200 [589] 1,278 [749] –743 [1,486] 5,573 [1,585]

Developed 2,686 [791] 1,628 [370] 2,003 [473] 3,234 [667]

Mechanically disturbed 172 [292] 101 [316] 656 [977] –48 [1,057]

Mining 286 [112] 386 [183] 323 [142] 412 [127]

Barren –75 [169] –367 [233] 499 [540] –89 [393]

Forest –1,253 [311] –567 [376] –804 [404] –1,083 [349]

Grassland/Shrubland –9,780 [3,417] –2,952 [3,277] 46,853 [7,084] 4,730 [5,262]

Agriculture 9,249 [2,780] 967 [3,268] –49,506 [7,094] –9,438 [5,166]

Wetland 305 [529] –473 [486] 682 [740] –3,596 [1,332]

Nonmechanically disturbed –1,390 [1,992] 0 [0] 36 [37] 305 [452]

Table 3. Net areal changes in land-use/land-cover classes in all 17 Great Plains ecoregions during each of 

four time periods and corresponding margin-of-error values for 85-percent confidence interval (in brackets).

[See appendix 3 for definitions of land-use/land-cover classifications]

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

−3

−2

−1

0

1

2

3

1973–1980 1980–1986 

Time period

Area changed, as percent of Great Plains Ecoregion 

1986–1992 1992–2000 

Figure 8. Estimated net change in all 17 Great Plains ecoregions 

by time period for each land-cover class. Bars above zero axis 

represent net gain, whereas bars below zero represent net loss. 

Note that not all land-cover classes shown in explanation may be 

represented in figure. See appendix 3 for definitions of land-use/

land-cover classifications.
10 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Agriculture Land-Cover Class

The agriculture land-cover class, one of two primary landcover classes in the Great Plains ecoregions, declined 2.2 percent 

(49,086 km2) between 1973 and 2000, which was the greatest 

amount of net change, and it had a gross change of 7.0 percent 

(156,841 km2), the second highest amount (table 4). Only three 

ecoregions had a net gain in agriculture throughout the entire 

study period: the Nebraska Sand Hills Ecoregion (1.5 percent), 

the Southern Texas Plains Ecoregion (1.0 percent), and the 

Edwards Plateau Ecoregion (0.6 percent). In most ecoregions, 

agriculture expanded between 1973 and 1980, a period in which 

overseas grain exports provided new economic opportunities 

and public policies encouraged farmers to expand their land in 

cultivation. Some expansion continued between 1980 and 1986 

in several ecoregions, although at a slower rate. The earlier gains 

in agriculture were more than offset between 1986 and 2000 

by conversions from agriculture to grassland/shrubland. In the 

Edwards Plateau Ecoregion, forest clearance and agricultural 

expansion were the leading changes between 1973 and 2000.

Between 1973 and 1986, much of the increase in 

agriculture occurred in the Western Plains Ecoregions group, 

which had substantial amounts of land that was marginal for 

cultivation. Conversely, ecoregions that had an advantageous 

climate, as well as level topography and suitable soils (for 

example, the Western Corn Belt Plains and Lake Agassiz 

Plain Ecoregions), tended to be relatively stable or have small 

declines in agriculture. The largest decline in agriculture 

between 1973 and 1986 occurred in the Texas Blackland 

Prairies Ecoregion, which also had a substantial increase in 

development that continued throughout the entire study period. 

Land-use/land-cover class

Gross spatial change (1973–2000)

[margin of error]

Net areal change (1973–2000)

[margin of error]

(km2

) (% of area) (km2) (% change)

Water 14,833 [2,360] 0.7 [0.1] 5,908 [1,802] 14.7

Developed 9,602 [1,789] 0.4 [0.1] 9,551 [2,012] 38.3

Mechanically disturbed 4,524 [1,384] 0.2 [0.1] 880 [436] 136.5

Mining 2,372 [452] 0.1 [<0.1] 1,407 [389] 116.6

Barren 2,636 [917] 0.1 [<0.1] –33 [611] –0.2

Forest 11,999 [1,369] 0.5 [0.1] –3,706 [911] –2.8

Grassland/Shrubland 159,861 [10,634] 7.2 [0.5] 38,851 [9,938] 4.1

Agriculture 156,841 [10,648] 7.0 [0.5] –48,728 [9,812] –4.8

Wetland 12,917 [2,125] 0.6 [0.1] –3,081 [1,356] –7.7

Nonmechanically disturbed 1,766 [2,065] 0.1 [0.1] –1,049 [2,042] –75.5

Table 4. Gross spatial changes and net areal changes in land-use/land-cover classes in all 17 Great Plains 

ecoregions for entire study period (1973 to 2000) and corresponding margin-of-error values for 85-percent 

confidence interval (in brackets).

[Percentages are of total area in all Great Plains ecoregions. See appendix 3 for definitions of land-use/land-cover classifications]

Between 1986 and 1992, when the Conservation Reserve 

Program (CRP) took effect, all ecoregions lost agriculture 

land cover, and most continued to decline between 1992 and 

2000. The total amount of CRP land in the United States 

reached a plateau in the early 1990s. The extent of CRP 

lands varied across the Great Plains: the Western High Plains 

Ecoregion had the most land enrolled in the program (9.5 

percent), and the Edwards Plateau Ecoregion had the least 

(0.0 percent) (U.S. Department of Agriculture, 1920–2002 

[various years]). Although the most common conversion 

during the 27-year study period was from agriculture to 

grassland/shrubland (106,603 km2), agriculture declines also 

were caused by urbanization, land abandonment, reservoir 

construction, wetland expansion, and mining. The trends 

of change during all four time periods indicate that land 

cover in the Great Plains ecoregions is capable of significant 

fluctuation, which is enabled by both their underlying 

biological and physical factors and the pressures of land-use 

and socioeconomic change (fig. 9).

Grassland/Shrubland Land-Cover Class

The grassland/shrubland land-cover class had the 

highest amount of gross change in the Great Plains 

ecoregions between 1973 and 2000, at 7.2 percent (159,861 

km2); in addition, it had the second highest amount of 

net change, at 1.7 percent (37,930 km2) (table 4). In 

many regards, the characteristics of land-cover change in 

grassland/shrubland are inverse to those in agriculture (fig. 

10). The total area of grassland/shrubland declined between 
Land-Cover Trends in the Great Plains of the United States—1973 to 2000 11

–60

60

–45

45

–30

30

0

–15

15

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Area changed, in thousands of square kilometers

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

−20

−10

0

−50

−40

–30

10

30

20

40

50

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, in thousands of square kilometers 

Figure 9. Gross change (area gained from, and lost to, other 

land-cover classes) in agriculture land-cover class in all 17 Great 

Plains ecoregions over entire study period (1973–2000). Colored 

bars above zero axis indicate land-cover classes that lost area 

to agriculture and amounts of area lost, whereas colored bars 

below zero axis indicate land-cover classes that gained area from 

agriculture and amounts of area gained.

Figure 10. Gross change (area gained from, and lost to, other

land-cover classes) in grassland/shrubland land-cover class in all 

17 Great Plains ecoregions over entire study period (1973–2000). 

Colored bars above zero axis indicate land-cover classes that lost 

area to grassland/shrubland and amounts of area lost, whereas 

colored bars below zero axis indicate land-cover classes that 

gained area from grassland/shrubland and amounts of area gained.

1973 and 1986 as agriculture expanded, but, after 1986, 

grassland/shrubland expanded greatly owing to a decline in 

agriculture land cover. For example, in the semiarid Western 

High Plains Ecoregion, agriculture gained nearly 1.6 percent 

from grassland/shrubland as irrigation expanded between 

1973 and 1980; however, this was followed by expansion of 

grassland/shrubland between 1986 and 2000, affecting about 

7.5 percent of the ecoregion. Overall, the extent of grassland/

shrubland change was highest in the Great Plains ecoregions 

between 1986 and 1992, supporting the premise that the 

CRP and other drivers of agricultural abandonment were 

important forces of grassland/shrubland change, including 

those changes that stem from the ongoing intensification, 

industrialization, and consolidation of agriculture.

Across the Great Plains ecoregions, grassland/shrubland 

converted to developed (3,152 km2) and to forest (2,958 km2), 

although the net result was often an increase in grassland/

shrubland because of its gains from agriculture. For example, 

the Texas Blackland Prairies Ecoregion had a net gain in 

grassland/shrubland during each time period as agriculture 
12 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Figure 11. Brush clearance in Southern Texas Plains Ecoregion.

Figure 12. Urban expansion in Texas Blackland Prairies 

Ecoregion.

Figure 13. Average annual gains in developed land-cover class 

from other land-cover classes in all 17 Great Plains ecoregions over 

entire study period (1973 to 2000). Colored bars indicate land-cover 

classes that lost area to developed land and amounts of area lost.

was abandoned or deintensified, despite a relatively large 

amount of urban expansion. Additional gross land-cover 

changes involving grassland/shrubland were found primarily 

in the Southern Plains Ecoregions group as a result of brush 

removal, a cyclical change that involves the conversion of 

grassland/shrubland to mechanically disturbed and then back 

to grassland/shrubland (4,524 km2) (fig. 11).

Grassland/shrubland either increased or was relatively 

constant in most ecoregions, the exception being small 

declines in the Central Great Plains Ecoregion (–0.1 percent), 

the Southern Texas Plains Ecoregion (–0.9 percent), and the 

Nebraska Sand Hills Ecoregion (–1.4 percent). Decreases 

in the Southern Texas Plains Ecoregion were caused by 

brush removal for livestock grazing and invasive-species 

control, as well as for agricultural expansion and increases 

in developed land and mining. Grassland/shrubland in the 

sparsely populated Nebraska Sand Hills Ecoregion declined 

primarily as cropland expanded along the margins of the 

ecoregion.

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

0

2

1

3

4

1973–1980 1980–1986 

Time period

Area changed, in thousands of square kilometers 

1986–1992 1992–2000 

Developed Land-Cover Class

Across the Great Plains ecoregions, new developed land 

for commercial, industrial, residential, transportation, water 

treatment, and other similar land uses increased by 0.4 percent 

(9,551 km2) of the total area between 1973 and 2000 (fig. 12). 

As a percentage of change, the area of developed land-cover 

class increased by 38.3 percent from its estimated 1973 extent. 

New developed land was found primarily around regional 

and subregional centers of service, retail, and manufacturing 

that are located in micropolitan (that is, populations of at 

least 10,000 but less than 50,000) and metropolitan (that is, 

populations of 50,000 or more) areas. At least 106 micropolitan 

areas and 46 metropolitan areas are within, or partly within, the 

Great Plains ecoregions (U.S. Census Bureau, 2003). 

Other developed land included recreational areas and, 

in some cases, additional industrial infrastructure. Some 

increases in amenity-based development occurred in localized 

areas, usually around existing or newly built reservoirs. In 
Land-Cover Trends in the Great Plains of the United States—1973 to 2000 13

addition, several isolated industrial complexes (for example, 

power plants) were built between 1973 and 2000. Some 

sections of the original interstate highway system were 

completed during the first two time periods (1973–1980, 

1980–1986), and subsequent additions of major multilane 

roads to federal and state highway systems occurred 

throughout the entire study period. 

Between 1973 and 2000, 97 percent of the new developed 

land cover came from three sources (fig. 13): developed 

gained an estimated 5,176 km2 from agriculture, an estimated 

3,152 km2 from grassland/shrubland, and an estimated 983 

km2 from forest. The ratios of conversion to new developed 

land remained relatively stable across the entire study period, 

although the conversion of forest to developed increased from 

6.6 percent during the first time period (1973–1980) to 12.0 

percent thereafter.

The Texas Blackland Prairies Ecoregion had the greatest 

increase in developed land cover, gaining 1,919 km2 (3.8 

percent), which is about 20 percent of the net increase in 

developed land in the Great Plains ecoregions. The Texas 

Blackland Prairies Ecoregion includes an axis of large urban 

areas in Texas, from Dallas in the north, through Austin, to San 

Antonio in the south. In terms of increased developed land, 

other leading ecoregions include the East Central Texas Plains 

Ecoregion (1.3 percent) and the Western Gulf Coastal Plain 

Ecoregion (1.2 percent). Growth in the Western Gulf Coastal 

Plain Ecoregion included coastal industrial and amenitybased development. However, sparsely populated ecoregions 

such as the Northwestern Great Plains, the Northwestern 

Glaciated Plains, and the Southwestern Tablelands Ecoregions 

experienced only small increases (less than 0.5 percent of 

ecoregion area) in developed land, especially those ecoregions 

that contain extensive rangeland.

Water Land-Cover Class

Climate in the Great Plains ecoregions, which ranges from 

semiarid to humid, can be highly variable both spatially and 

temporally, having long periods of drought in some ecoregions 

and cycles of above-average precipitation in others. Because 

of climate variability, many ecoregions rely on water storage 

in reservoirs to irrigate crops, as well as for livestock, for 

confined-feeding operations, and for household consumption. 

All of these water uses are related to land change. 

Overall, the changes affecting the water land-cover class 

accounted for an estimated 14,833 km2

 of the total gross 

land-cover change detected in the 17 Great Plains ecoregions 

between 1973 and 2000. Total net change, an increase of 0.3 

percent, was much less, at an estimated 5,908 km2. 

The top two changes affecting water land cover were 

both associated with wetland land cover. The wetland-towater conversion was the leading change (8,494 km2

), and the 

water-to-wetland conversion was the second-leading change 

(4,541 km2), both of which occurred primarily in the Glaciated 

Plains Ecoregions group. Much of this change was driven 

by climatic conditions that varied between dry years, which 

caused lakes and ponds to become seasonal wetlands, and wet 

years, which caused open water to persist in wetland areas. The 

wetter-than-normal conditions during the 1990s in the Northern 

Glaciated Plains Ecoregion and the Northwestern Glaciated 

Plains Ecoregion (located in the “prairie pothole” region of the 

northern Great Plains) accounted for most of the wetland-towater expansion (Garbrecht and Rossel, 2002).

The Northwestern Great Plains Ecoregion, which contains 

four of the six main-stem reservoirs along the Missouri River, 

experienced similar water and wetland changes, but for slightly 

different reasons. Decreases in upstream water availability 

caused by regional droughts and exacerbated by the resulting 

decreases in mountain snowpack, as well as changes in 

reservoir management in response to these conditions, likely 

contributed to decreased reservoir storage. As water levels 

dropped, wetland vegetation grew in embayments formed by 

tributary streams. These changes took place in the late 1980s 

and early 1990s; however, the reservoirs had mostly recovered 

by the year 2000 (U.S. Army Corps of Engineers, 2004). 

Conversions of grassland/shrubland to water, agriculture 

to water, and water to grassland/shrubland were the third-, 

fourth-, and fifth-leading changes, respectively, that affected the 

water land-cover class in the Great Plains ecoregions. Changes 

from grassland/shrubland to water across the ecoregions were 

caused primarily by the construction of new reservoirs and also 

by flooding from expanding lakebeds. A large number of small 

reservoirs, commonly called “stock dams” or “stock tanks,” 

were built for livestock water supply, especially in more arid 

ecoregions such as the Northwestern Great Plains, Central Great 

Plains, Southern Texas Plains, and Southwestern Tablelands 

Ecoregions. Larger, multiuse reservoirs also were built. In 

addition, natural flooding of grassland/shrubland occurred 

primarily in the Glaciated Plains Ecoregions group, where 

wetter-than-normal years caused some lakebeds of glacial origin 

to increase in size. These water bodies may persist as larger 

surface areas for years before cyclical climatic conditions (for 

example, periods of drought or below-normal precipitation) 

reduce their size (Todhunter and Rundquist, 2004; Shapley and 

others, 2005). Conversions of water to grassland/shrubland 

resulted when reservoirs, especially small “stock dams,” dried 

up during periods of below-normal precipitation. Overall, water 

land cover experienced a small net gain of an estimated 440 km2

from grassland/shrubland land cover between 1973 and 2000.

Wetland Land-Cover Class

Changes in the wetland land-cover class, the fifth-leading 

gross change in the Great Plains ecoregions, are closely 

associated with changes in the water land-cover class. As a 

percentage of land area in the 17 Great Plains ecoregions, 

wetland land cover decreased by 0.1 percent. As a percentage 

of the wetland areas in 1973, wetland land cover had 

decreased by an estimated 7.7 percent (3,081 km2) by the year 

2000. The net decline was caused primarily by wetter climatic 

conditions, which caused wetland areas to be replaced with 

persistent open water.
14 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Much of the expansion of wetlands occurred in the 

Northern Glaciated Plains Ecoregion (part of the “prairie 

pothole” region) in the mid-1980s and mid- to late 1990s, 

when wetter-than-normal climatic conditions caused many 

temporary and seasonal wetlands that were previously 

farmed to stay persistently wet, keeping them out of crop 

production. The Western Corn Belt Plains Ecoregion, 

traditionally included in the “prairie pothole” region before 

its wetlands were mostly drained or modified to enable 

cultivation in the late 19th and early 20th centuries, also 

experienced wetland expansion, but it was only a small 

fraction when compared to the neighboring Northern 

Glaciated Plains Ecoregion (an estimated 74 km2 versus 

1,356 km2).

In the Western Gulf Coastal Plain Ecoregion, 

conversions of agriculture to wetland had different factors 

that influenced this type of change. Substantial amounts of 

ground subsidence in coastal areas may have created wetland 

conditions on former agricultural land (Davidson and Mace, 

2006). Several National Wildlife Refuges also were created 

in the ecoregion, including the Cameron Prairie National 

Wildlife Refuge in southwestern Louisiana, where former 

agricultural land was converted back to wetlands (U.S. Fish 

and Wildlife Service, 2009).

Other changes affecting the wetland land-cover class 

were conversions from grassland/shrubland to wetland 

(an estimated gross change of 450 km2) and wetland to 

grassland/shrubland (an estimated gross change of 447 km2). 

These conversions took place primarily in the Glaciated 

Plains Ecoregions group, as well as in several ecoregions 

in the Southern Plains Ecoregions group, as changes in 

precipitation patterns contributed to fluctuations in wetland 

extent. Conversions from forest to wetland also occurred 

in the Southern Plains Ecoregions group, where reservoirs 

for metropolitan drinking water were constructed. As these 

reservoirs filled, upland forest areas were drowned and, thus, 

were replaced by wetland areas. 

The Western Gulf Coastal Plain Ecoregion has a 

wide variety of wetlands within it, some of which include 

the western range of bald cypress (Taxodium distichum), 

a commercially valuable wetland tree. This ecoregion 

experienced the highest amount of conversion from wetland 

to mechanically disturbed land, a result of forest harvest. The 

Western Gulf Coastal Plain Ecoregion was also the leading 

ecoregion for conversion from wetland to developed land, 

primarily caused by increased urbanization and industrial 

growth.

Forest Land-Cover Class

A net decline in the forest land-cover class of 0.1 

percent (about 3,706 km2) of the total area of the Great Plains 

ecoregions occurred during the 27-year study period. However, 

most forest change was in the Southern Plains Ecoregions 

group. The largest net decline occurred as agriculture expanded 

between 1973 and 2000 (about 2,678 km2). Loss of forest to 

developed land, clearcutting (mechanically disturbed land), and 

reservoir construction also made significant contributions to the 

rates of forest land-cover change (fig. 14). 

Mining Land-Cover Class

A net gain in the mining land-cover class of less than 

0.1 percent (about 1,407 km2) of the total area of the Great 

Plains ecoregions occurred between 1973 and 2000. Although 

this was a small amount of change, it more than doubled the 

area of the mining land-cover class. Most of the increase 

came from the conversion to mining from agriculture and 

grassland/shrubland. The expansion of quarrying, mineral 

excavation, and oil and gas extraction provided most of the 

increase in mining land cover, whereas declines resulted from 

mine abandonment and the revegetation of reclaimed mine 

sites. A small amount of mining land cover was abandoned or 

purposely converted to ponds for recreation or wildlife. 

Figure 14. Gross change (area gained from, and lost to, other 

land-cover classes) in forest land-cover class over entire study 

period (1973–2000). Colored bars above zero axis indicate landcover classes that lost area to forest and amounts of area lost, 

whereas colored bars below zero axis indicate land-cover classes 

that gained area from forest and amounts of area gained. 

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

Area changed, in thousands of square kilometers 

1986–1992 1992–2000 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS
Land-Cover Trends in the Great Plains of the United States—1973 to 2000 15

Mechanically Disturbed and Nonmechanically 

Disturbed Land-Cover Classes

Three main processes resulted in a net expansion 

in the mechanically disturbed land-cover class and a net 

decline in the nonmechanically disturbed land-cover class. 

Expanded forest cutting in the Southern Plains Ecoregions 

group (1,121 km2) increased mechanically disturbed land. 

Large amounts of gross change associated with the cycles of 

woody-brush clearance and subsequent regrowth resulted in 

a small net gain of mechanically disturbed land. Changes in 

nonmechanically disturbed land (about 1,766 km2 of gross 

change, and a net-change decline of 1,049 km2) occurred 

as grassland/shrubland burned and then reestablished itself 

following fire disturbance.

Barren Land-Cover Class

A gross change of 2,636 km2 in the barren land-cover class 

was associated mostly with fluctuations in the extent of natural 

water bodies and grassland/shrubland. Transitions to and from 

barren land caused by changes in precipitation amounts resulted 

in a small net decline of 33 km2 of the barren land-cover class. 

Summary

The highest amount of land-cover change that took 

place in the Great Plains ecoregions was due to fluctuations 

in agriculture, much of it on marginal land, as economic 

opportunities, sociocultural dynamics, agricultural 

technologies, and government farm policies changed. Most 

of the Great Plains ecoregions experienced an overall decline 

in agricultural land, which was facilitated by the policies and 

incentives of the Conservation Reserve PrHyperogram. The 

decline followed an earlier period of agricultural expansion 

between 1973 and 1980 at the expense of grassland/shrubland. 

The drier Western Plains Ecoregions group and the 

brushy Southern Plains Ecoregions group had relatively high 

rates of change that reflect substantial fluctuations between 

agriculture and grassland/shrubland. Ecoregions having 

biological and physical conditions that were favorable to 

agriculture tended to have lower rates of change. Variability 

in precipitation patterns and temperature levels had effects 

on land-cover change that could be characterized as veiled 

to obvious. The expansion of surface water area in the 

Glaciated Plains Ecoregions group was an important story 

that is tied to both climate and human activity, as reservoirs 

were constructed throughout the region for flood control, 

crop irrigation, livestock and residential water supply, and 

industrial use. 

All 17 Great Plains ecoregions saw small but steady 

increases in the developed land-cover class. Most increases 

in developed land occurred in the Southern Plains Ecoregions 

group as urbanization spread onto agricultural land and 

References Cited

Davidson, S.C., and Mace, R.E., 2006, Aquifers of the Gulf 

Coast of Texas—An overview, in Mace, R.E., Davidson, 

S.C., Angle, E.S., and Mullican, W.F., III, eds., Aquifers of 

the Gulf Coast of Texas: Texas Water Development Board, 

Report 365, p. 1–21, available at https://www.twdb.texas.

gov/publications/reports/numbered_reports/doc/R365/

R365_Composite.pdf.

Dennehy, K.F., Litke, D.W., and McMahon, P.B., 2002, The 

High Plains Aquifer, USA—Groundwater development 

and sustainability, in Hiscock, K.M., Rivett, M.O., 

and Davison, R.M., eds., Sustainable groundwater 

development: London, Geological Society, Special 

Publications, v. 193, p. 99–119, available at http://

sp.lyellcollection.org/content/193/1/99.abstract.

Engle, D.M., Coppedge, B.R., and Fuhlendorf, S.D., 2008, 

From the Dust Bowl to the Green Glacier—Human activity 

and environmental change in Great Plains grasslands, in

van Auken, O.W., Western North American Juniperus

communities—A dynamic vegetation type: New York, 

Springer, Ecological Studies 196, p. 253–271, available at 

http://link.springer.com/chapter/10.1007%2F978-0-387-

34003-6_14#page-1.

Gallant, A.L., Loveland, T.R., Sohl, T.L., and Napton, D.E., 

2004, Using an ecoregion framework to analyze land-cover 

and land-use dynamics: Environmental Management, v. 34, 

p. S89–S110.

Garbrecht, J.D., and Rossel, F.E., 2002, Decade-scale 

precipitation increase in the Great Plains at the end of the 

20th century: Journal of Hydrologic Engineering, v. 7, no. 

1, p. 64–75. 

Loveland, T.R., Sohl, T.L., Stehman, S.V., Gallant, A.L., 

Sayler, K.L., and Napton, D.E., 2002, A strategy for 

estimating the rates of recent United States land-cover 

changes: Photogrammetric Engineering & Remote Sensing, 

v. 68, no. 10, p. 1,091–1,099.

grassland/shrubland. Cycles of grassland/shrubland clearance 

in the Southern Plains Ecoregions group also contributed to 

high rates of gross land-cover change. The trajectories and 

causes of land-use/land-cover change varied substantially 

within each ecoregion, giving some indication of the 

complexity of land-cover-change processes at work across 

the Great Plains. To aid in the understanding of land-use/

land-cover change in greater detail, the remaining chapters 

in this report contain summaries of change for each of the 

17 Great Plains ecoregions; these summaries document the 

rates, types, and drivers of late 20th century land-use/landcover change in the Great Plains of the United States.
16 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

McMahon, G., Gredonis, S.M., Waltman, S.W., Omernik, 

J.M., Thorson, T.D., Freeouf, J.A., Rorick, A.H., and Keys, 

J.E., 2001, Developing a spatial framework of common 

ecological regions for the conterminous United States: 

Environmental Management, v. 28, no. 3, p. 293–316.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Rossum, S., and Lavin, S., 2000, Where are the Great Plains? 

A cartographic analysis: Professional Geographer, v. 52, no. 

3, p. 543–552.

Shapley, M.D., Johnson, W.C., Engstrom, D.R., and 

Osterkamp, W.R., 2005, Late-Holocene flooding and 

drought in the northern great plains, USA, reconstructed 

from tree rings, lake sediments, and ancient shorelines: The 

Holocene, v. 15, no. 1, p. 29–41.

Stehman, S.V., Sohl, T.L., and Loveland, T.R., 2003, Statistical 

sampling to characterize recent United States land-cover 

change: Remote Sensing of Environment, v. 86, no. 4, p. 

517–529.

Stehman, S.V., Sohl, T.L., and Loveland, T.R., 2005, An evaluation of sampling strategies to improve precision of estimates 

of gross change in land use and land-cover: International 

Journal of Remote Sensing, v. 26, no. 22, p. 4,941–4,957.

Todhunter, P.E., and Rundquist, B.C., 2004, Terminal lake 

flooding and wetland expansion in Nelson County, North 

Dakota: Physical Geography, v. 25, p. 68–85.

U.S. Army Corps of Engineers, 2004, Summary—Missouri 

River final environmental impact statement, master water 

control manual review and update: U.S. Army Corps of Engineers Northwestern Division, accessed February 19, 2009, at 

http://www.nwd-mr.usace.army.mil/mmanual/Summary.pdf.

U.S. Census Bureau, 2003, State-based metropolitan and 

micropolitan statistical areas maps: U.S. Census Bureau 

database, accessed February 10, 2009, at http://www.census.

gov/geo/maps-data/maps/statecbsa.html.

U.S. Department of Agriculture, 1920–2002 [various 

years], Census of agriculture, geographic area series: 

U.S. Government Printing Office, U.S. Department of 

Agriculture National Agricultural Statistics Service, 

available at http://www.agcensus.usda.gov/Publications/

Historical_Publications/index.php. 

U.S. Environmental Protection Agency, 1997, Descriptions 

of level III ecological regions for the CEC report on 

ecological regions of North America: U.S. Environmental 

Protection Agency database, accessed April 12, 2006, 

at http://www.epa.gov/wed/pages/ecoregions/na_eco.

htm#Downloads.

U.S. Environmental Protection Agency, 1999, Level 

III ecoregions of the continental United States: U.S. 

Environmental Protection Agency National Health 

and Environmental Effects Research Laboratory, scale 

1:7,500,000, available at ftp://ftp.epa.gov/wed/ecoregions/

us/Eco_Level_III_US.pdf.

U.S. Fish and Wildlife Service, 2009, Cameron Prairie 

National Wildlife Refuge: U.S. Fish and Wildlife Service, 

accessed February 26, 2009, at http://www.fws.gov/

southeast/pubs/facts/camcon.pdf.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Western Plains Ecoregions

Chapter 1

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

102° 100° 98° 42°

40°

38°

36°

34°

32°

Western

High Plains

Flint

Hills

Edwards Plateau

Nebraska Sand Hills

NSH

Central

Oklahoma/Texas

Plains

SWT

SWT

SWT

AV

SCP

Texas

Blackland

Prairies

ECTP

CD ECTP

Western

High Plains

Western Corn

Belt Plains

0 50 100 MILES

0 50 100 KILOMETERS

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

Ecoregion boundary

Sample block (10 x 10 km)

EXPLANATION

High Plains

(Ogallala) Aquifer

Abilene

Rainwater Basin

Wetland Management

District

CANADIAN

COUNTY

NEBRASKA

COLORADO

TEXAS

OKLAHOMA

KANSAS

Oklahoma

City

Wichita

Platte River

Central Great Plains Ecoregion

By Mark A. Drummond

Ecoregion Description

The Central Great Plains Ecoregion 

is a large, elongated area that covers about 

273,189 km2 (105,479 mi2) from central 

Nebraska through Kansas and Oklahoma into 

north-central Texas (Omernik, 1987; U.S. 

Environmental Protection Agency, 1997) (fig. 1).

The ecoregion is bounded on the west by the 

Western High Plains and the Southwestern 

Tablelands Ecoregions; on the north by the 

Nebraska Sand Hills Ecoregion; on the east by 

the Western Corn Belt Plains, Flint Hills, and 

Central Oklahoma/Texas Plains Ecoregions; and 

on the south by the Edwards Plateau Ecoregion 

and a small part of the Chihuahuan Deserts 

Ecoregion (Omernik, 1987).

Agriculture is the primary land use in 

the Central Great Plains Ecoregion where 

level topography, water availability, fertile 

soils, and a long growing season contribute 

to high productivity among several crops. 

Overall, about one-half of the ecoregion is 

in cropland, and much of the other one-half 

includes confined animal-feeding operations and 

livestock grazing. Agriculture is aided by warm 

summer temperatures. With a strong northsouth temperature gradient for much of the year, 

average July temperatures are at or above 27oC 

for most of the ecoregion. Annual precipitation 

levels range from about 500 mm (20 in.) per year 

in the western part of the ecoregion to 800 mm 

(32 in.) per year in the eastern part (National 

Atlas of the United States, 2008).

Native grasslands in the ecoregion consist 

primarily of a mixed-grass prairie that includes 

little bluestem (Schizachyrium scoparium) and 

grama (Bouteloua spp.) grasses, interspersed with 

mesquite (Prosopis spp.) shrublands in the south. 

Some grasslands and wetlands are managed as 

protected areas: in particular, the migratorybird habitat along the Platte River and in the 

Rainwater Basin Wetland Management District 

in south-central Nebraska. Millions of water 

birds migrating along the Central Flyway funnel 

Figure 1. Map of Central Great Plains Ecoregion and surrounding ecoregions,

showing land-use/land-cover classes from 1992 National Land Cover Dataset 

(Vogelmann and others, 2001); note that not all land-use/land-cover classes 

shown in explanation may be depicted on map; note also that, for this “Status 

and Trends of Land Change” study, transitional land-cover class was subdivided 

into mechanically disturbed and nonmechanically disturbed classes. Squares 

indicate locations of 10 x 10 km sample blocks analyzed in study. Index map shows 

locations of geographic features mentioned in text. Abbreviations for Great Plains 

ecoregions are listed in appendix 2. Also shown are parts of one Western United 

States ecoregion (Chihuahuan Deserts [CD]) and two Midwest–South Central 

United States ecoregions (Arkansas Valley [AV] and South Central Plains [SCP]). 

See appendix 3 for definitions of land-use/land-cover classifications.
20 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Figure 2. Harvesting of winter wheat in Central Great Plains 

Ecoregion.

Figure 3. Large grain elevator, used to weigh, store, and convey 

grain, in Central Great Plains Ecoregion.

Figure 4. Furrow irrigation in Central Great Plains Ecoregion. 

Figure 5. Confined animal-feeding operation in Central Great 

Plains Ecoregion.

into this narrow area each spring. Small, shallow playa lakes, 

which are common throughout the western and central parts of 

the Great Plains, also provide an ephemeral water source and 

seasonal-wildlife habitat. Natural and seminatural disturbance 

regimes that affect vegetation include periodic drought, 

wildfires that maintain grasslands and prevent encroachment 

of woody species, and grazing by wildlife and livestock.

The Central Great Plains Ecoregion covers much of the 

hard winter-wheat area of Kansas and Oklahoma, which is 

a mainstay of Great Plains agriculture (fig. 2). Wheat crops 

covered an average of 17.5 percent of the ecoregion during 

the study period (U.S. Department of Agriculture, 1970–2000 

[various years]). In drier areas, wheat fields traditionally have 

lain fallow every other year, whereas areas of the ecoregion 

that have adequate moisture grow wheat continuously. Kansas 

is the top wheat-producing state, and several large grain 

elevators and flour mills operate in the ecoregion (fig. 3). 

Agriculture in the northern part of the ecoregion is heavily 

irrigated along the Platte River in Nebraska, as well as in areas 

overlying the eastern extent of the High Plains (Ogallala) 

aquifer, the largest groundwater complex in the nation, where 

feed corn is the principal crop (fig. 4). About 30 percent of 

groundwater used for crop irrigation in the United States is 

pumped from the High Plains aquifer (Dennehy, 2000), which 

also underlies the adjacent Western High Plains Ecoregion and 

the rangelands of the Nebraska Sand Hills Ecoregion. 

As with other areas of the Great Plains, watermanagement issues are central to the Central Great Plains 

Ecoregion. For example, large-scale confined-feeding 

operations have expanded in the ecoregion, and they require 

a readily available source of water, bringing them into 

competition with other agricultural uses (fig. 5). The area of 

cropland irrigation also has increased more than 10 times 

in south-central Kansas, causing declining streamflows 

and groundwater levels and, thus, affecting water quality 

(Sophocleous and others, 1999). High evapotranspiration 

rates and variable amounts of rainfall also increase the need 

for irrigation. Cotton is an important crop in the southern 

part of the ecoregion, along with wheat, sorghum, and hay. 

The Conservation Reserve Program (CRP), which was 

initiated in 1985 to provide income to farmers for keeping 

fragile soils and wetlands out of crop production, accounted 
Chapter 1—Central Great Plains Ecoregion 21

Figure 6. Small town in Central Great Plains Ecoregion, many of 

which are facing dwindling rural populations.

for 3 percent of the total ecoregion area in 2000 (U.S. 

Department of Agriculture, 1970–2000 [various years]). 

The population of the Central Great Plains Ecoregion was 

2.5 million in 2000, a 12 percent increase since 1970; however, 

65 percent of the counties lost population (U.S. Census Bureau, 

1970–2000 [various years]). Most rural counties that had less 

than 10,000 people in 1970 lost population by 2000. Although 

the ecoregion is largely agricultural, modern farming methods 

often require only a small, seasonal workforce, and many farmers 

do not live on farms year-round (fig. 6). The consolidation of 

small family farms into large corporate operations also may 

account for some of the population shift. The seven largest 

counties in 1970, having at least 50,000 people, all gained in 

population by 2000. Canadian County, Oklahoma, gained the 

most population between 1970 and 2000, from 32,245 to 87,697 

people. This 172 percent increase may relate to the proximity 

of Canadian County to Oklahoma City, Oklahoma, the largest 

metropolitan area in the ecoregion. Wichita, Kansas, and Abilene, 

Texas, are other large population centers. 

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Central Great Plains 

Ecoregion between 1973 and 2000 is estimated at 8.3 percent 

(table 1). Compared to other Great Plains ecoregions, change 

in the Central Great Plains Ecoregion was moderate (fig. 7): 

most of the area that changed (7.2 percent) did so in only one 

time period, 0.9 percent changed during two time periods, 

and 0.1 percent changed during three time periods. Multiple 

changes were caused mainly by successive conversions 

between agriculture and grassland/shrubland during two 

or more time periods but also by natural fluctuations in 

the surface extent of water and wetland areas. Overall, the 

estimated annual rates of change during each of the four time 

periods were relatively consistent (about 0.2–0.3 percent), 

except between 1986 and 1992 when the annual rate was 0.6 

percent of the ecoregion (fig. 8).

Figure 7. Overall spatial change in Central Great Plains 

Ecoregion (CGP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that experienced change during one, 

two, three, or four time periods; highest level of spatial change 

in Central Great Plains Ecoregion (four time periods) labeled for 

clarity. See table 4 for years covered by each time period. See 

appendix 2 for key to ecoregion abbreviations.

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Figure 8. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Central Great 

Plains Ecoregion are represented by red bars in each time period.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods
22 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Although most of the land-cover changes were 

conversions between agriculture and grassland/shrubland, 

the resulting net changes were relatively small over the 

entire 27-year study period. The most common land-cover 

conversion between 1973 and 1980 was grassland/shrubland 

to agriculture (3,933 km2) (table 2), a time when export 

prices for wheat, corn, and soybeans increased substantially. 

The expansion of economic opportunity contributed to 

an estimated 1.0 percent decline in grassland/shrubland 

between 1973 and 1980, from 41.3 percent to 40.3 percent 

of ecoregion area (table 3). Access to surface water and to 

High Plains aquifer groundwater, particularly in the northern 

part of the ecoregion, facilitated an increase in agriculture. 

Agricultural expansion continued, although at a substantially 

slower pace (0.1 percent), between 1980 and 1986, a time of 

financial distress and declining farmland prices. Although the 

real estate price of farmland during the 1970s had the largest 

decadal rate of increase on record, farmland values decreased 

between 1980 and 1986 at the steepest rates on record 

(nearly 10 percent annually) (Lindert, 1988).

The trend changed significantly between 1986 and 

1992, when the CRP was enacted and much agricultural land 

was converted to grassland/shrubland (6,045 km2) (table 2). 

Grassland/shrubland increased by 1.4 percent during this 

time period (fig. 9); this also was the period that had the 

highest percentage of total gross change, when 3.4 percent

of the ecoregion changed (table 4), caused largely by 

agricultural land converting to grassland/shrubland through 

the CRP. Between 1992 and 2000, agriculture had little 

net change, as some CRP contracts expired and land was 

returned to crop production while other cropland was newly 

enrolled in the program.

Over the entire 27-year study period, the dynamics of 

land-use expansion and decline resulted in a similar amount 

of conversion from agriculture to grassland/shrubland 

(10,868 km2) and from grassland/shrubland to agriculture 

(10,261 km2) (table 2). Although the net result was only 

a small decrease in agriculture, the results suggest that 

agricultural land-cover class can be quite dynamic, as a 

substantial amount of marginal land is either in cultivation 

or abandoned, depending on economic conditions and farm 

policies.

A loss of 0.6 percent in agricultural land between 1973 

and 2000 (fig. 10) was caused by conversion to developed 

land and by smaller net conversions to grassland/shrubland 

Figure 10. Estimates of net land-cover change in Central Great 

Plains Ecoregion for each land-cover class between 1973 and 

2000. Bars above zero axis represent net gain, whereas bars 

below zero represent net loss. See appendix 3 for definitions of 

land-use/land-cover classifications.

Figure 9. Normalized average net change in Central Great Plains 

Ecoregion by time period for each land-cover class. Bars above 

zero axis represent net gain, whereas bars below zero represent 

net loss. Note that not all land-cover classes shown in explanation 

may be represented in figure. See appendix 3 for definitions of 

land-use/land-cover classifications.

2

1

0

−1

−2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

0.8

0.6

0.4

0.2

0

−0.2

−0.4

−0.6

−0.8

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

EXPLANATION

Land-use/land-cover class
Chapter 1—Central Great Plains Ecoregion 23

Table 1. Percentage of Central Great Plains Ecoregion land cover 

that changed at least one time during study period (1973–2000) and 

associated statistical error.

[Most sample pixels remained unchanged (91.7 percent), whereas 8.3 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 7.2 1.1 6.1 8.3 0.8 10.5

2 0.9 0.4 0.6 1.3 0.3 28.2

3 0.1 0.0 0.0 0.1 0.0 35.9

4 0.0 0.0 0.0 0.0 0.0 84.2

Overall 

spatial 

change

8.3 1.4 6.8 9.7 1.0 11.8

and water. The conversion to water primarily was caused by 

an increase in impounded water. However, agricultural land 

remained the dominant land-cover class throughout the entire 

study period (table 3). Grassland/shrubland decreased by 

0.1 percent between 1973 and 2000, mostly attributable to

the increase in development, mining, and water uses. 

Developed land had the highest percentage of net 

change, with an increase of 0.7 percent (1,869 km2). Much 

of the increase in developed land likely is related to urban 

growth around metropolitan areas, as well as the 12 percent 

overall increase in the population of the ecoregion. The 

expansion of developed land generally is a permanent 

change, whereas spatial changes between agriculture and 

grassland/shrubland over the long term resulted in much 

gross change and little net change.
24 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 2. Principal land-cover conversions in Central Great Plains Ecoregion, showing amount of area changed (and margin of error, 

calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study period. 

See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 3,933 957 654 1.4 59.6

Agriculture Grassland/Shrubland 1,514 576 393 0.6 22.9

Grassland/Shrubland Developed 396 505 345 0.1 6.0

Agriculture Developed 305 378 258 0.1 4.6

Grassland/Shrubland Water 50 39 27 0.0 0.8

Other Other 401 n/a n/a 0.1 6.1

Totals 6,599 2.4 100.0

1980–1986 Grassland/Shrubland Agriculture 2,026 758 517 0.7 43.1

Agriculture Grassland/Shrubland 1,549 381 260 0.6 33.0

Agriculture Developed 171 193 132 0.1 3.6

Wetland Water 143 202 138 0.1 3.0

Grassland/Shrubland Developed 125 166 113 0.0 2.7

Other Other 681 n/a n/a 0.2 14.5

Totals 4,695 1.7 100.0

1986–1992 Agriculture Grassland/Shrubland 6,045 2,828 1,930 2.2 65.8

Grassland/Shrubland Agriculture 2,125 479 327 0.8 23.1

Agriculture Developed 231 276 188 0.1 2.5

Grassland/Shrubland Mining 139 100 68 0.1 1.5

Forest Agriculture 96 115 79 0.0 1.0

Other Other 549 n/a n/a 0.2 6.0

Totals 9,185 3.4 100.0

1992–2000 Grassland/Shrubland Agriculture 2,178 884 604 0.8 41.5

Agriculture Grassland/Shrubland 1,761 586 400 0.6 33.5

Agriculture Developed 353 269 184 0.1 6.7

Grassland/Shrubland Developed 222 245 167 0.1 4.2

Water Mechanically disturbed 160 220 150 0.1 3.0

Other Other 578 n/a n/a 0.2 11.0

Totals 5,251 1.9 100.0

1973–2000 Agriculture Grassland/Shrubland 10,868 3,662 2,499 4.0 42.2

(overall) Grassland/Shrubland Agriculture 10,261 1,925 1,314 3.8 39.9

Agriculture Developed 1,061 1,049 716 0.4 4.1

Grassland/Shrubland Developed 790 949 648 0.3 3.1

Forest Agriculture 338 365 249 0.1 1.3

Other Other 2,411 n/a n/a 0.9 9.4

Totals 25,730 9.4 100.0
Chapter 1—Central Great Plains Ecoregion 25

Table 3. Estimated area (and margin of error) of each land-cover class in Central Great Plains Ecoregion, calculated five times between 

1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/

Shrubland Agriculture Wetland

Nonmechanically

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.7 0.3 1.0 0.5 0.0 0.0 0.1 0.0 0.7 0.4 2.3 0.5 41.3 5.9 53.4 5.7 0.5 0.5 0.0 0.0

1980 0.7 0.3 1.3 0.7 0.0 0.0 0.1 0.0 0.7 0.4 2.3 0.5 40.3 5.8 54.2 5.7 0.5 0.5 0.0 0.0

1986 0.8 0.3 1.4 0.8 0.0 0.0 0.1 0.1 0.6 0.4 2.2 0.5 40.0 5.8 54.3 5.7 0.4 0.4 0.0 0.0

1992 0.8 0.3 1.5 0.8 0.0 0.0 0.2 0.1 0.6 0.4 2.2 0.5 41.4 5.8 52.8 5.7 0.5 0.4 0.0 0.0

2000 0.8 0.3 1.7 1.0 0.1 0.1 0.2 0.1 0.6 0.4 2.1 0.5 41.2 5.8 52.8 5.7 0.5 0.5 0.0 0.0

Net

change 0.1 0.2 0.7 0.5 0.1 0.1 0.2 0.1 –0.1 0.1 –0.2 0.2 -0.1 1.3 –0.6 1.3 0.0 0.0 0.0 0.0

Gross

change 0.3 0.2 0.7 0.5 0.1 0.1 0.2 0.1 0.1 0.1 0.2 0.2 5.7 1.4 5.8 1.4 0.1 0.1 0.0 0.0

Area, in square kilometers

1973 1,878 711 2,788 1,376 0 0 158 73 1,810 1,224 6,245 1,398 112,936 15,984 146,004 15,612 1,371 1,252 0 0

1980 1,940 725 3,492 1,835 10 14 199 95 1,829 1,205 6,185 1,391 110,040 15,808 148,119 15,470 1,377 1,257 0 0

1986 2,151 772 3,790 2,061 74 94 361 193 1,717 1,097 6,094 1,374 109,402 15,853 148,389 15,571 1,212 1,166 0 0

1992 2,205 816 4,079 2,307 1 2 531 311 1,698 1,024 5,978 1,346 113,177 15,913 144,252 15,534 1,269 1,221 0 0

2000 2,099 717 4,657 2,612 179 221 606 346 1,635 980 5,812 1,302 112,540 15,773 144,348 15,447 1,313 1,242 0 0

Net

change 221 445 1,869 1,402 179 221 449 311 –175 310 –433 415 –396 3,513 –1,656 3,450 –59 59 0 0

Gross

change 855 542 1,869 1,402 327 408 449 311 389 339 468 413 15,491 3,892 15,829 3,854 350 374 0 0

Table 4. Raw estimates of change in Central Great Plains Ecoregion land cover, computed 

for each of four time periods between 1973 and 2000, and associated error at 85-percent 

confidence level.

[Estimates of change per period normalized to annual rate of change for each time period]

Period

Total 

change

(% of 

ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper 

bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average 

rate

(% per 

year)

Estimate of change, in percent stratum

1973–1980 2.4 0.4 2.0 2.8 0.3 12.1 0.3

1980–1986 1.7 0.4 1.4 2.1 0.2 14.4 0.3

1986–1992 3.4 1.0 2.3 4.4 0.7 21.2 0.6

1992–2000 1.9 0.5 1.5 2.4 0.3 16.2 0.2

Estimate of change, in square kilometers

1973–1980 6,599 1,171 5,429 7,770 799 12.1 943

1980–1986 4,695 989 3,706 5,684 675 14.4 782

1986–1992 9,185 2,858 6,326 12,043 1,951 21.2 1,531

1992–2000 5,251 1,246 4,005 6,497 850 16.2 656
26 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Dennehy, K.F., 2000, High Plains regional ground-water 

study: U.S. Geological Survey Fact Sheet 091–00, 6 p., 

available at http://pubs.usgs.gov/fs/2000/0091/report.pdf.

Lindert, P.H., 1988, Long-run trends in American farmland 

values: Agricultural History, v. 62, p. 45–85.

National Atlas of the United States, 2008, Average annual 

precipitation: National Atlas of the United States database, 

accessed May 21, 2013, at http://www.nationalatlas.gov.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Sophocleous, M.A., Koelliker, J.K., Govindaraju, R.S., Birdie, 

T., Ramireddygari, S.R., and Perkins, S.P., 1999, Integrated 

numerical modeling for basin-wide water management—

The case of the Rattlesnake Creek basin in south-central 

Kansas: Journal of Hydrology, v. 214, p. 179–196.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed September 1, 2008, at http://www.census.gov/

prod/www/decennial.html.

U.S. Department of Agriculture, 1970–2000 [various years], 

Census of Agriculture: U.S. Department of Agriculture database, accessed September 1, 2008, at http://www.agcensus.

usda.gov/.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Chapter 2

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Nebraska Sand Hills Ecoregion

By Janis L. Taylor

Ecoregion Description 

The Nebraska Sand Hills Ecoregion covers about 60,541 

km2 (23,375 mi2), almost entirely within the state of Nebraska 

(fig. 1). The ecoregion is surrounded by (clockwise, from the 

north) the Northwestern Great Plains, Northwestern Glaciated 

Plains, Western Corn Belt Plains, Central Great Plains, and 

Western High Plains Ecoregions (fig. 1). Nebraska’s Sand 

Hills is an area of grass-stabilized sand dunes considered to be 

one of the most distinct and homogeneous ecoregions in North 

America (Omernik, 1987; U.S. Environmental Protection 

Agency, 1997). According to the Grassland Foundation 

(2005), Nebraska’s Sand Hills is one of the largest and 

best examples of grasslands left in North America (fig. 2). 

Topographic relief varies by as much as 60 m, and the sand 

layers range in thickness from a few meters to more than 122 

m (Huntzinger and Ellis, 1993).

Figure 1. Map of Nebraska Sand Hills Ecoregion and 

surrounding ecoregions, showing land-use/land-cover 

classes from 1992 National Land Cover Dataset (Vogelmann 

and others, 2001); note that not all land-use/land-cover 

classes shown in explanation may be depicted on map; 

note also that, for this “Status and Trends of Land Change” 

study, transitional land-cover class was subdivided into 

mechanically disturbed and nonmechanically disturbed 

classes. Squares indicate locations of 10 x 10 km sample 

blocks analyzed in study. Index map shows locations of 

geographic features mentioned in text. Abbreviations for 

Great Plains ecoregions are listed in appendix 2. Also 

shown is part of one Western United States ecoregion, 

Middle Rockies (MRK). See appendix 3 for definitions of 

land-use/land-cover classifications.

103° 102° 101° 100° 99° 98°

Western

High Plains

Central

Great Plains

Northwestern

Great Plains

Northwestern

Glaciated Plains

NGP

WCBP

MRK

SOUTH DAKOTA

NEBRASKA

C O

Valentine

O’Neill

Amelia S A N D H I L L S Thedford

Hyannis

Missouri R i ver

P l a t t e R i v e r

Loup River

Elkhorn River

Nio b r ara River

43°

42°

41°

0 25 50 75 MILES

0 50 75 25 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

Nebraska EXPLANATION

Sand Hills

Ecoregion

SD

NE
28 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

A

A

B

B

C

The climate is considered semiarid, as the Nebraska Sand 

Hills Ecoregion is in the rain shadow of the Rocky Mountains to 

the west. The Gulf of Mexico is the principal source of moisture, 

with most precipitation falling during May and June. Soils in 

the Nebraska Sand Hills Ecoregion are classified as Aridisols—

sandy soils that have a coarse texture and low water-holding 

capacity—which have high infiltration rates and little runoff 

after precipitation falls. The water-holding capacity of the soil 

root zone is less than 100 mm (4 in.). Thus, ranchers and farmers 

involved in hay and range-livestock production are at high risk 

during periods of drought (Wilhelm and Wichita, 2002).

Wetlands are scattered throughout the Nebraska Sand 

Hills Ecoregion, in shallow, wet meadows, in the margins of 

lakes, and in backwaters associated with spring-fed streams. 

Wetlands are somewhat common in the valleys between dunes 

where the water table is at or near the surface (fig. 3). The 

Loup and Elkhorn Rivers originate in the Nebraska Sand Hills 

Ecoregion, and the Niobrara River flows across the northern 

part of the ecoregion. These rivers and their tributaries are 

sustained by shallow groundwater, and they have a consistent 

base flow (Bleed and Flowerday, 1998). 

Most land within the Nebraska Sand Hills Ecoregion is 

privately owned, and the primary land uses include rangeland 

cattle grazing and hay production (fig. 4). Valentine, Hyannis, 

and Thedford are examples of small ranching communities 

found within the ecoregion. These rural towns and the counties 

Figure 2. Grasslands extending as far as the eye can see in all 

directions, in Nebraska Sand Hills Ecoregion. A, Long gravel road. 

B, Functional windmill. C, Large field of grass. Figure 3. Wetlands in Nebraska Sand Hills Ecoregion. A, Pond 

and surrounding wetlands. B, Meandering river.
Chapter 2—Nebraska Sand Hills Ecoregion 29

A

A

B

B

C

D

in which they lie are heavily dependent on agriculture (fig.5). 

Between 1970 and 2000, Lincoln County was the only one 

of the 17 counties in the Nebraska Sand Hills Ecoregion that 

increased in population (table 1) (U.S. Census Bureau, 1995; 

Nebraska Department of Economic Development, 2013). 

In addition to decreasing populations, all 17 counties in 

the ecoregion have had increases in the median age of their 

residents (U.S. Census Bureau, 1995; Nebraska Department of 

Economic Development, 2013).

Figure 4. Livestock production and agriculture in Nebraska Sand 

Hills Ecoregion. A, Cattle grazing. B, Freshly baled hay. C, Centerpivot irrigation.

Figure 5. Rural character of Nebraska Sand Hills Ecoregion. A, 

Grain elevator along railroad tracks. B, Cattle ranch. C, Downtown 

O’Neill, Nebraska. D, Amelia, Nebraska.

C
30 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

Land-use/land-cover class

Contemporary Land-Cover Change 

(1973 to 2000) 

The overall spatial change (the percentage of land area 

that changed at least one time) in the Nebraska Sand Hills 

Ecoregion between 1973 and 2000 is 4.0 percent (2,422 km2) 

(table 2). Compared to other Great Plains ecoregions, change 

in the ecoregion was low (fig. 6). Of the 4.0 percent land cover 

that changed, 3.1 percent changed one time, and 0.9 percent 

changed more than one time (table 2). Multiple changes during 

the study period primarily were related to conversions back and 

forth between grassland/shrubland and agriculture. Total change 

in each of the four time periods of the study ranged from a low 

of 0.8 percent between 1992 and 2000 to a high of 2.1 percent 

between 1973 and 1980 (table 3). After normalizing to an 

annual rate of change to account for the varying lengths in study 

periods, the rates ranged from a low of 0.1 percent per year 

between 1980 and 1986 and between 1992 and 2000 to a high 

of 0.3 percent per year between 1973 and 1980 (table 4; fig. 7). 

Figure 6. Overall spatial change in Nebraska Sand Hills 

Ecoregion (NSH; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that changed during one, two, three, 

or four time periods; highest level of spatial change in Nebraska 

Sand Hills Ecoregion (four time periods) labeled for clarity. See 

table 3 for years covered by each time period. See appendix 2 for 

key to ecoregion abbreviations.

Figure 7. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Nebraska Sand 

Hills Ecoregion are represented by red bars in each time period.

Figure 8. Normalized average net change in Nebraska Sand Hills 

Ecoregion by time period for each land-cover class. Bars above 

zero axis represent net gain, whereas bars below zero represent 

net loss. Note that not all land-cover classes shown in explanation 

may be represented in figure. See appendix 3 for definitions of 

land-use/land-cover classifications.
Chapter 2—Nebraska Sand Hills Ecoregion 31

Grassland/shrubland, agriculture, and wetland constituted 

about 97 percent of the land cover in the ecoregion during 

the entire study period. Grassland/shrubland decreased by 

1.4 percent (874 km2), from 87.1 percent of the ecoregion 

in 1973 to 85.7 percent in 2000 (table 4; fig. 8). Agricultural 

land increased by 1.5 percent (926 km2), from 5.5 percent of 

the ecoregion in 1973 to 7.0 percent in 2000 (table 4; fig. 8). 

Wetlands decreased by only 0.2 percent (139 km2) between 

1973 and 2000, from 4.6 percent of the ecoregion to 4.4 

percent in 2000 (table 4; fig. 8).

Between 1973 and 2000, the two most common landcover conversions were from grassland/shrubland to agriculture 

(1,691 km2) and from agriculture to grassland/shrubland (791 

km2). Overall, these two conversions constituted nearly 84 

percent of all changes in the ecoregion during the study period 

(table 5; fig. 8). Grassland/shrubland to agriculture was the 

leading conversion in all time periods except between 1986 and 

1992. During this time period, the leading conversion was from 

agriculture to grassland/shrubland, as land was enrolled in the 

Conservation Reserve Program (CRP) of the U.S. Department 

of Agriculture’s Farm Service Agency. The CRP paid farmers 

to retire highly erodible cropland or other environmentally 

sensitive acreage from cultivation. 

The third most common land-cover conversion during the 

study period was from wetland to water (table 5). During the 

entire study period, 121 km2 of wetlands became open water, 

likely because of climatic fluctuations such as increases in 

rainfall. The fourth most common conversion was from wetland 

to agriculture (table 5). This conversion was most common 

during the last three time periods (1980–1986, 1986–1992, 

1992–2000) when wetlands were used for hay production in 

years when they were dry enough to accommodate machinery.

Overall, the Nebraska Sand Hills Ecoregion had little 

land-cover change during the study period, in contrast to 

adjacent ecoregions. The Western High Plains and Central 

Great Plains Ecoregions to the west and south and the 

Northwestern Great Plains Ecoregion to the north all changed 

much more than the Nebraska Sand Hills Ecoregion (12.5, 8.3, 

and 7.4 percent, respectively) (fig. 6). The deep sandy soils in 

the Nebraska Sand Hills Ecoregion limit its suitability to land 

uses other than grazing and hay production, which have been 

the main land uses for decades. 

The changes that occurred (primarily the conversions 

between grassland/shrubland and agriculture) are due to water 

availability and fluctuations in agricultural economics. For 

example, agriculture increased in the ecoregion during the 1970s 

as center-pivot irrigation became economically and technically 

viable. However, the topography and deep sandy soils of the 

Nebraska Sand Hills Ecoregion were not suited to most centerpivot practices, and many newly farmed areas were subsequently 

abandoned. After 1986, many marginal lands still being farmed 

were placed in the CRP. However, along the south and west edges 

of the ecoregion, where sand sheets were thinner, agriculture 

persisted and continued to expand over the study period. Recent 

efforts to protect wetlands in order to improve the recharge of 

the High Plains (Ogalalla) aquifer and to enhance natural areas 

Table 1. Population levels between 1970 and 2000, as well as 

median age in year 2000, in counties that intersect Nebraska Sand 

Hills Ecoregion.

[Data from U.S. Census Bureau (1995) and Nebraska Department of Economic Development (2013). All counties listed are in Nebraska]

County Population Median age

1970 1980 1990 2000 2000

Arthur 606 513 462 444 40.3

Blaine 847 867 675 583 39.8

Brown 4,021 4,377 3,657 3,525 43.1

Cherry 6,846 6,758 6,307 6,148 39.4

Garden 2,929 2,802 2,460 2,292 45.6

Garfield 2,411 2,363 2,141 1,902 45.8

Grant 1,019 877 769 747 39.9

Holt 12,933 13,552 12,599 11,551 40.5

Hooker 939 990 793 783 45

Lincoln 29,538 36,455 32,508 34,632 37.8

Logan 991 983 878 774 41.8

Loup 854 859 683 712 42.9

McPherson 623 593 546 544 40.6

Rock 2,231 2,383 2,019 1,756 44

Sheridan 7,285 7,544 6,750 6,198 42

Thomas 954 973 851 729 44.2

Wheeler 1,054 1,060 948 886 40.4

Median age, all counties 41.9

Table 2. Percentage of Nebraska Sand Hills Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (96.0 percent), whereas 4.0 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 3.1 1.2 1.9 4.4 0.8 26.5

2 0.8 0.5 0.3 1.2 0.3 39.9

3 0.1 0.0 0.0 0.1 0.0 51.0

4 0.0 0.0 0.0 0.0 0.0 64.3

Overall 

spatial 

change 4.0 1.5 2.5 5.5 1.0 24.5

for wildlife have altered the direction of human-lead change. As 

agricultural communities struggle economically, more emphasis 

is placed on enhancing grassland and wetlands for wildlife, 

thereby expanding opportunities for hunters, anglers, and wildlife 

enthusiasts in general (Grassland Foundation, 2005).
32 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Raw estimates of change in Nebraska Sand Hills Ecoregion land cover, computed for each of 

four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.1 1.1 1.0 3.3 0.8 35.4 0.3

1980–1986 0.9 0.3 0.6 1.2 0.2 23.0 0.1

1986–1992 1.1 0.4 0.6 1.5 0.3 26.6 0.2

1992–2000 0.8 0.4 0.5 1.2 0.3 30.2 0.1

Estimate of change, in square kilometers

1973–1980 1,294 679 615 1,973 458 35.4 185

1980–1986 533 181 351 714 122 23.0 89

1986–1992 638 252 387 890 170 26.6 106

1992–2000 502 225 278 727 152 30.2 63

Table 4. Estimated area (and margin of error) of each land-cover class in Nebraska Sand Hills Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 1.2 0.7 0.2 0.2 0.0 0.0 0.0 0.0 0.3 0.1 1.0 1.0 87.1 2.3 5.5 2.1 4.6 1.6 0.0 0.0

1980 1.2 0.7 0.2 0.3 0.0 0.0 0.0 0.0 0.3 0.1 1.0 1.0 85.5 2.8 7.1 2.9 4.6 1.6 0.0 0.0

1986 1.2 0.7 0.3 0.3 0.0 0.0 0.0 0.0 0.3 0.1 1.0 1.0 85.2 2.8 7.4 2.9 4.6 1.6 0.0 0.0

1992 1.3 0.8 0.3 0.3 0.0 0.0 0.0 0.0 0.2 0.1 1.0 1.0 85.7 2.8 7.0 2.8 4.5 1.5 0.0 0.0

2000 1.4 0.8 0.3 0.3 0.0 0.0 0.0 0.0 0.2 0.1 1.0 1.0 85.7 2.9 7.0 2.9 4.4 1.5 0.0 0.0

Net

change 0.1 0.2 0.1 0.1 0.0 0.0 0.0 0.0 –0.1 0.0 0.0 0.0 –1.4 0.9 1.5 0.9 –0.2 0.2 0.0 0.0

Gross

change 0.3 0.2 0.1 0.1 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 3.1 1.5 3.2 1.5 0.5 0.2 0.0 0.0

Area, in square kilometers

1973 745 436 121 116 0 0 3 3 187 90 593 590 52,756 1,406 3,329 1,287 2,809 952 0 0

1980 757 451 151 158 0 0 4 4 157 79 592 588 51,779 1,714 4,293 1,764 2,808 952 0 0

1986 746 437 158 166 0 0 5 4 153 77 590 587 51,597 1,721 4,482 1,784 2,811 949 0 0

1992 793 488 161 169 0 0 5 4 147 76 591 587 51,884 1,670 4,219 1,684 2,742 936 0 0

2000 829 514 166 176 0 0 5 4 143 77 593 588 51,881 1,732 4,255 1,728 2,670 918 0 0

Net

change 84 94 45 63 0 0 2 2 –44 27 0 5 –874 554 926 551 –139 93 0 0

Gross

change 165 118 45 63 0 0 2 2 51 29 8 6 1,877 927 1,929 920 281 119 0 0
Chapter 2—Nebraska Sand Hills Ecoregion 33

Table 5. Principal land-cover conversions in Nebraska Sand Hills Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall 

study period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent 

of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 1,066 645 435 1.8 82.4

Agriculture Grassland/Shrubland 91 61 41 0.2 7.0

Grassland/Shrubland Developed 24 35 23 0.0 1.8

Agriculture Wetland 18 20 14 0.0 1.4

Barren Grassland/Shrubland 17 14 9 0.0 1.3

Other Other 78 n/a n/a 0.1 6.0

Totals 1,294 2.1 100.0

1980–1986 Grassland/Shrubland Agriculture 312 129 87 0.5 58.5

Agriculture Grassland/Shrubland 128 67 45 0.2 24.0

Wetland Agriculture 22 19 13 0.0 4.1

Water Wetland 21 16 11 0.0 4.0

Agriculture Wetland 14 11 7 0.0 2.6

Other Other 36 n/a n/a 0.1 6.8

Totals 533 0.9 100.0

1986–1992 Agriculture Grassland/Shrubland 388 233 157 0.6 60.7

Grassland/Shrubland Agriculture 120 75 51 0.2 18.9

Wetland Water 55 60 40 0.1 8.6

Wetland Agriculture 21 26 18 0.0 3.3

Agriculture Wetland 14 12 8 0.0 2.1

Other Other 41 n/a n/a 0.1 6.4

Totals 638 1.1 100.0

1992–2000 Grassland/Shrubland Agriculture 192 105 71 0.3 38.3

Agriculture Grassland/Shrubland 184 159 107 0.3 36.6

Wetland Water 41 33 22 0.1 8.2

Wetland Agriculture 33 24 16 0.1 6.5

Wetland Grassland/Shrubland 12 17 12 0.0 2.4

Other Other 40 n/a n/a 0.1 7.9

Totals 502 0.8 100.0

1973–2000

(overall)

Grassland/Shrubland Agriculture 1,691 809 546 2.8 57.0

Agriculture Grassland/Shrubland 791 398 269 1.3 26.7

Wetland Water 121 100 67 0.2 4.1

Wetland Agriculture 83 49 33 0.1 2.8

Water Wetland 53 31 21 0.1 1.8

Other Other 228 n/a n/a 0.4 7.7

Totals 2,967 4.9 100.0
34 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Bleed, A.S., and Flowerday, C.A., eds., 1998, An atlas of 

the Sand Hills (RA-5b): Lincoln, University of Nebraska, 

Conservation and Survey Division, 260 p., available at 

http://nebraskamaps.unl.edu/productcart/pc/home.asp.

Grassland Foundation, 2005, Economic benefits of grassland 

protected areas: Lincoln, Neb., 64 p., available at http://

grasslandfoundation.org/publications/.

Huntzinger, T.L., and Ellis, M.J., 1993, Central Nebraska river 

basins, Nebraska: Water Resources Bulletin, v. 29, no. 4, p. 

533–574.

Nebraska Department of Economic Development, 2013, 

Population—Population by age, sex, and ethnicity: 

Nebraska Department of Economic Development database, 

accessed on September 25, 2008, at http://www.neded.org/

business/data-a-research/population.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125. 

U.S. Census Bureau, 1995, Nebraska—Population of counties 

by decennial census, 1900 to 1990: U.S. Census Bureau 

database, accessed September 25, 2008, at http://www.

census.gov/population/cencounts/ne190090.txt.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Wilhelmi, O.V., and Wilhite, D.A., 2002, Assessing 

vulnerability to agricultural drought—A Nebraska case 

study: Natural Hazards, v. 25, p. 37–58.
Chapter 3

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Northwestern Great Plains Ecoregion

By Kristi L. Sayler

Ecoregion Description 

The Northwestern Great Plains Ecoregion is a large 

ecoregion that covers about 346,883 km2 (133,932 mi2) of eastern 

Montana, northeastern Wyoming, western North Dakota, western 

South Dakota, and northern Nebraska (fig.1) (Omernik, 1987;

U.S. Environmental Protection Agency, 1997). The Missouri 

River and its system of dams and reservoirs (for example, Lake 

Sakakawea in North Dakota and Fort Peck Lake in Montana) 

make up the northern border of the ecoregion. The ecoregion 

is bounded by (clockwise, from the north) the Northwestern 

Glaciated Plains, Nebraska Sand Hills, Western High Plains, 

Southern Rockies, Wyoming Basin, Middle Rockies, Northern 

Figure 1. Map of Northwestern Great Plains and surrounding ecoregions, 

showing land-use/land-cover classes from 1992 National Land Cover 

Dataset (Vogelmann and others, 2001); note that not all land-use/land-cover 

classes shown in explanation may be depicted on map; note also that, for 

this “Status and Trends of Land Change” study, transitional land-cover class 

was subdivided into mechanically disturbed and nonmechanically disturbed 

classes. Squares indicate locations of 10 x 10 km sample blocks analyzed 

in study. Index map shows locations of geographic features mentioned in 

text. Abbreviations for Great Plains ecoregions are listed in appendix 2. Also 

shown are parts of five Western United States ecoregions: Middle Rockies 

(MRK), Montana Valley and Foothill Prairies (MVFP), Northern Rockies 

(NRK), Southern Rockies (SRK), and Wyoming Basin (WB). See appendix 3 

for definitions of land-use/land-cover classifications.

110° 108° 106° 104° 102° 100°

48°

46°

44°

42°

Wyoming

Basin

Northwestern Glaciated Plains

NWGLP

NGP

Middle Rockies

Middle

Rockies

Nebraska

Sand Hills

MRK

WB

Northern

Glaciated Plains

Western

High Plains

MVFP

MVFP

SRK

NRK

NRK

MRK

MVFP

MVFP

0 50 75 MILES

0 50 75

25

25 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

Northwestern

Great Plains

Ecoregion

MONTANA

WYOMING

NEBRASKA

Lake

Sakakawea

Billings

Bismark

Rapid City

Buffalo

Casper

RICHLAND

COUNTY

POWDER

RIVER

COUNTY

Fort Peck

Lake

SOUTH DAKOTA

NORTH DAKOTA

YellowstoneRiver

Missouri River

Missouri River

NE

WY

MT ND

SD
36 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Rockies, and Montana Valley and Foothill Prairies Ecoregions (fig. 

1). The Northwestern Great Plains Ecoregion contains much tribal, 

Federal, and State lands, including Indian reservations, national 

grasslands, Bureau of Land Management lands, national parks, 

and Montana State Trust Lands.

The Northwestern Great Plains Ecoregion is a semiarid 

rolling plain of shale- and sandstone-derived soils, punctuated 

by buttes and badlands (fig. 2). The badlands of North Dakota 

and South Dakota are unique features of the ecoregion and 

have been incorporated into national parks. The elevation of 

the ecoregion ranges from 450 to 1,200 m (McNab and Avers, 

1994). This mostly unglaciated plain consists of shallow soils 

that have clayey textures not conducive to growing crops but 

are suitable for grazing. The climatic conditions include erratic 

annual precipitation amounts of 250 to 510 mm (10–20 in.), 

falling mostly during the summer growing season. Native 

semiarid grasslands cover most of the ecoregion, including 

western wheatgrass (Pascopyrum smithii), needlegrass 

(Achnatherum spp.), blue grama (Bouteloua gracilis), and 

buffalograss (Buchloe dactyloides) (Woods and others, 2002).

Figure 2. Grassland and cropland in Richland County, Montana, 

in Northwestern Great Plains Ecoregion. 

Figure 3. Mosaic of forested hills and grassland in Powder River 

County, Montana, in Northwestern Great Plains Ecoregion.

The most common land use in the Northwestern Great 

Plains Ecoregion is livestock grazing of cattle and sheep. Crop 

agriculture is limited by soil quality, precipitation levels, and 

the limited access to water for irrigation. The main agricultural 

areas, which are located in the Missouri Plateau physiographic 

province in North Dakota, South Dakota, and Montana, are 

composed mostly of dryland farming (Bryce and others, 

1998). Spring wheat is the predominant crop, but smaller areas 

are planted with barley, oats, sunflowers, and alfalfa and other 

hay crops. However, drought-resistant, genetically modified 

crops such as soybeans are becoming increasingly common in 

the eastern part of the ecoregion (Higgins and others, 2002).

In 2000, the land cover of the ecoregion was an estimated 

77.1 percent grassland/shrubland, 15.4 percent agriculture, and 

2 to 3 percent each of forest (2.7 percent), barren (2.3 percent), 

and water (2.1 percent) (table 1). Most forest land is limited 

to areas of ponderosa pine (Pinus ponderosa) in southeastern 

Montana, as well as small forests along major river valleys of 

the ecoregion (fig. 3). Mining (including petroleum extraction) 

also is a minor land use in the ecoregion, as oil, gas, and coal 

deposits are scattered throughout the Powder River Basin of 

southeastern Montana and northeastern Wyoming. 

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Northwestern Great 

Plains between 1973 and 2000 is 7.4 percent (table 2). 

Compared to other Great Plains ecoregions, change was 

moderate (fig. 4). An estimated 5.2 percent of the ecoregion 

changed only once during the 27-year study period, but other 

areas changed multiple times during the study period (table 1). 

Areas that experienced multiple changes included marginal 

agricultural land that was taken out of production early in the 

study period, which at first reverted to grassland/shrubland but 

later was converted back to agricultural land.

The total change per time period varied slightly between 

1973 and 2000. The last two time periods (1986–1992, 

1992–2000) had greater change than the first two time periods 

(1973–1980, 1980–1986) (table 3). When normalized to 

account for the varying lengths in study periods, the period 

between 1986 and 1992 had the greatest rate of change per 

year, at 0.5 percent, compared to 0.3 percent per year for the 

other three time periods (table 3; fig. 5).

Agriculture and grassland/shrubland had the most change 

during the study period (table 1). Agriculture decreased 1.8 

percent, with most of the decrease coming from conversion 

of agricultural land to grassland/shrubland (table 1; fig. 5). 

Grassland/shrubland increased 2.2 percent (table 1; fig. 6). In 

terms of the amount of area changed, the largest conversions 

during the study period were from agriculture to grassland/

shrubland (17,239 km2) and from grassland/shrubland to 

agriculture (11,013km2) (table 4). These two conversions 
Chapter 3—Northwestern Great Plains Ecoregion 37

Figure 4. Overall spatial change in Northwestern Great Plains 

Ecoregion (NWGP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that changed during one, two, three, or 

four time periods; highest level of spatial change in Northwestern 

Great Plains Ecoregion (four time periods) labeled for clarity. See 

table 3 for years covered by each time period. See appendix 2 for 

key to ecoregion abbreviations.

Figure 5. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Northwestern 

Great Plains Ecoregion are represented by red bars in each time 

period.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

together constituted at least 82 percent of change in all time 

periods except between 1973 and 1980.

The first two time periods (1973–1980, 1980–1986) 

saw large conversions of grassland/shrubland to agriculture, 

which were driven mainly by changes in the agricultural 

economy, as well as by farm policies such as the Conservation 

Reserve Program (CRP). The CRP, which the U.S. Congress 

implemented in 1985 (U.S. Department of Agriculture, 2004), 

is a voluntary, long-term cropland retirement program that 

pays participants to retire highly erodible and environmentally 

sensitive cropland and pastureland from production for a period 

of 10 to 15 years. Because much of the land in the Northwestern 

Great Plains Ecoregion is marginal for crop production, it was 

more economical for landowners to enroll their properties in 

the CRP rather than to continue using them for agricultural 

purposes. After 1986, the conversions reversed, as marginal 

croplands in the ecoregion could be more profitable as 

grassland/shrubland in the CRP. Nevertheless, about 2,400 km2

of land in the ecoregion was enrolled in the CRP by the end of 

1990 (U.S. Department of Agriculture, 2009).

Another significant change occurred during the first 

time period (1973–1980), in which a large area (1,390 km2) 

of nonmechanically disturbed land converted to grassland/

shrubland. This was largely because of a burned area that was 

mapped as nonmechanically disturbed in one of the sample 

blocks in 1973 but that had reverted to grassland/shrubland by 

1980. Less significant conversions during the study period were 

noted between the water class and the grassland/shrubland, 

wetland, and barren classes, which fluctuated because of 

variations in precipitation over time in the ecoregion. 
38 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 1. Estimated area (and margin of error) of each land-cover class in Northwestern Great Plains Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications. 

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 2.3 2.3 0.2 0.1 0.0 0.0 0.0 0.0 2.2 1.5 2.7 1.1 74.9 5.3 17.2 5.3 0.2 0.1 0.4 0.6

1980 2.2 2.3 0.2 0.1 0.0 0.0 0.0 0.0 2.2 1.5 2.7 1.1 75.0 5.3 17.4 5.3 0.3 0.2 0.0 0.0

1986 2.4 2.3 0.2 0.1 0.0 0.0 0.0 0.0 2.2 1.5 2.7 1.1 74.4 5.2 18.0 5.2 0.2 0.1 0.0 0.0

1992 1.9 2.0 0.2 0.1 0.0 0.0 0.0 0.0 2.3 1.5 2.7 1.1 76.5 4.9 16.1 4.9 0.3 0.2 0.0 0.0

2000 2.1 2.1 0.2 0.1 0.0 0.0 0.0 0.0 2.3 1.5 2.7 1.1 77.1 4.9 15.4 4.8 0.2 0.2 0.0 0.0

Net

change –0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.0 2.2 1.4 –1.8 1.3 0.1 0.1 –0.4 0.6

Gross

change 1.0 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.3 0.0 0.0 6.4 1.9 5.9 1.9 0.4 0.4 0.4 0.6

Area, in square kilometers

1973 7,856 7,883 580 421 0 0 22 26 7,741 5,367 9,315 3,829 259,725 18,436 59,619 18,411 636 410 1,390 2,029

1980 7,673 7,886 580 421 7 10 22 26 7,643 5,359 9,256 3,806 260,330 18,394 60,498 18,364 875 659 0 0

1986 8,182 7,981 580 421 0 0 23 26 7,623 5,355 9,256 3,806 258,123 17,990 62,468 18,133 629 418 0 0

1992 6,625 6,769 591 426 2 2 25 26 8,088 5,353 9,241 3,796 265,213 17,129 55,966 17,045 1,131 758 0 0

2000 7,308 7,296 596 427 20 26 23 26 8,097 5,347 9,264 3,810 267,376 17,075 53,345 16,792 854 619 0 0

Net

change –548 711 17 13 20 26 1 1 355 483 –50 75 7,650 4,863 –6,274 4,447 218 291 –1,390 2,029

Gross

change 3,301 2,321 17 13 35 32 6 7 1,046 874 166 116 22,344 6,700 20,564 6,653 1,318 1,294 1,390 2,029

−4

−2

0

2

4

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Figure 6. Normalized average 

net change in Northwestern 

Great Plains Ecoregion by 

time period for each landcover class. Bars above 

zero axis represent net gain, 

whereas bars below zero 

represent net loss. Note that 

not all land-cover classes 

shown in explanation may be 

represented in figure. See 

appendix 3 for definitions 

of land-use/land-cover 

classifications.
Chapter 3—Northwestern Great Plains Ecoregion 39

Table 2. Percentage of Northwestern Great Plains Ecoregion 

land cover that changed at least one time during study period 

(1973–2000) and associated statistical error. 

[Most sample pixels remained unchanged (92.6 percent), whereas 7.4 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 5.2 1.6 3.7 6.8 1.1 20.4

2 1.9 0.8 1.2 2.7 0.5 26.8

3 0.2 0.1 0.1 0.3 0.1 39.7

4 0.0 0.0 0.0 0.1 0.0 59.0

Overall 

spatial 

change

7.4 2.0 5.4 9.4 1.4 18.4

Table 3. Raw estimates of change in Northwestern Great Plains Ecoregion land cover, computed for 

each of four time periods between 1973 and 2000, and associated error at an 85-percent confidence level. 

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.1 0.7 1.4 2.9 0.5 22.7 0.3

1980–1986 2.0 0.7 1.2 2.7 0.5 25.9 0.3

1986–1992 3.0 1.2 1.9 4.2 0.8 26.1 0.5

1992–2000 2.7 0.9 1.8 3.7 0.6 23.9 0.3

Estimate of change, in square kilometers

1973–1980 7,458 2,487 4,970 9,945 1,694 22.7 1,065

1980–1986 6,820 2,588 4,232 9,409 1,763 25.9 1,137

1986–1992 10,535 4,034 6,501 14,569 2,748 26.1 1,756

1992–2000 9,381 3,291 6,090 12,673 2,242 23.9 1,173
40 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 4. Principal land-cover conversions in Northwestern Great Plains Ecoregion, showing amount of area changed (and margin 

of error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent 

of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 3,158 840 572 0.9 42.3

Agriculture Grassland/Shrubland 2,264 1,044 711 0.7 30.4

Nonmechanically disturbed Grassland/Shrubland 1,390 2,029 1,382 0.4 18.6

Water Wetland 241 346 236 0.1 3.2

Barren Grassland/Shrubland 105 135 92 0.0 1.4

Other Other 299 n/a n/a 0.1 4.0

Totals 7,458 2.1 100.0

1980–1986 Grassland/Shrubland Agriculture 4,058 2,413 1,644 1.2 59.5

Agriculture Grassland/Shrubland 2,082 755 514 0.6 30.5

Grassland/Shrubland Water 275 282 192 0.1 4.0

Wetland Water 244 322 220 0.1 3.6

Barren Grassland/Shrubland 54 70 47 0.0 0.8

Other Other 107 n/a n/a 0.0 1.6

Totals 6,820 2.0 100.0

1986–1992 Agriculture Grassland/Shrubland 7,609 3,448 2,349 2.2 72.2

Grassland/Shrubland Agriculture 1,125 620 422 0.3 10.7

Water Grassland/Shrubland 677 609 415 0.2 6.4

Water Wetland 474 465 317 0.1 4.5

Water Barren 431 517 352 0.1 4.1

Other Other 219 n/a n/a 0.1 2.1

Totals 10,535 3.0 100.0

1992–2000 Agriculture Grassland/Shrubland 5,284 2,797 1,905 1.5 56.3

Grassland/Shrubland Agriculture 2,671 911 620 0.8 28.5

Grassland/Shrubland Water 308 198 135 0.1 3.3

Wetland Water 241 312 212 0.1 2.6

Barren Water 231 261 178 0.1 2.5

Other Other 646 n/a n/a 0.2 6.9

Totals 9,381 2.7 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 17,239 6,193 4,218 5.0 50.4

Grassland/Shrubland Agriculture 11,013 3,342 2,277 3.2 32.2

Nonmechanically disturbed Grassland/Shrubland 1,390 2,029 1,382 0.4 4.1

Water Grassland/Shrubland 846 610 416 0.2 2.5

Water Wetland 722 744 507 0.2 2.1

Other Other 2,984 n/a n/a 0.9 8.7

Totals 34,195 9.9 100.0
Chapter 3—Northwestern Great Plains Ecoregion 41

References Cited

Bryce, S.A., Omernik, J.M., Pater, D.E., Ulmer, Michael, Schaar, 

Jerome, Freeouf, Jerry, Johnson, Rex, Kuck, Pat, and Azevedo, 

S.H., 1998, Ecoregions of North and South Dakota: U.S. Geological Survey Ecoregion Map Series, scale 1:500,000, available 

at http://www.epa.gov/wed/pages/ecoregions/ndsd_eco.htm.

Higgins, K.F., Naugle, D.E., and Forman, K.J., 2002, A case study 

of changing land use practices in the northern Great Plains, 

U.S.A.—An uncertain future for waterbird conservation, in 

Parsons, K.C., Brown, S.C., Erwin, R.M., Czech, H.A., and 

Coulson, J.C., eds., Managing wetlands for waterbirds—

Integrated approaches: Waterbirds—The International Journal of 

Waterbird Biology, v. 25, Special Publication 2, p. 42–50.

McNab, W.H., and Avers, P.E., 1994, Great Plains—Palouse Dry 

Steppe, in Ecological subregions of the United States: U.S. 

Department of Agriculture, Forest Service, WO-WSA-5, chap. 

41, available at http://www.fs.fed.us/land/pubs/ecoregions/ch41.

html#toc”.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

U.S. Department of Agriculture, 2004, The Conservation Reserve 

Program—Economic implications for rural America: U.S. 

Department of Agriculture, Economic Research Service, 

Agricultural Economic Report No. 834, 112 p., available at 

http://www.ers.usda.gov/publications/aer-agricultural-economicreport/aer834.aspx.

U.S. Department of Agriculture, 2009, Conservation Reserve 

Program—Cumulative enrollment by year (by county, FY 

1986–FY 2007): U.S. Department of Agriculture, Farm 

Services Agency database, accessed June 12, 2009, at 

http://www.fsa.usda.gov/Internet/FSA_File/public.xls.

U.S. Environmental Protection Agency, 1997, Descriptions 

of level III ecological regions for the CEC report on 

ecological regions of North America: U.S. Environmental 

Protection Agency database, accessed June 12, 2006, 

at http://www.epa.gov/wed/pages/ecoregions/na_eco.

htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Woods, A.J., Omernik, J.M., Nesser, J.A., Shelden, J., 

Comstock, J.A., Azevedo, S.H., 2002, Ecoregions of 

Montana (2d ed.): U.S. Geological Survey Ecoregion Map 

Series, scale 1:1,500,000, available at http://www.epa.gov/

wed/pages/ecoregions/mt_eco.htm.

Chapter 4

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2014

Southwestern Tablelands Ecoregion 

By Carl L. Rich and Mark A. Drummond

Ecoregion Description

The Southwestern Tablelands Ecoregion encompasses 

about 159,938 km2 (61,752 mi2) in Colorado, New Mexico, 

Texas, Oklahoma, and Kansas (fig. 1) (Omernik, 1987; U.S. 

Environmental Protection Agency, 1997). The ecoregion is 

bounded on the west by the Southern Rockies and the Arizona/

New Mexico Plateau Ecoregions, as well as a small part of the 

Chihuahuan Deserts Ecoregion; on the north and south by the 

Western High Plains Ecoregion; and on the east by the Central 

Great Plains Ecoregion (Omernik, 1987).

106° 104° 102° 100°

38°

40°

36°

34°

Central

Great Plains

Western

High Plains

Western

High Plains

Southern

Rockies

ANMP

ANMP

ANMM

ANMM

Chihuahuan

Deserts

CD

SRK

Central

Oklahoma/Texas

Plains

0 50 100 MILES

0 50 100 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

River

Pueblo

Colorado Springs

Denver

Arkansas

River

Canadian

COLORADO

TEXAS

NEW

MEXICO

OKLAHOMA

KANSAS

NE

The Southwestern Tablelands Ecoregion generally is 

more rugged than the surrounding ecoregions of the Great 

Plains, with moderate to considerable local relief. Topographic 

features include areas of moderately rolling terrain and 

canyons that dissect the tablelands (fig. 2). Elevation varies 

from about 400 m in Kansas in the northeastern corner of 

the ecoregion to about 2,700 m in northeastern New Mexico 

(National Atlas of the United States, 2008). The highest 

elevations are at the tops of several old volcanic cones in this 

part of the Southwestern Tablelands Ecoregion.

Figure 1. Map of Southwestern

Tablelands Ecoregion and 

surrounding ecoregions, 

showing land-use/land-cover 

classes from 1992 National 

Land Cover Dataset (Vogelmann 

and others, 2001); note that 

not all land-use/land-cover 

classes shown in explanation 

may be depicted on map; note 

also that, for this “Status and 

Trends of Land Change” study, 

transitional land-cover class was 

subdivided into mechanically 

disturbed and nonmechanically 

disturbed classes. Squares 

indicate locations of 10 x 10 km 

sample blocks analyzed in study. 

Index map shows locations of 

geographic features mentioned 

in text. Abbreviations for Great 

Plains ecoregions are listed in 

appendix 2. Also shown are parts 

of four Western United States 

ecoregions: Arizona/New Mexico 

Mountains (ANMM), Arizona/

New Mexico Plateau (ANMP), 

Chihuahuan Deserts (CD), and 

Southern Rockies (SRK). See 

appendix 3 for definitions of landuse/land-cover classifications.
44 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Precipitation in the Southwestern Tablelands Ecoregion 

ranges from about 250 mm (10 in.) per year in parts of 

Colorado and New Mexico to about 630 to 760 mm (25–30 

in.) per year in Kansas (National Atlas of the United States, 

2008). Grassland/shrubland dominates the land cover on most 

of the elevated tablelands and vast mesas in the ecoregion; 

much of it is used for grazing.

The natural vegetation in most of the area is blue grama 

(Bouteloua gracilis) and buffalo grass (Buchloe dactyloides); 

in the southeastern part of the ecoregion, it is mesquite 

(Prosopis spp.) and buffalo grass. Along the Canadian River 

in the Southwestern Tablelands Ecoregion is a vegetation 

community known as shinnery (U.S. Environmental Protection 

Agency, 2002), a midgrass prairie with open-to-dense broadleaf 

deciduous shrubs such as Gambel’s oak (Quercus gambelii) 

and scrub oak (Quercus turbinella), with a few needleleaf 

evergreen low trees or shrubs (Kuchler, 1964). Although 

grassland/shrubland dominates the ecoregion, some forest lands 

also are present on the escarpments of the tablelands.

Land use in the Southwestern Tablelands Ecoregion 

differs from that of most of the surrounding ecoregions of the 

Great Plains by its relatively sparse cropland, except along the 

Arkansas River and in the wetter eastern parts of the ecoregion 

(figs. 3,4). The most common crop is wheat (Triticum 

aestivum) (U.S. Department of Agriculture, 1970–2000 

[various years]). Livestock grazing on grassland/shrubland is 

the most extensive type of land use (fig. 5).

Minor but important land cover classes include developed 

and mining. Most of the Southwestern Tablelands Ecoregion 

is rural, with small towns scattered across the landscape. 

However, Colorado Springs and Pueblo, Colorado (populations 

in 2000 of 360,890 and 102,121, respectively), are two of the 

largest cities within the ecoregion (U.S. Census Bureau, 2000). 

The Southwestern Tablelands Ecoregion also includes the 

southern suburbs of Denver. Much of the population growth 

since 1970 has been in these urban areas of Colorado (U.S. 

Census Bureau, 1970–2000 [various years]). Petroleum and 

natural gas production is important in the ecoregion, especially 

in Texas. Although oil and gas extraction are included in the 

mining land-cover class in this study, many of the wells and 

pads are smaller than the minimum mapping unit of 60 m, and 

so this land-cover class is likely undermapped.

Figure 2. Rangeland, with tablelands in distance, in 

Southwestern Tablelands Ecoregion. 

Figure 4. Field of soybeans in Southwestern Tablelands 

Ecoregion. No-till farming methods often are used to leave soils 

and crop residue intact.

Figure 3. Sandy soil recently tilled in Southwestern Tablelands 

Ecoregion.

Figure 5. Livestock grazing, a common land use in Southwestern 

Tablelands Ecoregion.
Chapter 4—Southwestern Tablelands Ecoregion 45

Contemporary Land-Cover Change 

(1973 to 2000) 

The most common types of land-cover change in the 

Southwestern Tablelands Ecoregion between 1973 and 

2000 were from agriculture to grassland/shrubland, and 

vice versa (table 1). Over the entire study period, these 

conversions constituted more than 90 percent of all landcover change. Other leading conversions included a onetime change from grassland/shrubland to nonmechanically 

disturbed between 1992 and 2000 caused by a fire in the 

Texas panhandle, and conversions from grassland/shrubland 

to water caused by water impoundment. However, 

fluctuations in water levels often caused additional types 

of land-cover change between the barren and grassland/

shrubland classes.

The fact that the dominant changes in the 

Southwestern Tablelands Ecoregion land cover involved 

grassland/shrubland and agriculture is not surprising 

given the overall composition of the land cover within 

the ecoregion. During all time periods, the ecoregion was 

composed of 80.0 to 81.9 percent grassland/shrubland 

and 16.1 to 18.1 percent agricultural land (table 2). Forest 

constituted an estimated 0.8 percent of the ecoregion, and 

developed land constituted an estimated 0.4 percent.

The overall spatial change (the percentage of land 

area that changed at least one time) in the Southwestern 

Tablelands Ecoregion between 1973 and 2000 is estimated 

at 8.8 percent (table 3). Most of the changes (7.3 percent of 

ecoregion area) occurred because of a one-time conversion; 

multiple changes were caused by switches between 

grassland/shrubland and agricultural land, as well as 

fluctuations in water levels of streams and impoundments 

that may be related to climate variability.

During the first time period (1973–1980), a small 

net increase occurred in the amount of agriculture land 

cover, 0.2 percent (table 2). The expansion took place 

during a period of increased grain exports; thus, it may 

have resulted, in part, from farm policies that encouraged 

expansion of cropland. However, unlike several other 

ecoregions in the Great Plains that experienced substantial 

agricultural expansion, expansion of cropland in the 

Southwestern Tablelands Ecoregion was relatively small. 

After 1980, agriculture land cover decreased.

During the last three time periods (1980–1986, 1986–

1992, 1992–2000), a net increase occurred in grassland/

shrubland, although the trend was nearly flat between 1980 

and 1986 (table 2). The greatest change from one class to 

another during a single time period was the change from 

agriculture to grassland/shrubland between 1986 and 1992 

(3,870 km2) (table 1) when grassland/shrubland increased 

by an estimated 1.6 percent (table 2; fig. 6). This change 

was caused, in part, by the introduction of the Conservation 

Reserve Program (CRP). The CRP paid farmers to convert 

easily erodible or otherwise environmentally sensitive, 

Figure 6. Normalized average net change in Southwestern 

Tablelands Ecoregion by time period for each land-cover class. 

Bars above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.

low-productivity agricultural lands to grasslands (U.S. 

Department of Agriculture, 2008).

Compared to other Great Plains ecoregions, landcover change in the Southwestern Tablelands Ecoregion 

was moderate (fig. 7). Despite a consistently large area 

of grassland/shrubland, which made up more than 80 

percent of the ecoregion’s area in all four time periods, 

fluctuations involving agricultural land use and water 

were particularly high during the last two time periods 

(1986–2000). The per-period change estimates ranged 

from a low of 1.9 percent between 1980 and 1986 to a high 

of 3.4 percent between 1986 and 1992 when agricultural 

land began to be enrolled in the CRP (table 4). When the 

per-period change data are normalized to produce average 

annual rates of land-cover change, the results range from 

0.3 percent between 1973 and 1980 to 0.6 percent between 

1986 and 1992 (table 4; fig. 8).

Much of the cropland in the Southwestern Tablelands 

Ecoregion is considered marginal because of climate 

and soil conditions. These conditions contributed to 

fluctuations between grassland/shrubland and agriculture as 

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS
46 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Figure 8. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Southwestern 

Tablelands Ecoregion are represented by red bars in each time 

period.

Figure 7. Overall spatial change in Southwestern Tablelands 

Ecoregion (SWT; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that experienced change during one, 

two, three, or four time periods; highest level of spatial change in 

Southwestern Tablelands Ecoregion (four time periods) labeled 

for clarity. See table 4 for years covered by each time period. See 

appendix 2 for key to ecoregion abbreviations.

precipitation levels and socioeconomic conditions varied. 

Because the natural vegetation for most of the ecoregion 

is grassland/shrubland, it is not surprising that agriculture 

is continuously reverting back to grassland/shrubland. The 

rural rangeland character of the ecoregion also contributes 

to the overall pattern of land-cover change, with developed 

land concentrated only along its western edge.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period
Chapter 4—Southwestern Tablelands Ecoregion 47

Table 1. Principal land-cover conversions in Southwestern Tablelands Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of

all changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 1,753 823 558 1.1 51.9

Agriculture Grassland/Shrubland 1,369 519 352 0.9 40.6

Barren Grassland/Shrubland 54 75 50 0.0 1.6

Grassland/Shrubland Water 32 25 17 0.0 1.0

Grassland/Shrubland Developed 28 33 23 0.0 0.8

Other Other 140 n/a n/a 0.1 4.2

Totals 3,377 2.1 100.0

1980–1986 Agriculture Grassland/Shrubland 1,475 782 530 0.9 48.3

Grassland/Shrubland Agriculture 1,301 942 638 0.8 42.6

Barren Water 52 75 51 0.0 1.7

Barren Grassland/Shrubland 42 46 31 0.0 1.4

Grassland/Shrubland Water 41 34 23 0.0 1.4

Other Other 139 n/a n/a 0.1 4.6

Totals 3,051 1.9 100.0

1986–1992 Agriculture Grassland/Shrubland 3,870 1,533 1,039 2.4 70.4

Grassland/Shrubland Agriculture 1,405 731 495 0.9 25.5

Water Grassland/Shrubland 65 63 43 0.0 1.2

Grassland/Shrubland Water 35 34 23 0.0 0.6

Water Barren 23 34 23 0.0 0.4

Other Other 103 n/a n/a 0.1 1.9

Totals 5,500 3.4 100.0

1992–2000 Agriculture Grassland/Shrubland 2,454 997 676 1.5 50.9

Grassland/Shrubland Agriculture 1,811 976 661 1.1 37.5

Grassland/Shrubland Nonmechanically disturbed 316 461 312 0.2 6.5

Wetland Water 63 62 42 0.0 1.3

Grassland/Shrubland Mining 44 31 21 0.0 0.9

Other Other 137 n/a n/a 0.1 2.8

Totals 4,825 3.0 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 9,169 3,259 2,208 5.7 54.7

Grassland/Shrubland Agriculture 6,270 2,303 1,560 3.9 37.4

Grassland/Shrubland Nonmechanically disturbed 316 461 312 0.2 1.9

Grassland/Shrubland Water 144 92 63 0.1 0.9

Barren Grassland/Shrubland 139 136 92 0.1 0.8

Other Other 716 n/a n/a 0.4 4.3

Totals 16,754 10.5 100.0
48 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 2. Estimated area (and margin of error) of each land-cover class in Southwestern Tablelands Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.1 0.0 0.4 0.2 0.0 0.0 0.0 0.0 0.3 0.1 0.8 0.4 80.3 5.3 17.9 5.3 0.2 0.1 0.0 0.0

1980 0.1 0.1 0.4 0.2 0.0 0.0 0.1 0.0 0.3 0.1 0.8 0.4 80.0 5.2 18.1 5.3 0.1 0.1 0.0 0.0

1986 0.1 0.1 0.4 0.2 0.0 0.0 0.1 0.0 0.2 0.1 0.8 0.4 80.1 5.0 18.0 5.1 0.2 0.1 0.0 0.0

1992 0.1 0.0 0.4 0.2 0.0 0.0 0.1 0.0 0.2 0.1 0.8 0.4 81.7 4.6 16.5 4.7 0.2 0.1 0.0 0.0

2000 0.2 0.1 0.4 0.2 0.0 0.0 0.1 0.0 0.2 0.1 0.8 0.4 81.9 4.2 16.1 4.3 0.1 0.1 0.2 0.3

Net

change 0.1 0.1 0.0 0.0 0.0 0.0 0.1 0.0 –0.1 0.1 0.0 0.0 1.6 2.2 –1.8 2.1 0.0 0.0 0.2 0.3

Gross

change 0.3 0.2 0.0 0.0 0.0 0.0 0.1 0.0 0.2 0.2 0.0 0.0 6.3 1.8 6.1 1.8 0.1 0.1 0.2 0.3

Area, in square kilometers

1973 157 60 627 320 0 1 64 28 470 208 1,335 692 128,432 8,427 28,610 8,556 243 199 0 0

1980 182 80 663 355 3 4 85 38 432 194 1,334 692 128,023 8,386 28,989 8,491 227 196 0 0

1986 219 130 669 356 4 4 95 41 340 136 1,351 694 128,185 8,052 28,813 8,168 264 201 0 0

1992 160 65 673 359 3 3 108 44 364 148 1,348 694 130,666 7,401 26,344 7,492 271 205 0 9

2000 263 120 675 360 2 3 153 69 325 134 1,348 694 130,950 6,741 25,688 6,860 219 164 316 461

Net

change 106 81 48 53 2 2 89 47 –146 164 13 19 2,518 3,503 –2,922 3,323 –24 62 316 461

Gross

change 444 280 58 54 5 5 93 48 269 264 20 21 10,152 2,920 9,709 2,832 155 101 316 461

Table 3. Percentage of Southwestern Tablelands Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (91.2 percent), whereas 8.8 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 7.3 1.8 5.5 9.2 1.2 17.1

2 1.2 0.5 0.7 1.7 0.3 30.1

3 0.2 0.2 0.1 0.4 0.1 50.5

4 0.0 0.0 0.0 0.1 0.0 82.2

Overall 

spatial 

change

8.8 2.3 6.5 11.0 1.5 17.4
Chapter 4—Southwestern Tablelands Ecoregion 49

Table 4. Raw estimates of change in Southwestern Tablelands Ecoregion land cover, computed for 

each of four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.1 0.7 1.4 2.9 0.5 23.9 0.3

1980–1986 1.9 0.9 1.0 2.8 0.6 30.7 0.3

1986–1992 3.4 1.2 2.3 4.6 0.8 22.8 0.6

1992–2000 3.0 1.0 2.0 4.1 0.7 23.5 0.4

Estimate of change, in square kilometers

1973–1980 3,377 1,192 2,185 4,568 807 23.9 482

1980–1986 3,051 1,383 1,668 4,434 937 30.7 509

1986–1992 5,500 1,854 3,647 7,354 1,256 22.8 917

1992–2000 4,825 1,676 3,150 6,501 1,135 23.5 603

References Cited

Kuchler, A.W., 1964, Manual to accompany the map—Potential natural vegetation of the conterminous United States: 

New York, American Geographical Society Special Publication 36, 116 p.

National Atlas of the United States, 2008, 100-meter resolution elevation of the United States: National Atlas of the 

United States database, accessed May 21, 2013, at http://

www.nationalatlas.gov.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed September 1, 2008, at http://www.census.gov/

prod/www/decennial.html.

U.S. Census Bureau, 2003, Technical documentation, 2000 

Census of population and housing, 108th Congressional 

District Summary File (100 Percent): U.S. Census Bureau, 

557 p., available at http://www.census.gov/prod/cen2000/

doc/cd108h.pdf.

U.S. Department of Agriculture, 1970–2000 [various years], 

Census of agriculture: U.S. Department of Agriculture database, 

accessed September 1, 2008, at http://www.agcensus.usda.gov/.

U.S. Department of Agriculture, 2008, Conservation Reserve 

Program: U.S. Department of Agriculture Farm Service 

Agency database, accessed September 1, 2008, at http://

www.nrcs.usda.gov/programs/crp/.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

U.S. Environmental Protection Agency, 2002, Primary distinguishing characteristics of level III ecoregions of the continental United States, Draft, April 2002: U.S. Environmental 

Protection Agency database, accessed April 12, 2006, at 

http://www.epa.gov/wed/pages/ecoregions/level_iii_iv.htm.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Chapter 5

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Western High Plains Ecoregion

By Mark A. Drummond

Ecoregion Description

The Western High Plains Ecoregion is a 

high-elevation, semiarid, shortgrass steppe that 

covers approximately 288,752 km2 (111,488 mi2) 

across parts of eight states (fig. 1) (Omernik, 

1987; U.S. Environmental Protection Agency, 

1997). The Southwestern Tablelands Ecoregion 

splits the Western High Plains Ecoregion into 

two large areas: the northern part is surrounded 

by the Northwestern Great Plains, Nebraska 

Sand Hills, Central Great Plains, Southwestern 

Tablelands, and Southern Rockies Ecoregions; 

the southern part is surrounded by the 

Southwestern Tablelands, Central Great Plains, 

and Chihuahuan Deserts Ecoregions. 

Surficial geology is the result of uplifted 

late Tertiary sediments that have been eroded 

from the uplifting Rocky Mountains, overlain by 

more recent wind-blown sediments. Agriculture 

is the dominant land use, with cropland, 

farmsteads, confined feeding operations, and 

Figure 1. Map of Western High Plains Ecoregion 

and surrounding ecoregions, showing land-use/

land-cover classes from 1992 National Land Cover 

Dataset (Vogelmann and others, 2001); note that 

not all land-use/land-cover classes shown in 

explanation may be depicted on map; note also 

that, for this “Status and Trends of Land Change” 

study, transitional land-cover class was subdivided 

into mechanically disturbed and nonmechanically 

disturbed classes. Squares indicate locations of 10 

x 10 km sample blocks analyzed in study. Index map 

shows locations of geographic features mentioned 

in text. Abbreviations for Great Plains ecoregions 

are listed in appendix 2. Also shown are parts of 

six Western United States ecoregions: Arizona/

New Mexico Mountains (ANMM), Arizona/New 

Mexico Plateau (ANMP), Chihuahuan Deserts, 

Middle Rockies (MRK), Southern Rockies (SRK), and 

Wyoming Basin (WB). See appendix 3 for definitions 

of land-use/land-cover classifications.

106° 104° 102° 100°

42°

40°

38°

36°

34°

32°

Southwestern

Tablelands

Chihuahuan Deserts

Nebraska

Sand Hills

NSH

Northwestern

Great Plains

MRK

Edwards Plateau

SRK

Central

Great Plains

Central

Great

Plains

WB

ANMP

ANMP

ANMM

COTP

CGP

NWGLP

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

TEXAS

Pueblo

Cheyenne

L L A N O E S T A C A D O

River

Platte

North

River

NEBRASKA

SOUTH DAKOTA

OKLAHOMA

NEW MEXICO WYOMING

Scottsbluff

FRONT RANGE

Odessa

Hugoton

Denver

Arkansas

FINNEY

COUNTY

ROCKY MOUNTAINS

High Plains

(Ogallala) Aquifer

South Platte

0 50 100 150MILES

0 50 100 150 200 KILOMETERS

KANSAS

COLORADO
52 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

other miscellaneous agricultural uses covering nearly 48 percent 

of the ecoregion in 2000. Wheat, corn, alfalfa, sorghum, cotton, 

and specialty crops such as sugar beets have replaced substantial 

areas of natural land cover within the ecoregion (fig. 2). Livestock 

grazing is present on much of the remaining grasslands, including 

large areas of sandy soil that are unsuitable for cultivation (fig. 3). 

Several National Grasslands lie in the heart of the historic Dust 

Bowl region in the central part of the ecoregion. Wetland habitat 

includes a high concentration of small but ecologically important 

playa lakes, which often are altered by agricultural land use and 

road construction. Since 1986, the Conservation Reserve Program 

(CRP), which pays farmers to convert environmentally sensitive 

land from crops to grassland, has become an important factor in 

the Western High Plains Ecoregion where many areas are marginal 

for cultivation. CRP lands covered more than 9 percent of the 

ecoregion in 2000 (U.S. Department of Agriculture, 1970–2000 

[various years]). Oil and natural-gas extraction also is important, 

and the large Hugoton Field in southwestern Kansas provides fuel 

for nearby groundwater pumps (fig. 4). 

The overall pattern of agricultural land use and the 

remaining grassland in the Western High Plains Ecoregion is 

driven largely by climate, soil type, and water availability, as 

well as by national farm policy, economic opportunity, and 

other technological and cultural adaptations to the limitations 

introduced by physical factors. Important physical forces 

driving the grassland and agricultural ecosystem include 

highly variable precipitation levels, which range from about 

300 mm per year (12 in.) in the western part of the ecoregion 

to 500 mm per year (under 20 in.) in the eastern part, as well 

as cycles of intense drought. High rates of evapotranspiration 

can exceed that of precipitation over long time periods and 

can contribute to a water deficit for growing crops. Average 

temperatures during the growing season are high and favor 

warm-season plants. The natural vegetation of the ecoregion 

primarily is shortgrass prairie dominated by blue grama 

(Bouteloua gracilis) and buffalo grass (Buchloe dactyloides). 

Dryland wheat-fallow cropping and no-tillage practices, which 

improve the retention of soil moisture, are used in areas where 

water availability is limited but soils are suitable for crops. 

Streamside irrigation and groundwater pumping are common 

practices where water is readily available, and these have 

helped to make the ecoregion important globally for smallgrain production and confined-livestock feeding (fig. 5). 

The High Plains (Ogallala) aquifer, the largest 

groundwater complex in the nation, underlies much of the 

Western High Plains Ecoregion. About 95 percent of the water 

pumped from the aquifer is used for crop irrigation (Dennehy 

and others, 2002). Early irrigation was concentrated in areas 

of the South Platte and North Platte Rivers and in the cotton 

region of the Llano Estacado in Texas. Turbine pumps used 

for groundwater irrigation were introduced in the 1930s, 

permitting modern farming and cattle-ranching practices 

(Brooks and others, 2001). Substantial pumping began in the 

1940s and intensified as cotton production expanded in the 

southern part of the ecoregion. Technological advances after 

World War II allowed for more efficient groundwater pumping 

that expanded the regional pattern of intensive crop production. 

The increasing use of center-pivot irrigation, beginning in 

the mid-1960s, allowed more intensive use of fields with 

uneven topography and sandy soils, where furrow irrigation is 

unfeasible (Lichtenberg, 1989). 

Aquifer declines of greater than 30 m had occurred in 

some areas by 1980 (Dennehy and others, 2002), causing 

an increase in the cost of extraction and making water more 

expensive to use as water levels decline (Terrell and others, 

2002). Aquifer recharge in many areas is minimal in relation 

Figure 2. Dryland farming, common in Western High Plains 

Ecoregion.

Figure 3. Rangeland cattle, which often rely on stock ponds of 

water, in semiarid Western High Plains Ecoregion.

Figure 4. Oil well, many of which dot agricultural landscapes in 

Western High Plains Ecoregion.
Chapter 5—Western High Plains Ecoregion 53

to pumping rates. As a result, the central and southern parts 

of the ecoregion have experienced groundwater depletion that 

makes long-term intensive use of the aquifer unsustainable. 

Other areas have large underground supplies despite declines in 

aquifer thickness. Recent conservation measures and improved 

irrigation technology may be slowing the rate of aquifer 

decline in some areas (McGuire and others, 2003). Streamside 

irrigation, practiced in areas of the North Platte, South Platte, 

and Arkansas Rivers, among others, also is vulnerable to 

low flows associated with regional drought and groundwater 

withdrawals that reduce streamflow, as well as to competition 

with urban and industrial uses. 

Although urban areas cover less than 1 percent of the 

ecoregion, they include large areas of the northern part of the 

“Front Range urban corridor,” which extends from Cheyenne, 

Wyoming, to Pueblo, Colorado, and includes many population 

centers from Scottsbluff, Nebraska, to Odessa, Texas (fig.6).

Combined population of the 89 counties of the ecoregion was 

2.57 million in 2000, a 28 percent increase since 1970 that 

occurred primarily in urban centers (U.S. Census Bureau, 1970–

2000 [various years]). The county with the highest percentage 

gain was Finney County in southwestern Kansas, which grew 

by 113 percent (about 19,000 people) from 1970 to 2000. 

Southwestern Kansas in general and Finney County in particular 

have a high concentration of irrigated feed-grain production, 

cattle feedlots, and beef-processing plants that provide 

employment (Harrington and Lu, 2002) and may be responsible 

for the population increase. Large cattle-feeding operations 

moved into the Western High Plains Ecoregion, and out of the 

Western Corn Belt Ecoregion, as well as out of the Central Corn 

Belt and Eastern Corn Belt Ecoregions in the Midwest–South 

Central United States, in part because the dry climate reduces the 

economic effects of animal disease (Harrington and Lu, 2002).

Contemporary Land-Cover Change 

(1973 to 2000)

Several trends emerge from analysis of the land-cover data, 

which indicate an expansion of agriculture prior to 1986 followed 

by a larger expansion of grassland/shrubland (fig. 7). Between 

1973 and 1980, grassland/shrubland was converted to agriculture 

because overseas markets for wheat increased and also because 

national farm policies favored expansion (table 1). Intensification 

of the agricultural industry, including both the concentration of 

animal-feeding operations and the expansion of irrigated feed-corn 

production into the ecoregion, also contributed to the land change. 

Some expansion continued between 1980 and 1986, although an 

economic downturn in agriculture caused the trend to nearly level 

out. Agriculture land cover increased by 1.8 percent between 1973 

and 1986 (table 2). 

Between 1986 and 1992, the trend reversed as 21,606 km2 of 

agriculture was converted back to grassland/shrubland, primarily 

in response to the CRP and other economically driven decisions to 

abandon crop production. The CRP provided economic incentives 

to limit crop production on marginal lands. Limited net expansion of 

grassland/shrubland continued between 1992 and 2000. Agriculture 

decreased by 7.6 percent between 1986 and 2000 (table 2). 

Between 1992 and 2000, the net loss of agriculture land cover 

was small, at 0.3 percent. However, shifts in the spatial location 

of grassland/shrubland and agriculture caused a large overall 

change that affected 4.7 percent of the ecoregion. During this 

time, CRP leases expired and grassland/shrubland was converted 

back to agriculture, while other cropland was enrolled in the CRP 

and planted with grass. Between 1973 and 2000, the total area 

of agriculture land cover decreased by an estimated 5.8 percent, 

whereas grassland/shrubland increased by 5.7 percent (fig. 7) 

(table 2). Grassland/shrubland increased from 44.1 percent of the 

ecoregion in 1973 to 49.8 percent in 2000. Agricultural land cover 

decreased from 53.6 percent to 47.8 percent (table 2). 

The overall spatial change (the percentage of land area 

that changed at least one time) in the Western High Plains 

Ecoregion between 1973 and 2000 is estimated at 12.5 percent 

(table 3). Compared to other Great Plains ecoregions, change in 

the Western High Plains Ecoregion was relatively high (fig. 8): 

most of the area that changed (10.1 percent) did so only once 

during the study period, 2.3 percent changed twice, and 0.1 

percent changed three times. These multiple changes typically 

were fluctuations between grassland/shrubland and agriculture. 

Overall, the most common conversion between 1973 and 2000 

Figure 5. Cropland irrigation in Western High Plains Ecoregion, 

commonly used along streams and in areas where High Plains 

(Ogallala) aquifer water is readily available. 

Figure 6. Small town in Western High Plains Ecoregion, many of 

which are potentially affected by long-term trends in agriculture. 
54 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

−8

−6

−4

−2

0

4

2

6

8

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Figure 9. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Western High 

Plains Ecoregion are represented by red bars in each time period.

was from agriculture to grassland/shrubland (29,847 km2), 

and the second most common conversion was from grassland/

shrubland to agriculture (13,188 km2) (table1). 

Expansion of developed land (net change, 0.1 percent) into 

areas of grassland/shrubland and agricultural land were the next 

two most common conversions (194 and 171 km2, respectively) 

but represent a relatively small proportion of the overall change. 

Changes among other land-cover classes affected less than 0.1 

percent of the ecoregion. The greatest amount of overall change 

occurred between 1986 and 1992, when 7.7 percent of the 

ecoregion changed as agricultural land was converted to grassland/

shrubland during the initial phase of the CRP (table 4); during this 

time period, an estimated 1.3 percent of the ecoregion changed 

annually (fig. 9; table 4). The period between 1980 and 1986 

experienced the least amount of change, at 0.8 percent, when the 

slow agricultural economy limited the expansion of agriculture. 

Land cover changed substantially in the Western High Plains 

Ecoregion between 1973 and 2000. This change partly resulted 

from its biological and physical setting (amplified by socioeconomic 

factors) and an increase in large farming interests, as well as 

government farm policies and subsidies. More land was used for crop 

production in good economic times, but marginal farmland was either 

Figure 7. Normalized average net change in Western High Plains 

Ecoregion by time period for each land-cover class. Bars above 

zero axis represent net gain, whereas bars below zero represent 

net loss. Note that not all land-cover classes shown in explanation 

may be represented in figure. See appendix 3 for definitions of 

land-use/land-cover classifications.

Figure 8. Overall spatial change in Western High Plains Ecoregion 

(WHP; darker bars) compared with that of all 17 Great Plains ecoregions 

(lighter bars). Each horizontal set of bars shows proportions of ecoregion 

that experienced change during one, two, three, or four time periods; 

highest level of spatial change in Western High Plains Ecoregion (three 

time periods) labeled for clarity. See table 4 for years covered by each 

time period. See appendix 2 for key to ecoregion abbreviations.

converted back to grassland/shrubland or abandoned when economic 

conditions worsened or drought cycles limited crop production. 

Overall, irrigated agriculture intensified and expanded; however, 

some areas were affected by declining water availability caused by 

climate variability, water overuse, or increased costs associated with 

pumping groundwater. Because of the continuing interaction between 

environmental and socioeconomic factors, the region is likely to 

continue to experience land-change fluctuations in the future.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in three

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period
Chapter 5—Western High Plains Ecoregion 55

Table 1. Principal land-cover conversions in Western High Plains Ecoregion, showing amount of area changed (and margin of error, 

calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study period. 

See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 4,718 1,667 1,138 1.6 87.9

Agriculture Grassland/Shrubland 453 215 147 0.2 8.4

Agriculture Developed 103 103 70 0.0 1.9

Grassland/Shrubland Developed 22 32 22 0.0 0.4

Grassland/Shrubland Mining 21 20 14 0.0 0.4

Other Other 49 n/a n/a 0.0 0.9

Totals 5,366 1.9 100.0

1980–1986 Grassland/Shrubland Agriculture 1,613 931 635 0.6 71.9

Agriculture Grassland/Shrubland 580 288 196 0.2 25.9

Grassland/Shrubland Developed 15 22 15 0.0 0.7

Agriculture Developed 14 16 11 0.0 0.6

Grassland/Shrubland Mining 8 11 8 0.0 0.3

Other Other 12 n/a n/a 0.0 0.5

Totals 2,243 0.8 100.0

1986–1992 Agriculture Grassland/Shrubland 21,606 4,895 3,341 7.5 97.3

Grassland/Shrubland Agriculture 539 257 175 0.2 2.4

Grassland/Shrubland Developed 16 20 14 0.0 0.1

Agriculture Developed 14 14 9 0.0 0.1

Grassland/Shrubland Mining 9 8 5 0.0 0.0

Other Other 14 n/a n/a 0.0 0.1

Totals 22,198 7.7 100.0

1992–2000 Agriculture Grassland/Shrubland 7,208 2,195 1,498 2.5 52.1

Grassland/Shrubland Agriculture 6,318 2,450 1,672 2.2 45.7

Grassland/Shrubland Developed 141 146 99 0.0 1.0

Agriculture Developed 41 44 30 0.0 0.3

Wetland Agriculture 28 37 26 0.0 0.2

Other Other 90 n/a n/a 0.0 0.7

Totals 13,825 4.8 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 29,847 6,602 4,506 10.3 68.4

Grassland/Shrubland Agriculture 13,188 3,530 2,410 4.6 30.2

Grassland/Shrubland Developed 194 216 147 0.1 0.4

Agriculture Developed 171 164 112 0.1 0.4

Grassland/Shrubland Mining 57 43 29 0.0 0.1

Other Other 175 n/a n/a 0.1 0.4

Totals 43,631 15.1 100.0
56 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 2. Estimated area (and margin of error) of each land-cover class in Western High Plains Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.2 0.1 0.4 0.3 0.0 0.0 0.1 0.0 0.3 0.2 0.8 1.1 44.1 7.3 53.6 7.5 0.4 0.1 0.0 0.0

1980 0.2 0.1 0.5 0.3 0.0 0.0 0.1 0.0 0.3 0.2 0.8 1.1 42.6 7.2 55.1 7.5 0.4 0.1 0.0 0.0

1986 0.2 0.1 0.5 0.3 0.0 0.0 0.1 0.0 0.3 0.2 0.8 1.1 42.3 7.2 55.4 7.5 0.4 0.1 0.0 0.0

1992 0.2 0.1 0.5 0.3 0.0 0.0 0.1 0.0 0.3 0.2 0.8 1.1 49.6 7.0 48.1 7.2 0.4 0.1 0.0 0.0

2000 0.2 0.1 0.6 0.3 0.0 0.0 0.1 0.0 0.3 0.2 0.8 1.1 49.8 7.2 47.8 7.4 0.4 0.1 0.0 0.0

Net

change 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.7 2.2 –5.8 2.1 0.0 0.0 0.0 0.0

Gross

change 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.9 2.6 12.9 2.6 0.0 0.0 0.0 0.0

Area, in square kilometers

1973 630 247 1,273 745 6 7 224 107 769 444 2,436 3,246 127,408 20,965 154,880 21,568 1,126 404 0 0

1980 631 246 1,398 822 1 1 246 123 755 444 2,436 3,246 123,123 20,928 159,057 21,556 1,105 402 0 0

1986 631 246 1,427 837 2 3 257 130 756 444 2,436 3,246 122,065 20,893 160,073 21,539 1,104 403 0 0

1992 634 247 1,457 854 0 0 266 133 754 445 2,436 3,246 143,111 20,247 138,987 20,782 1,106 404 0 0

2000 644 253 1,639 926 4 6 292 140 754 444 2,436 3,246 143,843 20,686 138,070 21,261 1,070 377 0 0

Net

change 14 24 366 273 –1 1 69 46 –15 15 0 0 16,435 6,210 –16,811 6,190 –56 55 0 0

Gross

change 42 23 366 273 12 15 78 46 21 15 0 0 37,339 7,404 37,258 7,427 95 58 0 0
Chapter 5—Western High Plains Ecoregion 57

Table 3. Percentage of Western High Plains Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (87.5 percent), whereas 12.5 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 10.1 2.0 8.1 12.0 1.3 13.3

2 2.3 0.9 1.5 3.2 0.6 25.3

3 0.1 0.1 0.0 0.2 0.1 58.7

4 0.0 0.0 0.0 0.0 0.0 0.0

Overall 

spatial 

change

12.5 2.3 10.2 14.8 1.6 12.7

Table 4. Raw estimates of change in Western High Plains Ecoregion land 

cover, computed for each of four time periods between 1973 and 2000, and 

associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period

Total 

change

(% of 

ecoregion)

Margin 

of error

(+/− %)

Lower 

bound

(%)

Upper 

bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average 

rate

(% per 

year)

Estimate of change, in percent stratum

1973–1980 1.9 0.6 1.3 2.5 0.4 22.2 0.3

1980–1986 0.8 0.3 0.4 1.1 0.2 28.8 0.1

1986–1992 7.7 1.7 6.0 9.4 1.2 15.1 1.3

1992–2000 4.8 1.1 3.7 5.9 0.7 15.6 0.6

Estimate of change, in square kilometers

1973–1980 5,366 1,745 3,621 7,110 1,191 22.2 767

1980–1986 2,243 947 1,296 3,190 646 28.8 374

1986–1992 22,198 4,911 17,287 27,109 3,352 15.1 3,700

1992–2000 13,825 3,168 10,657 16,993 2,162 15.6 1,728
58 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Brooks, E., Emel, J., Jokisch, B., and Robbins, P., 2001, The 

Llano Estacado of the US Southern High Plains—Environmental transformation and the prospect for sustainability: 

New York, United Nations University Press, 176 p.

Dennehy, K.F., Litke, D.W., and McMahon, P.B., 2002, The 

High Plains aquifer, USA—Groundwater development and 

sustainability, in Hiscock, K.M., Rivett, M.O., and Davison, 

R.M., eds., Sustainable groundwater development: London, 

Geological Society, Special Publications, v. 193, p. 99–119.

Harrington, L.M.B., and Lu, M., 2002, Beef feedlots in southwestern Kansas—Local change, perceptions, and the global change 

context: Global Environmental Change, v. 12, p. 273–282.

Lichtenberg, E., 1989, Land quality, irrigation development, 

and cropping patterns in the northern High Plains: American 

Journal of Agricultural Economics, v. 71, p. 187–194.

McGuire, V.L., Johnson, M.R., Schieffer, R.L., Stanton, J.S., 

Sebree, S.K., and Verstraeten, I.M., 2003, Water in storage 

and approaches to ground-water management, High Plains 

aquifer, 2000: U.S. Geological Survey Circular 1243, 51 p., 

available at http://pubs.usgs.gov/circ/2003/circ1243/.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Terrell, B.E., Johnson, P.N., and Segarra, E., 2002, Ogallala 

aquifer depletion—Economic impact on the Texas high 

plains: Journal of Water Policy, v. 4, no. 1, p. 33–46.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed September 1, 2008, at http://www.census.gov/

prod/www/decennial.html.

U.S. Department of Agriculture, 1970–2000 [various years], 

Census of agriculture: U.S. Department of Agriculture database, accessed September 1, 2008, at http://www.agcensus.

usda.gov/.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Glaciated Plains Ecoregions

98° 97° 96°

49°

48°

47°

46°

Northern

Glaciated

Plains

Northern Minnesota Wetlands

NCHF

NLF

CANADA

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

MINNESOTA

CANADA

NORTH

DAKOTA

SOUTH

DAKOTA

Grand Forks

Moorhead

East Grand Forks

CLEARWATER

COUNTY

AGASSIZ

NATIONAL

WILDLIFE

REFUGE

Red River

Fargo

MN

ND

SD

Lake Agassiz Plain

Ecoregion

0 50 MILES

0 50

25

25 KILOMETERS

Chapter 6

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Lake Agassiz Plain Ecoregion 

By Mark S. Brooks

Ecoregion Description

The Lake Agassiz Plain Ecoregion 

covers 40,636 km2 (15,690 mi2) in eastern 

North Dakota, northwestern Minnesota, and 

a small part of northeastern South Dakota 

(fig 1) (Omernik, 1987; U.S. Environmental 

Protection Agency, 1997). The ecoregion 

is bounded, on the west and south, by the 

Northern Glaciated Plains Ecoregion and, on 

the east, by the Northern Minnesota Wetlands 

and North Central Hardwood Forests 

Ecoregions; the Canadian border forms the 

northern border of the ecoregion (fig. 1).

The modern-day landscape of the Lake 

Agassiz Plain Ecoregion formed about 10 

thousand years ago when the great continental 

glaciers of North America started to recede. 

Blocked by large ice sheets, glacial meltwater 

formed many large glacial lakes. The last 

proglacial lake to fill the modern-day Red 

River valley was Glacial Lake Agassiz. What 

remains today is an extremely flat plain that 

has an average gradient of about 9 cm per km, 

as well as a lake-washed till plain and gently 

rolling uplands along the east and west edges 

of the Red River valley. Because of its poorly 

defined floodplains, the Red River valley has 

experienced numerous floods throughout its 

young geologic history.

The ecoregion has a continental climate: 

January average low and high temperatures are 

about -22°C and 11°C, respectively, and July 

average low and high temperatures are about 

13°C and 28°C, respectively. The average 

annual number of frost-free days ranges 

from 95 to 125 days, and the average annual 

precipitation amount is about 530 mm (21 in.).

During the 19th century, much of the 

native tallgrass prairie of the Red River 

valley was replaced with a mostly agricultural 

land, and agriculture is the principal landcover class in the ecoregion. The rich, deep, 

loamy soils, as well as the construction of an 

extensive drainage system to remove surface 

Figure 1. Map of Lake Agassiz Plain Ecoregion and surrounding ecoregions, 

showing land-use/land-cover classes from 1992 National Land Cover Dataset 

(Vogelmann and others, 2001); note that not all land-use/land-cover classes shown 

in explanation may be depicted on map; note also that, for this “Status and Trends of 

Land Change” study, transitional land-cover class was subdivided into mechanically 

disturbed and nonmechanically disturbed classes. Squares indicate locations of 10 

x 10 km sample blocks analyzed in study. Index map shows locations of geographic 

features mentioned in text. Abbreviations for Great Plains ecoregions are listed 

in appendix 2. Also shown are parts of two Midwest–South Central United States 

ecoregions: North Central Hardwood Forests (NCHF) and Northern Minnesota 

Wetlands. See appendix 3 for definitions of land-use/land-cover classifications.
62 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

water quickly from agricultural lands (fig. 2), have enabled 

the Red River valley to become one of the most productive 

agricultural areas in the Great Plains. Major crops produced 

throughout the Lake Agassiz Plain Ecoregion include potatoes, 

sugar beets, sunflowers, wheat, barley, corn, and soybeans 

(figs. 3,4). Pasture and hay production are common in areas of 

marginal soils (fig. 5).

Secondary land-cover classes include grassland/

shrubland, forest, and wetland, which tend to be located away 

from the high-intensity agriculture found along the Red River 

valley, with the exception of riparian forest cover (fig. 1). 

Grassland/shrubland primarily is present in the lake-washed 

till plains, on the beach ridges and sand deltas around the edge 

of Glacial Lake Agassiz (Bryce and others, 1998). Wetland 

and forest more commonly are present in the northeastern 

upland area of the ecoregion where soils are not as rich. One 

of the largest remaining wetland lies within this upland area, 

part of the Agassiz National Wildlife Refuge (U.S. Fish and 

Wildlife Service, 2009).

Developed land-cover class includes two urban areas 

situated along the Red River: the Fargo, North Dakota–

Moorhead, Minnesota metropolitan statistical area (population, 

174,367 in 2000) and the Grand Forks, North Dakota–East 

Grand Forks, Minnesota metropolitan area (population, 97,478 

in 2000) (U.S. Census Bureau, 2003). During the study period, 

the population in both urban areas remained stable, while 

the population of rural communities declined as younger 

residents migrated to larger cities in search of better social and 

economic opportunities.

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Lake Agassiz Plain 

Ecoregion between 1973 and 2000 is about 1.5 percent 

(table 1), the lowest amount of change among all 17 Great 

Plains ecoregions (fig. 6). In addition, the total land-use/landcover change estimated for each time period was extremely 

Figure 2. Drainage ditch and rolls of tile piping used for field 

drainage, in Lake Agassiz Plain Ecoregion. 

Figure 4. Sunflower field in Lake Agassiz Plain Ecoregion.

Figure 3. Soybean field ready for harvest, in Lake Agassiz Plain 

Ecoregion.

Figure 5. Cattle grazing along County Route 60, in northwestern 

Clearwater County, Minnesota, Lake Agassiz Plain Ecoregion.
Chapter 6—Lake Agassiz Plain Ecoregion 63

Figure 8. Normalized average net change in Lake Agassiz 

Plain Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.

Figure 6. Overall spatial change in Lake Agassiz Plain Ecoregion 

(LAP; darker bars) compared with that of all 17 Great Plains 

ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that changed during one, two, three, or 

four time periods; highest level of spatial change in Lake Agassiz 

Plain Ecoregion (four time periods) labeled for clarity. See table 2 

for years covered by each time period. See appendix 2 for key to 

ecoregion abbreviations. 

Figure 7. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Lake Agassiz 

Plain Ecoregion are represented by red bars in each time period. 

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

−1

−0.5

0

0.5

1

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

low: the estimated change was 0.2 percent between 1973 and 

1980 and between 1980 and 1986, 0.7 percent between 1986 

and 1992, and 0.5 percent between 1992 and 2000 (table 2). 

When normalized to an annual rate of change to adjust for 

uneven time periods, all time periods had an estimated annual 

rate of change of 0.1 percent or less (table 2; fig. 7). 

The composition of land-use/land-cover classes in the 

Lake Agassiz Plain Ecoregion changed very little during the 

study period. In 2000, agriculture was the predominant landcover class in the ecoregion (about 80.9 percent), followed 

by grassland/shrubland (about 7.3 percent), forest (about 5.5 

percent), and wetland (about 4.7 percent). The remaining landcover classes combined constituted about 1.6 percent of the 

ecoregion (table 3).

The largest overall net change during the study period 

was a 0.6 percent decrease (about 247 km2) in agriculture, the 

greatest amount of change occurring between 1986 and 1992. 

In contrast, grassland/shrubland increased by 0.5 percent (196 

km2) over the study period (table 3; fig. 8). The large amount 

of change between agriculture and grassland/shrubland 

between 1986 and 1992 was associated with the enrollment 

of cropland in the Conservation Reserve Program (CRP). The 

CRP is a Federal program implemented in the mid-1980s to 

reduce soil erosion and improve water quality and wildlife 

habitat by paying farmers to remove marginal and erodible 

cropland from production and to restore it to native grasslands 

and other natural landscapes.
64 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 1. Percentage of Lake Agassiz Plain Ecoregion land cover 

that changed at least one time during study period (1973–2000) and 

associated statistical error.

[Most sample pixels remained unchanged (98.5 percent), whereas 1.5 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 1.3 0.4 0.9 1.7 0.2 18.8

2 0.1 0.1 0.0 0.3 0.1 44.3

3 0.0 0.0 0.0 0.1 0.0 63.1

4 0.0 0.0 0.0 0.0 0.0 70.9

Overall 

spatial 

change

1.5 0.4 1.1 1.9 0.3 19.1

The most common land-cover conversions during the 

27-year study period highlight the strong influence that 

agriculture had on the ecoregion. Agriculture was part of each 

of the top five conversions, which included both losses to and 

gains from other land-cover classes (table 4). The leading 

changes were the conversions of an estimated 297 km2 of 

agricultural land to grassland/shrubland and an estimated 104 

km2 of grassland/shrubland to agricultural land; these two 

conversions constituted nearly 60 percent of all change in 

the ecoregion. Other changes involving agriculture included 

the conversions of an estimated 80 km2 of agriculture to 

developed, 44 km2 of forest to agriculture, and 28 km2 of 

wetland to agriculture (table 4).

The fact that the Lake Agassiz Plain Ecoregion had the 

lowest amount land-cover change among the 17 Great Plains 

ecoregions was mainly because of the dominance and stability 

of agriculture. Although the ecoregion was relatively stable, 

conversions between agriculture and other land-use/land-cover 

classes were observed in each time period. The CRP had a 

moderate influence on land-cover change in the ecoregion; 

the National Agricultural Statistics Service reported a 6 

percent increase in cropland enrollment in the CRP between 

1987 and 1997 (Blann and others, 2009), which explains the 

large amount of agricultural land that converted to grassland/

shrubland between 1986 and 1992. Other government 

programs have been implemented to mitigate the effects of 

re-engineered natural waterways and intensive agricultural 

production that have increased the severity of flooding and soil 

erosion, reduced water quality, and fragmented wildlife habitat 

within the Red River valley. 
Chapter 6—Lake Agassiz Plain Ecoregion 65

Table 2. Raw estimates of change in Lake Agassiz Plain Ecoregion land cover, computed for each of 

four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period

Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 0.2 0.1 0.2 0.3 0.1 24.9 0.0

1980–1986 0.2 0.1 0.1 0.3 0.1 26.6 0.0

1986–1992 0.7 0.3 0.4 1.0 0.2 29.3 0.1

1992–2000 0.5 0.2 0.4 0.7 0.1 21.5 0.1

Estimate of change, in square kilometers

1973–1980 101 37 64 138 25 24.9 14

1980–1986 98 39 59 137 26 26.6 16

1986–1992 278 121 157 398 81 29.3 46

1992–2000 212 68 144 279 46 21.5 26

Table 3. Estimated area (and margin of error) of each land-cover class in Lake Agassiz Plain Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/

Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.4 0.2 0.7 0.3 0.0 0.0 0.1 0.1 0.0 0.0 5.6 1.6 6.8 4.3 81.5 5.8 4.8 1.7 0.0 0.0

1980 0.4 0.2 0.8 0.3 0.0 0.0 0.1 0.1 0.0 0.0 5.6 1.6 6.9 4.3 81.5 5.8 4.7 1.7 0.0 0.0

1986 0.4 0.2 0.8 0.3 0.0 0.0 0.1 0.1 0.0 0.0 5.5 1.6 6.8 4.3 81.5 5.8 4.7 1.7 0.0 0.0

1992 0.4 0.2 0.9 0.3 0.0 0.0 0.1 0.1 0.0 0.0 5.5 1.6 7.3 4.3 81.1 5.8 4.7 1.7 0.0 0.0

2000 0.5 0.2 1.0 0.4 0.0 0.0 0.1 0.1 0.0 0.0 5.5 1.6 7.3 4.3 80.9 5.7 4.7 1.7 0.0 0.0

Net

change 0.0 0.0 0.3 0.1 0.0 0.0 0.0 0.0 0.0 0.0 –0.1 0.1 0.5 0.2 –0.6 0.3 0.0 0.0 0.0 0.0

Gross

change 0.1 0.0 0.3 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.1 0.8 0.3 1.1 0.3 0.1 0.1 0.0 0.0

Area, in square kilometers

1973 169 86 288 115 8 12 45 37 0 0 2,288 653 2,782 1,756 33,121 2,345 1,935 691 0 0

1980 170 87 318 122 0 0 44 37 0 0 2,268 648 2,799 1,762 33,108 2,344 1,929 692 0 0

1986 174 86 339 135 2 3 47 37 0 0 2,253 644 2,777 1,756 33,126 2,338 1,918 683 0 0

1992 174 85 358 138 2 2 40 28 0 0 2,246 643 2,948 1,756 32,948 2,341 1,921 680 0 0

2000 186 85 390 158 0 0 43 28 0 0 2,245 644 2,978 1,767 32,874 2,335 1,919 682 0 0

Net

change 17 11 102 52 –8 12 –2 13 0 0 –43 30 196 101 –247 109 –15 18 0 0

Gross

change 29 15 102 52 15 13 23 13 0 0 55 29 340 133 455 135 54 29 0 0
66 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 4. Principal land-cover conversions in Lake Agassiz Plain Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall 

study period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin 

of error

Standard 

error Percent of 

ecoregion

Percent 

of all 

changes (km2) (+/− km2) (km2)

1973–1980 Agriculture Developed 22 15 10 0.1 21.5

Forest Agriculture 20 12 8 0.0 19.4

Agriculture Grassland/Shrubland 19 17 12 0.0 19.1

Grassland/Shrubland Agriculture 11 11 7 0.0 11.3

Mechanically disturbed Developed 8 12 8 0.0 8.1

Other Other 21 n/a n/a 0.1 20.6

Totals 101 0.2 100.0

1980–1986 Grassland/Shrubland Agriculture 30 21 14 0.1 30.2

Agriculture Developed 17 13 9 0.0 17.0

Forest Agriculture 12 11 7 0.0 12.1

Agriculture Grassland/Shrubland 10 8 5 0.0 9.8

Wetland Agriculture 9 10 6 0.0 9.3

Other Other 21 n/a n/a 0.1 21.5

Totals 98 0.2 100.0

1986–1992 Agriculture Grassland/Shrubland 188 99 67 0.5 67.7

Grassland/Shrubland Agriculture 18 12 8 0.0 6.3

Agriculture Wetland 13 13 9 0.0 4.8

Wetland Agriculture 11 15 10 0.0 4.0

Agriculture Developed 10 7 5 0.0 3.7

Other Other 37 n/a n/a 0.1 13.5

Totals 278 0.7 100.0

1992–2000 Agriculture Grassland/Shrubland 80 37 25 0.2 37.6

Grassland/Shrubland Agriculture 46 39 26 0.1 21.5

Agriculture Developed 32 24 16 0.1 15.0

Wetland Water 11 9 6 0.0 5.1

Agriculture Wetland 7 7 5 0.0 3.4

Other Other 37 n/a n/a 0.1 17.4

Totals 212 0.5 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 297 134 90 0.7 43.1

Grassland/Shrubland Agriculture 104 56 38 0.3 15.1

Agriculture Developed 80 45 31 0.2 11.7

Forest Agriculture 44 28 19 0.1 6.3

Wetland Agriculture 28 33 22 0.1 4.1

Other Other 136 n/a n/a 0.3 19.7

Totals 689 1.7 100.0
Chapter 6—Lake Agassiz Plain Ecoregion 67

References Cited

Blann, Kristen, Webb, Tim, Keeney, Dennis, and Light, 

Steve, 2009, Alternatives to crisis—An adaptive 

management model for the Red River Basin of the U.S. 

and Canada, in Light, Stephen S., ed., 2004, The role 

of biodiversity conservation in the transition to rural 

sustainability, Series V: Amsterdam, The Netherlands, 

IOS Press, Science and Technology Policy, v. 41, p. 173–

198, accessed April 2009, at http://www.worldcat.org/

title/role-of-biodiversity-conservation-in-the-transitionto-rural-sustainability/oclc/191037976/viewport?bib_

key=ISBN:9781586033958.

Bryce, S.A., Omernik, J.M., Pater, D.E., Ulmer, Michael, 

Schaar, Jerome, Freeouf, Jerry, Johnson, Rex, Kuck, Pat, 

and Azevedo, S.H., 1998, Ecoregions of North and South 

Dakota: U.S. Geological Survey Ecoregion Map Series, 

scale 1:500,000, accessed June 3, 2013 at http://www.

epa.gov/wed/pages/ecoregions/ndsd_eco.htm.

Omernik, J.M., 1987, Ecoregions of the conterminous 

United States: Annals of the Association of American 

Geographers, v. 77, no. 1, p. 118–125.

U.S. Census Bureau, 2003, Ranking tables for population of 

metropolitan statistical areas, micropolitan statistical areas, 

combined statistical areas, New England city and town areas, 

and combined New England city and town areas—1990 and 

2000: U.S. Census Bureau database, accessed March 16, 

2009, at http://www.census.gov/population/www/cen2000/

briefs/phc-t29/tables/tab03a.pdf.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

U.S. Fish and Wildlife Service, 2009, Agassiz National Wildlife 

Refuge: U.S. Fish and Wildlife Service Web site, accessed 

March 15, 2009, at http://www.fws.gov/refuge/agassiz/.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., Wylie, 

B.K., and van Driel, N., 2001, Completion of the 1990s National 

Land Cover Data Set for the conterminous United States from 

Landsat Thematic Mapper data and ancillary data sources: 

Photogrammetric Engineering & Remote Sensing, v. 67, p. 

650–662.

104° 102° 100° 98° 96°

46°

48°

44°

46°

44°

Northwestern

Great Plains

Northwestern

Glaciated

Plains

Lake Agassiz

Plain

Western

Corn Belt

Plains

WHP NSH

NLF

NSH

NCHF

NMW

MRK

CANADA

0 50 100 150 MILES

0 50 100 150 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

SOUTH DAKOTA

NORTH DAKOTA

MINNESOTA

CANADA

NEBRASKA

IOWA

Lake

Thompson

Devils Lake

MARSHALL

McHENRY

COUNTY

CODINGTON COUNTY

DAY

Minot

Menno

Sioux Falls

Hamberg

LINCOLN

COUNTY

COTEAU DES

Waubay Lake

PRAIRIES

TURTLE

MOUNTAINS

Chapter 7

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Northern Glaciated Plains Ecoregion

By Roger F. Auch

Ecoregion Description 

The Northern Glaciated Plains Ecoregion, which covers 

about 141,340 km2 (54,572 mi2), runs north-south across 

eastern North Dakota and South Dakota, widening to the 

east into western Minnesota (fig. 1) (Omernik, 1987; U.S. 

Environmental Protection Agency, 1997). The ecoregion is 

surrounded by (clockwise, from the east) the Lake Agassiz 

Plain, North Central Hardwood Forests, Western Corn Belt 

Plains, and Northwestern Glaciated Plains Ecoregions; the 

Canadian border forms its northern border (fig. 1).

The climate of the Northern Glaciated Plains Ecoregion 

is considered to be continental (hot or warm summers and 

cold winters). Average annual precipitation amounts range 

from about 510 to 610 mm (20 to 24 in.) for most of the 

ecoregion, but they decrease to the northwest and increase 

to the southeast (Kottek and others, 2006; PRISM Climate 

Group, 2006). This subhumid climate makes the ecoregion 

a “transitional grassland,” meaning that it contains both 

tallgrass- and shortgrass-prairie communities. Although the 

ecoregion historically has been dominated by grasslands, 

Euro-American settlers converted most of it to farmland. 

The recent (less than 25,000 years ago) glaciation of most 

of the Northern Glaciated Plains Ecoregion (Johnson and 

Higgins, 1997) left many glacial landforms, contributing 

greatly to the land-use/land-cover classes seen today [2013]. 

Drift plains, large glacial-lake basins, and shallow river 

valleys that have level-to-undulating surfaces and deep soils 

provide the substrate for crop agriculture. Grasslands remain 

where glaciers left behind large deposits of rock, gravel, 

and sand, and they generally are used for grazing livestock. 

This geological history also has resulted in an immature 

Figure 1. Map of Northern Glaciated Plains Ecoregion and 

surrounding ecoregions, showing land-use/land-cover classes from 

1992 National Land Cover Dataset (Vogelmann and others, 2001); 

note that not all land-use/land-cover classes shown in explanation 

may be depicted on map; note also that, for this “Status and Trends 

of Land Change” study, transitional land-cover class was subdivided 

into mechanically disturbed and nonmechanically disturbed classes. 

Squares indicate locations of 10 x 10 km sample blocks analyzed in 

study. Index map shows locations of geographic features mentioned 

in text. Abbreviations 

for Great Plains 

ecoregions are listed 

in appendix 2. Also 

shown are parts of 

three Midwest–South 

Central United States 

ecoregions: North 

Central Hardwood 

Forests (NCHF), 

Northern Lakes and 

Forests (NLF), and 

Northern Minnesota 

Wetlands (NMW). 

See appendix 3 for 

definitions of landuse/land-cover 

classifications.
70 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

drainage system, and the ecoregion is dotted with wetland 

depressions that vary widely in size and permanence, as well 

as subregional concentrations of glacially formed permanent 

lakes. Agricultural land, grasslands, wetlands, and water form 

the general mosaic of land cover in the ecoregion. 

Agriculture is the most common land-cover class in the 

ecoregion, and grain and cattle production are the dominant 

land uses. Although most agricultural land cover is cropland, 

farming is limited by certain soil, topographic, and wetland 

conditions, and latitudinal and longitudinal differences 

influence the combinations of crops that can be grown. The 

main crops grown in the ecoregion are corn and soybeans 

in the southern part; soybeans and wheat in the central part; 

and wheat, other small grains, and canola (rapeseed) in the 

northern part (fig. 2). Hay production, especially from alfalfa, 

also is a common use of cropland. Small, intensively used 

pastures also are included in the agriculture land-cover class.

Livestock grazing on large expanses of grasslands 

typically is considered a localized and low-intensity land use 

(fig. 3). Rocky soils and steep slopes are the main reasons 

grasslands persist in these areas, and, to a lesser extent, in 

the ecoregion in general. Grassland/shrubland land-cover 

Figure 2. Field of canola (rapeseed) in flower, surrounding 

wetland in extreme north-central North Dakota, Northern 

Glaciated Plains Ecoregion.

Figure 3. Cattle grazing on distant grassy hillside, in Marshall 

County, South Dakota, Northern Glaciated Plains Ecoregion.

class also is present on wildlife habitat areas such as federally 

owned and state-owned wildlife refuges and waterfowl 

production areas, as well as other public lands.

Wetland and water are common land-cover classes in the 

Northern Glaciated Plains Ecoregion, but their concentration 

varies (both in number and in size) locally. Water is present 

mostly in permanent lakes, in semipermanent “wetland” lakes 

that may be open water in some years and wetland vegetation 

in others, and in a few reservoirs (fig. 4).

Minor land-cover classes include forest, developed, 

and mining. Forested land, which is limited and tends to be 

subregionally concentrated, is present in the Turtle Mountains, 

in the Coteau des Prairies, and in the northern parts of the 

ecoregion (Bryce and others, 1998) (fig. 5). Larger riparian 

areas and farm shelterbelts also may have forest cover but 

may not have been wide enough (that is, discernable using 

a 60-m-wide mapping unit) to map continuously, although 

exceptions are common. Developed land, which was 

present within cities and towns, constitutes a small part of 

the ecoregion. Most small towns in the Northern Glaciated 

Plains Ecoregion grew little in area during the study period, 

and many of them are declining in population and economic 

diversity (fig. 6). Aggregate mining also occurs in the 

ecoregion, owing to its glacial geology, but it tends to be 

limited in size.

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Northern Glaciated 

Plains Ecoregion between 1973 and 2000 is 7.4 percent (table 

1). Compared to other Great Plains ecoregions, change in 

the ecoregion was moderate (fig. 7). The Northern Glaciated 

Plains Ecoregion changed less than the Northwestern 

Glaciated Plains Ecoregion to the west but more than either 

the Lake Agassiz Plain Ecoregion to the east-northeast or the 

Western Corn Belt Plains Ecoregion to the south (fig. 7). Most 

of the change (6.0 percent) occurred only one time during 

the study period, but some areas (1.4 percent) experienced 

multiple changes (table 1). The multiple changes typically 

involved either the back-and-forth conversions between 

wetlands and open, persistent water owing to changes in 

climatic cycles or the conversions of grassland to crop 

production early in the study period and then back to grassland 

upon enrollment in the Conservation Reserve Program (CRP) 

after 1985. The last two time periods (1986–1992, 1992–2000) 

had more change than the first two time periods (1973–1980, 

1980–1986) (table 2). When normalized to an annual rate to 

account for the varying lengths in study periods, the periods 

between 1973 and 1980 and between 1980 and 1986 had 

the lowest rate of change (0.2 percent) (table 2). The rate 

of change continued to increase after 1986, and the period 
Chapter 7—Northern Glaciated Plains Ecoregion 71

between 1992 and 2000 had the highest rate of change (0.5 

percent) (table 2; fig. 8).

The agriculture and water land-cover classes had the 

most net change during the study period, followed by wetland 

and grassland/shrubland (table 3; fig. 9). Agriculture had a net 

loss of 2.0 percent, changing primarily to grassland/shrubland, 

wetland, water, developed, and mining. With the exception of 

Figure 4. Wetland and water areas in Northern Glaciated Plains 

Ecoregion. A, Cattle grazing in dried-up wetland, in Codington 

County, South Dakota. B, Common scene of grass and wetlands, 

in Day County, South Dakota. C, More permanent natural lake, in 

Lincoln County, Minnesota. 

Figure 5. Patch of natural forest surrounded by grasslands, in

McHenry County, North Dakota, Northern Glaciated Plains Ecoregion. 

Cattle ranching is dominant land use in this part of ecoregion. 

the conversions to developed, all of this agriculture land-use/

land-cover change could be temporary. The most common 

conversion over the study period was from agriculture to 

grassland/shrubland. An estimated 3,386 km2 of agriculture 

changed to grassland/shrubland (table 4), most of it during 

the last two time periods (1986–1992, 1992–2000) when the 

CRP was in effect. The CRP paid farmers to retire marginal 

cropland to native grasslands through contracts, usually 10 

years in duration. Although some land in the ecoregion may 

have been under a second CRP contract by the year 2000, 

this did not assure a permanent change from agriculture to 

grassland/shrubland (Leathers and Harrington, 2000). A 

more ephemeral change was the conversion of agriculture 

to wetland, as wetter than normal climatic conditions kept 

many temporary and seasonal wetlands out of crop production 

(Kirby and others, 2002). A series of wet years in the mid1980s and mid- to late 1990s contributed to most of the 

agriculture-to-wetland change.

Water land cover increased by a net 2.0 percent during 

the study period (table 3). Water gained mostly from wetland, 

agriculture, and grassland/shrubland. The second most 

common conversion during the study period was wetland to 

water. An estimated 3,244 km2 of wetland changed to water 

(table 4), most of it during the last time period (1992–2000). 

Although gains in water from wetland may be more of an 

ephemeral event owing to wetter climatic conditions (table 4), 

gains in water from agriculture and grassland/shrubland could 

represent a longer term but still cyclic change in which many 

larger glacial lake basins flooded during the study period. 

Water bodies such as Lake Thompson and Waubay Lake in 

South Dakota, Devils Lake in North Dakota, and many more 

minor lakes expanded in size from the mid-1980s onwards. 

These water bodies may persist as large surface areas for years 

(Todhunter and Rundquist, 2004; Shapley and others, 2005; 

South Dakota Game, Fish and Parks, 2006).

Wetland land cover decreased by a net 0.9 percent 

between 1973 and 2000 (table 3), much of it a change to 

A

B

C
72 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Figure 6. Developed areas in Northern Glaciated Plains 

Ecoregion. A, New developed land on outskirts of Minot, North 

Dakota. New development was limited almost exclusively 

to periphery of ecoregion’s cities. B, Farming community of 

Menno, South Dakota. Although many small towns in ecoregion 

experienced little physical growth, they appeared to be 

economically stable. C, Former post office in small central 

North Dakota town of Hamberg. As communities decline, some 

developed areas are abandoned.

Figure 7. Overall spatial change in Northern Glaciated Plains

Ecoregion (NGP; darker bars) compared with that of all 17 Great Plains 

ecoregions (lighter bars). Each horizontal set of bars shows proportions 

of ecoregion that changed during one, two, three, or four time periods; 

highest level of spatial change in Northern Glaciated Plains Ecoregion 

(four time periods) labeled for clarity. See table 2 for years covered by 

each time period. See appendix 2 for key to ecoregion abbreviations.

Figure 8. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Northern Glaciated 

Plains Ecoregion are represented by red bars in each time period.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

A

B

C
Chapter 7—Northern Glaciated Plains Ecoregion 73

open-water conditions. Although this change may reverse 

itself during drier climatic cycles, the trend from the 1980s 

onwards was that of wetlands converting to open water, 

especially during the period between 1992 and 2000. 

Although grassland/shrubland land cover increased by a 

net 0.7 percent during the study period (table 3), the change 

was variable across the ecoregion. It also is possible that 

multiple conversions affecting grassland/shrubland negated 

stronger directional trends. Gross change in grassland/

shrubland was much higher, at 2.7 percent (table 3). One 

of the major factors affecting grassland/shrubland was the 

dynamic relation between grassland/shrubland and agriculture. 

When the estimated changes from agriculture to grassland/

shrubland and from grassland/shrubland to agriculture are the 

Table 1. Percentage of Northern Glaciated Plains Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (92.6 percent), whereas 7.4 percent 

changed at least once throughout study period] 

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 6.0 1.1 4.9 7.1 0.8 12.7

2 1.1 0.3 0.8 1.5 0.2 19.2

3 0.3 0.1 0.2 0.4 0.1 20.0

4 0.0 0.0 0.0 0.1 0.0 19.8

Overall 

spatial 

change

7.4 1.4 6.1 8.8 0.9 12.5

Figure 9. Normalized average net change in Northern Glaciated 

Plains Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional 

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

only changes considered (table 4), they show that grassland/

shrubland lost to agriculture during the first two time periods 

(1973–1980, 1980–1986), a time of agricultural economic 

expansion, but that the trend reversed itself during the last 

two time periods (1986–1992, 1992–2000), mostly owing to 

the CRP. The grassland/shrubland net gain decreased between 

1992 and 2000, as some of the first CRP contracts expired 

and were not renewed (Leistritz and others, 2002) and as 

formerly unbroken grassland/shrubland areas were converted 

to cropland for the first time (Higgins and others, 2002). 

The major factors that affected land-change dynamics 

in the Northern Glaciated Plains Ecoregion during the study 

period were (1) shifts in the agricultural economy and in 

Federal farm policies, causing conversions between grassland/

shrubland and agriculture, and (2) cyclic climatic conditions, 

resulting in conversions between wetland and water and 

between agriculture and wetland. All these were temporal 

pulses of change: more grassland/shrubland was converted 

to agriculture during the first two time periods (1973–1980, 

1980–1986), whereas the reverse occurred in the last two time 

periods (1986–1992, 1992–2000), after implementation of the 

CRP. Wetland-to-water and agriculture-to-wetland conversions 

were much more dominant in the second half of the study 

period than in the first half, owing to a series of wet years. For 

the most part, such conversions were temporary in nature. In 

some cases, however, the conversion of grassland/shrubland 

and wetland back to agriculture may be permanent because 

restoration efforts can be cost prohibitive, and, furthermore, 

they usually do not produce results as ecologically complex as 

native grassland/shrubland and wetlands.
74 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Estimated area (and margin of error) of each land-cover class in Northern Glaciated Plains Ecoregion, calculated five 

times between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/

Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 3.5 2.1 1.4 1.6 0.0 0.0 0.1 0.1 0.0 0.0 3.0 2.6 17.7 4.4 68.5 5.7 5.9 1.0 0.0 0.0

1980 3.3 2.1 1.5 1.6 0.0 0.0 0.1 0.0 0.0 0.0 3.0 2.5 17.5 4.4 68.6 5.7 6.0 1.0 0.0 0.0

1986 3.4 2.1 1.5 1.6 0.0 0.0 0.1 0.1 0.0 0.0 3.0 2.5 17.7 4.5 68.4 5.7 6.0 1.0 0.0 0.0

1992 3.7 2.1 1.6 1.8 0.0 0.0 0.1 0.1 0.0 0.0 3.0 2.5 18.5 4.7 67.5 5.8 5.6 1.0 0.0 0.0

2000 5.5 2.3 1.6 1.8 0.0 0.0 0.1 0.1 0.0 0.0 3.0 2.5 18.4 4.7 66.4 5.8 4.9 1.0 0.0 0.0

Net

change 2.0 0.7 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.7 –2.0 0.9 –0.9 0.6 0.0 0.0

Gross

change 2.9 0.8 0.2 0.2 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.9 0.5 0.3 0.3 2.3 0.6 0.0 0.0

Area, in square kilometers

1973 4,938 2,946 1,949 2,211 12 18 116 110 0 0 4,266 3,605 25,009 6,266 96,762 8,070 8,289 1,382 0 0

1980 4,651 2,930 2,080 2,271 8 12 82 66 0 0 4,256 3,591 24,787 6,283 96,970 8,060 8,506 1,419 0 0

1986 4,747 2,952 2,116 2,307 0 0 101 86 0 0 4,258 3,591 24,995 6,377 96,661 8,121 8,462 1,422 0 0

1992 5,294 3,017 2,248 2,475 15 14 107 87 0 0 4,251 3,585 26,104 6,642 95,473 8,241 7,849 1,350 0 0

2000 7,769 3,240 2,283 2,491 5 7 140 103 0 0 4,238 3,574 26,034 6,698 93,916 8,135 6,956 1,477 0 0

Net

change 2,830 932 334 297 –7 20 24 30 0 0 –27 34 1,026 959 –2,846 1,245 –1,333 854 0 0

Gross

change 4,094 1,125 334 297 54 43 127 92 0 0 66 33 3,790 902 4,817 1,181 3,316 892 0 0

Table 2. Raw estimates of change in Northern Glaciated Plains Ecoregion land cover, computed for 

each of four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 1.4 0.3 1.1 1.7 0.2 13.0 0.2

1980–1986 1.4 0.3 1.1 1.7 0.2 14.4 0.2

1986–1992 2.4 0.5 1.8 2.9 0.4 15.2 0.4

1992–2000 4.1 1.0 3.1 5.2 0.7 16.8 0.5

Estimate of change, in square kilometers

1973–1980 2,008 386 1,622 2,393 261 13.0 287

1980–1986 1,960 418 1,542 2,378 282 14.4 327

1986–1992 3,333 749 2,584 4,082 507 15.2 556

1992–2000 5,860 1,458 4,402 7,318 986 16.8 733
Chapter 7—Northern Glaciated Plains Ecoregion 75

Table 4. Principal land-cover conversions in Northern Glaciated Plains Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 496 204 138 0.4 24.7

Water Wetland 478 220 149 0.3 23.8

Agriculture Grassland/Shrubland 296 186 126 0.2 14.7

Wetland Agriculture 198 78 52 0.1 9.8

Wetland Water 193 64 43 0.1 9.6

Other Other 347 n/a n/a 0.2 17.3

Totals 2,008 1.4 100.0

1980–1986 Agriculture Grassland/Shrubland 564 278 188 0.4 28.8

Wetland Water 344 122 83 0.2 17.6

Grassland/Shrubland Agriculture 339 204 138 0.2 17.3

Water Wetland 255 72 48 0.2 13.0

Agriculture Wetland 186 72 49 0.1 9.5

Other Other 272 n/a n/a 0.2 13.9

Totals 1,960 1.4 100.0

1986–1992 Agriculture Grassland/Shrubland 1414 558 378 1.0 42.4

Wetland Water 791 312 211 0.6 23.7

Water Wetland 247 94 63 0.2 7.4

Grassland/Shrubland Agriculture 226 130 88 0.2 6.8

Wetland Agriculture 211 73 49 0.1 6.3

Other Other 444 n/a n/a 0.3 13.3

Totals 3,333 2.4 100.0

1992–2000 Wetland Water 1,916 496 335 1.4 32.7

Agriculture Grassland/Shrubland 1,113 486 328 0.8 19.0

Agriculture Wetland 895 620 419 0.6 15.3

Grassland/Shrubland Agriculture 855 344 232 0.6 14.6

Agriculture Water 428 296 200 0.3 7.3

Other Other 654 n/a n/a 0.5 11.2

Totals 5,860 4.1 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 3,386 1,180 798 2.4 25.7

Wetland Water 3,244 814 550 2.3 24.6

Grassland/Shrubland Agriculture 1,915 602 407 1.4 14.6

Agriculture Wetland 1,356 758 513 1.0 10.3

Water Wetland 1,107 325 220 0.8 8.4

Other Other 2,152 n/a n/a 1.5 16.4

Totals 13,161 9.3 100.0
76 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Bryce, S.A., Omernik, J.M., Pater, D.E., Ulmer, Michael, 

Schaar, Jerome, Freeouf, Jerry, Johnson, Rex, Kuck, Pat, 

and Azevedo, S.H., 1998, Ecoregions of North and South 

Dakota: U.S. Geological Survey Ecoregion Map Series, 

scale 1:500,000, available at http://www.epa.gov/wed/

pages/ecoregions/ndsd_eco.htm.

Higgins, K.F., Naugle, D.E., and Forman, K.J., 2002, A case 

study of changing land use practices in the northern Great 

Plains, U.S.A.—An uncertain future for waterbird conservation, in Parsons, K.C., Brown, S.C., Erwin, R.M., 

Czech, H.A., and Coulson, J.C., eds., Managing wetlands 

for waterbirds—Integrated approaches: Waterbirds—The 

International Journal of Waterbird Biology, v. 25, Special 

Publication 2, p. 42–50.

Johnson, R.R., and Higgins, K.F., 1997, Formation of eastern 

South Dakota basins, Appendix A, in Wetland resources 

of eastern South Dakota (version July 22, 1999): Brookings, S. Dak., South Dakota State University, and Jamestown, N. Dak., U.S. Geological Survey Northern Prairie 

Wildlife Research Center database, accessed October 23, 

2008, at http://www.fws.gov/wetlands/Documents/WetlandResources-of-Eastern-South-Dakota.pdf.

Kirby, D.R., Krabbenhoft, K.D., Sedivec, K.K., and DeKeyeser, 

E.S., 2002, Wetlands in northern plains prairies—Benefitting 

wildlife and livestock: Rangelands, v. 24, no. 2, p. 22–25.

Kottek, M.J., Grieser, J., Beck, C., Rudolf, B., and Rubel, F., 

2006, World map of the Köppen-Geiger climate classification updated: Meteorologische Zeitschrift, v. 15, no. 3, p. 

259–263, available at http://www.schweizerbart.de/papers/

metz/detail/15/55034/World_Map_of_the_Koppen_.

Leathers, N., and Harrington, L.M.B., 2000, Effectiveness of conservation reserve programs and land “slippage” in southwestern 

Kansas: Professional Geographer, v. 52, no. 1, p. 83–93. 

Leistritz, F.L., Hodur, N.M., and Bangsund, D.A., 2002, 

Socioeconomic impacts of the conservation reserve program 

in North Dakota: Rural America, v. 17, no. 3, p. 57–65.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

PRISM Climate Group, 2006, Precipitation—Annual climatology (1971–2000): PRISM Climate Group, Oregon State University database, accessed August 29, 2008, at http://www.

prism.oregonstate.edu/documents/.

Shapley, M.D., Johnson, W.C., Engstrom, D.R., and Osterkamp, W.R., 2005, Late-Holocene flooding and drought 

in the northern great plains, USA, reconstructed from tree 

rings, lake sediments, and ancient shorelines: The Holocene, 

v. 15, no. 1, p. 29–41.

South Dakota Game, Fish and Parks, 2006, Lake Thompson 

recreation area: South Dakota Game, Fish and Parks database, accessed August 29, 2008, at http://gfp.sd.gov/stateparks/directory/lake-thompson/.

Todhunter, P.E., and Rundquist, B.C., 2004, Terminal lake 

flooding and wetland expansion in Nelson County, North 

Dakota: Physical Geography, v. 25, p. 68–85.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Chapter 8

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Northwestern Glaciated Plains Ecoregion

By Janis L. Taylor

Ecoregion Description

The Northwestern Glaciated Plains Ecoregion stretches 

from the Rocky Mountains across northern Montana, through 

northwestern and central North Dakota and central South 

Dakota, into northern Nebraska, covering about 160,684 km2

(62,040 mi2). The Canadian border forms the northern limit 

of the ecoregion, and the Missouri River makes up much of 

its southern and western border (fig. 1), although the large 

reservoirs along the Missouri River created by dams on the 

98°

50°

46°

48°

44°

112° 110° 108° 106° 104° 102° 100°

46°

44°

42°

Northwestern

Great Plains

Wyoming

Basin

WCBP

Middle

Rockies

MRK

WHP Nebraska

Sand Hills

Northern

Glaciated Plains

LAP

LAP

MVFP

MRK

MRK

SRK

SRB

CBR

MVFP

MVFP

MVFP

MVFP

MVFP

NRK

NRK

NRK

MRK

MRK

CANADA

0 50 100 150 200 Miles

0 50 100 150 200 Kilometers

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

NEBRASKA

WYOMING

MONTANA

CANADA

Lake Sakakawea Fort Peck

Reservation

Fort Berthold

Reservation

Rocky Boy’s

Reservation Fort

Belknap

Reservation

Fort Peck

Lake

Chester

Marias

River

M issouri River

Milk River

SOUTH

DAKOTA

NORTH

DAKOTA

MT

WY SD

NE

ND

Northwestern

Glaciated

Plains Ecoregion

Missouri River

river (for example, Lake Sakakawea in North Dakota and 

Fort Peck Lake in Montana) are not part of the ecoregion. 

This ecoregion is located between the more level and moister 

Northern Glaciated Plains Ecoregion to the east and the more 

topographically irregular and drier Northwestern Great Plains 

Ecoregion to the south (Omernik, 1987; U.S. Environmental 

Protection Agency, 1997; Woods and others, 1999). Other 

ecoregions that abut the Northwestern Glaciated Plains 

Figure 1. Map of Northwestern Glaciated Plains Ecoregion and surrounding ecoregions, showing land-use/land-cover classes from 

1992 National Land Cover Dataset (Vogelmann and others, 2001); note that not all land-use/land-cover classes shown in explanation 

may be depicted on map; note also that, for this “Status and Trends of Land Change” study, transitional land-cover class was subdivided 

into mechanically disturbed and nonmechanically disturbed classes. Squares indicate locations of 10 x 10 km sample blocks analyzed 

in study. Index map shows locations of geographic features mentioned in text. Abbreviations for Great Plains ecoregions are listed in 

appendix 2. Also shown are parts of two Western United States ecoregions: Montana Valley and Foothill Prairies (MVFP) and Northern 

Rockies (NRK). See appendix 3 for definitions of land-use/land-cover classifications.
78 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

gravel benches and in the alluvial river valleys. Further east, 

extensive grain farms of wheat, soybeans, sunflowers (fig. 

4A), and corn are common, as are hay and oilseed crops (fig. 

4B). The native vegetation is a mixed-grass prairie consisting 

primarily of blue grama (Bouteloua gracilis), needlegrass 

(Stipa spp.), and wheatgrass (Pascopyrum spp.). Oil and gas 

production also occurs throughout the ecoregion, primarily in 

the western part.

Most of the land within the Northwestern Glaciated 

Plains Ecoregion is privately owned. Towns are small and 

there is little developed land. The four Indian reservations 

in the ecoregion are the Fort Berthold Reservation in North 

Dakota and the Rocky Boy’s, Fort Belknap, and Fort Peck 

Reservations in Montana. The rural counties and small towns 

(fig. 5) that constitute this ecoregion mostly are dependent on 

agricultural and are isolated from larger metropolitan areas. 

From 1970 to 2000, only 5 of the 38 counties that are entirely 

or partly within the ecoregion increased in population (table 1) 

(U.S. Census Bureau, 1970–2000 [various years]).

Ecoregion are the Western Corn Belt Plains and the Nebraska 

Sand Hills Ecoregions to the south and the Montana Valley 

and Foothill Prairies and the Northern Rockies Ecoregions to 

the west (fig. 1).

Continental glaciers deposited the gravelly outwash 

material that marks the western and southwestern border of the 

ecoregion. Brown clay loam soils and gravelly areas derived 

from glacial tills are common. Groundwater is shallow and 

plentiful, and the area is dotted with numerous semipermanent 

and seasonal wetlands, locally referred to as “prairie potholes” 

(fig. 2). These wetlands and larger, shallow lakes are rich in 

wildlife. Rivers that flow through the Northwestern Glaciated 

Plains Ecoregion include the Marias, Milk, and Missouri Rivers.

The ecoregion, which is in the rain shadow of the 

Rocky Mountains, has a semiarid climate characterized 

by cold winters, hot summers, low humidity, light rainfall, 

and plentiful sunshine. Land uses such as dryland farming 

and grazing have been shaped by the semiarid climate and 

strong, drying winds. In the west, rangeland and wheat fields 

are widespread (fig. 3), with agriculture on the undissected 

Figure 2. Typical prairie pothole, in Northwestern Glaciated 

Plains Ecoregion.

Figure 3. Wheat fields in distance and grassland in foreground, 

in Northwestern Glaciated Plains Ecoregion.

Figure 4. Agricultural land uses in Northwestern Glaciated 

Plains Ecoregion. A, Field of sunflowers. B, Safflower in bloom.

A

B
Chapter 8—Northwestern Glaciated Plains Ecoregion 79

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Northwestern Glaciated 

Plains Ecoregion between 1973 and 2000 is 14.1 percent 

(table 2). Of that total, 10.7 percent changed one time, and 3.4 

percent changed two or more times (table 2). This ecoregion 

had the highest overall spatial change among all 17 Great 

Plains ecoregions (fig. 6).

Total change during the study period ranged from a low 

of 2.6 percent of the ecoregion between 1973 and 1980 and 

between 1980 and 1986 to a high of 6.6 percent between 

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in

four time

periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Figure 5. Washington Avenue, a main street in Chester, Montana, 

in Northwestern Glaciated Plains Ecoregion. 

Figure 6. Overall spatial change in Northwestern Glaciated 

Plains Ecoregion (NWGLP; darker bars) compared with that of all 

17 Great Plains ecoregions (lighter bars). Each horizontal set of 

bars shows proportions of ecoregion that experienced change 

during one, two, three, or four time periods; highest level of spatial 

change in Northwestern Glaciated Plains Ecoregion (four time 

periods) labeled for clarity. See table 3 for years covered by each 

time period. See appendix 2 for key to ecoregion abbreviations.

Figure 7. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Northwestern 

Glaciated Plains Ecoregion are represented by red bars in each 

time period.

1992 and 2000 (table 3). After normalizing to an annual rate 

of change to adjust for uneven time periods (fig. 7), the rates 

ranged from a low of 0.4 percent per year between 1973 and 

1980 and between 1980 and 1986 to a high of 1.0 percent 

per year between 1986 and 1992 (table 3; fig. 7). The period 

between 1992 and 2000 had an annual rate of change of 0.8 

percent per year (table 3; fig. 7).

Agriculture, grassland/shrubland, and wetland constituted 

97.9 percent (157,130 km2) of the ecoregion in 1973 (table 4). 

Agriculture decreased from 60.8 percent of the ecoregion in 

1973 to 57.1 percent in 2000 (table 4). Grassland/shrubland 

increased from 33.9 percent in 1973 to 37.3 percent in 2000 

(table 4). Grassland/shrubland and agriculture both had a gross 

change (the total area converting into and out of a class) of 

about 9.9 percent of ecoregion area during the entire study 

period, whereas wetland decreased 1.2 percent and water 

increased 1.3 percent during that same period (table 4; fig. 8).

Between 1973 and 2000, the most common land-cover 

conversion was from agriculture to grassland/shrubland 

(14,688 km2), which constituted 50.9 percent of all changes 

(table 5). The second most common conversion was grassland/

shrubland to agriculture (9,027 km2), 31.3 percent of all 

changes (table 5). Conversion from grassland/shrubland to 

agriculture was the leading conversion in the first two time 

periods (table 5). After 1986, the leading conversion was 

from agriculture to grassland/shrubland. Between 1986 and 

1992, more than three times the area that was converted to 

agriculture in the two previous time periods was converted 

to grassland/shrubland (fig. 8). Other notable conversions 

included wetland to water and water to wetland. Between 

1992 and 2000, the area of water more than doubled, most of 

it coming from the wetland land-cover class.
80 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

−6

−4

−2

0

2

4

6

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Figure 8. Normalized average net change in Northwestern 

Glaciated Plains Ecoregion by time period for each land-cover 

class. Bars above zero axis represent net gain, whereas bars 

below zero represent net loss. Note that not all land-cover classes 

shown in explanation may be represented in figure. See appendix 

3 for definitions of land-use/land-cover classifications.

Most of the change that occurred in the Northwestern 

Glaciated Plains Ecoregion between 1973 and 2000 can be 

attributed to anthropogenic drivers, specifically the gains and 

losses of grassland/shrubland and agriculture. In the 1970s, 

soaring wheat prices driven by foreign grain purchases, 

government incentives, and high land values resulted in the 

conversion of large areas of grazing land or native grassland 

to agriculture (Watts and others, 1983; Garrett-Davis, 2004). 

The practice of fallowing in alternating summers allowed for 

successful small-grain farming, even in areas having marginal 

soils (Bryce and others, 1998; Woods and others, 1999). 

However, in the 1980s, foreign exports of grain declined 

sharply and farm land prices plummeted. In 1985, the U.S. 

Department of Agriculture established the Conservation 

Reserve Program (CRP) to remove highly erodible land 

from agricultural production (Ribaurdo and others, 1990). 

By the year 2000, more land in Montana was enrolled in 

CRP than in either North Dakota or South Dakota (table 6) 

(U.S. Department of Agriculture, 2008). Conversion from 

agriculture to grassland/shrubland peaked between 1986 and 

1992, and this trend continued throughout the 1990s, although 

at a slower rate. 

Also in the 1990s, soybeans and other genetically 

modified crops were planted in areas once considered too dry 

to support them, especially in North Dakota and South Dakota. 

These new crops, along with crop insurance, decreased the 

risk of farming in drier areas that had poorer soil quality 

(Higgins and others, 2002). Agriculture and livestock grazing 

will remain as the major land uses in the ecoregion as new 

crops and farming methods will continue to create changes. 

The trend towards biofuel production also will generate 

change in the coming years, perhaps increasing incentives for 

producing certain crops.

Changes to water and wetland primarily were driven by 

wet-and-dry weather cycles, the 1990s being a much wetter 

decade than previous decades (Garbrecht and Rossel, 2002). 

However, some wetland change resulted from the expansion 

of arable land. In drier years, farmers have access to wetland 

areas to harvest wild grass hay. In some cases, wetlands are 

drained and the land is incorporated in adjacent cropland 

(Leitch and Danielson, 1979). 

Protection of grasslands and wetlands for wildlife habitat 

is being promoted by conservationists, the tourism industry, 

and outfitters. Some consider grasslands to be the most 

threatened ecosystem in the United States (Johnson, 2000). 

The tourism industry sees improvements in wildlife habitat 

as a means of attracting more visitors to small towns to view 

wildlife; outfitters see it as a means to attract more hunters and 

fishermen into the ecoregion. Collectively, increased visitation 

improves economic vitality of these small towns, as people 

work hard to make a living in the Northwestern Glaciated 

Plains Ecoregion. Other changes to the rural communities 

across the ecoregion will be stimulated as economic 

opportunities expand.
Chapter 8—Northwestern Glaciated Plains Ecoregion 81

Table 1. Population levels and total amounts of population change between 1970 and 2000, 

as well as future population estimates, of counties that intersect Northwestern Glaciated 

Plains Ecoregion (U.S. Census Bureau, 1970–2000 [various years]).

[n/a, not available]

State County

Population Population 

change, 

1970–2000

Estimated 

population, 2007 1970 1980 1990 2000

Montana Blaine 6,727 6,999 6,728 7,009 282 6,550

Chouteau 6,473 6,092 5,452 5,970 –503 5,254

Daniels 3,083 2,835 2,266 2,017 –1,066 1,650

Hill 17,358 17,985 17,654 16,673 –685 16,568

Liberty 2,359 2,329 2,295 2,158 –201 1,796

Phillips 5,386 5,367 5,163 4,601 –785 3,948

Richland 9,837 12,243 10,716 9,667 –170 9,182

Roosevelt 10,365 10,467 10,999 10,620 255 10,148

Sheridan 5,779 5,414 4,732 4,105 –1,674 3,373

Valley 11,471 10,250 8,239 7,675 –3,796 6,899

Toole 5,839 5,559 5,046 5,267 –572 5,144

Estimated 

population, 2006

North Dakota

Burleigh 40,714 54,811 60,131 69,416 28,702 75,384

Divide 4,564 3,494 2,899 2,283 –2,281 2,092

Emmons 7,200 5,877 4,830 4,331 –2,869 3,645

Kidder 4,362 3,833 3,332 2,753 –1,609 2,453

Logan 4,245 3,493 2,847 2,308 –1,937 1,999

McIntosh 5,545 4,800 4,021 3,390 –2,155 2,956

McLean 11,251 12,383 10,457 9,311 –1,940 8,543

Mountrail 8,437 7,679 7,021 6,631 –1,806 6,442

Sheridan 3,232 2,819 2,148 1,710 –1,522 1,408

Stutsman 23,550 24,154 22,241 21,908 –1,642 20,761

Wells 7,847 6,979 5,864 5,102 –2,745 4,432

Williams 19,301 22,237 21,129 19,761 460 19,456

Estimated 

population, 2006

South Dakota Aurora 4,183 3,628 3,135 3,058 –1,125 n/a 

Brule 5,870 5,245 5,485 5,364 –506 5,167

Campbell 2,866 2,243 1,965 1,782 –1,084 1,494

Charles Mix 9,994 9,680 9,131 9,350 –644 9,224

Douglas 4,569 4,181 3,746 3,458 –1,111 3,168

Edmunds 5,548 5,159 4,356 4,367 –1,181 4,062

Faulk 3,893 3,327 2,744 2,640 –1,253 2,339

Gregory 6,710 6,015 5,359 4,792 –1,918 4,268

Hand 5,883 4,948 4,272 3,741 –2,142 3,323

Hughes 11,632 14,220 14,817 16,481 4,849 16,946

Jerauld 3,310 2,929 2,425 2,295 –1,015 2,071

McPherson 5,022 4,027 3,228 2,904 –2,118 2,565

Potter 4,449 3,674 3,190 2,693 –1,756 2,321

Sully 2,362 1,990 1,589 1,556 –806 1,435

Walworth 7,842 7,011 6,087 5,974 –1,868 5,425
82 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 2. Percentage of Northwestern Glaciated 

Plains Ecoregion land cover that changed at least one 

time during study period (1973–2000) and associated 

statistical error.

[Most sample pixels remained unchanged (85.9 percent), 

whereas 14.1 percent changed at least once throughout study 

period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 10.7 1.8 8.9 12.5 1.2 11.4

2 3.0 0.8 2.2 3.8 0.5 18.2

3 0.3 0.2 0.1 0.5 0.1 40.1

4 0.1 0.0 0.0 0.1 0.0 44.9

Overall 

spatial 

change

14.1 2.2 11.9 16.4 1.5 10.7

Table 3. Raw estimates of change in Northwestern Glaciated Plains 

Ecoregion land cover, computed for each of four time periods between 1973 

and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each time period]

Period

Total change

(% of 

ecoregion)

Margin 

of error

(+/− %)

Lower 

bound

(%)

Upper 

bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average 

rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.6 0.6 2.0 3.2 0.4 15.6 0.4

1980–1986 2.6 0.7 1.9 3.3 0.5 18.5 0.4

1986–1992 6.1 1.3 4.8 7.4 0.9 14.3 1.0

1992–2000 6.6 1.5 5.1 8.1 1.0 15.0 0.8

Estimate of change, in square kilometers

1973–1980 4,210 973 3,237 5,183 658 15.6 601

1980–1986 4,158 1,136 3,022 5,294 768 18.5 693

1986–1992 9,838 2,081 7,757 11,919 1,407 14.3 1,640

1992–2000 10,628 2,356 8,271 12,984 1,593 15.0 1,328
Chapter 8—Northwestern Glaciated Plains Ecoregion 83

Table 4. Estimated area (and margin of error) of each land-cover class in Northwestern Glaciated Plains Ecoregion, calculated five 

times between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed Mechanically 

disturbed Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 1.3 0.5 0.3 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.5 0.3 33.9 5.9 60.8 5.9 3.2 1.1 0.0 0.0

1980 1.4 0.6 0.3 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.5 0.3 32.9 5.7 61.6 5.8 3.1 1.1 0.0 0.0

1986 1.5 0.6 0.3 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.5 0.3 32.7 5.6 61.9 5.6 3.0 1.0 0.0 0.0

1992 1.2 0.5 0.4 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.5 0.3 37.1 5.8 57.4 5.9 3.3 1.1 0.0 0.0

2000 2.6 1.0 0.4 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.5 0.3 37.3 5.8 57.1 5.9 2.0 0.6 0.0 0.0

Net

change 1.3 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.4 1.7 –3.6 1.7 –1.2 0.6 0.0 0.0

Gross

change 2.5 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.9 2.0 9.9 2.0 2.3 1.0 0.0 0.0

Area, in square kilometers

1973 2,109 831 499 278 0 0 8 6 116 103 822 480 54,410 9,457 97,635 9,478 5,085 1,798 0 0

1980 2,265 889 520 294 6 8 9 8 112 103 827 476 52,939 9,214 99,012 9,295 4,993 1,717 0 0

1986 2,467 913 528 300 0 0 10 7 116 103 832 476 52,486 8,972 99,457 9,039 4,788 1,656 0 0

1992 1,911 842 569 326 1 1 17 15 118 103 835 477 59,669 9,382 92,260 9,416 5,305 1,846 0 0

2000 4,248 1,554 578 332 0 1 19 13 113 103 833 477 59,942 9,248 91,774 9,484 3,175 999 0 0

Net

change 2,139 1,072 80 66 0 1 11 9 –3 4 11 19 5,532 2,772 –5,860 2,775 –1,910 1,002 0 0

Gross

change 4,062 1,673 80 66 14 17 24 20 15 22 24 18 15,970 3,212 15,952 3,234 3,692 1,572 0 0
84 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 5. Principal land-cover conversions in Northwestern Glaciated Plains Ecoregion, showing amount of area changed (and 

margin of error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during 

overall study period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” class are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 2,438 840 568 1.5 57.9

Agriculture Grassland/Shrubland 1,000 317 214 0.6 23.8

Wetland Water 376 240 162 0.2 8.9

Water Wetland 254 157 106 0.2 6.0

Agriculture Wetland 33 28 19 0.0 0.8

Other Other 109 n/a n/a 0.1 2.6

Totals 4,210 2.6 100.0

1980–1986 Grassland/Shrubland Agriculture 1,976 739 500 1.2 47.5

Agriculture Grassland/Shrubland 1,529 669 452 1.0 36.8

Wetland Water 383 227 154 0.2 9.2

Water Wetland 173 100 67 0.1 4.2

Agriculture Wetland 19 13 9 0.0 0.5

Other Other 78 n/a n/a 0.0 1.9

Totals 4,158 2.6 100.0

1986–1992 Agriculture Grassland/Shrubland 7,997 1,968 1,331 5.0 81.3

Grassland/Shrubland Agriculture 833 337 228 0.5 8.5

Water Wetland 674 370 250 0.4 6.8

Wetland Water 139 89 60 0.1 1.4

Wetland Agriculture 37 19 13 0.0 0.4

Other Other 159 n/a n/a 0.1 1.6

Totals 9,838 6.1 100.0

1992–2000 Agriculture Grassland/Shrubland 4,162 1,508 1,020 2.6 39.2

Grassland/Shrubland Agriculture 3,780 1,209 817 2.4 35.6

Wetland Water 2,276 1,089 736 1.4 21.4

Grassland/Shrubland Water 120 100 68 0.1 1.1

Water Wetland 112 103 70 0.1 1.1

Other Other 179 n/a n/a 0.1 1.7

Totals 10,628 6.6 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 14,688 3,103 2,098 9.1 50.9

Grassland/Shrubland Agriculture 9,027 1,947 1,316 5.6 31.3

Wetland Water 3,172 1,388 939 2.0 11.0

Water Wetland 1,212 514 347 0.8 4.2

Grassland/Shrubland Water 159 110 74 0.1 0.6

Other Other 574 n/a n/a 0.4 2.0

Totals 28,834 17.9 100.0
Chapter 8—Northwestern Glaciated Plains Ecoregion 85

State County Area (km2)

1986 1992 2000

Montana Blaine 0 469 651

Chouteau 4 613 950

Daniels 13 592 594

Hill 0 675 1,078

Liberty 0 331 486

Phillips 16 515 682

Richland 8 296 453

Roosevelt 13 571 694

Sheridan 14 697 596

Valley 0 821 824

Totals 68 5,579 6,357

North Dakota Burleigh 3 409 382

Divide 4 396 269

Emmons 2 250 285

Kidder 29 438 446

Logan 0 238 232

McIntosh 2 183 237

McLean 1 401 292

Mountrail 0 383 204

Sheridan 0 261 240

Stutsman 3 675 711

Wells 1 268 271

Williams 0 219 217

Totals 45 4,121 3,786

South Dakota Aurora 4 42 55

Brule 0 27 19

Campbell 0 125 161

Charles Mix 0 33 28

Douglas 0 6 16

Edmunds 0 289 99

Faulk 0 93 41

Gregory 0 20 10

Hand 0 70 131

Hughes 0 48 41

Jerauld 0 87 47

McPherson 2 256 185

Potter 0 160 112

Sully 0 84 79

Walworth 0 124 63

Totals 6 1,464 1,087

Table 6. Areas (in square kilometers) of cumulative enrollment in 

Conservation Reserve Program by year of counties that intersect 

Northwestern Glaciated Plains Ecoregion (U.S. Department of 

Agriculture, 2008). 
86 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Bryce, S.A., Omernik, J.A., Pater, D.E., Ulmer, Michael, 

Schaar, Jerome, Freeouf, Jerry, Johnson, Rex, Kuck, Pat, 

and Azevedo, S.H., 1998, Ecoregions of North and South 

Dakota: U.S. Geological Survey Ecoregion Map Series, 

scale 1:500,000, available at http://www.epa.gov/wed/

pages/ecoregions/ndsd_eco.htm.

Garbrecht, J.D., and Rossel, F.E., 2002, Decade-scale precipitation increase in the Great Plains at end of 20th century: 

Journal of Hydrologic Engineering, v. 7, no. 1, p. 64–75.

Garrett-Davis, Josh, 2004, The greening of the plains: High 

Country News, August 2, 2004, accessed August 5, 2005, at 

http://www.hcn.org/issues/279/14896.

Higgins, K.F., Naugle, D.E., and Forman, K.J., 2002, A 

case study of changing land use practices in the northern 

Great Plains, U.S.A.—An uncertain future for waterbird 

conservation, in Parsons, K.C., Brown, S.C., Erwin, R.M., 

Czech, H.A., and Coulson, J.C., eds., Managing wetlands 

for waterbirds—Integrated approaches: Waterbirds—The 

International Journal of Waterbird Biology, v. 25, Special 

Publication 2, p. 42–50.

Johnson, D.H., 2000, Grassland bird use of Conservation 

Reserve Program fields in the Great Plains, in Heard, 

L.P., Allen, A.W., Best, L.B., Brady, S.J., Burger, W., 

Esser, A.J., Hackett, E., Johnson, D.H., Pederson, R.L., 

Reynolds, R.E., Rewa, C., Ryan, M.R., Molleur, R.T., 

and Buck., P. (Hohman, W.L., and Halloum, D.J., eds.), A 

comprehensive review of farm bill contributions to wildlife 

conservation, 1985–2000: U.S. Department of Agriculture, 

Natural Resources Conservation Service, Wildlife Habitat 

Management Institute, Technical Report USDA/NRCS/

WHMI-2000, p. 19–33, accessed January 9, 2006, at 

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/

nrcs143_012881.pdf.

Leitch, J.A., and Danielson, L.E., 1979, Social, economic, 

and institutional incentives to drain or preserve prairie 

wetlands: St. Paul, University of Minnesota, Department 

of Agriculture and Applied Economics, Economic Report 

ER79-6.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Ribaurdo, M.O., Colacicco, D., Langner, L.L., Piper, S., and 

Schaible, G.D., 1990, Natural resources and users benefit 

from the Conservation Reserve Program: U.S. Department 

of Agriculture, Resource and Technology Division, 

Economic Research Service, Agricultural Economic Report 

No. 627, p. 6–17.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed December 3, 2008, at http://www.census.gov/prod/

www/decennial.html.

U.S. Department of Agriculture, 2008, Conservation Reserve 

Program—Cumulative enrollment by year (by county, FY 

1986–FY 2007): U.S. Department of Agriculture, Farm 

Services Agency database, accessed December 3, 2008, at 

http://www.fsa.usda.gov/Internet/FSA_File/public.xls.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Watts, M.J., Bender, L.D., and Johnson, J.B., 1983, Economic 

incentives for converting rangeland to cropland: Bozeman, 

Montana State University, Cooperative Extension Service 

Bulletin 1302, p. 8–18.

Woods, A.J., Omernik, J.M., Nesser, J.A., Shelden, J., and 

Azevedo, S.H., 1999, Ecoregions of Montana: U.S. Geological 

Survey Ecoregion Map Series, scale 1:1,500,000, available at 

http://www.epa.gov/wed/pages/ecoregions/mt_eco.htm.
98° 96° 94° 92° 90°

44°

42°

40°

Driftless Area

Central

Irregular Plains

Northern

Glaciated Plains

Central

Great Plains

North Central

Hardwood Forests

NLF

Flint Hills

CCBP

IRL

OH

NSH

NWGLP

0 50 75 25 MILES

0 5025 75 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

IOWA

MINNESOTA

WISCONSIN

NEBRASKA

SOUTH

DAKOTA

I L

MISSOURI

KANSAS

Des Moines

Omaha

Lincoln

Norfolk Manning

Cedar

Rapids

Dubuque

IOWA

COUNTY

Sioux City

WINNEBAGO

COUNTY

Walford

Sioux Falls

MINNEHAHA COUNTY WATONWAN

COUNTY

Miss ouri Ri v e r

D e s M o i n e s R i v e r

M i s s issi p p i R i v e r

Chapter 9

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Western Corn Belt Plains Ecoregion

By Roger F. Auch

Ecoregion Description 

The Western Corn Belt Plains Ecoregion is centered in Iowa, 

with parts extending into southern Minnesota, eastern Nebraska, 

northeastern Kansas, northwestern Missouri, and small areas 

of western Wisconsin and southeastern South Dakota (fig.1),

covering about 216,363 km2 (83,538 mi2). The ecoregion is 

surrounded by (clockwise, from 

its northernmost point) the North 

Central Hardwood Forests, Driftless 

Area, Central Corn Belt Plains, 

Interior River Lowlands, Central 

Irregular Plains, Flint Hills, Central 

Great Plains, Nebraska Sand Hills, 

Northwestern Glaciated Plains, 

and Northern Glaciated Plains 

Ecoregions (fig. 1) (Omernik, 1987; 

U.S. Environmental Protection 

Agency, 1997).

The climate of the Western 

Corn Belt Plains Ecoregion is 

considered to be continental (hot 

summers and cold winters). Average 

annual precipitation amounts range 

from 610 to 915 mm (24–36 in.), 

slightly less in the northwestern part of the ecoregion (Kottek 

and others, 2006; PRISM Climate Group, 2006). The topography 

is level-to-rolling plains underlain by glaciated till, with hilly 

loess-covered plains in the western part (Omernik, 1987; U.S. 

Environmental Protection Agency, 2002) (fig. 2).

Figure 1. Map of Western Corn Belt 

Plains Ecoregion and surrounding 

ecoregions, showing land-use/landcover classes from 1992 National Land 

Cover Dataset (Vogelmann and others, 

2001); note that not all land-use/landcover classes shown in explanation 

may be depicted on map; note also 

that, for this “Status and Trends of 

Land Change” study, transitional landcover class was subdivided into mechanically disturbed and nonmechanically 

disturbed classes. Squares indicate locations of 10 x 10 km sample blocks 

analyzed in study. Index map shows locations of geographic features mentioned 

in text. Abbreviations for Great Plains ecoregions are listed in appendix 2. Also 

shown are five Midwest–South Central United States ecoregions: Central Corn 

Belt Plains (CCBP), Driftless Area, Interior River Lowland (IRL), North Central 

Hardwood Forests, and Northern Lakes and Forests (NLF). See appendix 3 for 

definitions of land-use/land-cover classifications.
88 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

The Western Corn Belt Plains Ecoregion in the first half 

of the 19th century was predominantly tallgrass prairie, forest 

(both riparian and oak-prairie savanna), and wetlands (both 

herbaceous marshes and wooded floodplains) (Dinsmore, 

1994; Karnitz and Asbjornsen, 2006). The combination of 

climate, topography, and soils in the ecoregion enabled EuroAmerican settlers during the second half of the 19th century 

to convert most of the existing land to farmland (primarily 

cropland). Draining of herbaceous wetlands to create more 

farmland peaked in the first decades of the 20th century 

(Vileisis, 1997; Timmerman, 2001). 

Agriculture continued to dominate the ecoregion during 

the study period (1973–2000). The Western Corn Belt Plains 

Ecoregion is a world leader in corn and soybean production 

(U.S. Environmental Protection Agency, 2002) (figs. 3A,B), 

although other crops such as alfalfa hay and wheat also are 

grown there. The agriculture land-use/land-cover class also 

includes pastureland used for livestock production such as 

hogs and beef cattle (figs. 3C,D).

Other land-use/land-cover classes present in smaller 

areas of the ecoregion include forest, grassland/shrubland, 

developed, wetland, water, and mining. Forests grew 

Figure 2. Landforms in Western Corn Belt Plains Ecoregion. A, Nearly level plains of glacial till in southwestern Minnesota. B, Hilly 

cropland in northeastern Nebraska. 

Figure 3. Crops and livestock production in Western Corn Belt Plains Ecoregion. A, Field of alfalfa hay and corn near Manning, Iowa. 

B, Soybean field in north-central Iowa. C, Hog confinement buildings in Watonwan County, Minnesota. D, Cattle feedlot in Minnehaha 

County, eastern South Dakota.

A

A

C

B

B

D
Chapter 9—Western Corn Belt Plains Ecoregion 89

Figure 4. Areas of grassland/shrubland in Western Corn Belt 

Plains Ecoregion. A, Grassy field on sloped land in Iowa County, 

Iowa. B, Prairie grasses, in wildlife habitat maintained by state and 

private conservation organizations, in southwestern Minnesota. C, 

Conservation Reserve Program field in northwestern Missouri.

Figure 5. Developed areas in Western Corn Belt Plains 

Ecoregion. A, Food-processing plant and other buildings in Cedar 

Rapids, Iowa. B, Farm equipment business, a common sight in 

many small towns in ecoregion.

primarily in the larger river valleys and in areas along the 

eastern and southern margins of the ecoregion (fig. 1). Other 

forested land may have been present in farm shelterbelts 

but may not have been wide enough (that is, discernable 

using a 60 m × 60 m mapping unit) to map continuously. 

Grassland/shrubland consisted of less intensively used grazing 

areas (usually in more topographically varied areas) and 

wildlife-habitat areas, as well as, in the latter parts of the 

study period, idled Conservation Reserve Program (CRP) 

farmland (fig. 4). Developed land was present in major cities 

such as Omaha, Nebraska, and Des Moines, Iowa, as well as 

in many small farm towns across the ecoregion (fig. 5). Little 

exurban development occurred except on the fringes of the 

cities. Wetland was a minor land-use/land-cover class in the 

ecoregion, present primarily in bottomland riparian areas and 

herbaceous marshes. 

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Western Corn Belt 

Plains Ecoregion between 1973 and 2000 is 3.2 percent 

(table 1). Compared to other Great Plains ecoregions, change 

in the ecoregion was low (fig. 6). The Western Corn Belt 

Plains Ecoregion changed less than the Northern Glaciated 

Plains and Northwestern Glaciated Plains Ecoregions to the 

B

B

A

A

C
90 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

northwest, the Nebraska Sand Hills and Central Great Plains 

Ecoregions to the southwest, and the Central Irregular Plains 

Ecoregion to the south, but it experienced more overall 

change than the Flint Hills Ecoregion to the south-southwest 

(fig. 6). Most of the change (2.6 percent) occurred only one 

time during the study period, but some areas (0.6 percent) 

experienced multiple changes (table 1). Typical examples 

of land that experienced multiple changes in the ecoregion 

were agricultural land taken out of production and converted 

to grassland/shrubland, as well as areas that shifted back and 

forth between wetland and water, owing to changing climatic 

cycles. The last two time periods (1986–1992, 1992–2000) 

had more change than the first two time periods (1973–1980, 

1980–1986) (table 2). When the uneven time periods were 

normalized to an annual rate of change, the periods between 

1986 and 1992 and between 1992 and 2000 had the highest 

rate of change (0.2 percent), and the periods between 1973 

and 1980 and between 1980 and 1986 had the lowest rate of 

change (0.1 percent) (fig. 7).

Land cover and land use within the Western Corn Belt 

Plains Ecoregion was fairly stable during the study period 

(1973–2000). Agriculture and grassland/shrubland had 

the most net change during the study period, followed by 

developed (table 3). Agriculture constituted 90 percent of 

the ecoregion in 1973, declining to 87.9 percent by 2000 

Figure 6. Overall spatial change in Western Corn Belt Plains 

Ecoregion (WCBP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that changed during one, two, three, or 

four time periods; highest level of spatial change in Western Corn 

Belt Plains Ecoregion (four time periods) labeled for clarity. See 

table 2 for years covered by each time period. See appendix 2 for 

key to ecoregion abbreviations.

Figure 7. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Western Corn Belt 

Plains Ecoregion are represented by red bars in each time period.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

(table 3) primarily through conversion to grassland/shrubland,

developed, and, to lesser extent, water and wetland (table 4). 

Related to this loss was a net gain of 1.4 percent in grassland/

shrubland (table 3). Most of the change from agriculture 

to grassland/shrubland occurred during the last two time 

periods (1986–1992, 1992–2000) when the CRP was in effect 

(table4). The CRP paid farmers to retire marginal cropland 

to native grasslands through contracts, usually 10 years in 

duration. The initial implementation of the CRP had the 

greatest effect between 1986 and 1992, when conversions 

from agriculture to grassland/shrubland increased substantially 

(table 4; fig. 8). Although some land in the ecoregion may have 

been under a second CRP contract by the year 2000, much 

grassland/shrubland reverted to agriculture between 1992 and 

2000, probably owing to CRP land being placed back into 

production (table 4; fig. 8) (Leathers and Harrington, 2000). 

The conversion of agriculture to water, mostly in the form of 

new reservoirs of various sizes, was a small but noteworthy 

factor in the loss of agriculture land cover. Agricultural land 

also was lost through grassland- and wetland-restoration 

efforts within the ecoregion, especially during the second half 

of the study period (Fletcher and Koford, 2003; Schilling and 

Spooner, 2006); however, on a ecoregional scale, such efforts 

affected only small areas of farmland. Grassland- and wetlandrestoration efforts can result in more permanent conversions 

of agricultural land, whereas conversions of agricultural land 

enrolled in the CRP can be temporary (fig. 9).

An increase in developed land was the third largest net 

change (0.5 percent) in the ecoregion between 1973 and 2000 

(table 3). The conversion of agriculture to developed was 

the most permanent change in the ecoregion. The Western 
Chapter 9—Western Corn Belt Plains Ecoregion 91

Figure 9. Restoration efforts in Western Corn Belt Plains 

Ecoregion. A, Tallgrass prairie conservation and restoration in 

northern Iowa. B, Wetlands restoration, in Winnebago County, 

Iowa, a cooperative effort by multiple parties. C, Federal- and statefunded wetlands restoration project in Winnebago County, Iowa. 

Figure 8. Normalized average net change in Western Corn Belt 

Plains Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications. 

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Corn Belt Plains Ecoregion gained an estimated 1,102 km2

of developed land (table 3), 1,033 km2 of which wasfrom 

agricultural land (table 4). The number of people needed 

to farm and support agricultural land continued to decrease 

during the study period, and many rural counties continued to 

decline in population (Waisanen, 2003). However, small- and 

medium-sized urban areas in the ecoregion attracted people, 

especially as service-based employment became a larger part 

of urban economies. Manufacturing remained as an important 

part of the economy of the ecoregion, and smaller cities 

benefited by physically growing by adding new, small-scale 

manufacturing plants (Waisanen, 2003) (fig. 10).

A

C

B
92 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Figure 10. Developed areas in Western Corn Belt Plains 

Ecoregion. A, Abandoned businesses in small east-central Iowa 

town, one of many farm towns in decline in ecoregion. B, New 

housing in Walford, Iowa, just southwest of Cedar Rapids. Most 

newly developed land was on edge of cities or in nearby small 

towns. C, New manufacturing plant that makes new steel products 

from scrap metal, in Norfolk, Nebraska, one of several small cities 

attracting new industries. 

A

C

B
Chapter 9—Western Corn Belt Plains Ecoregion 93

Table 2. Raw estimates of change in Western Corn Belt Plains Ecoregion land cover, 

computed for each of four time periods between 1973 and 2000, and associated error at 

85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each time period]

Period

Total change

(% of

ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average 

rate

(% per year)

Estimate of change, in percent stratum

1973–1980 0.5 0.2 0.3 0.7 0.1 28.6 0.1

1980–1986 0.5 0.2 0.3 0.6 0.1 23.0 0.1

1986–1992 1.4 0.4 1.0 1.7 0.2 17.7 0.2

1992–2000 1.6 0.4 1.2 2.0 0.3 17.3 0.2

Estimate of change, in square kilometers

1973–1980 1,002 421 581 1,422 286 28.6 143

1980–1986 991 334 657 1,326 228 23.0 165

1986–1992 2,972 771 2,201 3,744 525 17.7 495

1992–2000 3,496 886 2,609 4,382 604 17.3 437

Table 1. Percentage of Western Corn Belt Plains Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (96.8 percent), whereas 3.2 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 2.6 0.7 1.9 3.3 0.5 17.5

2 0.6 0.2 0.4 0.7 0.1 20.0

3 0.0 0.0 0.0 0.1 0.0 35.1

4 0.0 0.0 0.0 0.0 0.0 44.6

Overall 

spatial 

change

3.2 0.8 2.5 4.0 0.5 16.1
94 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Estimated area (and margin of error) of each land-cover class in Western Corn Belt Plains Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/

Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.8 0.5 1.7 0.7 0.0 0.0 0.1 0.0 0.0 0.0 3.3 0.9 2.5 0.7 90.0 2.0 1.6 0.9 0.0 0.0

1980 0.8 0.5 1.8 0.8 0.0 0.0 0.1 0.0 0.0 0.0 3.2 0.9 2.5 0.7 89.8 2.1 1.7 1.0 0.0 0.0

1986 0.8 0.5 1.9 0.8 0.0 0.0 0.1 0.0 0.0 0.0 3.3 0.9 2.6 0.7 89.6 2.1 1.7 1.0 0.0 0.0

1992 0.8 0.5 2.0 0.9 0.0 0.0 0.1 0.0 0.0 0.0 3.3 0.9 3.7 0.9 88.4 2.3 1.7 1.0 0.0 0.0

2000 0.9 0.5 2.2 1.0 0.0 0.0 0.1 0.1 0.0 0.0 3.3 0.9 3.9 1.0 87.9 2.4 1.7 1.0 0.0 0.0

Net

change 0.1 0.2 0.5 0.3 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 1.4 0.4 –2.1 0.6 0.0 0.1 0.0 0.0

Gross

change 0.4 0.2 0.5 0.3 0.0 0.0 0.1 0.1 0.0 0.0 0.2 0.1 2.0 0.5 2.7 0.7 0.3 0.1 0.0 0.0

Area, in square kilometers

1973 1,745 1,121 3,670 1,479 9 13 131 59 9 13 7,061 1,924 5,452 1,460 194,763 4,378 3,523 2,040 0 0

1980 1,683 1,098 3,984 1,691 15 15 172 79 3 4 7,003 1,913 5,517 1,472 194,370 4,520 3,615 2,179 0 0

1986 1,776 1,123 4,109 1,775 9 10 178 81 9 12 7,073 1,934 5,731 1,504 193,890 4,613 3,588 2,166 0 0

1992 1,741 1,114 4,321 1,944 2 2 217 104 8 9 7,093 1,956 7,987 2,010 191,340 4,998 3,655 2,205 0 0

2000 1,952 1,159 4,772 2,143 17 16 245 122 11 14 7,088 1,943 8,406 2,066 190,276 5,267 3,597 2,216 0 0

Net

change 207 356 1,102 717 8 5 114 81 2 2 26 91 2,955 882 –4,487 1,331 74 210 0 0

Gross

change 774 391 1,102 717 50 37 218 114 20 27 341 111 4,414 1,151 5,794 1,443 560 258 0 0
Chapter 9—Western Corn Belt Plains Ecoregion 95

Table 4. Principal land-cover conversions in Western Corn Belt Plains Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of 

all changes (km2) (+/− km2) (km2)

1973–1980 Agriculture Developed 301 236 161 0.1 30.1

Water Wetland 159 153 104 0.1 15.9

Agriculture Grassland/Shrubland 155 80 54 0.1 15.4

Grassland/Shrubland Agriculture 89 74 51 0.0 8.9

Wetland Water 65 55 37 0.0 6.4

Other Other 233 n/a n/a 0.1 23.3

Totals 1,002 0.5 100.0

1980–1986 Agriculture Grassland/Shrubland 303 120 81 0.1 30.6

Agriculture Developed 114 95 65 0.1 11.5

Wetland Water 106 83 56 0.0 10.7

Water Wetland 69 52 35 0.0 7.0

Grassland/Shrubland Forest 55 38 26 0.0 5.5

Other Other 344 n/a n/a 0.2 34.7

Totals 991 0.5 100.0

1986–1992 Agriculture Grassland/Shrubland 2,311 702 478 1.1 77.8

Agriculture Developed 198 192 131 0.1 6.7

Water Wetland 89 83 57 0.0 3.0

Agriculture Wetland 46 46 31 0.0 1.6

Grassland/Shrubland Forest 42 27 19 0.0 1.4

Other Other 285 n/a n/a 0.1 9.6

Totals 2,972 1.4 100.0

1992–2000 Agriculture Grassland/Shrubland 1,514 606 413 0.7 43.3

Grassland/Shrubland Agriculture 1,014 403 274 0.5 29.0

Agriculture Developed 419 226 154 0.2 12.0

Agriculture Water 98 103 70 0.0 2.8

Wetland Water 59 50 34 0.0 1.7

Other Other 391 n/a n/a 0.2 11.2

Totals 3,496 1.6 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 4,283 1,137 774 2.0 50.6

Grassland/Shrubland Agriculture 1,175 461 314 0.5 13.9

Agriculture Developed 1,033 691 471 0.5 12.2

Water Wetland 334 203 138 0.2 4.0

Wetland Water 264 127 87 0.1 3.1

Other Other 1,372 n/a n/a 0.6 16.2

Totals 8,461 3.9 100.0
96 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Dinsmore, J.J., 1994, A country so full of game—The story of 

wildlife in Iowa: Iowa City, University of Iowa Press, 249 p.

Fletcher, R.J., Jr., and Koford, R.R., 2003, Changes in breeding bird populations with habitat restoration in northern 

Iowa: American Midland Naturalist, v. 150, p. 83–94.

Karnitz, Holly, and Asbjornsen, Heidi, 2006, Composition and 

age structure of a degraded tallgrass oak savanna in central 

Iowa: Natural Areas, v. 26, p. 179–186.

Kottek, M.J., Grieser, J., Beck, C., Rudolf, B., and Rubel, F., 

2006, World map of the Köppen-Geiger climate classification updated: Meteorologische Zeitschrift, v. 15, no. 3, p. 

259–263, available at http://www.schweizerbart.de/papers/

metz/detail/15/55034/World_Map_of_the_Koppen_Geiger_climate_classificat.

Leathers, N., and Harrington, L.M.B., 2000, Effectiveness of conservation reserve programs and land “slippage” in southwestern 

Kansas: Professional Geographer, v. 52, no. 1, p. 83–93. 

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

PRISM Climate Group, 2006, Precipitation—Annual climatology (1971–2000): PRISM Climate Group, Oregon 

State University database, accessed August 29, 2008, at 

http://prism.nacse.org/documents/.

Schilling, K.E., and Spooner, Jean, 2006, Effects of watershedscale land-use change on stream nitrate concentrations: 

Journal of Environmental Quality, v. 35, p. 2,132–2,145.

Timmerman, Janet, 2001, Draining the great oasis, in Amato, 

A.J., Timmerman, J., and Amato, J.A., eds., Draining the 

great oasis—An environmental history of Murray County, 

Minnesota: Marshall, Minn., Crossings Press, p. 125–141.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

U.S. Environmental Protection Agency, 2002, Primary distinguishing characteristics of level III ecoregions of the 

continental United States: U.S. Environmental Protection 

Agency database, accessed September 22, 2008, at http://

www.epa.gov/wed/pages/ecoregions/level_iii.htm.

Vileisis, Ann, 1997, Discovering the unknown landscape—A 

history of America’s wetlands: Washington, D.C., Island 

Press, 433 p.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Waisanen, P.J., 2003, Land-use and land-cover change in the 

Western Corn Belt Plains Ecoregion, 1970-2000: Brookings, South Dakota State University, M.S. thesis, 124 p.
East-Central Plains Ecoregions

Chapter 10

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Central Irregular Plains Ecoregion

By Krista A. Karstensen

Ecoregion Description 

The Central Irregular Plains Ecoregion encompasses 

122,589 km2 (47,332 mi2) of southern Iowa, northern and 

central Missouri, eastern Kansas, and northeastern Oklahoma 

(fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 

1997). The ecoregion is surrounded by (clockwise, from the 

north) the Western Corn Belt Plains, Interior River Lowland, 

Ozark Highlands, Boston Mountains, Arkansas Valley, Central 

Oklahoma/Texas Plains, and Flint Hills Ecoregions (fig. 1). The 

most populous cities in the ecoregion are Kansas City, Missouri, 

and Tulsa, Oklahoma, with populations of 441,545 and 393,049, 

respectively, in the year 2000 (U.S. Census Bureau, 2010).

The topography of the Central Irregular Plains Ecoregion 

is more variable than that of the Western Corn Belt Plains 

Ecoregion to the north but less irregular and less forested than 

that of the ecoregions to the south and east (Chapman and 

others, 2002). The northern part of the ecoregion (in northern 

Missouri and southern Iowa) ranges from flat to moderately 

hilly, and it includes natural wetlands along the Grand River.

The natural vegetation in the ecoregion is a grassland–oak 

woodland mosaic. The prairie grassland primarily is composed 

of little bluestem (Schizachyrium scoparium) and sideoats 

grama (Bouteloua curtipendula) grasses (Chapman and others, 

2002), both native grasses that have agricultural uses: little 

bluestem is a forage species that is readily grazed by livestock 

and also is suitable for hay, and sideoats grama is one of the 

most important range grasses as it can lengthen the grazing 

season and, therefore, increase the forage production (U.S. 

Department of Agriculture, 2002a,b). 

In addition to the Grand River, the Central Irregular Plains 

Ecoregion includes stretches of the Missouri, Chariton, Des 

Moines, Kansas, Arkansas, and Thompson Rivers and their 

tributaries. The ecoregion, which is in a mesic temperature 

regime, receives a mean annual precipitation of 800–1,000mm

96° 94° 92°

40°

38°

36°

Ozark

Highlands

COTP

Flint

Hills

Western Corn

Belt Plains

Boston Mountains

IRL

MAP

AV

CCBP

0 50 100 MILES

0 50 100 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

MISSOURI

KANSAS

IOWA

ARKANSAS

OKLAHOMA

N E I L

Des Moines

Grand

Thompson

Jasper

Tulsa Arkansas River

MississippiR.

Chari ot n

Graysville

KansasRiver

Hamilton

Misso uri Rive r

Figure 1. Map of Central Irregular Plains Ecoregion and surrounding 

ecoregions, showing land-use/land-cover classes from 1992 National 

Land Cover Dataset (Vogelmann and others, 2001); note that not all 

land-use/land-cover classes shown in explanation may be depicted 

on map; note also that, for this “Status and Trends of Land Change” 

study, transitional land-cover class 

was subdivided into mechanically 

disturbed and nonmechanically 

disturbed classes. Squares indicate 

locations of 10×10 km sample blocks

analyzed in study. Index map shows 

locations of geographic features 

mentioned in text. Abbreviations for 

Great Plains ecoregions are listed in 

appendix 2. Also shown are parts of

five Midwest–South Central United 

States ecoregions: Arkansas Valley 

(AV), Boston Mountains, Central Corn 

Belt Plains (CCBP), Interior River 

Lowland (IRL), and Ozark Highlands. 

See appendix 3 for definitions of landuse/land-cover classifications.
100 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

(32–40 in.) (Chapman and others, 2002). In 1993, the 

Mississippi River system flood (known informally as the “Great 

Flood of 1993;” Johnson and others, 2004) inundated a large part 

of the ecoregion’s agricultural areas in northern Missouri and 

southern Iowa. Although patterns of flooding in this ecoregion 

depend on basin size and topography, the high incidence of 

large floods in the central Midwest and upper Mississippi River 

valley (for example, the 1993 flood) also is due to the mesoscale 

convective complexes—large, multiple-celled, persistent 

thunderstorm systems largely fed by moisture from the Gulf of 

Mexico—that frequently strike the ecoregion (O’Connor and 

Costa, 2003).

Glacial tills form the parent material for most of the 

soil in Iowa and the northern part of Missouri, whereas the 

southern part of the ecoregion was not glaciated (Chapman 

and others, 2002). Loess deposits generally increase near the 

Missouri River (Chapman and others, 2002). The southwestern 

part of the ecoregion (west-central Missouri, western Kansas, 

and northern Oklahoma) has claypan soils and a smoother 

topography (Chapman, and others, 2002). 

Although the Central Irregular Plains Ecoregion has 

a variety of land uses, agriculture dominates much of the 

landscape. The gently rolling topography and generally fertile 

soils are conducive to various agricultural practices such as 

contour farming, which is common in Iowa and northern 

Missouri (Chapman and others, 2002). Crops common to 

the ecoregion include corn, soybeans, wheat (fig. 2), and 

sorghum (U.S. Department of Agriculture, 2009b,c,d,e). Cattle 

production also is an important land use (U.S. Department 

of Agriculture, 2009b,c,d,e). Most Iowa counties in this 

ecoregion have 50 percent or more of their land in agricultural 

production (U.S. Department of Agriculture, 2009b). The 

Conservation Reserve Program (CRP) is a Federal program 

created in 1985 to provide financial assistance to eligible 

farmers to help manage natural resource concerns on their 

land, particularly through the conversion of marginal 

agricultural land to grassland/shrubland.

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Central Irregular Plains 

Ecoregion between 1973 and 2000 is 7.3 percent (table 1).

Compared to other Great Plains ecoregions, change in the 

ecoregion was moderate, but it was greater than in two 

neighboring ecoregions: the Flint Hills Ecoregion, mostly 

rangeland, and the intensively cropped Western Corn Belt Plains 

Ecoregion (fig. 3). An estimated 6.5 percent of the ecoregion 

changed one time during the 27-year study period, while 0.7 

percent changed two times and 0.1 percent changed three times.

Change percentages varied only slightly from 1973 to 

2000, with the total change (percent of the ecoregion affected) 

ranging from a low of 1.8 percent to a high of 2.2 percent 

(table 2). The average annual rate of change was highest 

between 1980 and 1986, at 0.4 percent (444 km2) per year 

(table 2; fig. 4). 

In 2000, agriculture was the largest land-cover class in 

the ecoregion, estimated at 59.9 percent (73,466 km2), with 

a net decrease of 3.0 percent over the study period (table 3;

fig.5). Large areas of agricultural land were converted to 

grassland/shrubland and developed land. Forest was the 

second largest land-cover class, encompassing 20.4 percent 

(24,956 km2) of the ecoregion in 1973 and 20.0 percent 

(24,539 km2) in 2000 (table 3). Grassland/shrubland, the

third most extensive land-cover class, increased from 13.5 

percent (16,572 km2) of the ecoregion in 1973 to 15.9 

percent (19,462 km2) in 2000 (table 3).

Figure 2. Wheat field near Jasper, Missouri, in Central Irregular 

Plains Ecoregion.

Figure 3. Overall spatial change in Central Irregular Plains 

Ecoregion (CIP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that experienced change during one, 

two, three, or four time periods; highest level of spatial change 

in Central Irregular Plains Ecoregion (four time periods) labeled 

for clarity. See table 2 for years covered by each time period. See 

appendix 2 for key to ecoregion abbreviations.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods Change in

four time

periods
Chapter 10—Central Irregular Plains Ecoregion 101

Overall, the most common land-cover conversion in 

every study period was the conversion from agriculture to 

grassland/shrubland. Between 1973 and 2000, 5,366 km2

were converted from agriculture to grassland/shrubland 

(table 4). However, this conversion did not result in a large 

net increase in grassland/shrubland because, during the 

same time period, the second most common conversion 

was from grassland/shrubland to agricultural land (2,128 

km2). The inception of the Conservation Reserve Program 

(CRP) and the economic crisis of the 1980s may explain 

much of this conversion. Forested land also declined in the 

ecoregion, which can be attributed primarily to clearing for 

agricultural expansion. 

Economics play an important role in the land-use story 

of the Central Irregular Plains Ecoregion. Major factors 

influencing conversion of agricultural land to grassland/

shrubland during the study period include the economic crisis 

of the 1980s, the socioeconomic repercussions of the “Great 

Flood of 1993” (Johnson and others, 2004), and the CRP.

 The economic climate of the 1970s encouraged 

farmers to expand production to benefit from improved 

export opportunities, strong commodity prices, increased 

farm income, and higher farmland values. Abundant credit 

financed the expansion as high rates of inflation and low real 

interest rates encouraged investment in farmland, and many 

farmers took on heavy debt loads, becoming vulnerable to 

sudden shifts in economic forces (Stam and Dixon, 2004; 

Cofer and others, 2009).

The economic crisis of the early 1980s greatly changed 

these conditions as export markets contracted and input 

Figure 4. Normalized average net change in Central Irregular 

Plains Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.

Figure 5. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Central Irregular 

Plains Ecoregion are represented by red bars in each time period.

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

prices and interest rates rose. The financial stress became 

more severe when declines in farm commodity prices, 

income, and land values (the asset used to secure debt) made 

it difficult for some farmers to service their debts (Stam 

and Dixon, 2004; Cofer and others, 2009). The crisis may 

have had an influence in the amount of agricultural land 

that was converted to grassland/shrubland in the 1980s. 

The associated banking crisis of the early 1980s imposed 

particular economic hardship on small, family-operated 

farms as many farm banks failed, and many farms faced 

foreclosure. Many of these farms may have been converted 

from agricultural land to grassland/shrubland.

The “Great Flood of 1993” devastated cropland, also 

influencing land-use changes in the Central Irregular Plains 

Ecoregion. From April 1 to August 31, 1993, precipitation 

amounts approached 1,219 mm (48 in.) in east-central Iowa, 

surpassing the normal annual precipitation average of 762 to 

914 mm (30–36 in.) in that area (Johnson and others, 2004). 

The extent of the damage caused by the flood to agricultural 

resources shows how climatic influences may affect landcover change by decreasing agricultural production. 

The inception of the CRP in 1985 contributed 

significantly to the conversion from agriculture to grassland/
102 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

shrubland (fig. 6). The CRP annual cumulative enrollment 

statistics show that the acreage enrolled in CRP greatly 

increased between 1986 and 1992, from 321 km2 (79,400 

acres) to 5,058 km2 (1,250,000 acres), respectively, before 

declining in 2000 by about 647 km2 (160,000 acres) (U.S. 

Department of Agriculture, 2009a).

No-till conservation tillage was encouraged in many 

parts of the ecoregion in the 1980s, and it continues to 

be widely practiced. Conservation tillage provides a 

more economical way to manage cropland, and it likely 

contributed to grassland/shrubland being converted back to 

agriculture (fig. 7) (U.S. Department of Agriculture, 1997). 

Between 1990 and 2010, the population and settlements 

of the Amish—a distinctly rural people who live on and 

cultivate small but diversified farms—increased throughout 

the ecoregion (Elizabethtown College, 2010), possibly 

adding to the increase in agriculture.

Table 1. Percentage of Central Irregular Plains Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (92.7 percent), whereas 7.3 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 6.5 1.7 4.8 8.2 1.1 17.5

2 0.7 0.4 0.4 1.0 0.2 32.1

3 0.1 0.1 0.0 0.1 0.0 64.1

4 0.0 0.0 0.0 0.0 0.0 98.8

Overall 

spatial 

change

7.3 2.0 5.4 9.3 1.3 18.1 Figure 6. Land enrolled in Conservation Reserve Program, near 

Graysville, Missouri, in Central Irregular Plains Ecoregion.

Figure 7. Conservation tillage on farm near Hamilton, Missouri, 

in Central Irregular Plains Ecoregion.
Chapter 10—Central Irregular Plains Ecoregion 103

Table 2. Raw estimates of change in Central Irregular Plains Ecoregion land cover, computed for each 

of four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 1.8 0.6 1.2 2.4 0.4 22.3 0.3

1980–1986 2.2 0.8 1.3 3.0 0.6 25.6 0.4

1986–1992 2.0 0.6 1.4 2.7 0.4 20.8 0.3

1992–2000 2.2 0.8 1.3 3.0 0.6 25.9 0.3

Estimate of change, in square kilometers

1973–1980 2,218 734 1,484 2,951 495 22.3 317

1980–1986 2,663 1,012 1,652 3,675 683 25.6 444

1986–1992 2,511 774 1,737 3,285 522 20.8 418

1992–2000 2,644 1,017 1,628 3,661 686 25.9 331
104 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Estimated area (and margin of error) of each land-cover class in Central Irregular Plains Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically

disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.7 0.2 1.4 0.4 0.0 0.0 0.0 0.0 0.0 0.0 20.4 3.1 13.5 3.3 62.9 4.4 1.0 0.4 0.0 0.0

1980 0.7 0.2 1.5 0.5 0.1 0.1 0.0 0.0 0.0 0.0 20.1 3.1 13.8 3.4 62.7 4.4 1.0 0.4 0.0 0.0

1986 0.8 0.2 1.6 0.5 0.0 0.0 0.0 0.0 0.0 0.0 20.0 3.1 14.3 3.5 62.1 4.5 1.0 0.4 0.0 0.0

1992 0.9 0.2 1.8 0.7 0.0 0.0 0.1 0.0 0.0 0.0 20.0 3.1 15.2 3.7 60.9 4.6 1.0 0.4 0.0 0.0

2000 0.9 0.2 2.1 0.8 0.0 0.0 0.1 0.0 0.0 0.0 20.0 3.1 15.9 3.8 59.9 4.8 1.0 0.4 0.0 0.0

Net

change 0.2 0.1 0.7 0.4 0.0 0.0 0.1 0.0 0.0 0.0 –0.3 0.2 2.4 1.5 –3.0 1.6 0.0 0.0 0.0 0.0

Gross

change 0.3 0.1 0.7 0.4 0.2 0.1 0.1 0.0 0.0 0.0 0.7 0.2 4.2 1.3 4.8 1.4 0.0 0.0 0.0 0.0

Area, in square kilometers

1973 821 218 1,722 540 29 35 28 24 28 37 24,956 3,782 16,572 4,055 77,166 5,344 1,266 517 0 0

1980 831 213 1,894 596 88 88 54 30 35 38 24,697 3,751 16,912 4,202 76,813 5,399 1,265 517 0 0

1986 1,011 246 2,022 660 0 0 58 31 30 37 24,564 3,755 17,575 4,321 76,072 5,518 1,257 512 0 0

1992 1,059 247 2,259 798 5 8 73 36 29 37 24,570 3,766 18,694 4,533 74,648 5,694 1,253 510 0 0

2000 1,100 247 2,611 975 8 7 110 57 42 39 24,539 3,741 19,462 4,692 73,466 5,920 1,251 509 0 0

Net

change 279 127 889 537 –21 36 82 52 14 13 –418 290 2,890 1,888 –3,700 2,009 –16 20 0 0

Gross

change 389 147 892 536 219 177 84 52 29 33 873 254 5,116 1,643 5,907 1,734 40 24 0 0
Chapter 10—Central Irregular Plains Ecoregion 105

Table 4. Principal land-cover conversions in Central Irregular Plains Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Agriculture Grassland/Shrubland 905 381 257 0.7 40.8

Grassland/Shrubland Agriculture 585 480 324 0.5 26.4

Forest Grassland/Shrubland 146 108 73 0.1 6.6

Forest Agriculture 144 65 44 0.1 6.5

Agriculture Developed 106 116 78 0.1 4.8

Other Other 331 n/a n/a 0.3 14.9

Totals 2,218 1.8 100.0

1980–1986 Agriculture Grassland/Shrubland 1,342 606 409 1.1 50.4

Grassland/Shrubland Agriculture 648 450 304 0.5 24.3

Forest Grassland/Shrubland 106 96 65 0.1 4.0

Grassland/Shrubland Forest 95 65 44 0.1 3.6

Forest Agriculture 85 44 30 0.1 3.2

Other Other 388 n/a n/a 0.3 14.6

Totals 2,663 2.2 100.0

1986–1992 Agriculture Grassland/Shrubland 1,663 594 401 1.4 66.2

Grassland/Shrubland Agriculture 391 289 195 0.3 15.6

Agriculture Developed 136 85 57 0.1 5.4

Grassland/Shrubland Forest 73 39 26 0.1 2.9

Grassland/Shrubland Developed 70 83 56 0.1 2.8

Other Other 178 n/a n/a 0.1 7.1

Totals 2,511 2.0 100.0

1992–2000 Agriculture Grassland/Shrubland 1,456 878 592 1.2 55.0

Grassland/Shrubland Agriculture 505 312 211 0.4 19.1

Agriculture Developed 206 139 94 0.2 7.8

Grassland/Shrubland Developed 105 107 72 0.1 4.0

Grassland/Shrubland Forest 89 54 36 0.1 3.4

Other Other 284 n/a n/a 0.2 10.7

Totals 2,644 2.2 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 5,366 2,005 1,353 4.4 53.5

Grassland/Shrubland Agriculture 2,128 1,243 839 1.7 21.2

Agriculture Developed 503 253 171 0.4 5.0

Forest Agriculture 323 125 84 0.3 3.2

Grassland/Shrubland Forest 304 124 84 0.2 3.0

Other Other 1,412 n/a n/a 1.2 14.1

Totals 10,036 8.2 100.0
106 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Chapman, S.S., Omernik, J.M., Griffith, G.E., Schroeder, 

W.A., Nigh, T.A., and Wilton, T.F., 2002, Ecoregions of 

Iowa and Missouri: U.S. Geological Survey Ecoregion Map 

Series, scale 1:1,800,000, available at http://www.epa.gov/

wed/pages/ecoregions/moia_eco.htm.

Cofer, R.D., Walser, J.W., and Osborne, T.D., 2009, Do record 

farmland prices portend another steep downturn for agriculture and farm banks?: Federal Deposit Insurance Corporation database, accessed March 18, 2009, at http://www.fdic.

gov/bank/analytical/quarterly/2008_vol2_4/farmland.html.

Elizabethtown College, 2010, Amish studies: Elizabethtown 

College, The Young Center for Anabaptist and Pietist 

Studies Web site, accessed November 4, 2010, at http://

www2.etown.edu/amishstudies/Index.asp.

Johnson, G.P., Holmes, R.R., and Waite, L.A., 2004, The Great 

Flood of 1993 on the upper Mississippi River—10 years 

later: U.S. Geological Survey Fact Sheet 2004–3024, 6 p., 

available at http://il.water.usgs.gov/pubs/fs2004-3024.pdf.

O’Connor, J.E., and Costa, J.E., 2003, Large floods in 

the United States—Where they happen and why: U.S. 

Geological Survey Circular 1245, p. 9, available at http://

pubs.usgs.gov/circ/2003/circ1245/.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Stam, J.M., and Dixon, B.L., 2004, Farmer bankruptcies and 

farm exits in the United States, 1899-2002: U.S. Department 

of Agriculture, Economic Research Service, Agriculture Information Bulletin No. 788, 36 p., accessed March 18, 2009, at 

http://www.ers.usda.gov/media/479214/aib788_1_.pdf.

U.S. Census Bureau, 2010, Census 2000—Demographic profiles: U.S. Census Bureau database, accessed November 4, 

2010, at http://www.census.gov/prod/www/decennial.html.

U.S. Department of Agriculture, 1997, Agricultural resources 

and environmental indicators: U.S. Department of Agriculture, Economic Research Service, Agricultural Handbook 

No. 712, 347 p. 

U.S. Department of Agriculture, 2002a, Plant fact sheet—

Little bluestem: U.S. Department of Agriculture, Natural 

Resources Conservation Service Plant Fact Sheet, 2 p., 

accessed November 1, 2010, at http://plants.usda.gov/

factsheet/pdf/fs_scsc.pdf.

U.S. Department of Agriculture, 2002b, Plant fact sheet—

Sideoats grama: U.S. Department of Agriculture, Natural 

Resources Conservation Service Plant Fact Sheet, 2 p., 

accessed November 1, 2010, at http://plants.usda.gov/

factsheet/pdf/fs_bocu.pdf.

U.S. Department of Agriculture, 2009a, Conservation 

programs—CRP contract and summary statistics: U.S. 

Department of Agriculture, Farm Service Agency database, accessed March 11, 2009, at http://www.fsa.usda.

gov/FSA/webapp?area=home&subject=copr&topic=cr

p-st.

U.S. Department of Agriculture, 2009b, Iowa statistics: U.S. 

Department of Agriculture, National Agricultural Statistics 

Service database, accessed March 11, 2009, at http://www.

nass.usda.gov/Statistics_by_State/Iowa/index.asp.

U.S. Department of Agriculture, 2009c, Kansas statistics: 

U.S. Department of Agriculture, National Agricultural Statistics Service database, accessed March 11, 2009, at http://

www.nass.usda.gov/Statistics_by_State/Kansas/index.asp.

U.S. Department of Agriculture, 2009d, Missouri statistics: 

U.S. Department of Agriculture, National Agricultural 

Statistics Service database, accessed March 11, 2009, at 

http://www.nass.usda.gov/Statistics_by_State/Missouri/

index.asp.

U.S. Department of Agriculture, 2009e, Oklahoma statistics: 

U.S. Department of Agriculture, National Agricultural 

Statistics Service database, accessed March 11, 2009, at 

http://www.nass.usda.gov/Statistics_by_State/Oklahoma/

index.asp.

U.S. Environmental Protection Agency, 1997, Descriptions 

of level III ecological regions for the CEC report on 

ecological regions of North America: U.S. Environmental 

Protection Agency database, accessed November 4, 2010, 

at http://www.epa.gov/wed/pages/ecoregions/na_eco.

htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Chapter 11

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Flint Hills Ecoregion

By Steven Kambly

Ecoregion Description

The Flint Hills Ecoregion, which 

extends about 350 km north-south from 

Marshall County, Kansas, to Osage County, 

Oklahoma, includes the Flint Hills in 

eastern Kansas and the Osage Hills in northcentral Oklahoma. The ecoregion covers 

an area of about 27,911 km2 (10,777 mi2) 

and is about 100 km wide at its widest 

point, between Lyon and Marion Counties, 

Kansas (fig. 1) (Omernik, 1987; U.S.

Environmental Protection Agency, 1997). 

The ecoregion is bounded on the west by 

the Central Great Plains Ecoregion, on 

the north by the Western Corn Belt Plains 

Ecoregion, and on the east by the Central 

Irregular Plains and Central Oklahoma/

Texas Plains Ecoregions.

A subhumid continental climate 

accounts for large daily and seasonal 

temperature fluctuations in the Flint Hills 

Ecoregion. Summer high temperatures may 

reach 38°C, whereas winter temperatures 

may fall as low as -12°C. The ecoregion 

receives about 760 to 960 mm (30–38 in.) 

of annual precipitation, the high end of the 

range occurring in the southern part of the 

ecoregion. Most precipitation falls during the 

growing season, from April to September.

Expansive areas of grazed uplands 

and cultivated lowlands characterize the 

Flint Hills Ecoregion. Upland topography 

includes rolling hills that have moderately 

steep to steep slopes and areas of relatively 

flat terrain. Soils are derived from underlying 

limestones, shales, and sandstones (Malin, 

1942). Many upland areas have thin soils 

underlain by limestone that contains bands 

of erosion-resistant chert, or flint, thus giving 

the ecoregion its name. Chert stones and 

rock outcroppings are scattered throughout 

the upland areas, making it difficult to plow 

for crop production. Some upland soils 

support farming, but cost efficiency and other 

Figure 1. Map of Flint Hills Ecoregion and surrounding ecoregions, showing land-use/

land-cover classes from 1992 National Land Cover Dataset (Vogelmann and others, 2001); 

note that not all land-use/land-cover classes shown in explanation may be depicted on 

map; note also that, for this “Status and Trends of Land Change” study, transitional landcover class was subdivided into mechanically disturbed and nonmechanically disturbed 

classes. Squares indicate locations of 10 x 10 km sample blocks analyzed in study. Index 

map shows locations of geographic features mentioned in text. Abbreviations for Great 

Plains ecoregions are listed in appendix 2. See appendix 3 for definitions of land-use/

land-cover classifications.

97° 96°

39°

38°

37°

Central

Great

Plains

Western Corn

Belt Plains

Central

Irregular

Plains

Central

Oklahoma/Texas

Plains

0 10 20 30 MILES

0 10 20 30 40 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

Flint Hills Ecoregion

OKLAHOMA

KANSAS

OSAGE

HILLS

MARSHALL

COUNTY

Emporia

El Dorado

FLINT HILLS

Pawhuska

MARION

COUNTY

Manhattan

River Kansas

Tallgrass Prairie

Preserve

Rossville

OKLAHOMA

KANSAS

Tallgrass Prairie

National Preserve

Konza Prairie

Biological Station

OSAGE

COUNTY

LYON

COUNTY

Cottonwood Falls

OSAGE

HILLS
108 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

factors (including historical and sociological circumstances) 

contribute to the lack of upland crop production (Kollmorgen 

and Simonett, 1965). The lowland and lower slope soils, 

which include deep and permeable silt loams and silty clay 

loams (Bragg and Hulbert, 1976), support various crops such 

as wheat, corn, sorghum, soybeans, alfalfa, and oats (figs. 

2, 3). Lowland fields tend to be medium to small in size, 

whereas upland rangelands typically are much larger.

The ecoregion’s leading land-cover class is grassland/

shrubland, dominated by warm-season grasses, particularly 

big bluestem (Andropogon gerardii), little bluestem 

(Schizachyrium scoparium), and Indiangrass (Sorghastrum 

nutans) (Briggs and others, 2002). Since the 1880s, the 

grasses have served as forage for cattle transported from 

Texas and other parts of the southwestern plains. The 

grazing season usually begins in early spring and continues 

during the summer, after which the cattle are shipped to 

slaughterhouses or feedlots. The grasses are maintained 

through spring burning of the lands to eliminate shrubs and 

small trees. With their growing tip near the surface, grasses 

withstand the burns and reemerge each year (Klinkenborg, 

2007). Before Euro-American settlement, Native Americans 

maintained grazing areas for bison using a similar 

management regime.

The Flint Hills Ecoregion is dotted with small towns 

(figs. 4,5), most of which have lost much population in the 

last several decades, a pattern typical of rural communities 

in the Great Plains (Licht, 1997). Some larger Kansas towns 

Figure 2. Wheat field adjacent to Kansas River, which traverses 

northern part of Flint Hills Ecoregion.

Figure 3. Corn field in Kansas River valley, in Flint Hills 

Ecoregion.

Figure 5. Chase County Courthouse, Cottonwood Falls, Kansas 

(population 966 in 2000), in Flint Hills Ecoregion. Completed in 

1873, courthouse was built using limestone that is available 

in abundance in Flint Hills and that has been used as building 

material since beginning of Euro-American settlement. 

Figure 4. Small town of Rossville, Kansas (population 1,014 in 

2000), in Flint Hills Ecoregion.
Chapter 11—Flint Hills Ecoregion 109

such as Emporia and El Dorado, which are not exclusively 

linked to the rural economy, grew by less than 5 percent 

between 1970 and 2000. Manhattan, Kansas, a college town, 

increased by 62 percent during this same time. Despite these 

population increases, the amount of developed lands in the 

ecoregion remained less than 1 percent during the entire 

27-year study period. 

Although widespread agricultural production in the 

Great Plains has resulted in the near-total loss of onceextensive native prairie lands, the Flint Hills Ecoregion 

includes the largest remnant of tallgrass prairie in North 

America (Knapp and Seastedt, 1998). In 1996, Congress 

passed legislation to create the Tallgrass Prairie National 

Preserve, near the geographic center of the ecoregion, to 

protect 44 km2 of tallgrass-prairie ecosystem. Additional 

preserves have been established in the Flint Hills Ecoregion, 

including the 35 km2 Konza Prairie Biological Station 

near Manhattan, Kansas, and the 166 km2 Tallgrass Prairie 

Preserve near Pawhuska, Oklahoma. Both preserves, which 

are owned partly by The Nature Conservancy, are research 

oriented and work jointly with local universities.

Potential changes to the Flint Hills Ecoregion include 

those resulting from certain grazing management practices 

that may affect the diversity and composition of tallgrassprairie plant communities (Hickman and others, 2004). In 

addition, grazing and burning practices have disturbed bird 

nesting habitats, particularly the habitat of the endangered 

Greater Prairie Chicken (Tympanuchus cupido) (Robbins 

and others, 2002). Moreover, invasion of eastern redcedar 

(Juniperus virginiana) populations (fig. 6) in the northern 

part of the Flint Hills Ecoregion has resulted in conversions 

of grasslands to forest; drivers include an increase in 

human settlement and overgrazing, which have led to fire 

suppression practices and low fire intensity, respectively 

(Briggs and others, 2002). Grasslands also are threatened 

by the spread of Sericea lespedeza, an Asian legume that 

diminishes the diversity of native grasses (Middendorf and 

others, 2008).

Figure 6. Eastern redcedar (Juniperus virginiana) trees invading 

prairie lands in eastern part of Flint Hills Ecoregion.

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Flint Hills Ecoregion 

between 1973 and 2000 is estimated at 2.2 percent (table 

1). Compared to other Great Plains ecoregions, change in 

the Flint Hills Ecoregion was small (fig. 7). An estimated 

1.9 percent of the ecoregion was converted from one 

land-cover class to another, and 0.3 percent underwent two 

changes (table 1). The small extent of change shows the 

overall stability of the ecoregion. Change occurred more 

frequently in lowland areas owing to conversions between 

grassland/shrubland and agriculture. Estimated change 

per time period ranged from a low of 0.4 percent between 

1980 and 1986 to a high of 0.8 percent between 1992 and 

2000 (table 2). The other two time periods (1973–1980, 

1986–1992) had changes of 0.6 percent and 0.7 percent, 

respectively. When change per time period is normalized 

by year, all four had a low change rate of 0.1 percent per 

year (table 2; fig. 8). The low change rates primarily reflect 

the stability of the ecoregion, although these rates can 

mask fluctuations in the extent of grassland/shrubland and 

agricultural lands.

Figure 7. Overall spatial change in Flint Hills Ecoregion (FH; 

darker bars) compared with that of all 17 Great Plains ecoregions 

(lighter bars). Each horizontal set of bars shows proportions of 

ecoregion that experienced change during one, two, three, or 

four time periods; highest level of spatial change in Flint Hills 

Ecoregion (four time periods) labeled for clarity. See table 2 for 

years covered by each time period. See appendix 2 for key to 

ecoregion abbreviations.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four Change in four time periods

time periods
110 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Figure 8. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Flint Hills 

Ecoregion are represented by red bars in each time period.

Figure 9. Normalized average net change in Flint Hills Ecoregion by

time period for each land-cover class. Bars above zero axis represent 

net gain, whereas bars below zero represent net loss. Note that not all 

land-cover classes shown in explanation may be represented in figure. 

See appendix 3 for definitions of land-use/land-cover classifications.

Grassland/shrubland and agriculture, which are 

the predominant land-cover classes, extending over an 

estimated 90 percent of the ecoregion, showed the greatest 

change per time period. Changes in these two were often 

complementary: as grassland/shrubland increased in area, 

agricultural land decreased in area (fig. 9). During the 

study period (1973–2000), grassland/shrubland increased 

overall, as well as in three of the four time periods 

(table 3), and agriculture decreased by amounts that are

similar to the increases in grassland/shrubland: grassland/

shrubland increased by 0.6 percent, while agricultural 

lands decreased by 0.7 percent (table 3; fig 9). The 

remaining land-cover classes showed small amounts of 

change as forested lands decreased consistently in each 

time period while developed lands increased. However, 

these changes, when added to changes within other landcover classes, constituted less than 0.1 percent of the 

ecoregion’s land area.

The most common land-cover conversion between 

1973 and 2000 (and the most common in each time period) 

was the conversion of an estimated 344 km2 of agricultural 

land to grassland/shrubland (table 4). The second most 

common was the conversion of about 148 km2 of 

grassland/shrubland to agriculture. These two leading 

conversions account for nearly 70 percent of the landcover conversions during the study period, possibly 

reflecting the activities of small farm operations as they 

convert grassland/shrubland to and from pasture or 

cropland (agriculture land-cover class).

−1

−0.5

0

0.5

1

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Other than the conversions between these two major 

land-cover types (agriculture and grassland/shrubland), 

land cover changed only infrequently in the ecoregion 

during the study period. The lack of change is partly 

due to steep slopes and thin, rocky soils on the uplands, 

which make it poorly suited to farming. In addition, 

the ongoing practices of burning and grazing have been 

essential to the maintenance of the tallgrass ecosystem 

(Middendorf and others, 2008). In areas where fire is 

suppressed, prairie grasses may be overtaken by forest 

(Briggs and others, 2002).

The small change that occurred was mostly in the 

lowlands where grassland/shrubland and agriculture are 

frequently situated next to each other. Many conversions 

from agriculture to grassland/shrubland after 1985 are 

likely due to participation in the Conservation Reserve 

Program (CRP), which was created by the U.S. Congress 

in 1985 and became a key factor in agriculture-tograssland/shrubland conversions. In Kansas, the CRP 
Chapter 11—Flint Hills Ecoregion 111

Table 1. Percentage of Flint Hills Ecoregion land cover that 

changed at least one time during study period (1973–2000) and 

associated statistical error.

[Most sample pixels remained unchanged (97.8 percent), whereas 2.2 percent 

changed at least once throughout study period] 

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 1.9 0.4 1.5 2.3 0.3 15.4

2 0.3 0.1 0.2 0.4 0.1 28.4

3 0.0 0.0 0.0 0.1 0.0 51.7

4 0.0 0.0 0.0 0.0 0.0 65.8

Overall 

spatial 

change

2.2 0.5 1.7 2.7 0.3 15.4

Table 2. Raw estimates of change in Flint Hills Ecoregion land cover, computed for each of 

four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period

Total 

change

(% of 

ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper 

bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average 

rate

(% per year)

Estimate of change, in percent stratum

1973–1980 0.6 0.2 0.4 0.8 0.1 21.7 0.1

1980–1986 0.4 0.1 0.3 0.6 0.1 19.8 0.1

1986–1992 0.7 0.2 0.6 0.9 0.1 15.0 0.1

1992–2000 0.8 0.3 0.5 1.1 0.2 22.3 0.1

Estimate of change, in square kilometers

1973–1980 160 51 109 211 35 21.7 23

1980–1986 124 36 88 161 25 19.8 21

1986–1992 198 44 154 241 30 15.0 33

1992–2000 228 75 152 303 51 22.3 28

has been responsible for about 11,700 km2 of conversions 

from agriculture to grassland/shrubland (Egbert and 

others, 2001). Although large areas of agriculture were 

being converted to grassland/shrubland, a smaller amount 

of land was being converted from grassland/shrubland to 

agriculture. The reasons for the loss of grassland/shrubland 

to agriculture are unclear, although some may be due 

to a process called “slippage,” in which farmers place 

additional agricultural lands into production to compensate 

for lands enrolled in the CRP (Peterson and others, 2004).

Future land-cover conversions would likely 

include an increase of residential home construction 

(developed land-cover class) on grassland/shrubland 

or agricultural lands. The Flint Hills and their environs 

have become increasingly known for their scenic value, 

and development pressures have begun to influence 

land-management decisions on the part of conservation 

organizations, landowners, and government.
112 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Estimated area (and margin of error) of each land-cover class in Flint Hills Ecoregion, calculated five times between 1973 and 

2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 1.2 0.4 0.9 0.3 0.0 0.0 0.0 0.0 0.1 0.1 6.2 1.1 50.9 6.5 40.4 6.7 0.4 0.2 0.0 0.0

1980 1.2 0.4 0.9 0.3 0.0 0.0 0.0 0.0 0.1 0.1 6.1 1.1 51.0 6.5 40.3 6.7 0.5 0.2 0.0 0.0

1986 1.2 0.4 0.9 0.3 0.0 0.0 0.0 0.0 0.0 0.0 6.1 1.1 51.0 6.5 40.3 6.7 0.5 0.2 0.0 0.0

1992 1.3 0.4 0.9 0.3 0.0 0.0 0.1 0.0 0.0 0.0 6.1 1.2 51.3 6.5 39.9 6.7 0.4 0.2 0.0 0.0

2000 1.2 0.4 0.9 0.4 0.0 0.0 0.1 0.1 0.1 0.1 6.1 1.2 51.5 6.5 39.7 6.7 0.5 0.2 0.0 0.0

Net

change 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 –0.1 0.1 0.6 0.3 –0.7 0.4 0.0 0.0 0.0 0.0

Gross

change 0.2 0.1 0.1 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.2 0.1 1.3 0.4 1.4 0.3 0.1 0.1 0.0 0.0

Area, in square kilometers

1973 326 104 239 91 0 0 9 6 19 19 1,725 316 14,200 1,818 11,270 1,872 123 62 0 0

1980 323 104 245 94 0 0 8 6 18 18 1,715 317 14,231 1,818 11,243 1,871 128 63 0 0

1986 339 106 247 95 0 0 9 8 10 13 1,709 318 14,230 1,817 11,241 1,873 126 64 0 0

1992 350 109 254 97 0 0 16 13 9 10 1,706 324 14,305 1,820 11,150 1,877 121 63 0 9

2000 334 103 263 99 0 0 20 14 19 19 1,701 323 14,369 1,818 11,075 1,870 130 62 0 0

Net

change 8 14 24 12 0 0 11 12 0 7 –24 28 169 91 –195 100 7 7 0 0

Gross

change 58 27 24 12 0 0 19 14 27 27 49 27 368 99 390 98 28 17 0 0
Chapter 11—Flint Hills Ecoregion 113

Table 4. Principal land-cover conversions in Flint Hills Ecoregion, showing amount of area changed (and margin of error, calculated at 

85-percent confidence level) for each conversion during each of four time periods and also during overall study period. See appendix 3 

for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of 

all changes (km2) (+/− km2) (km2)

1973–1980 Agriculture Grassland/Shrubland 71 33 22 0.3 44.2

Grassland/Shrubland Agriculture 42 27 18 0.1 26.1

Water Barren 8 8 6 0.0 5.2

Barren Water 8 7 5 0.0 4.7

Forest Agriculture 7 6 4 0.0 4.3

Other Other 25 n/a n/a 0.1 15.5

Totals 160 0.6 100.0

1980–1986 Agriculture Grassland/Shrubland 42 22 15 0.2 33.8

Grassland/Shrubland Agriculture 34 20 13 0.1 27.2

Barren Water 11 13 9 0.0 9.0

Forest Agriculture 8 7 5 0.0 6.1

Grassland/Shrubland Water 5 5 3 0.0 4.4

Other Other 24 n/a n/a 0.1 19.6

Totals 124 0.4 100.0

1986–1992 Agriculture Grassland/Shrubland 111 39 27 0.4 56.2

Grassland/Shrubland Agriculture 24 11 8 0.1 12.3

Grassland/Shrubland Forest 8 8 6 0.0 3.9

Forest Agriculture 7 6 4 0.0 3.7

Barren Water 6 8 5 0.0 2.9

Other Other 42 n/a n/a 0.1 21.0

Totals 198 0.7 100.0

1992–2000 Agriculture Grassland/Shrubland 120 62 42 0.4 52.7

Grassland/Shrubland Agriculture 48 25 17 0.2 21.0

Water Wetland 11 9 6 0.0 4.8

Water Barren 11 10 7 0.0 4.6

Grassland/Shrubland Developed 6 6 4 0.0 2.6

Other Other 32 n/a n/a 0.1 14.2

Totals 228 0.8 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 344 120 81 1.2 48.4

Grassland/Shrubland Agriculture 148 55 37 0.5 20.8

Water Barren 28 27 18 0.1 3.9

Forest Agriculture 26 19 13 0.1 3.6

Barren Water 26 25 17 0.1 3.6

Other Other 139 n/a n/a 0.5 19.6

Totals 709 2.5 100.0
114 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Bragg, T.B., and Hulbert, L.C., 1976, Woody plant invasion 

of unburned Kansas bluestem prairie: Journal of Range 

Management, v. 29, no. 1, p. 19–24.

Briggs, J.M., Hoch, G.A., and Johnson, L.C., 2002, Assessing 

the rate, mechanisms, and consequences of the conversion 

of tallgrass prairie to Juniperus virginiana forest: 

Ecosystems, v. 5., no. 6, p. 578–586.

Egbert, S.L., Peterson, D.L., Stewart, A.M., Lauver, C.L., 

Blodgett, C.F., Price, K.P., and Martinko, E.A., 2001, The 

Kansas GAP land cover map final report: Kansas Biological 

Survey Report 99.

Hickman, K.R., Hartnett, D.C., Cochran, R.C., and Owensby, 

C.E., 2004, Grazing management effects on plant species 

diversity in tallgrass prairie: Journal of Range Management, 

v. 57, no. 1, p. 58–65. 

Klinkenborg, Verlyn, 2007, Splendor of the grass: National 

Geographic Magazine Online, April 2007, accessed May 

23, 2013, at http://ngm.nationalgeographic.com/2007/04/

tallgrass-prairie/klinkenborg-text.

Knapp, A.K., and Seastedt, T.R., 1998, Introduction—

Grasslands, Konza Prairie, and long-term ecological 

research, in Knapp, A.K., Briggs, J.M., Hartnett, D.C., 

and Collins, S.L, eds., Grassland Dynamics—Long-Term 

Ecological Research in Tallgrass Prairie: New York, Oxford 

University Press, p. 3–15.

Kollmorgen, W.M, and Simonett, D.S., 1965, Grazing 

operations in the Flint Hills-bluestem pastures of Chase 

County, Kansas: Annals of the Association of American 

Geographers, v. 55, no. 2, p. 260–290. 

Licht, D.S., 1997, Ecology and economics of the Great Plains: 

Lincoln, University of Nebraska Press, 225 p.

Malin, J.C., 1942, An introduction to the history of the 

bluestem pasture region of Kansas: Kansas Historical 

Quarterly, v. 11, no. 2, p. 3–28.

Middendorf, Gerad, Cline, Derrick, and Bloomquist, Leonard, 

2008, Agrarian landscape transition in the Flint Hills of 

Kansas—Legacies and resilience, in Redman, C.L., and 

Foster, D.R., eds., 2008, Agrarian landscapes in transition—

Comparisons of long-term ecological and cultural change: 

New York, Oxford University Press, p. 206–237.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Peterson, D.L., Egbert, S.L., Price, K.P., and Marinko, E.A., 

2004, Identifying historical and recent land-cover changes 

in Kansas using post-classification change detection 

techniques: Transactions of the Kansas Academy of 

Science, v. 107, no. 3–4, p. 105–118.

Robbins, M.B., Peterson, A.T., and Ortega-Huerta, M.A., 

2002, Major negative impacts of early intensive cattle 

stocking on tallgrass prairies—The case of the greater 

prairie-chicken (Tympanuchus cupido): North American 

Birds, v. 56, no. 2, p. 239–244.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662. 
Southern Plains Ecoregions

Chapter 12

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Central Oklahoma/Texas Plains Ecoregion 

By Michael P. Stier

Ecoregion Description 

The Central Oklahoma/Texas Plains 

Ecoregion covers more than 103,412 km2

(39,928 mi2) of southeastern Kansas, central 

Oklahoma, and north-central Texas (fig. 1).

The ecoregion is bounded on the west by 

the Central Great Plains Ecoregion; on 

the north by the Flint Hills Ecoregion; on 

the east by the Central Irregular Plains, 

Arkansas Valley, Ouachita Mountains, South 

Central Plains, and Texas Blackland Prairies 

Ecoregions; and on the south by the Edwards 

Plateau Ecoregion (Omernik, 1987; U.S. 

Environmental Protection Agency, 1997).

Figure 1. Map of Central Oklahoma /Texas Plains Ecoregion and surrounding 

ecoregions, showing land-use/land-cover classes from 1992 National Land Cover 

Dataset (Vogelmann and others, 2001); note that not all land-use/land-cover classes 

shown in explanation may be depicted on map; note also that, for this “Status and 

Trends of Land Change” study, transitional land-cover class was subdivided into 

mechanically disturbed and nonmechanically disturbed classes. Squares indicate 

locations of 10 x 10 km sample blocks analyzed in study. Index map shows locations 

of geographic features mentioned in text. Abbreviations for Great Plains ecoregions 

are listed in appendix 2. Also shown are parts of three Midwest–South Central United 

States ecoregions: Arkansas Valley, Ouachita Mountains (OM), and South Central 

Plains. See appendix 3 for definitions of land-use/land-cover classifications.

100°W 98° 96°

36°

34°

32°

Central

Great Plains

Flint Hills

Edwards Plateau

Arkansas

Valley

Texas Blackland

Prairies

South

Central Plains

Southwestern

Tablelands

SWT

East Central

Texas Plains

OM

CIP Central

Great

Plains

OH

BM

0 50 100MILES

0 50 100 KILOMETERS

TEXAS

OKLAHOMA

KANSAS

Fort Worth

Gainesville

Stillwater

Oklahoma City

Tulsa

Glen Rose

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

The Central Oklahoma/

Texas Plains Ecoregion, also 

referred to as “Cross Timbers,” 

is characterized by a complex 

mosaic of upland deciduous 

forest, savanna, and prairie 

communities (fig. 2) that make 

up the broad ecotone between the 

forested low mountains of eastern 

Oklahoma and the grasslands to 

the west. Two large forest zones, 

which run northeast to southwest 

from central Oklahoma to northcentral Texas, are dominated 

by blackjack oak (Quercus 

marilandica), post oak (Quercus 

stellata), and eastern redcedar 

(Juniperus virginiana). Fourhundred-year-old post oaks live 

in the “Cross Timbers” region. 

These forests, which are among 

the least disturbed forests east 

of the Rocky Mountains, have 

survived because they were not 

ideal for lumber production, and 

their steep terrain is unsuitable 

for farming (fig. 3) (University of

Arkansas Tree-Ring Laboratory, 

2007; see also, Stahle and others, 
118 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

2003). The large, gently sloping prairie that separates these 

forests consists of thin soils over hard layers of resistant 

limestone. Other areas of the ecoregion include patches 

of mixed-grass prairie habitat embedded within the oak 

woodlands.

The topography of the Central Oklahoma/Texas Plains 

Ecoregion is rolling to hilly uplands separated by narrow 

stream valleys that have steep gradients. Elevations range 

from 100 to 400 m (McNab and Avers, 1996). The climate 

is considered subhumid, with average annual precipitation 

levels that vary from 525 mm (20 in.) in the southwestern 

part of the ecoregion to 900 mm (35 in.) in the northeastern 

part. Most precipitation falls in spring, and winter is the 

driest season.

The most common land use is livestock ranching of 

cattle, sheep, and goats. Crops grown in the deeper and 

more fertile soils include small grains, sorghum, cotton, 

and alfalfa. Peanuts, tree fruits, and vegetables are grown 

in the south (U.S. Department of Agriculture, 1981). 

Overall, nearly 75 percent of the natural vegetation has 

been cleared for ranching and cultivation (McNab and 

Avers, 1996). Grassland/shrubland is the most extensive 

land-cover class, followed by agricultural land. 

Lease hunting is common on large ranches, providing 

an additional source of income to private landowners. 

Big-game species commonly hunted, especially in the 

Texas part of the ecoregion, include white-tailed deer 

(Odocoileus virginianus), pronghorn (Antilocapra 

americana), mule deer (Odocoileus hemionus), wild turkey 

(Meleagris gallopavo), and javelina (Pecari tajacu). 

Other land uses include urban and exurban 

development and oil and gas extraction (fig. 4). Much of 

the increase in the ecoregion’s population is supported by 

the growing oil industry, which attracts numerous jobs to 

the area. Nearly all the counties in the ecoregion increased 

in population from 1980 to 2005 (U.S. Census Bureau, 

2005). As the population grew, urban centers benefitting 

from the oil and gas industry expanded, causing new 

development along the ecoregion’s periphery near Tulsa, 

Oklahoma, and Fort Worth, Texas. 

A growing concern in this ecoregion is the loss and 

fragmentation of wildlife habitat owing to land-use/

land-cover change. The clearing of brush and forests 

for pasture, cropland, or development affects wildlife 

resources. Threatened or endangered species observed in 

this area include the black-capped vireo (Vireo atricapilla), 

the golden-cheeked warbler (Dendroica chrysoparia), the 

Texas kangaroo rat (Dipodomys elator), and the Texas 

horned lizard (Phrynosoma cornutum). Long-term declines 

in big-game species such as the pronghorn or white-tailed 

deer are attributed primarily to habitat loss, competition 

with livestock for food and forage, and losses to predators 

(Texas Parks and Wildlife, 2007). Figure 2. Savanna landscape with grasses and scattered trees 

surrounding pasture in Central Oklahoma/Texas Plains Ecoregion.

Figure 3. Post oak forest in Central Oklahoma/Texas Plains 

Ecoregion.

Figure 4. Oil pump next to irrigated pasture in Central Oklahoma/

Texas Plains Ecoregion.
Chapter 12—Central Oklahoma/Texas Plains Ecoregion 119

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the Central Oklahoma/

Texas Plains Ecoregion between 1973 and 2000 is estimated

at 6.5 percent (table 1). Compared to other Great Plains 

ecoregions, change in the Central Oklahoma/Texas Plains 

Ecoregion was moderate (fig. 5). Of the land that changed, 

5.6 percent changed one time, 0.8 percent changed two 

times, and 0.1 percent changed three times (table 1). For 

those few land areas that changed two or more times, the 

change generally was back and forth between two land-cover 

classes: for example, between agriculture and grassland/

shrubland. Although the total change per time period was 

less than 2 percent in three of the four time periods (table 2),

the period between 1986 and 1992 had a slightly higher 

percentage of land-cover change, at 2.6 percent. Much of this 

increase was a result of conversion of agricultural land to 

grassland/shrubland (table 3). When normalized to account 

for varying time-period lengths, the estimated annual rates 

of change increased gradually in the first three time periods 

(1973–1980, 1980–1986, 1986–1992), from 0.2 to 0.4 

percent of the ecoregion per year, before dropping to 0.2 

percent between 1992 and 2000 (table 2; fig. 6). 

Figure 5. Overall spatial change in Central Oklahoma/Texas 

Plains Ecoregion (COTP; darker bars) compared with that of all 

17 Great Plains ecoregions (lighter bars). Each horizontal set of 

bars shows proportions of ecoregion that experienced change 

during one, two, three, or four time periods; highest level of spatial 

change in Central Oklahoma/Texas Plains Ecoregion (four time 

periods) labeled for clarity. See table 2 for years covered by each 

time period. See appendix 2 for key to ecoregion abbreviations.

Grassland/shrubland, agriculture, and forest areas 

constitute an estimated 93 percent of the land cover in 

this ecoregion. Grassland/shrubland, the dominant landcover class, remained relatively stable between 1973 and 

2000, ranging from 46.5 to 46.9 percent of the ecoregion 

(table 4). Between 1973 and 2000, forest decreased by 

0.4 percent, from 19.6 to 19.2 percent of the ecoregion 

(table 4). In the early part of the study period, forest was 

cleared for agriculture and grassland/shrubland. Much of 

the cleared forest land was used to support the growing 

livestock industry. As part of the forest-clearing process, 

aerial applications of broadleaf herbicides were used to 

kill oaks and to release understory grasses for grazing. The 

resulting dead trees were gathered in piles and burned. In 

some cases, large areas of ancient post oaks, red cedar, and 

blackjack oaks were removed and replaced by rangeland 

(Francaviglia, 2003). 

The largest net changes over the entire study period 

(1973–2000) were a 0.7 percent increase in developed 

land and a 0.7 decrease in agricultural land. Developed 

land steadily increased throughout the study period, with 

an estimated net increase of 677 km2 (table 4). About 50 

percent of the new developed land was formerly grassland/

shrubland (table 3). A steady increase in population likely 

contributed to the increase in developed land throughout the 

ecoregion. Overall, the decline in agriculture resulted from 

new development and also participation in the Conservation 

Reserve Program (CRP). The CRP provided economic 

incentives to farmers to convert highly erodible cropland or 

other environmentally sensitive acreage to vegetative cover, 

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Figure 6. Estimates of land-cover change per time period,

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Central 

Oklahoma/Texas Plains Ecoregion are represented by red bars in 

each time period.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods
120 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

such as grasses and forbes, specific wildlife plantings, 

trees, filter strips (vegetated surfaces designed to treat 

surface runoff), or riparian buffers (U.S. Department of 

Agriculture, 2008). 

Between 1973 and 2000, the most significant landcover conversions in the Central Oklahoma/Texas Plains 

Ecoregion were fluctuations between grassland/shrubland 

and agriculture that were influenced by government 

Figure 7. Normalized average net change in Central Oklahoma/

Texas Plains Ecoregion by time period for each land-cover class. 

Bars above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.

Figure 8. Cattle grazing in open pasture in Central Oklahoma/

Texas Plains Ecoregion.

policies and the global economic climate. Conversions to 

and from grassland/shrubland and agriculture were nearly 

equal between 1973 and 1980 and between 1992 and 2000 

(table 3). In the other two time periods, however, this 

was not the case. Between 1980 and 1986, agriculture 

decreased, likely owing to the global recession in the early 

1980s that caused a reduced grain demand and a decrease 

in farm land values. Between 1986 and 1992, the rapid 

increase in the conversion of agriculture back to grassland/

shrubland likely was related to the initiation of the CRP 

(U.S. Department of Agriculture, 2009). Between 1992 and 

2000, the conversion of grassland/shrubland to agriculture 

was significantly less, probably owing to CRP land going 

back into crop production.

Another notable change in the ecoregion was the 

steady increase in development, especially exurban 

development (fig. 7). Population growth in Oklahoma City, 

Tulsa, and Stillwater, Oklahoma, as well as in Gainesville, 

Glen Rose, and Fort Worth, Texas, contributed to the 

expansion of developed land. In addition, new developed 

land near or along reservoirs and lakes increased as people 

built homes near outdoor recreational sites. 

Rangeland expanded at times during the study period 

as forest areas were converted to grassland/shrubland for 

livestock grazing (fig. 8). Tall brush, which includes mesquite 

(Prosopis spp.) and live oak (Quercus virginiana) was cleared 

for raising cattle and, to a lesser degree, along with some 

forest areas, for growing hay and expanding pastures. 

−1

−0.5

0

0.5

1

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS
Chapter 12—Central Oklahoma/Texas Plains Ecoregion 121

Table 1. Percentage of Central Oklahoma/Texas Plains Ecoregion 

land cover that changed at least one time during study period 

(1973–2000) and associated statistical error.

[Most sample pixels remained unchanged (93.5 percent), whereas 6.5 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 5.6 1.0 4.6 6.6 0.7 12.6

2 0.8 0.3 0.5 1.1 0.2 28.2

3 0.1 0.0 0.0 0.1 0.0 34.1

4 0.0 0.0 0.0 0.0 0.0 67.0

Overall 

spatial 

change

6.5 1.2 5.2 7.7 0.8 13.0

Table 2. Raw estimates of change in Central Oklahoma/Texas Plains Ecoregion land-cover, computed 

for each of four time periods between 1973 and 2000, and associated error at 85-percent confidence 

level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 1.5 0.4 1.1 2.0 0.3 19.2 0.2

1980–1986 1.8 0.5 1.3 2.2 0.3 17.9 0.3

1986–1992 2.6 0.8 1.8 3.4 0.6 21.7 0.4

1992–2000 1.6 0.3 1.3 1.9 0.2 13.4 0.2

Estimate of change, in square kilometers

1973–1980 1,595 452 1,144 2,047 307 19.2 228

1980–1986 1,842 485 1,357 2,326 329 17.9 307

1986–1992 2,664 852 1,812 3,516 579 21.7 444

1992–2000 1,616 319 1,296 1,935 217 13.4 202
122 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Principal land-cover conversions in Central Oklahoma/Texas Plains Ecoregion, showing amount of area changed (and margin 

of error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” class are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of 

all changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 474 286 194 0.5 29.7

Agriculture Grassland/Shrubland 458 214 145 0.4 28.7

Forest Grassland/Shrubland 128 75 51 0.1 8.0

Grassland/Shrubland Developed 106 83 56 0.1 6.6

Grassland/Shrubland Forest 81 58 39 0.1 5.1

Other Other 349 n/a n/a 0.3 21.9

Totals 1,595 1.5 100.0

1980–1986 Agriculture Grassland/Shrubland 678 331 225 0.7 36.8

Grassland/Shrubland Agriculture 404 198 135 0.4 21.9

Forest Grassland/Shrubland 115 75 51 0.1 6.2

Forest Agriculture 113 98 66 0.1 6.1

Grassland/Shrubland Forest 94 45 30 0.1 5.1

Other Other 439 n/a n/a 0.4 23.8

Totals 1,842 1.8 100.0

1986–1992 Agriculture Grassland/Shrubland 1,160 451 306 1.1 43.6

Grassland/Shrubland Agriculture 796 626 425 0.8 29.9

Grassland/Shrubland Forest 109 58 40 0.1 4.1

Wetland Water 69 97 66 0.1 2.6

Forest Grassland/Shrubland 56 33 22 0.1 2.1

Other Other 474 n/a n/a 0.5 17.8

Totals 2,664 2.6 100.0

1992–2000 Grassland/Shrubland Agriculture 447 149 101 0.4 27.7

Agriculture Grassland/Shrubland 442 139 94 0.4 27.3

Grassland/Shrubland Forest 107 90 61 0.1 6.6

Grassland/Shrubland Developed 104 49 34 0.1 6.4

Forest Grassland/Shrubland 102 41 28 0.1 6.3

Other Other 414 n/a n/a 0.4 25.6

Totals 1,616 1.6 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 2,738 861 585 2.6 35.5

Grassland/Shrubland Agriculture 2,120 809 550 2.1 27.5

Forest Grassland/Shrubland 401 173 118 0.4 5.2

Grassland/Shrubland Forest 391 171 116 0.4 5.1

Grassland/Shrubland Developed 328 139 94 0.3 4.2

Other Other 1,739 n/a n/a 1.7 22.5

Totals 7,717 7.5 100.0
Chapter 12—Central Oklahoma/Texas Plains Ecoregion 123

Table 4. Estimated area (and margin of error) of each land-cover class in Central Oklahoma/Texas Plains Ecoregion, calculated five 

times between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 2.3 1.8 2.9 1.2 0.0 0.0 0.1 0.0 0.0 0.0 0.0 19.6 3.0 46.5 6.0 4.4 1.0 0.7 0.0 0.0

1980 2.3 1.8 3.0 1.2 0.0 0.0 0.1 0.0 0.0 0.1 0.1 19.5 3.0 46.5 5.9 4.4 1.0 0.7 0.0 0.0

1986 2.3 1.8 3.2 1.3 0.0 0.0 0.2 0.1 0.1 0.1 0.1 19.3 3.0 46.7 5.8 4.3 1.0 0.8 0.0 0.0

1992 2.4 1.8 3.3 1.3 0.0 0.0 0.1 0.1 0.1 0.1 0.1 19.3 3.0 46.9 5.9 4.3 0.9 0.7 0.0 0.0

2000 2.4 1.8 3.5 1.4 0.0 0.0 0.2 0.1 0.1 0.1 0.1 19.2 3.0 46.7 5.9 4.3 1.0 0.7 0.0 0.0

Net

change 0.1 0.0 0.7 0.2 0.0 0.0 0.1 0.1 0.1 0.1 0.1 –0.4 0.2 0.2 0.9 1.0 0.0 0.0 0.0 0.0

Gross

change 0.2 0.1 0.7 0.2 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.9 0.2 3.3 0.8 0.9 0.1 0.1 0.0 0.0

Area, in square kilometers

1973 2,409 1,848 2,963 1,229 12 10 110 47 36 24 20,257 3,150 48,136 6,208 28,473 4,577 1,016 720 0 0

1980 2,378 1,847 3,135 1,249 7 7 118 47 71 70 20,122 3,102 48,058 6,141 28,489 4,502 1,034 745 0 0

1986 2,401 1,852 3,291 1,293 29 23 157 64 65 59 19,963 3,059 48,279 5,982 28,184 4,398 1,044 776 0 0

1992 2,484 1,856 3,424 1,334 13 9 148 56 94 100 19,988 3,062 48,526 6,127 27,756 4,479 981 712 6 9

2000 2,489 1,854 3,640 1,406 40 26 211 88 112 121 19,876 3,056 48,333 6,124 27,714 4,444 994 725 0 0

Net

change 80 49 677 258 28 25 101 90 76 101 –381 234 197 914 –759 1,008 –22 35 0 0

Gross

change 211 151 677 258 93 58 240 113 91 124 962 255 3,413 876 3,449 949 133 142 0 0
124 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Francaviglia, Richard, 2003, The cast iron forest—A natural 

and cultural history of the North American cross timbers: 

Austin, University of Texas Press, 296 p.

McNab, W.H., and Avers, Peter, 1996, Prairie parkland 

(subtropical)—Cross timbers and prairie, in Ecological 

subregions of the United States: U.S. Department of 

Agriculture, Forest Service, WO-WSA-5, Section 255A, p. 

1–6, available at http://www.fs.fed.us/land/pubs/ecoregions/

ch29.html.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p.118–125.

Stahle, D.W., Therrell, M.D., and Clements, K.L., 2003, The 

Ancient Cross Timbers Consortium for Research, Education, 

and Conservation—A proposal from the Tree-Ring Laboratory, 

University of Arkansas, August 2003: Fayetteville, University 

of Arkansas, Tree-Ring Laboratory, 15 p., available at http://

www.uark.edu/misc/xtimber/consortium.pdf.

Texas Parks and Wildlife, 2007, Big game: Texas Parks and 

Wildlife database, accessed October 30, 2007, at http://

www.tpwd.state.tx.us/landwater/land/habitats/cross_

timbers/big_game/.

U.S. Census Bureau, 2005, Census of population and housing: 

U.S. Census Bureau database, accessed February 26, 2008, 

at http://www.census.gov/prod/www/decennial.html.

U.S. Department of Agriculture Natural Resources 

Conservation Service, 2006, Land resource regions 

and major land resource areas of the United States, the 

Caribbean, and the Pacific Basin: U.S. Department of 

Agriculture Handbook 296, 669 p., available at http://

www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/

nrcs142p2_050898.pdf.

U.S. Department of Agriculture, 2008, Conservation Reserve 

Program: U.S. Department of Agriculture Farm Service 

Agency database, accessed February 26, 2008, at http://

www.nrcs.usda.gov/programs/crp/.

U.S. Environmental Protection Agency, 1997, Descriptions 

of level III ecological regions for the CEC report on 

ecological regions of North America: U.S. Environmental 

Protection Agency database, accessed February 26, 2008, 

at http://www.epa.gov/wed/pages/ecoregions/na_eco.

htm#Downloads.

University of Arkansas Tree-Ring Laboratory, 2007, Ancient 

Cross Timbers Consortium: University of Arkansas TreeRing Laboratory database, accessed February 26, 2008, at 

http://www.uark.edu/misc/xtimber/index.html.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the coterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Chapter 13

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

East Central Texas Plains Ecoregion

By Krista A. Karstensen

Ecoregion Description

The East Central Texas Plains Ecoregion, which 

encompasses 44,076 km2 (17,018 mi2) in east Texas (Omernik, 

1987; U.S. Environmental Protection Agency, 1997) (fig. 1), 

extends north from just south of the San Antonio River to an 

area near the Oklahoma border. The ecoregion is bounded 

by (clockwise, from its east end) the South Central Plains, 

Figure 1. Map of 

East Central Texas 

Plains Ecoregion and 

surrounding ecoregions, 

showing land-use/landcover classes from 1992 

National Land-Cover 

Dataset (Vogelmann 

and others, 2001); note 

that not all land-use/

land-cover classes 

shown in explanation 

may be depicted on 

map; note also that, 

for this “Status and 

Trends of Land Change” 

study, transitional 

land-cover class 

was subdivided into 

mechanically disturbed 

and nonmechanically 

disturbed classes. 

Squares indicate 

locations of 10 x 10 km 

sample blocks analyzed 

in study. Index map 

shows locations of geographic 

features mentioned in text. 

Abbreviations for Great Plains 

ecoregions are listed in 

appendix 2. Also shown is part 

of one Midwest–South Central 

United States ecoregion, South 

Central Plains. See appendix 3 

for definitions of land-use/landcover classifications.

Western Gulf Coastal Plain, and Southern Texas Plains 

Ecoregions, as well as the northern section of the Texas 

Blackland Prairies Ecoregion; in addition, it almost completely 

surrounds the separate, smaller, southern section of the Texas 

Blackland Prairies Ecoregion (fig. 1).

The East Central Texas Plains Ecoregion includes 

the San Antonio, North Sulphur, South Sulphur, Trinity, 

Navasota, Brazos, Colorado, and Guadalupe Rivers; Lake 

99° 98°

Central

Oklahoma/

Texas

Plains

Edwards

Plateau

Edwards

Plateau

0 25 50 75 MILES

0 5025 75 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

TEXAS

East Central

Texas Plains

Ecoregion

97°

98°

96°

33°

32°

31°

30°

29°

28°

Texas

Blackland

Prairies

TBP

Edwards

Plateau

Western Gulf

 Coastal Plain

South

Central

Plains

Southern

Texas Plains GULF of

MEXICO

C o l o r a d o R i v e r

Antonio

San

River

River

Navasota 

Guadalupe R.

B r a z o s R i v e r

River

Trinity

GOLIAD

CALDWELL

Somerville

Lake

San Antonio

Austin

Houston

College Station

Bryan

Dallas

OKLAHOMA

TEXAS

Forth Worth Lake

Tawakoni

RichlandChambers

Reservoir

Sulphur River

Cedar

Creek

Reservoir

Lake

Fork

Res.
126 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Tawakoni and Somerville Lake; and Lake Fork, RichlandChambers, and Cedar Creek Reservoirs. Two neighboring 

cities in the ecoregion, Bryan and College Station, Texas, had 

a combined population of 152,415 in April 2000, an increase 

of 9.7 percent since 1990 (U.S. Census Bureau, 2001).

Elevations in the ecoregion increase gradually from 

southeast to northwest. The topography is characterized by 

irregular plains that have acidic soils along the parallel ridges 

and valleys, sandy and sandy loam soils on the uplands, 

and clay and clay loams in the low-lying areas (Griffith 

and others, 2004). Additionally, much of the ecoregion 

is underlain by claypan, which affects the movement and 

availability of water for plant growth (Griffith and others, 

2004). Annual precipitation amounts range from 1,000 to 

1,200 mm (40–48 in.) north of Cedar Creek Reservoir and 

from 700 to 1,000 mm (28–40 in.) south of the Trinity River.

Historically, fire has played an essential role in maintaining 

grassy clearings. In the absence of fire, woody invasions 

have taken place (Griffith and others, 2004). The clearing of 

woody vegetation has permitted the regrowth of mixed native 

or introduced grasses and forbs on grassland sites or mixed 

herbaceous communities (Texas Parks and Wildlife, 2008). The 

deciduous forest in the East Central Texas Plains Ecoregion mostly 

is composed of post oak (Quercus stellata) and blackjack oak 

(Quercus marilandica). Post oak forests are prevalent on sandy 

soils in the ecoregion, particularly in the area north of College 

Station (Yantis, 1984; Amy Hays, Texas A&M University, oral 

commun., 2009). The south-central part of the ecoregion, along the 

Colorado River, has the westernmost tract of longleaf pine (Pinus

palustris) in the United States (Griffith and others, 2004; Amy 

Hays, Texas A&M University, oral commun., 2009).

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land area 

that changed at least one time) in the East Central Texas Plains 

Ecoregion between 1973 and 2000 is estimated at 12.1 percent 

(table 1). Compared to the other Great Plains ecoregions, 

change in the East Central Texas Plains Ecoregion was the 

second highest (fig. 2). An estimated 10.5 percent of the 

ecoregion changed only one time, whereas 1.5 percent and 

0.1 percent changed two and three times, respectively, during 

the entire 27-year study period (table 1). When normalized to 

account for varying lengths of study periods, annual rates of 

change ranged from a low of 0.4 percent per year, between 1973 

and 1980 and between 1992 and 2000, to a high of 0.7 percent 

per year, between 1986 and 1992 (table 2; fig. 3). 

Agriculture covered 46.3 percent of the ecoregion in 2000, 

despite an overall net decrease of 2.7 percent by the end of the 

study period (table 3). Forest was the second leading land-cover 

class, at 30.5 percent of the ecoregion in 2000, despite an overall 

net decrease of 1.8 percent since 1973 (table 3). Grassland/

shrubland constituted 14.4 percent of the ecoregion in 2000. 

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Figure 2. Overall spatial change in East Central Texas Plains 

Ecoregion (ECTP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that changed during one, two, three, or 

four time periods; highest level of spatial change in East Central 

Texas Plains Ecoregion (four time periods) labeled for clarity. See 

table 2 for years covered by each time period. See appendix 2 for 

key to ecoregion abbreviations.

Figure 3. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for East Central Texas 

Plains Ecoregion are represented by red bars in each time period.

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in

four time

periods
Chapter 13—East Central Texas Plains Ecoregion 127

Of all the land-cover classes in the East Central Texas Plains 

Ecoregion, grassland/shrubland, developed, and water had the 

largest overall net increases, at 1.3 percent (table 3; fig. 4).

Between 1973 and 2000, the five most common land-cover 

conversions were (1) agriculture to grassland/shrubland, (2) forest 

to agriculture, (3) grassland/shrubland to forest, (4) grassland/

shrubland to agriculture, and (5) agriculture to forest (table 4). 

Although conversions to developed were not among the top five 

leading land-cover conversions during the study period, the net 

increase of 1.3 percent (581 km2) in developed land was significant.

The East Central Texas Plains Ecoregion is a mosaic of 

improved pastureland, rangeland, and cropland (Griffith and 

others, 2004). Although agricultural lands declined overall during 

the study period, it still constitutes the largest land-cover class in 

the ecoregion. Between 1970 and 2000, about 1,000 new farms 

and ranches were established in Texas each year, even though 

the total area in farms and ranches has declined by almost 3 

million acres during the same time period, a statewide trend that 

is apparent in the East Central Texas Plains Ecoregion (U.S. 

Department of Agriculture, 2009).

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Figure 4. Normalized average net change in East Central Texas 

Plains Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.

Figure 5. Cattle in pasture in Caldwell County, Texas, in East 

Central Texas Plains Ecoregion.

The East Central Texas Plains Ecoregion historically has 

been a mix of post oak and blackjack oak forest and savanna 

on sandy soils, interspersed with midgrass and tallgrass prairie 

on areas of heavier soil (Chuck Kowaleski, Texas Parks and 

Wildlife, written commun., 2009). Although much of this 

land originally was farmed, the sandier sites quickly lost their 

fertility (Chuck Kowaleski, Texas Parks and Wildlife, written 

commun., 2009). The average land-ownership size increased 

as old farms were consolidated into ranches (Yantis, 1984). In 

1974, the central part of the ecoregion had about 18 people, 104 

cattle, and 11 hogs per square mile (Yantis, 1984). Starting in 

the 1980s, Texas A&M AgriLife Extension Service promoted 

the idea of converting native grasses to coastal Bermudagrass 

(Cynodon dactylon) tame pastures, which, when limed and 

fertilized, allowed much higher stocking rates (1 cow per acre) 

than can be achieved on native ranges (Chuck Kowaleski, 

Texas Parks and Wildlife, written commun., 2009) (fig. 5). 

Although the land use in the 1980s was similar to that of the 

1970s, the continued increase in human population was bringing 

more “weekend ranchers” to the area, and the average size of 

landholdings was decreasing (Yantis, 1984).

The impact of population on land use in the later part 

of the study period is correlated with changes in ownership 

and size of tracts (Wilkins and others, 2003). Between 1992 

and 2001, the most notable land-use trend was the conversion 

of native rangelands and croplands to nonnative “improved 

pastures” (Wilkins and others, 2003). Unlike the consolidation 

that occurred in the early 1970s, fragmentation of rural acreage 

became dominant in the 1990s as large properties were divided 

into smaller parcels (Wilkins and others, 2003). This may help 

to describe the principal land-cover change in this ecoregion, 

namely agriculture to grassland/shrubland. As the land becomes 

fragmented, the tracts become too small for traditional farming 

and ranching (Wilkins and others, 2003) (fig. 6). 

Land in the ecoregion also has become increasingly valuable 

with the expanding population of the nearby metropolitan areas. 

In about 1994, a trend began in which land use shifted from 

high intensity (crop production) to low intensity (rangeland). 

Such lands are not considered abandoned agriculture; rather, 
128 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 1. Percentage of East Central Texas Plains Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (87.9 percent), whereas 12.1 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 10.5 1.5 8.9 12.0 1.0 10.1

2 1.5 0.3 1.2 1.8 0.2 15.2

3 0.1 0.0 0.1 0.2 0.0 24.0

4 0.0 0.0 0.0 0.0 0.0 39.5

Overall 

spatial 

change

12.1 1.8 10.3 13.9 1.2 10.2

the owners simply find more economic value in holding these 

lands than in growing crops on them (Amy Hays, Texas A&M 

University, oral commun., 2009). Additionally, the shift from 

high intensity to low intensity, or tame pasture, has allowed many 

of the former savanna areas to become heavily overgrown with 

a yaupon (Ilex vomitoria) understory (Chuck Kowaleski, Texas 

Parks and Wildlife, written commun., 2009).

Figure 6. Ranchland in Goliad County, Texas, in East Central 

Texas Plains Ecoregion.
Chapter 13—East Central Texas Plains Ecoregion 129

Table 2. Raw estimates of change in East Central Texas Plains Ecoregion land cover, computed for 

each of four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.5 0.5 2.0 2.9 0.3 12.4 0.4

1980–1986 3.5 0.8 2.8 4.3 0.5 14.8 0.6

1986–1992 4.5 1.4 3.1 5.9 1.0 21.2 0.7

1992–2000 3.4 0.5 2.9 3.9 0.3 10.1 0.4

Estimate of change, in square kilometers

1973–1980 1,100 200 900 1,300 136 12.4 157

1980–1986 1,558 338 1,219 1,896 231 14.8 260

1986–1992 1,977 615 1,362 2,592 419 21.2 329

1992–2000 1,487 219 1,267 1,706 149 10.1 186
130 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Estimated area (and margin of error) of each land-cover class in East Central Texas Plains Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed Mechanically 

disturbed Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 2.6 1.3 1.8 0.5 0.0 0.0 0.2 0.1 0.1 0.1 32.3 4.0 13.0 3.0 49.0 4.5 1.0 0.3 0.0 0.0

1980 2.6 1.3 2.0 0.6 0.1 0.0 0.3 0.2 0.1 0.1 31.9 3.9 13.4 3.0 48.6 4.4 1.0 0.3 0.0 0.0

1986 3.1 1.4 2.3 0.7 0.1 0.1 0.4 0.2 0.1 0.1 31.6 3.8 13.5 2.9 48.0 4.3 1.0 0.3 0.0 0.0

1992 4.0 1.7 2.8 0.8 0.1 0.0 0.4 0.2 0.1 0.1 30.9 3.8 14.0 2.9 46.8 4.3 1.1 0.3 0.0 0.0

2000 4.0 1.7 3.2 0.9 0.2 0.2 0.4 0.2 0.1 0.1 30.5 3.7 14.4 3.0 46.3 4.3 1.1 0.3 0.0 0.0

Net

change 1.3 1.3 1.3 0.5 0.2 0.2 0.2 0.1 0.0 0.0 –1.8 1.0 1.3 0.8 –2.7 1.4 0.1 0.1 0.0 0.0

Gross

change 1.6 1.3 1.3 0.5 0.6 0.3 0.3 0.2 0.0 0.0 3.6 0.8 3.7 0.6 5.5 1.0 0.2 0.1 0.0 0.0

Area, in square kilometers

1973 1,154 560 812 240 3 4 92 56 29 30 14,225 1,769 5,735 1,331 21,590 1,972 434 147 0 0

1980 1,156 559 903 270 33 21 118 79 30 30 14,059 1,700 5,907 1,324 21,434 1,929 436 147 0 0

1986 1,350 600 1,020 303 62 47 155 106 32 30 13,910 1,662 5,934 1,294 21,174 1,909 437 144 0 0

1992 1,756 758 1,232 370 28 19 159 108 31 30 13,640 1,671 6,150 1,291 20,613 1,907 465 145 0 0

2000 1,747 751 1,393 418 98 72 161 101 31 30 13,444 1,632 6,330 1,310 20,403 1,898 470 146 0 0

Net

change 593 564 581 230 94 72 69 48 1 2 –782 432 595 357 –1,187 604 36 30 0 0

Gross

change 685 563 581 230 268 119 119 73 6 5 1,603 341 1,642 279 2,406 461 69 42 0 0
Chapter 13—East Central Texas Plains Ecoregion 131

Table 4. Principal land-cover conversions in East Central Texas Plains Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Agriculture Grassland/Shrubland 334 98 67 0.8 30.3

Forest Agriculture 208 85 58 0.5 18.9

Grassland/Shrubland Forest 102 48 32 0.2 9.3

Grassland/Shrubland Agriculture 91 37 25 0.2 8.3

Agriculture Forest 74 37 25 0.2 6.7

Other Other 291 n/a n/a 0.7 26.5

Totals 1,100 2.5 100.0

1980–1986 Agriculture Grassland/Shrubland 369 116 79 0.8 23.7

Forest Agriculture 197 48 33 0.4 12.7

Grassland/Shrubland Forest 189 69 47 0.4 12.1

Grassland/Shrubland Agriculture 139 55 38 0.3 9.0

Agriculture Forest 114 54 36 0.3 7.3

Other Other 549 n/a n/a 1.2 35.3

Totals 1,558 3.5 100.0

1986–1992 Agriculture Grassland/Shrubland 563 154 105 1.3 28.5

Forest Water 200 202 138 0.5 10.1

Grassland/Shrubland Agriculture 175 81 55 0.4 8.9

Agriculture Water 149 199 135 0.3 7.5

Grassland/Shrubland Forest 149 51 35 0.3 7.5

Other Other 741 n/a n/a 1.7 37.5

Totals 1,977 4.5 100.0

1992–2000 Agriculture Grassland/Shrubland 430 153 104 1.0 28.9

Forest Agriculture 197 73 50 0.4 13.3

Grassland/Shrubland Forest 147 38 26 0.3 9.9

Grassland/Shrubland Agriculture 139 52 35 0.3 9.4

Forest Grassland/Shrubland 78 37 25 0.2 5.3

Other Other 496 n/a n/a 1.1 33.3

Totals 1,487 3.4 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 1,695 338 230 3.8 27.7

Forest Agriculture 746 179 122 1.7 12.2

Grassland/Shrubland Forest 587 163 111 1.3 9.6

Grassland/Shrubland Agriculture 545 177 121 1.2 8.9

Agriculture Forest 326 123 84 0.7 5.3

Other Other 2,222 n/a n/a 5.0 36.3

Totals 6,121 13.9 100.0
132 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Griffith, G.E., Bryce, S.A., Omernik, J.M., Comstock, J.A., 

Rogers, A.C., Harrison, B., Hatch, S.L., and Bezanson, D., 

2004, Ecoregions of Texas: U.S. Geological Survey Ecoregion Map Series, scale 1:2,500,000, accessed September 9, 

2008, at ftp://ftp.epa.gov/wed/ecoregions/tx/tx_front.pdf.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Texas Parks and Wildlife, 2008, The vegetation types of Texas: 

Texas Parks and Wildlife database, accessed September 25, 

2008, at http://www.tpwd.state.tx.us/publications/pwdpubs/

pwd_bn_w7000_0120/grassland/.

U.S. Census Bureau, 2001, Ranking tables for metropolitan areas—1990 and 2000: U.S. Census Bureau database, accessed April 1, 2009, at http://www.census.gov/

population/www/cen2000/briefs/phc-t3/tables/tab03.txt.

U.S. Department of Agriculture, 2009, Texas statistics: U.S. 

Department of Agriculture, National Agricultural Statistics 

Service database, accessed April 1, 2009, at http://www.

nass.usda.gov/Statistics_by_State/Texas/.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Wilkins, N., Hays, A., Kubenka, D., Steinbach, D., Grant, W., 

Gonzalez, E., Kjelland, M., and Shackelford, J., 2003, Texas 

rural lands—Trends and conservation implications for the 

21st century: Texas Wildlife Association, 26 p., available 

at http://www.texas-wildlife.org/program-areas/texas-rurallands-trends-and-conservation-implications-for-the-21stcentury.

Yantis, J.H., 1984, The Lexington-Marquez wildlife unit: 

Texas Parks and Wildlife, Federal Aid Series No. 23, 27 p.
Chapter 14

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Edwards Plateau Ecoregion

By Michael P. Stier and Beverly A. Friesen

Ecoregion Description 

The Edwards Plateau Ecoregion covers about 58,634 km2

(22,639 mi2) in south-central Texas (fig. 1). It is mainly an 

eroded and uplifted limestone plateau commonly referred to as 

the “hill country” (fig. 2). In the south and east, the ecoregion 

is characterized by hilly topography, and it is separated from 

neighboring ecoregions further south and east by a geologic 

101° 100° 99° 98°

31°

32°

30°

Central

Great Plains

Southern Texas Plains

ECTP

ECTP

ECTP

Texas

Blackland

Prairies

TBP

Central Oklahoma/

Texas Plains

Chihuahuan

Deserts

WHP

MEXICO

TEXAS

Edwards Plateau

Ecoregion

0 50 100 MILES

0 50 100 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

TEXAS

MEXICO

San Marcos

Honey Creek

Cave

Edwards Aquifer San Antonio

H I L L C O U N T R Y

B A L C O N E S E S C A R P M E N T

TRAVIS

COUNTY

Guadalupe Riv e r

Austin

Figure 1. Map of Edwards Plateau Ecoregion and surrounding ecoregions, showing land-use/land-cover classes from 1992 National Land 

Cover Dataset (Vogelmann and others, 2001); note that not all land-use/land-cover classes shown in explanation may be depicted on map; 

note also that, for this “Status and Trends of Land Change” study, transitional land-cover class was subdivided into mechanically disturbed 

and nonmechanically disturbed classes. Squares indicate locations of 10 x 10 km sample blocks analyzed in study. Index map shows 

locations of geographic features mentioned in text. Abbreviations for Great Plains ecoregions are listed in appendix 2. Also shown is part 

of one Western United States ecoregion, Chihuahuan Deserts. See appendix 3 for definitions of land-use/land-cover classifications.

feature known as the “Balcones Escarpment,” a fault zone 

containing numerous cliffs and springs. The ecoregion 

is surrounded by (clockwise, from its southwest end) the 

Chihuahuan Deserts, Central Great Plains, Central Oklahoma/

Texas Plains, Texas Blackland Prairies, and Southern Texas 

Plains Ecoregions (Omernik, 1987; U.S. Environmental 

Protection Agency, 1997).
134 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Elevations in the Edwards Plateau Ecoregion range 

from about 100 m to more than 1,000 m. Average annual 

rainfall amounts are 380 to 840 mm (15–33 in.), increasing 

from west to east and peaking in May, June, and September. 

The Edwards Plateau Ecoregion is one of the largest areas 

of continuous karst topography in the United States. Karst 

terrain, formed by the erosion of limestone bedrock, is 

characterized by sinkholes and caves that allow water to 

flow in underground drainage systems. Cave and karst 

aquifers, such as the large Edwards aquifer, are important 

economic and scientific resources (fig. 3). Honey Creek

Cave, a tributary of the Guadalupe River, is the longest cave 

in Texas (32 km long) and is still being explored (Texas State 

Historical Association, 2007).

Vegetation primarily consists of small trees, shrubs, and 

grasses in juniper (Juniperus spp.) and oak (Quercus spp.) 

associations, mesquite (Prosopis spp.) and oak savannas, and 

scrub oak (Quercus turbinella) forests (fig. 4). The major 

land use is livestock grazing of beef cattle, sheep, and goats 

(fig. 5). In addition to livestock production, many ranches

offer commercial hunting of exotic and native species to 

provide an additional source of income. In more populated 

areas throughout the ecoregion, the diverse economy is 

driven by tourism, pharmaceutical and high-tech companies, 

military installations, and numerous universities and colleges 

(for example, University of Texas at Austin, as well as Texas 

State University, in San Marcos). 

The two largest urban centers in the Edwards Plateau 

Ecoregion are San Antonio and Austin, which lie near its 

southeastern edge. Nearly all municipal, industrial, and irrigation 

water used in the San Antonio area comes from the Edwards 

aquifer (Blome and others, 2006). Although the ecoregion 

historically has been a semiarid, sparsely populated rangeland, 

development in this rugged area has expanded. As urban areas 

and economic activities continue to flourish, the population of 

the ecoregion is expected to grow considerably. Travis County 

(which includes Austin) is the most populous county in the 

ecoregion, and its population is expected to nearly double 

between 2000 and 2050 (El-Hage and Moulton, 1999). Expected 

population growth and the increasing demand for water raise 

concerns for the sustainability of the Edwards aquifer and the 

future availability of water resources in the ecoregion.

Figure 2. “Hill country” in Edwards Plateau Ecoregion.

Figure 3. Source water for Edwards aquifer flowing through 

limestone, in Edwards Plateau Ecoregion.

Figure 4. Prairie oak savanna with post oak (Quercus stellata) and 

live oak (Quercus virginiana) mixed with Indiangrass (Sorghastrum 

nutans) and little bluestem (Schizachyrium scoparium) grasses, in 

Edwards Plateau Ecoregion.

Figure 5. Cattle and goats grazing in open pasture in Edwards 

Plateau Ecoregion.
Chapter 14—Edwards Plateau Ecoregion 135

Figure 6. Overall spatial change in Edwards Plateau Ecoregion 

(EP; darker bars) compared with that of all 17 Great Plains ecoregions 

(lighter bars). Each horizontal set of bars shows proportions of 

ecoregion that experienced change during one, two, three, or four time 

periods; highest level of spatial change in Edwards Plateau Ecoregion 

(four time periods) labeled for clarity. See table 2 for years covered by 

each time period. See appendix 2 for key to ecoregion abbreviations.

Figure 7. Estimates of land-cover change per time period, 

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Edwards Plateau 

Ecoregion are represented by red bars in each time period.

Contemporary Land-Cover Change 

(1973 to 2000)

The overall spatial change (the percentage of land 

area that changed at least one time) in the Edwards Plateau 

Ecoregion between 1973 and 2000 is estimated at 5.5 percent 

(table 1). Compared to other Great Plains ecoregions, change 

in the Edwards Plateau Ecoregion was moderate (fig. 6). 

Of the land that changed, 4.7 percent changed one time, 

and 0.7 percent changed two times (table 1). Two or more 

changes occurred when forest and grassland/shrubland areas 

were cleared for pasture (agriculture land-cover class) or to 

enhance rangeland for grazing (mechanically disturbed landcover class). Over time, however, some of these cleared areas 

reverted back to their original forested state if they were not 

continually managed. 

Land-use/land-cover change per time period was 

relatively small for the first three time periods (1973–1980, 

1980–1986, 1986–1992), ranging from about 1.2 to 1.6 

percent (table 2). Between 1992 and 2000, change across 

the ecoregion increased by a modest 2.3 percent. Comparing 

normalized annual rates of land-cover change (table 2; fig. 7),

the period between 1986 and 1992 experienced nearly the 

same normalized annual rate of change as the period between 

1992 and 2000, but they experienced different types of landcover conversions (table 3). 

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Grassland/shrubland and forest constitute nearly 83 

percent of the ecoregion’s area (table 4). The dominant land 

cover is grassland/shrubland; throughout the study period 

(1973–2000), the amount of grassland/shrubland remained 

stable at about 56 percent of the ecoregion. Forest and 

agriculture were not as stable as grassland/shrubland during 

the study period: forest declined from 28.5 to 27.0 percent of 

the ecoregion, while agriculture increased from 13.7 to 14.3 

percent of the ecoregion (table 4; figure 8). 

The dominant land-cover conversions between 1986 and 

1992 were in the grassland/shrubland class. During this time 

period, however, grassland/shrubland increased rather than 

decreased in coverage at the expense of forest and agricultural 

land (table 3). Contributing to these land-cover conversions 

were extensive brush management to improve livestock 

pasture, as well as the enactment of the Conservation Reserve 

Program (CRP) in 1985, which provided incentives to convert 

highly erodible cropland to permanent vegetative cover.

Over the entire study period (1973–2000), the dominant 

factor influencing land-use/land-cover change in the Edwards 

Plateau Ecoregion was the clearing of forest to expand 

rangeland for livestock grazing and to create open range for 

lease hunting on ranchlands (table 3). Trees and shrubs were 

removed to increase the diversity needed to support a range of 

wildlife. Lease hunting offered by ranchers was an important 

recreational and economic activity in the ecoregion. 

Additionally, ranchers clear mesquite and other brush 

to improve conditions for white-tailed deer (Odocoileus 

virginianus), quail (Colinus virginianus and Callipepla 

squamata), wild turkey (Meleagris gallopavo), javelina 

(Pecari tajacu), and blackbuck (Antilope cervicapra), as well 

as endangered wildlife species such as the black-capped vireo 
136 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

(Vireo atricapilla) (Texas Parks and Wildlife, 2007). Ranchers 

use mechanical methods such as root plowing to thin out or 

remove unwanted brush, and they also use herbicides and 

biological methods to keep brush from returning (Bovey, 2001). 

Agricultural land increased slightly between 1973 and 

2000 as grassland/shrubland was converted to pasture for 

enhanced livestock grazing (table 3). Developed lands also 

increased throughout the study period, resulting in a net gain 

of more than 0.5 percent (314 km2) between 1973 and 2000 

(table 4; fig. 8). Population gains in the urbanizing areas 

surrounding the Austin and San Antonio metropolitan regions 

contributed most of this increase (U.S. Census Bureau, 

1970–2000 [various years]). After 1986, most development 

occurred on forest or grassland/shrubland (fig. 8).

The Edwards Plateau Ecoregion is changing from a 

characteristically rural region to an urban one. Since 1940, 

the population growth rate of the Edwards Plateau Ecoregion 

has surpassed that of the United States as a whole, with most 

of the population increases occurring in the ecoregion’s urban 

areas. As population grows and land development expands, 

one of the main challenges within the ecoregion will be to 

maintain an adequate supply of clean water from the Edwards 

aquifer. Declining groundwater levels of the Edwards 

aquifer are making the water susceptible to contamination. 

As groundwater levels decline, salt-water intrusion from the 

Texas Gulf Coast into the aquifer is possible (McCormick 

and others, unpub. data, 2004). Additionally, expanding 

land development is causing groundwater to become more 

susceptible to urban-pollutant runoff. To address these issues, 

communities within the Edwards Plateau Ecoregion are 

working with scientists and urban and regional planners to 

ensure that the water resources of the Edwards aquifer will be 

adequate for future generations.

Figure 8. Normalized average net change in Edwards Plateau 

Ecoregion by time period for each land-cover class. Bars above 

zero axis represent net gain, whereas bars below zero represent 

net loss. Note that not all land-cover classes shown in explanation 

may be represented in figure. See appendix 3 for definitions of 

land-use/land-cover classifications.

−1

−0.5

0

0.5

1

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Mechanically disturbed

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS
Chapter 14—Edwards Plateau Ecoregion 137

Table 1. Percentage of Edwards Plateau Ecoregion land cover 

that changed at least one time during study period (1973–2000) and 

associated statistical error.

[Most sample pixels remained unchanged (94.5 percent), whereas 5.5 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 4.7 1.0 3.7 5.7 0.8 14.5

2 0.8 0.4 0.4 1.1 0.2 34.6

3 0.0 0.0 0.0 0.0 0.0 49.8

4 0.0 0.0 0.0 0.0 0.0 97.2

Overall 

spatial 

change

5.5 1.2 4.3 6.7 0.8 14.5

Table 2. Raw estimates of change in Edwards Plateau Ecoregion land cover, 

computed for each of four time periods between 1973 and 2000, and associated 

error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period

Total 

change

(% of ecoregion)

Margin

of error

(+/− %)

Lower 

bound

(%)

Upper 

bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average 

rate

(% per 

year)

Estimate of change, in percent stratum

1973–1980 1.2 0.6 0.7 1.8 0.4 30.1 0.2

1980–1986 1.2 0.4 0.7 1.6 0.3 24.6 0.2

1986–1992 1.6 0.4 1.2 2.0 0.3 17.2 0.3

1992–2000 2.3 0.5 1.8 2.8 0.4 15.6 0.3

Estimate of change, in square kilometers

1973–1980 729 324 405 1,053 220 30.1 104

1980–1986 676 245 431 921 166 24.6 113

1986–1992 950 242 709 1,192 164 17.2 158

1992–2000 1,352 311 1,041 1,663 211 15.6 169
138 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Principal land-cover conversions in Edwards Plateau Ecoregion, showing amount of area changed (and margin of error, 

calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study period. 

See appendix 3 for definitions of land-cover classifications.

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Forest Grassland/Shrubland 145 91 61 0.2 19.8

Mechanically disturbed Grassland/Shrubland 143 203 138 0.2 19.6

Forest Agriculture 114 136 92 0.2 15.7

Grassland/Shrubland Mechanically disturbed 108 136 92 0.2 14.8

Grassland/Shrubland Agriculture 96 72 49 0.2 13.1

Other Other 124 n/a n/a 0.2 17.0

Totals 729 1.2 100.0

1980–1986 Forest Grassland/Shrubland 180 129 87 0.3 26.7

Mechanically disturbed Grassland/Shrubland 100 136 92 0.2 14.8

Grassland/Shrubland Agriculture 97 46 31 0.2 14.4

Grassland/Shrubland Forest 91 104 71 0.2 13.4

Agriculture Grassland/Shrubland 67 67 46 0.1 10.0

Other Other 140 n/a n/a 0.2 20.7

Totals 676 1.2 100.0

1986–1992 Forest Grassland/Shrubland 315 180 122 0.5 33.1

Agriculture Grassland/Shrubland 148 67 46 0.3 15.6

Grassland/Shrubland Agriculture 100 53 36 0.2 10.5

Grassland/Shrubland Forest 92 57 39 0.2 9.6

Grassland/Shrubland Mechanically disturbed 91 65 44 0.2 9.6

Other Other 204 n/a n/a 0.3 21.5

Totals 950 1.6 100.0

1992–2000 Grassland/Shrubland Agriculture 291 146 99 0.5 21.5

Grassland/Shrubland Mechanically disturbed 232 163 110 0.4 17.2

Agriculture Grassland/Shrubland 200 137 93 0.3 14.8

Forest Grassland/Shrubland 168 77 52 0.3 12.4

Grassland/Shrubland Forest 134 74 50 0.2 9.9

Other Other 328 n/a n/a 0.6 24.3

Totals 1,352 2.3 100.0

1973–2000

(overall)

Forest Grassland/Shrubland 807 369 250 1.4 21.8

Grassland/Shrubland Agriculture 584 210 142 1.0 15.7

Grassland/Shrubland Mechanically disturbed 472 277 187 0.8 12.7

Agriculture Grassland/Shrubland 436 209 141 0.7 11.8

Grassland/Shrubland Forest 322 153 104 0.5 8.7

Other Other 1,087 n/a n/a 1.9 29.3

Totals 3,708 6.3 100.0
Chapter 14—Edwards Plateau Ecoregion 139

Table 4. Estimated area (and margin of error) of each land-cover class in Edwards Plateau Ecoregion, calculated five times between 

1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed Mechanically 

disturbed Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.3 0.1 1.2 0.6 0.3 0.4 0.1 0.0 0.2 0.1 28.5 6.0 55.7 6.5 13.7 4.3 0.0 0.0 0.0 0.0

1980 0.3 0.1 1.4 0.7 0.2 0.2 0.1 0.0 0.2 0.1 28.0 5.9 55.8 6.5 14.0 4.3 0.0 0.0 0.0 0.0

1986 0.3 0.1 1.5 0.7 0.1 0.1 0.1 0.0 0.2 0.1 27.8 5.8 55.9 6.5 14.1 4.3 0.0 0.0 0.0 0.0

1992 0.3 0.1 1.6 0.8 0.2 0.1 0.1 0.0 0.2 0.1 27.3 5.6 56.2 6.4 14.1 4.3 0.0 0.0 0.0 0.0

2000 0.3 0.1 1.8 0.9 0.5 0.3 0.1 0.0 0.2 0.1 27.0 5.5 55.8 6.2 14.3 4.2 0.0 0.0 0.0 0.0

Net

change 0.0 0.0 0.6 0.3 0.2 0.2 0.0 0.0 0.0 0.0 –1.5 0.8 0.1 0.9 0.6 0.5 0.0 0.0 0.0 0.0

Gross

change 0.0 0.0 0.5 0.3 1.3 0.8 0.0 0.0 0.0 0.0 2.0 0.7 3.8 0.9 1.6 0.5 0.0 0.0 0.1 0.1

Area, in square kilometers

1973 174 51 725 381 179 217 31 12 136 72 16,705 3,525 32,642 3,823 8,032 2,529 8 7 0 0

1980 174 51 797 398 115 136 36 14 137 72 16,439 3,466 32,701 3,838 8,227 2,514 8 7 0 0

1986 181 52 853 433 53 47 38 15 135 72 16,283 3,385 32,805 3,786 8,278 2,510 8 7 0 0

1992 180 52 938 489 114 66 45 18 134 72 15,983 3,297 32,974 3,737 8,244 2,508 8 7 13 19

2000 181 52 1,040 543 297 167 49 20 134 72 15,811 3,233 32,697 3,650 8,410 2,469 8 6 7 11

Net

change 7 11 314 183 117 141 18 14 –2 6 –894 444 55 518 377 317 0 0 7 11

Gross

change 21 9 314 183 755 452 23 13 9 7 1,196 429 2,218 547 963 289 0 0 34 39
140 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Blome, C.D., Faith, J.R., and Ozuna, G.B., 2006, Geohydrologic framework of the Edwards and Trinity aquifers, southcentral Texas: U.S. Geological Survey Fact Sheet 2006–

3145, 4 p., available at http://pubs.usgs.gov/fs/2006/3145/.

Bovey, W. Rodney, 2001, Woody plants and woody plant management—Ecology, safety, and environmental impact: Boca 

Raton, Fla., CRC Press, p. 379–381.

El-Hage, Albert, and Moulton, D.W., 1999, Area study—

Williamson and parts of adjacent counties, evaluation of 

selected natural resources within Williamson and parts of 

adjacent counties, Texas: Texas Parks and Wildlife, 23 p., 

available at www.tpwd.state.tx.us/publications/pwdpubs/

media/pwd_rp_t3200_1050e.pdf.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Texas Parks and Wildlife, 2007, South Texas wildlife management—Historical perspective: Texas Parks and Wildlife 

database, accessed April 27, 2007, at http://www.tpwd.state.

tx.us/huntwild/wild/species/.

Texas State Historical Association, 2007, The handbook of 

Texas online: Texas State Historical Association database, 

accessed April 27, 2007, at http://www.tshaonline.org/

handbook/online.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed April 27, 2007, at http://www.census.gov/prod/

www/decennial.html.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E, Howard, S.M., Yang, L., Larson, C.R., Wylie, 

B.K., and van Driel, N., 2001, Completion of the 1990s 

National Land Cover Data Set for the conterminous United 

States from Landsat Thematic Mapper data and ancillary 

data sources: Photogrammetric Engineering & Remote 

Sensing, v. 67, p. 650–662. 
Chapter 15

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Southern Texas Plains Ecoregion

By Michael P. Stier

Ecoregion Description

The Southern Texas Plains Ecoregion covers an area 

of about 54,744 km2 (21,137 mi2) that stretches from just 

southwest of San Antonio, Texas, south to the Mexican border 

(fig.1) (Omernik, 1987; U.S. Environmental Protection Agency, 

1997). The Balcones Escarpment, which extends eastward from 

the Rio Grande, near the city of Del Rio, Texas, to San Antonio, 

is the northern boundary of the ecoregion. The ecoregion is 

surrounded by, from northwest to southeast, the Chihuahuan 

Deserts, Edwards Plateau, Texas Blackland Prairies, East Central 

Texas Plains, and Western Gulf Coastal Plain Ecoregions.

101° 100° 99° 98°

29°

28°

27°

27°

28°

Edwards Plateau

Western Gulf

Coastal Plain

East Central

Texas Plains

TBP

CD

MEXICO

0 50 100 MILES

0 50 100 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

Del Rio

Eagle Pass ZAVALA FRIO

DIMMIT LA

SALLE

WEBB

ZAPATA

MCMULLEN

Waco

Austin

San Antonio

WINTER GARDEN

Laredo

Zapata

MEXICO

G r a n d e

R i o

TEXAS

Southern Texas Plains

Ecoregion

BALCONES ESCARPMENT

Figure 1. Map of Southern Texas Plains Ecoregion and surrounding ecoregions, showing land-use/land-cover classes from 1992 National 

Land Cover Dataset (Vogelmann and others, 2001); note that not all land-use/land-cover classes shown in explanation may be depicted 

on map; note also that, for this “Status and Trends of Land Change” study, transitional land-cover class was subdivided into mechanically 

disturbed and nonmechanically disturbed classes. Squares indicate locations of 10 x 10 km sample blocks analyzed in study. Index map 

shows locations of geographic features mentioned in text. Abbreviations for Great Plains ecoregions are listed in appendix 2. Also shown is 

part of one Western United States ecoregion, Chihuahuan Deserts (CD). See appendix 3 for definitions of land-use/land-cover classifications.

The terrain in the Southern Texas Plains Ecoregion is 

relatively flat, with areas of rolling hills that range in elevation 

from 30 to 300 m (fig. 2). The ecoregion consists of three 

major subdivisions: (1) the Interior Lowland Belt, which 

is characterized by black soils; (2) the Coastal Belt, which 

is blanketed by a thick cover of sand; and (3) the Central 

Dissected Belt, which consists of mostly calcareous clays and 

some areas of deep sand (Texas State Historical Association, 

2007). Average annual rainfall amounts range from 510 to 

760 mm (20–30 in.), increasing from west to east across the 

ecoregion (Conservation History Association of Texas, 2008). 
142 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

This ecoregion is characterized by savannas, plains, 

and shrublands that are dominated by drought-tolerant, and 

often thorn-laden, small trees and shrubs (Omernik, 1987). 

Mesquite (Prosopis spp.), which often is the dominant woody 

species, is found as scattered individuals or in grouped stands 

in grasslands. Historically, grasses were a major component 

of the ecoregion prior to settlement. As grasses were grazed 

by livestock, the fragile soil structure eroded away, leaving 

mostly rocky, dry soils that mainly support woody species 

(Texas A&M Forest Service, 2008). Today (2014), as a result 

of overgrazing and the suppression of natural wildfires, 

mesquite, pricklypear (Opuntia spp.) cactus, eastern redcedar 

(Juniperus virginiana), Ashe’s juniper (Juniperus ashei), 

and abundant blackbrush (Coleogyne ramosissima) are 

encroaching into the grasslands (Harker, 1999). Because of 

woody encroachment into grassland areas, brush management 

is often necessary to improve range for livestock grazing.

Although the predominant land cover is grassland/

shrubland, agriculture is present in subregional concentrations. 

Major crops grown include hay, wheat, oats, cotton, sorghum, 

and sunflowers. Bermuda onions, cabbage, spinach, beets, 

and other vegetables are grown in the “Winter Garden” region 

Figure 2. Shrub-dominated grassland/shrubland in Southern 

Texas Plains Ecoregion.

Figure 3. Field of irrigated cabbage in “Winter Garden” 

agricultural area, located in south Texas, north of Laredo and 

southwest of San Antonio, in Southern Texas Plains Ecoregion.

(fig. 3), located in the northeast corner of the Southern Texas 

Plains Ecoregion, north of Laredo, Texas, and centered around 

Dimmit, Zavala, Frio, and La Salle Counties. This irrigated 

area also produces melons and nuts. Most land outside the 

irrigated areas is rangeland devoted to livestock production. 

Other major rural industries include petroleum and natural-gas 

extraction and lease hunting. 

Border cities such as Laredo and Eagle Pass, Texas, play 

an increasingly important role in the economy of the ecoregion 

through cross-border trade with Mexico, including trucking 

and health services (Patrick, 2000; Gilmer and others, 2001). 

The population within the ecoregion grew considerably during 

the study period (1973–2000). Webb County, which includes 

Laredo, the largest city in the ecoregion, grew from 99,258 

in 1980 to 193,117 in 2000 (U.S. Census Bureau, 1970–2000 

[various years]). Only the already sparsely populated McMullen 

County decreased in population, from 879 in 1980 to 851 in 

2000 (U.S. Census Bureau, 1970–2000 [various years]).

Contemporary Land-Cover Change 

(1973 to 2000) 

The overall spatial change (the percentage of land area 

that changed at least one time) in the Southern Texas Plains 

Ecoregion between 1973 and 2000 is estimated at 12 percent 

(table 1). Compared to other Great Plains ecoregions, change 

in the Southern Texas Plains Ecoregion was moderately high 

(fig. 4). Of the land that changed, 7.2 percent changed one 

time, 4.2 percent change two times, and 0.5 percent changed 

three times (table 1). In many instances, grassland/shrubland 

was converted to agriculture or mechanically disturbed in 

one time period, only to revert to grassland/shrubland in a 

subsequent time period. 

Change per time period was moderate between 1973 and 

1980 (3.0 percent) and between 1980 and 1986 (3.6 percent) 

(table 2). During the last two time periods (1986–1992, 

1992–2000), land-use/land-cover change was significantly 

higher (5.8 percent and 4.8 percent, respectively). Much of 

this change can be attributed to brush-management activities 

to improve livestock grazing and wildlife habitat. Principal 

land-cover conversions during these last two time periods 

involved grassland/shrubland and mechanically disturbed 

land (table 3). When normalized to account for varying 

lengths in study periods, annual rates of change increased 

gradually between 1973 and 1992, from 0.4 percent to 1.0 

percent, and then decreased to 0.6 percent between 1992 and 

2000 (table 2; fig. 5). 

Grassland/shrubland and agriculture make up almost 

92 percent of the ecoregion. The largest net change that 

occurred between 1973 and 2000 was a 1.0 percent (544 km2) 

increase in agricultural land and a 0.9 percent (517 km2) 

decrease in grassland/shrubland (table 4).

Between 1973 and 2000, mechanically disturbed land had 

little net increase but experienced a gross change equivalent 
Chapter 15—Southern Texas Plains Ecoregion 143

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in

four time

periods

Figure 4. Overall spatial change in Southern Texas Plains 

Ecoregion (STP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that experienced change during one, 

two, three, or four time periods; highest level of spatial change in 

Southern Texas Plains Ecoregion (four time periods) labeled for 

clarity. See table 2 for years covered by each time period. See 

appendix 2 for key to ecoregion abbreviations.

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

−4

−2

0

2

4

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Figure 5. Estimates of land-cover change per time period,

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Southern Texas 

Plains Ecoregion are represented by red bars in each time 

period.

to 4.2 percent of the ecoregion (2,279 km2). A large amount of 

grassland/shrubland was converted to mechanically disturbed 

land between 1986 and 1992 (table 3). By 2000, most of the 

mechanically disturbed land was converted back to grassland/

shrubland, and, as a result, the amount of mechanically 

disturbed land showed very little net change between 1973 and 

2000. This also was true for grassland/shrubland, which had 

large amounts of gross change (8.4 percent) and much less net 

change (–0.9 percent) (table 4). 

Other net changes generally were minor in terms of 

total area affected. Surface-water area decreased by 283 km2

(table 4). Wetland expanded by 129 km2 as surface water 

retreated from small lakes, reservoirs, and ponds likely because 

of annual or seasonal variation in precipitation levels (table 4). 

A slight increase in mining land of 115 km2 was caused by the 

expansion of gas- and oil-drilling activities (table 4). 

Developed land steadily increased throughout the study 

period: in 1973, it covered 0.5 percent of the ecoregion (296 

km2), and by 2000, it covered 0.8 percent of the ecoregion 

(454 km2) (table 4; fig. 6). Population gains in the urbanizing 

areas of Laredo, Del Rio, and Zapata, Texas, contributed 

to the expansion of developed land (U.S. Census Bureau, 

1970–2000 [various years]). Most development expanded 

Figure 6. Normalized average net change in Southern Texas 

Plains Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications.
144 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

onto grassland/shrubland and agricultural land, especially 

during the last two time periods (1986–1992, 1992–2000).

The four most common land-cover conversions were 

grassland/shrubland to agriculture, agriculture to grassland/

shrubland, grassland/shrubland to mechanically disturbed, 

and mechanically disturbed to grassland/shrubland (table 3). 

Agricultural land increased over the entire study period, at the 

expense of grassland/shrubland. Demand for livestock and 

agricultural products such as wheat, vegetables, and cotton 

led to the expansion of agriculture, specifically in the irrigated 

“Winter Garden” region. Not all of the grassland/shrublandto-agriculture conversions were successful, however, 

especially when crops were grown on poor soils with limited 

water supplies. The failure of farmers and ranchers to raise 

crops in these areas caused some of the agricultural land to 

revert to grassland/shrubland. 

Another major factor that influenced land-use/land-cover 

change in the Southern Texas Plains Ecoregion was brush 

clearing to improve wildlife habitat and grazing conditions 

for livestock, which caused a temporary increase in the 

amount of mechanically disturbed land between 1986 and 

1992 (most of the cleared land had reverted to grassland/

shrubland by 2000). Ranchers used mechanical means such 

as root plowing and front-end stacking, as well as fire, 

herbicides, and biological means, to thin out mesquite and 

other woody brush (Bovey, 2001). In many areas of the 

ecoregion, “checkerboard,” or “patchwork style” brushclearing patterns were created by the ranchers (Archer and 

others, 2011) to provide the diversity of cover needed to 

Figure 7. White-tailed deer in brush-cleared lane on ranch in 

Southern Texas Plains Ecoregion.

support a range of wildlife species, including white-tailed 

deer (Odocoileus virginianus), quail (Cyrtonyx montezumae, 

Callipepla squamata, and Colinus virginianus), the 

endangered black-capped vireo (Vireo atricapilla), mourning 

dove (Zenaida macroura), white-winged dove (Zenaida

asiatica), javelina (Pecari tajacu), and blackbuck (Antilope 

cervicapra) (Texas Parks and Wildlife, 2007) (fig. 7). The 

rows of brush that were left unplowed provided cover for 

many birds, whereas the brush-cleared rows that were 

reseeded with grass improved grazing for both livestock and 

wildlife, including game wildlife, and so the lease hunting 

offered by ranchers flourished in the ecoregion. As these 

brush-management techniques increased, so, too, did the 

amount of land-cover change during the study period. 
Chapter 15—Southern Texas Plains Ecoregion 145

Table 1. Percentage of Southern Texas Plains Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (88.0 percent), whereas 12.0 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 7.2 1.2 6.0 8.4 0.8 11.4

2 4.2 2.1 2.1 6.3 1.4 33.7

3 0.5 0.5 0.0 0.9 0.3 62.2

4 0.0 0.0 0.0 0.0 0.0 66.1

Overall 

spatial 

change

12.0 2.5 9.4 14.5 1.7 14.4

Table 2. Raw estimates of change in Southern Texas Plains Ecoregion land cover, computed for each of 

four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 3.0 0.7 2.2 3.7 0.5 16.8 0.4

1980–1986 3.6 1.0 2.7 4.6 0.6 17.9 0.6

1986–1992 5.8 2.3 3.5 8.1 1.6 26.8 1.0

1992–2000 4.8 1.9 3.0 6.7 1.3 26.2 0.6

Estimate of change, in square kilometers

1973–1980 1,625 402 1,223 2,027 272 16.8 232

1980–1986 1,979 522 1,456 2,501 354 17.9 330

1986–1992 3,172 1,255 1,917 4,426 850 26.8 529

1992–2000 2,639 1,021 1,619 3,660 692 26.2 330
146 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Principal land-cover conversions in Southern Texas Plains Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 689 267 181 1.3 42.4

Agriculture Grassland/Shrubland 338 161 109 0.6 20.8

Grassland/Shrubland Mechanically disturbed 168 107 72 0.3 10.3

Mechanically disturbed Grassland/Shrubland 136 99 67 0.2 8.4

Grassland/Shrubland Mining 61 82 55 0.1 3.7

Other Other 233 n/a n/a 0.4 14.4

Totals 1,625 3.0 100.0

1980–1986 Grassland/Shrubland Agriculture 640 269 182 1.2 32.4

Agriculture Grassland/Shrubland 413 156 105 0.8 20.8

Grassland/Shrubland Mechanically disturbed 296 328 222 0.5 14.9

Mechanically disturbed Grassland/Shrubland 125 85 58 0.2 6.3

Water Grassland/Shrubland 124 165 112 0.2 6.3

Other Other 381 n/a n/a 0.7 19.3

Totals 1,979 3.6 100.0

1986–1992 Grassland/Shrubland Mechanically disturbed 976 982 666 1.8 30.8

Agriculture Grassland/Shrubland 755 259 176 1.4 23.8

Grassland/Shrubland Agriculture 395 153 104 0.7 12.5

Mechanically disturbed Grassland/Shrubland 230 222 151 0.4 7.3

Grassland/Shrubland Water 116 115 78 0.2 3.7

Other Other 699 n/a n/a 1.3 22.0

Totals 3,172 5.8 100.0

1992–2000 Mechanically disturbed Grassland/Shrubland 834 961 651 1.5 31.6

Grassland/Shrubland Agriculture 377 165 111 0.7 14.3

Agriculture Grassland/Shrubland 360 133 90 0.7 13.6

Grassland/Shrubland Mechanically disturbed 178 129 88 0.3 6.7

Water Wetland 147 135 91 0.3 5.6

Other Other 744 n/a n/a 1.4 28.2

Totals 2,639 4.8 100.0

1973–2000

(overall)

Grassland/Shrubland Agriculture 2,101 591 400 3.8 22.3

Agriculture Grassland/Shrubland 1,865 546 370 3.4 19.8

Grassland/Shrubland Mechanically disturbed 1,618 1,155 783 3.0 17.2

Mechanically disturbed Grassland/Shrubland 1,326 1,046 709 2.4 14.1

Water Wetland 311 223 151 0.6 3.3

Other Other 2,194 n/a n/a 4.0 23.3

Totals 9,414 17.2 100.0
Chapter 15—Southern Texas Plains Ecoregion 147

Table 4. Estimated area (and margin of error) of each land-cover class in Southern Texas Plains Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed Mechanically 

disturbed Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.8 0.7 0.5 0.4 0.6 0.4 0.2 0.1 0.1 0.1 5.5 2.3 79.1 4.7 12.5 3.4 0.8 0.3 0.0 0.0

1980 0.9 0.6 0.6 0.4 0.6 0.4 0.2 0.2 0.1 0.1 5.4 2.3 78.4 4.8 13.1 3.6 0.7 0.3 0.0 0.0

1986 0.5 0.2 0.6 0.4 0.9 0.8 0.3 0.2 0.1 0.1 5.4 2.3 77.7 4.9 13.6 3.7 0.9 0.3 0.0 0.0

1992 0.8 0.5 0.7 0.4 2.1 1.9 0.3 0.2 0.1 0.1 5.3 2.3 76.6 5.0 13.2 3.7 1.0 0.4 0.0 0.0

2000 0.3 0.1 0.8 0.5 0.6 0.4 0.4 0.2 0.1 0.1 5.1 2.2 78.1 5.0 13.5 3.8 1.0 0.4 0.0 0.0

Net

change –0.5 0.6 0.3 0.2 0.1 0.3 0.2 0.1 0.0 0.0 –0.3 0.2 –0.9 1.2 1.0 1.1 0.2 0.2 0.0 0.0

Gross

change 1.5 1.2 0.3 0.2 4.2 3.6 0.4 0.2 0.1 0.1 0.5 0.2 8.4 3.3 4.7 1.0 0.6 0.4 0.0 0.0

Area, in square kilometers

1973 448 357 296 200 306 220 83 62 61 72 2,998 1,243 43,294 2,573 6,831 1,887 426 165 0 0

1980 477 354 320 205 353 229 124 115 55 63 2,941 1,239 42,896 2,640 7,195 1,973 383 159 0 0

1986 291 129 354 212 468 417 155 124 43 46 2,933 1,249 42,562 2,689 7,459 2,007 479 187 0 0

1992 423 288 393 221 1,129 1,015 167 113 39 41 2,904 1,246 41,924 2,738 7,226 2,004 538 212 0 0

2000 165 74 454 246 350 217 198 95 50 55 2,819 1,227 42,777 2,756 7,376 2,061 555 206 0 0

Net

change –283 346 158 96 44 187 115 66 –12 17 –179 87 –517 630 544 628 129 108 0 0

Gross

change 839 641 159 96 2,279 1,990 206 134 33 47 256 111 4,606 1,830 2,588 537 351 196 0 0
148 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Archer, S.R., Davies, K.W., Fulbright, T.E., McDaniel, K.C., Wilcox, 

B.P., and Predick, K.I., 2011, Brush management as a rangeland 

conservation strategy—A critical evaluation, in Briske, D.D., 

ed., Conservation benefits of rangeland practices—Assessment, 

recommendations, and knowledge gaps: U.S. Department of 

Agriculture, Natural Resources Conservation Service, p. 105–170, 

accessed September 9, 2013, at http://www.nrcs.usda.gov/Internet/

FSE_DOCUMENTS/stelprdb1045798.pdf.

Bovey, W. Rodney, 2001, Woody plants and woody plant 

management—Ecology, safety, and environmental impact: Boca 

Raton, Fla., CRC Press, p. 379–381.

Conservation History Association of Texas, 2008, Rio Grande 

valley, in The Texas Legacy Project: Conservation History 

Association of Texas database, accessed October 6, 2008, at 

http://texaslegacy.org/m/regions/riograndevalley.html.

Gilmer, R.W., Gurch, M., and Wang, T., 2001, Texas border cities—

An income growth perspective: Federal Reserve Bank of Dallas, 

accessed March 17, 2009, at http://www.dallasfed.org/assets/

documents/research/border/tbe_gilmer.pdf.

Harker, F. Donald, 1999, Landscape restoration handbook: Boca 

Raton, Fla., CRC Press, p. 231–238.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, v. 

77, no. 1, p. 118–125.

Patrick, Michael, 2000, The Texas border region enjoys a decade 

of strong growth: Texas A&M International University, Texas 

Center for Border Economic and Enterprise Development, 

accessed March 17, 2009, at http://texascenter.tamiu.edu/pdf_

vision/vision0300present.pdf.

Texas A&M Forest Service, 2008, Trees of Texas: Texas 

A&M Forest Service database, accessed November 3, 

2008, at http://texastreeid.tamu.edu/.

Texas Parks and Wildlife, 2007, Wildlife Fact Sheets: Texas 

Parks and Wildlife database, accessed April 27, 2007, at 

http://www.tpwd.state.tx.us/huntwild/wild/species/.

Texas State Historical Association, 2007, The handbook of 

Texas online: Texas State Historical Association database, 

accessed November 3, 2008, at http://www.tshaonline.org/

handbook/online.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed October 6, 2008, at http://www.census.gov/prod/

www/decennial.html.

U.S. Environmental Protection Agency, 1997, Descriptions 

of level III ecological regions for the CEC report on 

ecological regions of North America: U.S. Environmental 

Protection Agency database, accessed April 12, 2006, 

at http://www.epa.gov/wed/pages/ecoregions/na_eco.

htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Chapter 16

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Texas Blackland Prairies Ecoregion 

By Roger F. Auch

Ecoregion Description 

The Texas Blackland Prairies Ecoregion, located in central 

Texas, consists of two disjunct sections (fig. 1) (Omernik, 1987; 

U.S. Environmental Protection Agency, 1997). The larger, 

northern section runs roughly north-south, from San Antonio, 

Texas, to the Oklahoma border north-northeast of Dallas, Texas; 

it is bounded by (clockwise, from its southwest end) the Southern 

Texas Plains, Edwards Plateau, Central Oklahoma/Texas Plains, 

South Central Plains, and East Central Texas Plains Ecoregions. 

The smaller, southern section, which is located about 88 km 

southeast of San Antonio and is oriented northeast-southwest, is 

commonly called the “Fayette Prairie” (Griffith and others, 2004). 

97° 96° 95°

99° 98°

34°

33°

32°

31°

30°

29°

Central

Oklahoma/

Texas

Plains

Edwards

Plateau

South Central

Plains

OM

East Central

Texas Plains

Western Gulf

Coastal Plain

Southern

Texas Plains

CGP

CGP

GULF of

MEXICO 0 50 100 MILES

0 50 100 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

TEXAS

Texas Blackland Prairies

Ecoregion

OKLAHOMA

Dallas

Fort Worth

Houston

Waco

Temple

Georgetown Granger

Rosebud

Coolidge

Austin

Lockhart

Saint Hedwig

KAUFMAN

COUNTY

COLLIN

FANNIN

ROCKWALL

FAYETTE

CALDWELL

HAYS

MILAM

HUNT

San

Antonio

Garland

Frisco

Westminster

WILLIAMSON

TEXASB r a z o s R i v e r

35

35

35

130

The southern section is almost entirely surrounded by the East 

Central Texas Plains Ecoregion; a small part of the South Central 

Plains Ecoregion abuts its east end. The entire Texas Blackland 

Prairies Ecoregion covers about 50,501 km2 (19,498 mi2). 

The climate is classified as warm temperate (hot summers 

and cool winters), with precipitation levels that range from 710 

to 1,015 mm (28–40 in.) in an average year. Precipitation is less 

in the western part of the ecoregion and more in the eastern part 

(Kottek and others, 2006; PRISM Climate Group, 2006). The 

landforms are level-to-rolling plains, and soils typically are fine 

textured, clayey, and high in shrink-and-swell potential (Omernik, 

1987; U.S. Environmental Protection Agency, 2002; U.S. 

Department of Agriculture, 2008b) (fig. 2). 

Figure 1. Map 

of Texas Blackland 

Prairies Ecoregion and 

surrounding ecoregions, 

showing land-use/landcover classes from 1992 

National Land Cover 

Dataset (Vogelmann 

and others, 2001); note 

that not all land-use/

land-cover classes 

shown in explanation 

may be depicted on 

map; note also that, for 

this “Status and Trends 

of Land Change” study, 

transitional land-cover 

class was subdivided into 

mechanically disturbed 

and nonmechanically 

disturbed classes. 

Squares indicate 

locations of 10 x 10 km 

sample blocks analyzed in study. Index 

map shows locations of geographic 

features mentioned in text. Abbreviations 

for Great Plains ecoregions are listed in 

appendix 2. Also shown are parts of two 

Midwest–South Central United States 

ecoregions: Ouachita Mountains (OM) 

and South Central Plains. See appendix 

3 for definitions of land-use/land-cover 

classifications.
150 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

The Texas Blackland Prairies Ecoregion at the beginning 

of the 19th century was predominantly tallgrass prairie, with 

forest along stream courses and in upland areas (White, 2006). 

By the end of the 1800s, most of the ecoregion had been 

converted to farmland (primarily cropland), although much 

of this cropland had been converted to well-maintained tame 

grass pastureland by 1973, the start of the study period (White, 

2006) (fig. 3). This pastureland is classified with cropland as 

agriculture land-cover class. 

Agriculture remained the predominant land-cover class in 

the ecoregion during the entire 27-year study period. The major 

crops grown in the Texas Blackland Prairies Ecoregion in 2002 

were hay, corn, wheat, sorghum, cotton, pecans, and soybeans. 

Types of livestock production were primarily beef cattle and 

some goats and horses, as well as poultry in localized areas 

(U.S. Department of Agriculture, 2008c) (fig. 4).

Other principal land-cover classes of the ecoregion during 

the study period included forest, grassland/shrubland, and 

developed. Minor land-cover classes included wetland, water, 

and mining. Forest was found primarily in stream drainages 

throughout the ecoregion and, in particular, where mesquite 

(Prosopis spp.) and juniper (Juniperus spp.) shrubland was 

allowed to grow into tree-height woodlands (fig. 5). Forested 

wetlands in riparian bottomlands were another minor natural 

land-cover class (Texas Parks and Wildlife, 1997). Grassland/

shrubland was found in less intensely used grazing land, which 

typically had more varied topography, and on land where 

woody vegetation, such as shrub-sized mesquite and juniper, 

was allowed to grow on pastureland. Later in the study period, 

other areas of grassland/shrubland may have been farmland 

that was idled as part of the Conservation Reserve Program 

(CRP), although this program was much less important in 

the Texas Blackland Prairies Ecoregion than in ecoregions 

of the northern and central Great Plains (U.S. Department of 

Agriculture, 2008a) (fig. 6).

Development occurred in a variety of places, from small 

farming communities to booming metropolitan areas such as the 

Figure 2. Harvested field in Hunt County, Texas, in northern part 

of Texas Blackland Prairies Ecoregion, showing soils that helped 

give ecoregion its name.

Figure 3. Well-maintained pastures in Texas Blackland Prairies 

Ecoregion. A, Level pasture with scattered oak trees in “Fayette 

Prairie” (southern section of Texas Blackland Prairies Ecoregion), 

east of Saint Hedwig, Texas. B, Cattle and cattle egrets (Bubulcus 

ibis), in pasture north of Lockhart, Texas. 

greater Dallas, Austin, and San Antonio, Texas, areas. Exurban 

residential development, although widespread throughout the 

ecoregion, was more prevalent in areas within commuting 

distances of the major urban centers (fig. 7). Water land-cover 

class was present primarily as reservoirs and stock ponds, some 

of which were constructed during the study period. Aggregate 

production was the dominant mining land use. 

Contemporary Land-Cover Change 

(1973 to 2000) 

The overall spatial change (the percentage of land area 

that changed at least one time) in the Texas Blackland Prairies 

Ecoregion between 1973 and 2000 is estimated at 11.1 percent 

(table 1). Compared to other Great Plains ecoregions, change 

in the Texas Blackland Prairies Ecoregion was relatively high 

(fig. 8). The amount of change was similar to that of the East 

Central Texas Plains and Southern Texas Plains Ecoregions 

but greater than that of the Central Oklahoma/Texas Plains 

and Edwards Plateau Ecoregions (fig. 8). Most of the land 

(10.0 percent) changed only once during the study period, but 

some areas (1.1 percent) changed multiple times (table 1). The 

multiple changes typically involved change between agriculture 

A

B
Chapter 16—Texas Blackland Prairies Ecoregion 151

Figure 4. Crops and livestock found in Texas Blackland Prairies 

Ecoregion. A, Cotton and corn fields in northern Caldwell County, 

Texas. B, Hay bales in field east of Rosebud, Texas. C, Sorghum 

field south of San Antonio, Texas, near southwest border of 

ecoregion. D, Cattle grazing and getting shade on pasture east of 

Georgetown, Texas.

Figure 5. Forested land in Texas Blackland Prairies Ecoregion. 

Patch of forest (A) that follows stream drainage behind cropland, 

in western Milam County, Texas; mesquite (B) and juniper (C) 

woodlands, which are becoming more common in ecoregion, from 

area east of Brazos River southeast of Waco, Texas (heights of 

trees are 5–7 m). 

(marginal farmland) and grassland/shrubland, as well as some 

conversion of agriculture to grassland/shrubland or forest. When 

change per time period is normalized to account for varying 

lengths in study periods, the annual rate of change was highest 

between 1986 and 1992, at 0.6 percent (296 km2) (table 2; fig.9).

The agriculture land-cover class had the most net change 

during the study period (table 3). Agriculture had a net loss of 

5.6 percent (2,814 km2) (table 3), primarily through conversion 

to grassland/shrubland and developed land (table 4) and,

to a lesser extent, to forest and mining. The conversion of 

agriculture to grassland/shrubland occurred mostly because of 

less intense management of pastureland and abandonment of 

A

B

C

A

B

C

D
152 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

agricultural land. The permanent conversion of agriculture to 

developed was caused mainly by the increasing population and 

the subsequent economic growth. Changes from agriculture to 

grassland/shrubland or to forest can be temporary because this 

land is easily returned to agricultural use.

Figure 6. Grassland/shrubland in Texas Blackland Prairies 

Ecoregion. (A) Less intensely used grazing land in eastern 

Fayette County, Texas. (B) Overgrown pasture with mesquite 

encroachment of shrub-sized woody vegetation, in pasture north 

of Coolidge, Texas. (C) Idled farmland, possibly from participation in 

Conservation Reserve Program, in northern Caldwell County, Texas.

Figure 7. Developed land in Texas Blackland Prairies Ecoregion. 

A, Agricultural infrastructure businesses in farming community of 

Granger, Texas. B, View of downtown Dallas skyline taken from 

south side of city. C, Exurban housing (common in ecoregion, 

usually on larger lots), in Fannin County, Texas, northeast of Dallas 

metropolitan area.

Between 1973 and 2000, the developed land-cover class had 

the second largest net change, an increase of 3.8 percent (table 3). 

The Texas Blackland Prairies Ecoregion gained an estimated 1,933 

km2 of developed land (table 3), from multiple sources: the increase 

in developed land came predominantly from agriculture (1,172 

km2) and grassland/shrubland (590 km2) (table 4), as well as from 

forest (158 km2) (fig. 10). Most new development was along the 

Interstate 35 corridor that follows the west side of the ecoregion 

from San Antonio to Dallas. Economic growth in metropolitan 

A

B

C

A

B

C
Chapter 16—Texas Blackland Prairies Ecoregion 153

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

Figure 8. Overall spatial change in Texas Blackland Prairies 

Ecoregion (TBP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that experienced change during one, 

two, three, or four time periods; highest level of spatial change 

in Texas Blackland Prairies Ecoregion (four time periods) labeled 

for clarity. See table 2 for years covered by each time period. See 

appendix 2 for key to ecoregion abbreviations.

Figure 9. Estimates of land-cover change per time period,

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Texas Blackland 

Prairies Ecoregion are represented by red bars in each time period.

Figure 10. New developed land in Texas Blackland Prairies 

Ecoregion. A, New construction in subdivision of larger lots 

associated with golf course, in Georgetown, Texas, north of 

Austin. B, Retail shopping center, in Garland, Texas. C, Newer 

housing on edge of Westminster, Texas, in northeast Collin County.

San Antonio, Austin, and Dallas, as well as in smaller cities 

such as Temple and Waco, Texas, fueled much of the increased 

development in the ecoregion (Scarbrough, 2005; Erlichman, 2006). 

Grassland/shrubland had the third largest net change 

during the study period, increasing by 0.9 percent (436 km2) 

(table 3), almost exclusively from agriculture. At the same 

time, grassland/shrubland was lost to developed, agriculture, 

and forest (fig. 11). This high rate of conversion into and out 

of grassland/shrubland gave that class a large gross change of 

A

B

C
154 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

3.9 percent (1,952 km2) that was much larger than the overall 

net change of 0.9 percent (table 3). Land held in speculation 

for future development on the periphery of metropolitan areas 

may have increased the amount of grassland/shrubland in 

the ecoregion. Other changes include the conversion from 

grassland/shrubland “brush” to forest-height woodlands as 

woody vegetation was allowed to mature. 

The main stories of change in the Texas Blackland 

Prairies Ecoregion between 1973 and 2000 were the 

deintensification of agriculture to both grassland/shrubland 

and forest, as well as the continued growth of the major 

metropolitan areas within the ecoregion. The deintensification 

of agriculture (usually converting to grassland/shrubland) 

occurred primarily because of less intense management of 

pastureland, outright agricultural abandonment, and extensive 

Figure 11. Normalized average net change in Texas Blackland 

Prairies Ecoregion by time period for each land-cover class. Bars 

above zero axis represent net gain, whereas bars below zero 

represent net loss. Note that not all land-cover classes shown 

in explanation may be represented in figure. See appendix 3 for 

definitions of land-use/land-cover classifications. 

Figure 12. More developed land in Texas Blackland Prairies 

Ecoregion post-2000. A, Rooftops of new residential housing 

advancing in Frisco, Texas, on north side of Dallas urbanized area. 

B, Earth-moving equipment poised to work on Texas State Highway 

130 toll road east of Austin, a divided highway that arcs around 

Austin urbanized area to relieve congestion on Interstate 35.

−2

−1

0

1

2

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

land speculation at the periphery of metropolitan areas. The 

conversion of agriculture to grassland/shrubland and even 

forest may have been the result of changing patterns of 

landownership, in which the emphasis by new owners was not 

on production of livestock but, instead, on wildlife habitat, 

aesthetic values, and other environmentally conscious land 

uses (Hamilton and Ueckert, 2004).

The conversions of agriculture, grassland/shrubland, 

and forest to developed accounted for about 31.0 percent of the 

estimated total area that changed during the study period. Conversions of agriculture and grassland/shrubland to developed 

were among the top land-use/land-cover changes during all 

four time periods (table 4). Altogether, developed land gained 

an estimated 1,933 km2 between 1973 and 2000 (table 3), and 

more increases in developed land are expected, as three counties on the outskirts of Dallas (Collin, Rockwall, and Kaufman 

Counties), as well as two counties that flank Austin to the north 

and southwest (Williamson and Hays Counties), ranked in the 

top 100 fastest growing counties in the United States between 

2000 and 2006 (Advertising Age, 2008) (fig. 12).

A

B
Chapter 16—Texas Blackland Prairies Ecoregion 155

Table 1. Percentage of Texas Blackland Prairies Ecoregion land 

cover that changed at least one time during study period (1973–

2000) and associated statistical error.

[Most sample pixels remained unchanged (88.9 percent), whereas 11.1 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 10.0 2.3 7.7 12.3 1.5 15.5

2 1.1 0.4 0.7 1.5 0.3 23.2

3 0.0 0.0 0.0 0.0 0.0 25.6

4 0.0 0.0 0.0 0.0 0.0 76.1

Overall 

spatial 

change

11.1 2.6 8.5 13.7 1.8 16.0

Table 2. Raw estimates of change in Texas Blackland Prairies Ecoregion land cover, computed for each 

of four time periods between 1973 and 2000, and associated error at 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.6 0.9 1.8 3.5 0.6 22.3 0.4

1980–1986 2.7 0.6 2.1 3.3 0.4 14.2 0.5

1986–1992 3.5 1.3 2.2 4.8 0.9 25.6 0.6

1992–2000 3.5 1.0 2.4 4.5 0.7 19.9 0.4

Estimate of change, in square kilometers

1973–1980 1,332 436 896 1,769 297 22.3 190

1980–1986 1,369 285 1,084 1,655 194 14.2 228

1986–1992 1,774 668 1,106 2,442 455 25.6 296

1992–2000 1,742 508 1,234 2,251 346 19.9 218
156 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 3. Estimated area (and margin of error) of each land-cover class in Texas Blackland Prairies Ecoregion, calculated five 

times between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed

Mechanically 

disturbed

Mining Barren Forest Grassland/

Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 0.8 0.2 8.9 4.7 0.0 0.0 0.2 0.1 0.0 0.0 14.0 1.7 11.8 2.9 63.4 4.9 0.9 0.3 0.0 0.0

1980 0.8 0.2 9.8 4.8 0.0 0.0 0.3 0.2 0.0 0.0 13.9 1.7 11.9 2.9 62.3 5.0 0.9 0.3 0.0 0.0

1986 0.8 0.2 10.7 5.0 0.0 0.0 0.4 0.3 0.0 0.0 14.0 1.7 12.2 2.8 60.9 5.1 0.9 0.3 0.0 0.0

1992 1.1 0.4 11.3 5.1 0.0 0.0 0.5 0.4 0.0 0.0 13.9 1.7 12.7 2.9 59.2 5.3 1.2 0.6 0.0 0.0

2000 1.2 0.5 12.7 5.4 0.0 0.0 0.6 0.4 0.0 0.0 13.9 1.7 12.7 2.8 57.8 5.5 1.1 0.5 0.0 0.0

Net

change 0.4 0.5 3.8 1.9 0.0 0.0 0.4 0.3 0.0 0.0 –0.2 0.4 0.9 1.1 –5.6 2.1 0.2 0.3 0.0 0.0

Gross

change 0.6 0.5 3.8 1.9 0.1 0.1 0.5 0.3 0.0 0.0 1.5 0.4 3.9 0.9 6.6 2.0 0.5 0.5 0.0 0.0

Area, in square kilometers

1973 407 102 4,490 2,362 5 5 81 55 17 14 7,074 875 5,965 1,471 32,011 2,468 452 138 0 0

1980 395 91 4,961 2,447 20 18 155 105 25 19 7,042 865 6,008 1,443 31,440 2,512 455 136 0 0

1986 406 91 5,396 2,531 16 16 206 154 18 15 7,062 868 6,159 1,434 30,776 2,582 463 137 0 0

1992 564 184 5,731 2,594 5 7 247 184 16 12 7,034 864 6,410 1,452 29,913 2,658 582 286 0 0

2000 617 243 6,423 2,713 6 4 304 213 14 10 6,995 850 6,401 1,416 29,196 2,755 544 238 1 1

Net

change 210 235 1,933 949 1 5 223 172 –3 8 –79 210 436 567 –2,814 1,069 92 133 1 1

Gross

change 315 234 1,933 949 67 44 263 173 21 16 760 196 1,952 461 3,345 1,018 245 239 1 1
Chapter 16—Texas Blackland Prairies Ecoregion 157

Table 4. Principal land-cover conversions in Texas Blackland Prairies Ecoregion, showing amount of area changed (and margin of 

error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Agriculture Grassland/Shrubland 351 161 109 0.7 26.3

Agriculture Developed 331 300 204 0.7 24.8

Grassland/Shrubland Agriculture 150 99 67 0.3 11.2

Grassland/Shrubland Developed 109 89 60 0.2 8.2

Forest Agriculture 71 37 25 0.1 5.3

Other Other 321 n/a n/a 0.6 24.1

Totals 1,332 2.6 100.0

1980–1986 Agriculture Grassland/Shrubland 444 137 94 0.9 32.4

Agriculture Developed 263 142 97 0.5 19.2

Grassland/Shrubland Forest 109 64 44 0.2 8.0

Grassland/Shrubland Developed 109 56 38 0.2 8.0

Grassland/Shrubland Agriculture 76 34 23 0.2 5.6

Other Other 369 n/a n/a 0.7 26.9

Totals 1,369 2.7 100.0

1986–1992 Agriculture Grassland/Shrubland 592 230 157 1.2 33.4

Agriculture Developed 204 98 67 0.4 11.5

Grassland/Shrubland Forest 115 53 36 0.2 6.5

Grassland/Shrubland Agriculture 108 40 27 0.2 6.1

Grassland/Shrubland Developed 105 57 39 0.2 5.9

Other Other 651 n/a n/a 1.3 36.7

Totals 1,774 3.5 100.0

1992–2000 Agriculture Grassland/Shrubland 453 146 99 0.9 26.0

Agriculture Developed 375 239 163 0.7 21.5

Grassland/Shrubland Developed 267 139 95 0.5 15.3

Grassland/Shrubland Agriculture 123 51 35 0.2 7.1

Grassland/Shrubland Forest 97 38 26 0.2 5.5

Other Other 429 n/a n/a 0.8 24.6

Totals 1,742 3.5 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 1,839 537 366 3.6 29.6

Agriculture Developed 1,172 698 476 2.3 18.8

Grassland/Shrubland Developed 590 298 203 1.2 9.5

Grassland/Shrubland Agriculture 456 144 98 0.9 7.3

Grassland/Shrubland Forest 376 148 101 0.7 6.1

Other Other 1,785 n/a n/a 3.5 28.7

Totals 6,218 12.3 100.0
158 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Advertising Age, 2008, Nation’s fastest-growing counties 

from 2000 to 2006: Advertising Age’s American Demographics, 100 Fastest growing counties—Summary, Excel 

spreadsheet, accessed October 3, 2008, at http://adage.

com/images/bin/excel/100counties0606.xls.

Erlichman, H.J., 2006, Camino del Norte—How a series of 

watering holes, fords, and dirt trails evolved into Interstate 

35 in Texas: College Station, Texas A&M University Press, 

284 p. 

Griffith, G.E., Bryce, S.A., Omernik, J.M., Comstock, J.A., 

Rogers, A.C., Harrison, B., Hatch, S.L., and Benzanson, 

D., 2004, Ecoregions of Texas: U.S. Geological Survey 

Ecoregion Map Series, scale 1:2,500,000, available at 

ftp://ftp.epa.gov/wed/ecoregions/tx/tx_front.pdf.

Hamilton, W.T., and Ueckert, D.N., 2004, Introduction – 

Rangeland woody plant and weed management—Past, 

present, and future, in Hamilton, W.T., McGinty, A., 

Ueckert, D.N., Hanselka, C.W., and Lee, M.R., eds., Brush 

management—Past, present, future: College Station, Texas 

A&M University Press, p. 3–13.

Kottek, M.J., Grieser, J., Beck, C., Rudolf, B., and Rubel, 

F., 2006, World map of the Köppen-Geiger climate 

classification updated: Meteorologische Zeitschrift, v. 15, 

no. 3, p. 259–263, available at http://www.schweizerbart.

de/papers/metz/detail/15/55034/World_Map_of_the_

Koppen_Geiger_climate_classificat.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

PRISM Climate Group, 2006, Precipitation—Annual 

climatology (1971–2000): PRISM Climate Group, Oregon 

State University database, accessed August 29, 2008, at 

http://prism.nacse.org/documents/.

Scarbrough, Linda, 2005, Road, river, and ol’ boy politics—

A Texas county’s path from farm to supersuburb: Austin, 

Texas State Historical Association, 402 p.

Texas Parks and Wildlife, 1997, Texas wetlands conservation 

plan: Texas Parks and Wildlife database, Texas Wetlands 

Conservation Program, Resource Protection Division, 64 p., 

available at https://tpwd.texas.gov/publications/pwdpubs/

media/pwd_pl_r2000_0005_textonly.pdf. 

U.S. Department of Agriculture, 2008a, Conservation programs—

Statistics: U.S. Department of Agriculture, Farm Service Agency 

database, accessed September 30, 2008, at http://www.fsa.usda.

gov/FSA/webapp?area=home&subject=copr&topic=crp-st.

U.S. Department of Agriculture, 2008b, The soil orders of 

Texas: U.S. Department of Agriculture, Natural Resources 

Conservation Service database, accessed September 30, 

2008, at http://www.nrcs.usda.gov/wps/portal/nrcs/detail/tx/

soils/?cid=nrcs144p2_003094.

U.S. Department of Agriculture, 2008c, 2002 Census publications—State and county profiles – Texas: U.S Department 

of Agriculture, Census of Agriculture database, accessed 

October 3, 2008, at http://www.agcensus.usda.gov/

Publications/2002/County_Profiles/Texas/index.asp. 

U.S. Environmental Protection Agency, 1997, Descriptions of level 

III ecological regions for the CEC report on ecological regions 

of North America: U.S. Environmental Protection Agency database, accessed September 30, 2008, at http://www.epa.gov/wed/

pages/ecoregions/na_eco.htm#Downloads.

U.S. Environmental Protection Agency, 2002, Primary 

distinguishing characteristics of level III ecoregions of the 

continental United States: U.S. Environmental Protection 

Agency database, accessed September 30, 2008, at http://

www.epa.gov/wed/pages/ecoregions/level_iii.htm.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., Wylie, 

B.K., and van Driel, N., 2001, Completion of the 1990s 

National Land Cover Data Set for the conterminous United 

States from Landsat Thematic Mapper data and ancillary 

data sources: Photogrammetric Engineering & Remote 

Sensing, v. 67, p. 650–662.

White, Matt, 2006, Prairie time—A Blackland portrait: College 

Station, Texas A&M University Press, 251 p. 
Chapter 17

Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Edited by Janis L. Taylor, William Acevedo, Roger F. Auch, and Mark A. Drummond 

U.S. Geological Survey Professional Paper 1794–B, 2015

Western Gulf Coastal Plain Ecoregion

By Mark A. Drummond

Ecoregion Description 

The Western Gulf Coastal Plain Ecoregion is an 

elongated, low-elevation area that covers 80,965 km2

(31,261 mi2). The ecoregion extends from west of the Mississippi River delta in southwestern Louisiana into Texas, 

running along the entire Gulf Coast of Texas to the Mexican 

border (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). It is surrounded by, from southwest to 

northeast, the Southern Texas Plains, East Central Texas 

Plains, South Central Plains, and Mississippi Alluvial Plain 

Ecoregions (fig. 1).

The Western Gulf Coastal Plain Ecoregion is a level 

plain composed mostly of sedimentary strata deposited by 

repeated cycles of sea-level fluctuations, overlain by finetextured clays and sand. Several major waterways (including 

Figure 1. Map of 

Western Gulf Coastal Plain 

Ecoregion and surrounding 

ecoregions, showing 

land-use/land-cover 

classes from 1992 National 

Land-cover Dataset 

(Vogelmann and others, 

2001); note that not all landuse/land-cover classes 

shown in explanation 

may be depicted on 

map; note also that, for 

this “Status and Trends 

of Land Change” study, 

transitional land-cover 

class was subdivided into 

mechanically disturbed 

and nonmechanically 

disturbed classes. Squares 

indicate locations of 10 x 10 

km sample blocks analyzed 

in study. Index map shows 

locations of geographic 

features mentioned in text. 

Abbreviations for Great 

Plains ecoregions are 

listed in appendix 2. Also shown are parts of two 

Midwest–South Central United States ecoregions: 

Mississippi Alluvial Plains (MAP) and South Central 

Plains. See appendix 3 for definitions of land-use/

land-cover classifications.

98° 96° 94° 92°

30°

28°

26°

South Central Plains

 East Central

Texas Plains

Edwards

Plateau

Texas

Blackland

Prairies 

TBP

STP

STP

MAP

GULF of MEXICO

MEXICO

0 50 75 MILES

0 50 75

25

25 KILOMETERS

Ecoregion boundary

Sample block (10 x 10 km)

Land-use/land-cover class

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

EXPLANATION

TEXAS LA

Western Gulf Coastal

Plain Ecoregion

C o l o r a d o R i v e r

Trinity

R i v e r

R i o G r a n d e

San Antonio

Lake Charles

Galveston Island

Galveston

Padre Island

Brownsville

Port

Arthur

Corpus Christi

Houston

Austin

Mississippi River

LOUISIANA

TN

MEXICO

GULF of MEXICO

TEXAS
160 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

the Trinity River, the Colorado River, and the Rio Grande) 

dissect the coastal plain, emptying into the Gulf of Mexico. 

The Coastal Lowlands aquifer, which underlies much of 

the ecoregion, is the main source of groundwater. However, 

aquifer pumping rates are a concern, especially in the greater 

Houston–Galveston, Texas, area where groundwater levels 

have declined by as much as 100 m, causing saltwater 

intrusion and land subsidence (Davidson and Mace, 2006). 

The Western Gulf Coastal Plain Ecoregion primarily 

is a flat grassland prairie, dominated by little bluestem 

(Schizachyrium scoparium) and other grasses. Woody 

vegetation has encroached on areas of intensive livestock 

grazing and also of fire suppression (Archer, 1990) (fig. 2). 

Loblolly pine (Pinus taeda), grown for both lumber and 

paper production, and hardwoods grow along the higher 

elevation margins of the ecoregion. In the southern part 

of the ecoregion, clusters of live oak (Quercus virginiana) 

grow on sandy ridges, known as oak mottes. Hardwoods 

also grow along numerous wooded bottomland floodplains 

throughout the ecoregion, although many of these forests 

have been cleared for cropland, pastureland, and urbanization. 

Coastal marshes and estuaries are extensive along the Gulf 

of Mexico, from the southern Louisiana parishes into eastern 

Texas (fig. 3). About 85 percent of wetlands are freshwater 

environments, and 15 percent are saltwater environments 

(Moulton and others, 1997). Long barrier islands and 

adjoining lagoons are more prevalent along the southern 

Texas coast, including the area from Galveston Island in the 

north to Padre Island in the south. Several large bays line the 

Texas coastline, including six deep-water harbors; the port of 

Houston is the largest of these harbors. 

Sand plains and dunes, which are found in a limited area 

north of the lower Rio Grande valley, support little cropland 

compared to the rest of the ecoregion, much of which is 

intensively cropped and irrigated. Honey mesquite (Prosopis

glandulosa) and granjeno (Celtis pallida) shrubs have 

invaded much of the valley. Natural habitat in the southern 

tip of Texas and elsewhere in the ecoregion supports various 

subtropical and marine bird communities, as well as Central 

Flyway species, making it an area of high species diversity.

Figure 2. Brush clearance of livestock pasture, in Western Gulf 

Coastal Plain Ecoregion.

Figure 3. Freshwater marsh in southwestern Louisiana, Western 

Gulf Coastal Plain Ecoregion.

Figure 4. Cotton field in Western Gulf Coastal Plain Ecoregion.

Figure 5. Catfish farm in Western Gulf Coastal Plain Ecoregion.
Chapter 17—Western Gulf Coastal Plain Ecoregion 161

Large areas in the Western Gulf Coastal Plain Ecoregion 

are used to grow crops and to graze livestock (fig. 4), and 

smaller areas are used for inland fish production (fig.5).

Agriculture is aided by a subtropical climate of mild 

winters and hot summers influenced by the Gulf of Mexico. 

Precipitation amounts in the ecoregion range from about 

650 mm (25 in.) in the southwest to 1,500 mm (60 in.) in 

the northeast. The southernmost part of the ecoregion has a 

long growing season, having frost-free periods of more than 

320 days, which allows cotton, corn, sorghum, sugarcane, 

citrus, melons, and vegetables to be grown along the Rio 

Grande floodplain (Griffith and others, 2004). About one-half 

of freshwater wetlands also are used for growing rice (often 

referred to as agricultural wetlands), particularly in the middle 

part of the ecoregion (Moulton and others, 1997).

Ecological goods and services from coastal wetlands and 

water bodies are important to the economy of the ecoregion; 

activities include commercial and recreational fishing, oyster 

harvesting and shrimp nurseries, waterfowl hunting, and 

birdwatching (Moulton and others, 1997). Overall, about 

70 percent of Texas industry and commerce happens within 

160 km of the coast, and more than one-half of petroleum 

production in the United States is located in the region (fig. 

6) (Texas General Land Office, 1995; Moulton and others, 

1997). Various human land uses (including canal dredging 

and channelization, aquifer drawdown, urbanization, and 

agriculture) contribute to wetland loss in southwestern 

Louisiana and Texas.

The largest population center in the ecoregion is 

Houston, Texas, where population nearly doubled during the 

study period. Between 1970 and 2000, the population of the 

ecoregion increased by 85 percent, and more than one-half 

of the increase was concentrated in the Houston area (U.S. 

Bureau of Census, 1970–2000 [various years]); only four 

counties lost population. The southern coastal cities of Texas 

have populations that are increasingly seasonal, as tourism 

increases and retirees and others temporarily move south for 

the mild climate during the winter months.

Figure 6. Petroleum processing plant in Western Gulf Coastal 

Plain Ecoregion. Petroleum-related industries are important to 

ecoregion’s economic base.

Figure 7. Overall spatial change in Western Gulf Coastal Plain 

Ecoregion (WGCP; darker bars) compared with that of all 17 Great 

Plains ecoregions (lighter bars). Each horizontal set of bars shows 

proportions of ecoregion that experienced change during one, 

two, three, or four time periods; highest level of spatial change in 

Western Gulf Coastal Plain Ecoregion (four time periods) labeled 

for clarity. See table 4 for years covered by each time period. See 

appendix 2 for key to ecoregion abbreviations.

Contemporary Land-Cover Change 

(1973 to 2000)

Land cover is diverse in the Western Gulf Coastal Plain 

Ecoregion, with agriculture, grassland/shrubland, wetland, forest, 

and water each constituting more than 10 percent of the total 

area during all time periods (table 1). The overall spatial change 

(the percentage of land area that changed at least one time) in 

the ecoregion between 1973 and 2000 is 9.9 percent (table 2; 

fig.7). Compared to other Great Plains ecoregions, change in the

ecoregion was higher than average (fig. 7). About 2.5 percent of 

the overall change was caused by multiple conversions (table 2),

representing large land areas shifting between grassland/

shrubland and agriculture. The large gross changes between 

grassland/shrubland and agriculture were the two most common 

conversions between 1973 and 2000 (table 3).

Although agriculture covered the most total area in 

the ecoregion, it declined from 31.6 percent in 1973 to 30.6 

percent in 2000 (table 1). The estimated 1.0 percent decline 

was the largest loss of land cover during the study period 

(fig. 8). Although substantial gross fluctuations between 

agriculture and grassland/shrubland occurred during the 

study period, most of the net loss of agriculture occurred 

because of conversion to wetland and developed land, 

0 5 10 15

Area, as percent of ecoregion

LAP

FH

WCBP

NSH

EP

COTP

CIP

NWGP

NGP

CGP

SWT

WGCP

TBP

WHP

STP

ECTP

NWGLP

Ecoregion 

EXPLANATION

Change in one time period

Change in two time periods

Change in three time periods

Change in four time periods

Change in four

time periods
162 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Figure 8. Estimates of net land-cover change in Western Gulf 

Coastal Plain Ecoregion for each land-cover class between 1973 

and 2000. Bars above zero axis represent net gain, whereas bars 

below zero represent net loss. See appendix 3 for definitions of 

land-use/land-cover classifications.

Figure 9. Normalized average net change in Western Gulf 

Coastal Plain Ecoregion by time period for each land-cover class. 

Bars above zero axis represent net gain, whereas bars below 

zero represent net loss. Note that not all land-cover classes 

shown in explanation may be represented in figure. See appendix 

3 for definitions of land-use/land-cover classifications.

as well as to grassland/shrubland and forest. The loss of 

agricultural land to wetlands may have been caused by land 

subsidence where coastal aquifer groundwater levels have 

declined or by wetland engineering. 

The largest single net gain among all land-cover classes 

in the ecoregion was an estimated 1.2 percent increase in 

developed land, increasing from 2.4 percent in 1973 to 

3.6 percent in 2000 (table 1). Most developed land was 

converted from agricultural land, particularly around large 

metropolitan areas such as Houston, Texas, but also in many 

smaller population centers across the ecoregion. Expansion of 

developed land was relatively steady across all time periods. 

Between 1973 and 1980, the largest net changes in land 

cover across the ecoregion were a decrease in grassland/

shrubland (0.5 percent) and an increase in developed 

(0.3percent) (fig. 9). Agriculture expanded at the expense of 

grassland/shrubland in response to favorable farm policies, 

as well as to economic opportunities such as increased 

grain exports, and developed land mainly expanded onto 

agricultural land. Between 1980 and 1986, agriculture 

decreased by 320 km2, and grassland/shrubland increased 

by 194 km2 (table 1); both trends likely are related to 

unfavorable economic conditions such as inflation and the 

steep decline in farmland value (Lindert, 1988). The decrease 

also was a result of continued increase in development, 

mainly on former agricultural land. 

−1

−0.5

0

0.5

1

1973–1980 1980–1986 

Time period

1986–1992 1992–2000 

Area changed, as percent of ecoregion 

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Nonmechanically disturbed

Ice/Snow

EXPLANATION

LAND-USE/LAND-COVER CLASS

Between 1986 and 1992, agriculture continued to 

decline by 301 km2 as it was converted to wetland, forest, 

developed, and grassland/shrubland (table 1). However, 

small gains in grassland/shrubland caused by agricultural 

abandonment were offset by conversions to forest elsewhere 

in the ecoregion. Conversion of forest to mechanically 

disturbed (primarily by forest clearcutting, but also by timber 

harvesting on loblolly pine plantations) also was a common 

type of land-cover conversion.

Between 1992 and 2000, developed land had the 

most net change, increasing by 342 km2 (table 1), with 

conversions dispersed among grassland/shrubland, 

agriculture, and forest. The leading land-cover conversions 

during this time period also were related to timber harvest 

and regrowth. While some forest was converted to 

mechanically disturbed, other clearcut areas revegetated to 

grassland/shrubland, often an intermediate stage between 

mechanically disturbed and forest.

Other important land-cover changes during the study 

period included conversions from grassland/shrubland to 

–1.5

–1.0

–0.5

0

0.5

1.0

1.5

Area changed, as percent of ecoregion

Water

Developed

Transitional

Mining

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

EXPLANATION

LAND-USE/LAND-COVER CLASS
Chapter 17—Western Gulf Coastal Plain Ecoregion 163

Figure 10. Estimates of land-cover change per time period,

normalized to annual rates of change for all 17 Great Plains 

ecoregions (gray bars). Estimates of change for Western Gulf Coastal 

Plain Ecoregion are represented by red bars in each time period.

0.2

0.0

0.4

0.6

1.0

1.2

0.8

1.4

1973 to 1980 1980 to 1986 1986 to 1992 1992 to 2000

Average annual change, as percent of ecoregion

Time period

mechanically disturbed and then back to grassland/shrubland. 

These changes are related to the removal of invading woody 

vegetation through mechanical means, prescribed burns, and 

herbicide treatments (Archer, 1990).

Overall, the estimated annual rates of change during each 

of the four time periods were relatively consistent, ranging from 

about 0.4 percent to 0.5 percent (table 4; fig. 10). The greatest 

rates of change were between 1980 and 1986, when agriculture 

had a large decline that likely was caused by the economic 

downturn, and between 1992 and 2000, when conversions 

involving developed land and forest were prominent.

During the entire study period, much of the change 

occurred between agriculture and grassland/shrubland 

(table 3), driven by agricultural expansion during economic 

booms followed by agricultural decline caused by cropland 

abandonment during economic downturns and also by 

conversions to developed land. However, much land-cover 

change also was caused by forest harvesting and regrowth. 

The largest net change between 1973 and 2000 was an 

expansion of developed land (table 1), caused by urban 

growth and population increase.
164 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

Table 2. Percentage of Western Gulf Coastal Plain Ecoregion 

land cover that changed at least one time during study period 

(1973–2000) and associated statistical error.

[Most sample pixels remained unchanged (90.1 percent), whereas 9.9 percent 

changed at least once throughout study period]

Number

of

changes

Percent

of

ecoregion

Margin

of error

(+/− %)

Lower

bound

(%)

Upper

bound

(%)

Standard

error

(%)

Relative

error

(%)

1 7.4 1.7 5.7 9.1 1.1 15.4

2 2.2 0.5 1.7 2.8 0.4 16.6

3 0.3 0.1 0.1 0.4 0.1 28.5

4 0.0 0.0 0.0 0.0 0.0 38.7

Overall 

spatial 

change

9.9 2.2 7.7 12.1 1.5 15.0

Table 1. Estimated area (and margin of error) of each land-cover class in Western Gulf Coastal Plain Ecoregion, calculated five times 

between 1973 and 2000. See appendix 3 for definitions of land-cover classifications.

Water Developed Mechanically 

disturbed Mining Barren Forest Grassland/Shrubland Agriculture Wetland

Nonmechanically 

disturbed

% +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/− % +/−

Area, in percent stratum

1973 17.5 7.8 2.4 0.7 0.1 0.1 0.0 0.0 2.1 2.4 12.1 3.5 20.4 5.9 31.6 6.0 13.8 4.4 0.0 0.0

1980 17.6 7.7 2.7 0.8 0.2 0.1 0.1 0.0 2.2 2.4 11.9 3.5 19.9 5.7 31.7 5.9 13.6 4.5 0.0 0.0

1986 17.5 7.8 2.9 0.8 0.2 0.1 0.1 0.0 2.1 2.2 11.9 3.5 20.2 5.7 31.3 5.9 13.7 4.4 0.0 0.0

1992 17.5 7.7 3.2 0.9 0.3 0.2 0.1 0.1 2.1 2.3 11.8 3.4 20.2 5.7 30.9 5.8 13.8 4.5 0.0 0.0

2000 17.5 7.7 3.6 1.1 0.6 0.4 0.1 0.1 2.0 2.2 11.5 3.3 20.4 5.7 30.6 5.7 13.7 4.4 0.0 0.0

Net

change –0.1 0.2 1.2 0.5 0.5 0.4 0.0 0.0 –0.1 0.2 –0.6 0.4 0.0 0.9 –1.0 0.9 –0.1 0.2 0.0 0.0

Gross

change 1.2 0.4 1.2 0.5 1.3 0.6 0.0 0.0 0.4 0.3 1.6 0.6 3.9 1.2 4.0 1.3 1.5 0.6 0.1 0.1

Area, in square kilometers

1973 14,192 6,280 1,918 571 75 44 34 32 1,739 1,936 9,758 2,862 16,526 4,749 25,581 4,853 11,141 3,598 0 0

1980 14,274 6,238 2,202 628 150 81 48 35 1,792 1,945 9,636 2,831 16,148 4,625 25,669 4,775 11,046 3,647 0 0

1986 14,166 6,277 2,373 688 200 118 55 37 1,680 1,816 9,672 2,840 16,342 4,640 25,349 4,740 11,128 3,584 0 0

1992 14,142 6,268 2,587 765 255 183 63 43 1,696 1,861 9,592 2,769 16,357 4,624 25,048 4,678 11,203 3,640 23 32

2000 14,133 6,251 2,929 928 499 307 67 43 1,656 1,802 9,311 2,639 16,509 4,588 24,764 4,595 11,079 3,600 17 21

Net

change –59 150 1,011 435 424 293 33 26 –83 138 –447 317 –17 733 –818 757 –62 140 17 21

Gross

change 979 315 1,012 435 1,038 449 38 26 292 256 1,312 472 3,167 1,011 3,266 1,014 1,226 459 58 65
Chapter 17—Western Gulf Coastal Plain Ecoregion 165

Table 3. Principal land-cover conversions in Western Gulf Coastal Plain Ecoregion, showing amount of area changed (and margin 

of error, calculated at 85-percent confidence level) for each conversion during each of four time periods and also during overall study 

period. See appendix 3 for definitions of land-cover classifications.

[Values given for “other” classes are combined totals of values for other land-cover classes not listed in that time period. Abbreviations: n/a, not applicable]

Period From class To class

Area 

changed

Margin of 

error

Standard 

error Percent of 

ecoregion

Percent of all 

changes (km2) (+/− km2) (km2)

1973–1980 Grassland/Shrubland Agriculture 635 373 254 0.8 27.0

Agriculture Grassland/Shrubland 349 169 115 0.4 14.8

Wetland Water 165 104 71 0.2 7.0

Agriculture Wetland 163 169 115 0.2 6.9

Agriculture Developed 146 132 90 0.2 6.2

Other Other 893 n/a n/a 1.1 38.0

Totals 2,351 2.9 100.0

1980–1986 Agriculture Grassland/Shrubland 478 268 183 0.6 18.5

Water Wetland 265 137 93 0.3 10.3

Wetland Agriculture 193 252 171 0.2 7.5

Wetland Water 167 137 93 0.2 6.5

Grassland/Shrubland Forest 160 114 78 0.2 6.2

Other Other 1,314 n/a n/a 1.6 51.0

Totals 2,577 3.2 100.0

1986–1992 Agriculture Grassland/Shrubland 331 144 98 0.4 15.4

Grassland/Shrubland Agriculture 243 125 85 0.3 11.3

Forest Mechanically disturbed 232 181 123 0.3 10.8

Agriculture Wetland 119 168 114 0.1 5.5

Grassland/Shrubland Forest 115 64 43 0.1 5.3

Other Other 1,105 n/a n/a 1.4 51.5

Totals 2,145 2.6 100.0

1992–2000 Agriculture Grassland/Shrubland 594 489 333 0.7 18.6

Grassland/Shrubland Agriculture 427 289 197 0.5 13.4

Forest Mechanically disturbed 381 264 180 0.5 11.9

Grassland/Shrubland Forest 167 76 52 0.2 5.2

Mechanically disturbed Grassland/Shrubland 151 121 82 0.2 4.7

Other Other 1,476 n/a n/a 1.8 46.2

Totals 3,196 3.9 100.0

1973–2000

(overall)

Agriculture Grassland/Shrubland 1,751 817 557 2.2 17.1

Grassland/Shrubland Agriculture 1,458 737 502 1.8 14.2

Forest Mechanically disturbed 779 510 348 1.0 7.6

Water Wetland 549 208 141 0.7 5.3

Grassland/Shrubland Forest 528 243 166 0.7 5.1

Other Other 5,204 n/a n/a 6.4 50.7

Totals 10,269 12.7 100.0
166 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000 

References Cited

Archer, Steve, 1990, Development and stability of grass/

woody mosaics in a subtropical savanna parkland, Texas, 

U.S.A.: Journal of Biogeography, v. 17, no. 4–5, p. 

453–462.

Davidson, S.C., and Mace, R.E., 2006, Aquifers of the Gulf 

Coast of Texas—An overview, in Mace, R.E., Davidson, 

S.C., Angle, E.S., and Mullican, W.F., III, Aquifers of the 

Gulf Coast of Texas: Texas Water Development Board 

Report 365, p. 1–21, available at http://www.twdb.texas.

gov/publications/reports/numbered_reports/doc/R365/

ch01_intro.pdf.

Griffith, G.E., Bryce, S.A., Omernik, J.M., Comstock, J.A., 

Rogers, A.C., Harrison, B., Hatch, S.L., and Bezanson, D., 

2004, Ecoregions of Texas: U.S. Geological Survey Ecoregion Map Series, scale 1:2,500,000, available at http://www.

epa.gov/wed/pages/ecoregions/tx_eco.htm.

Lindert, P.H., 1988, Long-run trends in American farmland 

values: Agricultural History, v. 62, p. 45–85.

Moulton, D.W., Dahl, T.E., and Dall, D.M., 1997, Texas 

coastal wetlands—Status and trends, mid-1950s to early 

1990s: U.S. Fish and Wildlife Service, 32 p.

Table 4. Raw estimates of change in Western Gulf Coastal Plain Ecoregion land cover, computed for 

each of four time periods between 1973 and 2000, and associated error at an 85-percent confidence level.

[Estimates of change per period normalized to annual rate of change for each period]

Period Total change

(% of ecoregion)

Margin of 

error

(+/− %)

Lower 

bound

(%)

Upper bound

(%)

Standard 

error

(%)

Relative 

error

(%)

Average rate

(% per year)

Estimate of change, in percent stratum

1973–1980 2.9 0.7 2.2 3.6 0.5 16.0 0.4

1980–1986 3.2 0.8 2.4 4.0 0.6 17.5 0.5

1986–1992 2.6 0.6 2.0 3.3 0.4 15.7 0.4

1992–2000 3.9 1.2 2.7 5.1 0.8 20.7 0.5

Estimate of change, in square kilometers

1973–1980 2,351 553 1,798 2,904 377 16.0 336

1980–1986 2,577 663 1,914 3,241 452 17.5 430

1986–1992 2,145 495 1,650 2,640 337 15.7 357

1992–2000 3,196 973 2,223 4,169 663 20.7 399

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Texas General Land Office, 1995, Coastal management 

program: Texas General Land Office database, available at 

http://www.glo.texas.gov/what-we-do/caring-for-the-coast/

grants-funding/cmp/.

U.S. Census Bureau, 1970–2000 [various years], Census of 

population and housing: U.S. Census Bureau database, 

accessed September 1, 2008, at http://www.census.gov/

prod/www/decennial.html.

U.S. Environmental Protection Agency, 1997, Descriptions of 

level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection 

Agency database, accessed April 12, 2006, at http://www.

epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Appendixes 1–4

Appendix 1. Map of Ecoregions in Conterminous United States 169

This volume—U.S. Geological Survey Professional Paper 1794–B, which covers 17 ecoregions in the Great Plains of the United 

States—provides an assessment of the rates and causes of land-use and land-cover change in the Great Plains of the United States region 

between 1973 and 2000. The other three volumes of this Professional Paper (1794–A, 1794–C, and 1794–D) provide similar analyses 

for the Western United States, the Midwest–South Central United States, and the Eastern United States regions, respectively.

The map contained in this appendix (fig. 1.1) shows all 84 ecoregions in the conterminous United States, as originally defined by 

Omernik and others (1987) and later modified by the U.S. Environmental Protection Agency (1999), in addition to the ecoregions that 

are contained in the Western United States, Great Plains of the United States, Midwest–South Central United States, and Eastern United 

States regions. Also shown are the land-use/land-cover classes from the 2001 National Land-Cover Database (Homer and others, 2004). 

References Cited

Homer, C., Huang, C., Yang, L., Wylie, B., and Coan, M., 2004, Development of a 2001 National Land-Cover Database for the 

United States: Photogrammetric Engineering and Remote Sensing, v. 70, no. 7, p. 829–840.

Omernik, J.M., 1987, Ecoregions of the conterminous United States: Annals of the Association of American Geographers, v. 77, 

no. 1, p. 118–125.

U.S. Environmental Protection Agency, 1997, Descriptions of level III ecological regions for the CEC report on ecological 

regions of North America: U.S. Environmental Protection Agency database, accessed April 12, 2006, at http://www.epa.gov/

wed/pages/ecoregions/na_eco.htm#Downloads.

Ecoregion Abbreviations Used on Map

[Map is on following pages]

ACPB Atlantic Coastal Pine Barrens Ecoregion

ANMM Arizona/New Mexico Mountains Ecoregion

CR Coast Range Ecoregion

CRK Canadian Rockies Ecoregion

EGLHL Eastern Great Lakes and Hudson Lowlands Ecoregion

HELP Huron/Erie Lake Plains Ecoregion

LPH Laurentian Plains and Hills Ecoregion

MACP Middle Atlantic Coastal Plain Ecoregion

MRK Middle Rockies Ecoregion

MVFP Montana Valley and Foothill Prairies Ecoregion

MVLP Mississippi Valley Loess Plains Ecoregion

NAPU Northern Appalachian Plateau and Uplands Ecoregion

NCA North Central Appalachians Ecoregion

NCHF North Central Hardwood Forests Ecoregion

NECZ Northeastern Coastal Zone Ecoregion

NEH Northeastern Highlands Ecoregion

NLF Northern Lakes and Forests Ecoregion

NMW Northern Minnesota Wetlands Ecoregion

PL Puget Lowland Ecoregion

SCCCOW Southern and Central California Chaparral and Oak Woodlands Ecoregion

SCM Southern California Mountains Ecoregion

SEWTP Southeastern Wisconsin Till Plains Ecoregion

SFCP Southern Florida Coastal Plain Ecoregion

TBP Texas Blackland Prairies Ecoregion

WUM Wasatch and Uinta Mountains Ecoregion

WV Willamette Valley Ecoregion

Appendix 1. Map of Ecoregions in Conterminous United States
170 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

100°

100°

110°

120° 110°

120°

50°

40°

30°

MEXICO

PA C I F I C

OCEAN

Blue Mountains

Central Basin

and Range

Central California Valley

Columbia Plateau

Colorado

Plateaus

Coast Range

Cascades

Klamath

Mountains

Madrean

Archipelago

Mojave Basin

and Range

Middle

Rockies

MVFP

Northern Basin

and Range

Northern

Rockies

PL

Sonoran Basin

and Range

SCCCOW

SCCCOW

SCM

Sierra Nevada

Snake River Basin

Southern

Rockies

Wyoming Basin

SCCCOW

CR

MRK

ANMM

WUM

Central G

Plain

Eas

W

Edwards

Plateau

G

Nebraska Sand Hills

Northwestern Great Plains

Southern

Texas Plains

Western

High Plains

Western

High Plains

North

Cascades

Chihuahuan Deserts

Northwestern Glaciated Plains

Southwestern

Tablelands

Cent

Oklahom

Plai

CRK

WV

Eastern

Cascades

Slopes and

Foothills

MRK

0 125 250 500 MILES

0 125 250 500 KILOMETERS

Arizona/

New Mexico

Plateau

Arizona/ 

 New Mexico

 Mountains

WESTERN UNITED STATES

GREAT PL

Figure 1.1. Map 

of ecoregions in 

conterminous 

United States.
Appendix 1. Map of Ecoregions in Conterminous United States 171

70°

70°

50°

80°

80°

90°

90°

40°

30°

CANADA

ATLANTIC

OCEAN

Gulf

of 

Mexico

SFCP

Southern

Coastal

Plain

Western

Allegheny

Plateau

Appalachians

Southwestern

Southeastern Plains

Northeastern

Highlands

Middle Atlantic Coastal Plain

Interior

Plateau Blue Ridge Mountains

Ridge and Valley

Northern Piedmont

ACPB

MACP

MACP

NEH

LPH

NEH

NEH

EGLHL

NAPU

NCA

NCA

Great

s

ast Central Texas Plains

Western Gulf Coastal Plain

TBP

Lake

Agassiz

Plain

Northern

Glaciated Plains

Western Corn Belt Plains

Central

Irregular

Plains

Boston Mountains

Central Corn

Belt Plains

Eastern Corn

Belt Plains

Erie Drift Plains

HELP

HELP

Interior

River Lowland

Northern Lakes

and Forests

NMW

Ozark Highlands

South

Central

Plains

Southern 

Michigan/

Northern 

Indiana 

Drift Plains 

NLF

Flint

Hills

Ouachita Mountains

Arkansas Valley

tral

a/Texas

ns

TBP

MVLP

Mississippi

Alluvial

Plain

NCHF

Driftless

Area SEWTP

NECZ

 Central

Appalachians

Piedmont

EXPLANATION

Water

Developed

Barren

Forest

Grassland/Shrubland

Agriculture

Wetland

Ice/Snow

Land-use/land-cover class

LAINS

 MIDWEST–

SOUTH CENTRAL

UNITED STATES

EASTERN UNITED STATES

Ecoregion boundary

Major ecoregion group boundary
172 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

CGP Central Great Plains Ecoregion

CIP Central Irregular Plains Ecoregion

COTP Central Oklahoma/Texas Plains Ecoregion

ECTP East Central Texas Plains Ecoregion

EP Edwards Plateau Ecoregion

FH Flint Hills Ecoregion

LAP Lake Agassiz Plain Ecoregion

NGP Northern Glaciated Plains Ecoregion

NSH Nebraska Sand Hills Ecoregion

NWGLP Northwestern Glaciated Plains Ecoregion

NWGP Northwestern Great Plains Ecoregion

STP Southern Texas Plains Ecoregion

SWT Southwestern Tablelands Ecoregion

TBP Texas Blackland Prairies Ecoregion

WCBP Western Corn Belt Plains Ecoregion

WGCP Western Gulf Coastal Plain Ecoregion

WHP Western High Plains Ecoregion

Appendix 2. Abbreviations for Ecoregions in the Great Plains of the United States
Appendix 3. Land-Cover Classification System Used in “Status and Trends of Land Change” Study 173

Appendix 3. Land-Cover Classification System Used in “Status and Trends 

of Land Change” Study

This analysis of land-use/land-cover change during the 

1973–2000 study period is based on land-cover classifications 

mapped for five study dates—1973, 1980, 1986, 1992, and 

2000. The use of moderate-resolution imagery—Landsat 

Multispectral Scanner, Thematic Mapper, and Enhanced 

Thematic Mapper Plus—necessitated a land-cover 

classification system that was fairly general in order to achieve 

high levels of accuracy and consistency in the interpretations. 

The classification system also needed to contain classes that 

could be used as an appropriate surrogate for land use. This 

classification, which is based on the Anderson Level I classes 

(Anderson and others, 1976), was used because the classes 

have been designed as use surrogates, but this system has 

been further modified by adding two transitional disturbance 

categories, mechanically disturbed (human induced) and 

nonmechanically disturbed (natural). 

The classification system used consists of the following 

11 general land-cover classes: water, developed, mechanically 

disturbed, mining, barren, forest, grassland/shrubland, 

agriculture, wetland, nonmechanically disturbed, and ice/

snow. Classes are defined as follows:

Water—Areas that are persistently covered with water, 

such as perennial streams, canals, rivers, lakes, reservoirs, 

bays, and oceans.

Developed—Areas of intensive use, in which much of 

the land is covered with structures or other anthropogenically 

induced, impermeable surfaces (for example, high-density 

residential, commercial, and industrial areas, as well as 

roads, highways, and other transportation corridors), or less 

intensive use, in which the land-cover matrix includes both 

vegetation and structures (for example, low-density residential 

areas, recreational facilities, cemeteries, parking lots, and 

utility corridors). Land that is functionally related to urban or 

built-up environments (for example, parks and golf courses) is 

also included.

Mechanically disturbed—Land in an altered and 

often unvegetated state owing to disturbance by mechanical 

(that is, human) means. Mechanically disturbed land is in 

transition from one land-cover class to another. Processes 

leading to mechanical disturbance include forest clearcutting, 

earthmoving, scraping, chaining, reservoir drawdown, and 

other types of anthropogenically induced changes.

Mining—Areas of extractive mining activities that have 

significant surface expression, including mining buildings and 

apparatus, quarry pits, evaporation and leach ponds, tailings and 

overburden piles, and other components related to mining, to 

the extent that these features can be detected.

Barren—Areas of bare soil, sand, or rock, in which less 

than 10 percent of the area is vegetated. Barren lands generally 

are naturally occurring.

Forest—Tree-covered land where the tree-cover density 

is greater than 10 percent. Cleared forest land is mapped 

(according to land cover at the time of the imagery) as either 

mechanically disturbed or grassland/shrubland.

Grassland/Shrubland—Land that is predominately 

covered with grasses, forbs, or shrubs. Vegetated cover must 

make up at least 10 percent of the area.

Agriculture—Land, in either a vegetated or an 

unvegetated state, used for the production of food or fiber. 

This includes cultivated and uncultivated croplands, hay lands, 

pasture, orchards, vineyards, and confined-livestock operations. 

However, forest plantations always are classified as forest, 

regardless of how the wood products are used.

Wetland—Land where water saturation is the determining 

factor in soil characteristics, vegetation types, and animal 

communities. Wetlands usually contain both water and 

vegetated cover.

Nonmechanically disturbed—Land in an altered and 

often unvegetated state owing to disturbance by nonmechanical 

(that is, natural) means. Nonmechanically disturbed land is 

in transition from one land-cover class to another. Causes of 

nonmechanical disturbance include fire, wind, floods, animals, 

and other similar phenomena.

Ice/Snow—Land where the accumulation of snow and 

ice does not completely melt during the summer period (for 

example, alpine glaciers and perennial snowfields).

Reference Cited

Anderson, J.R., Hardy, E.E., Roach, J.T., and Witmer, R.E., 

1976, A Land Use and Land Cover Classification System 

for Use with Remote Sensor Data: U.S. Geological Survey 

Professional Paper 964, 28 p., available at http://pubs.usgs.

gov/pp/0964/report.pdf.
174 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Appendix 4. Methodology Used in “Status and Trends of Land Change” Study

This appendix describes the methodology used to 

document the temporal and spatial rates, trends, and types 

of change documented in this “Status and Trends of Land 

Change” study. The methodology is based on a statistical 

sampling approach, manual classification of land use and 

land cover, and postclassification comparisons of land cover 

over five different study dates (Loveland and others, 2002). 

U.S. Environmental Protection Agency’s (1999) Level III 

ecoregions provided the geographic framework for regional 

land-cover change estimates, and land-use/land-cover change 

was estimated on an ecoregion-by-ecoregion basis using a 

probability sample of randomly selected blocks within each of 

84 ecoregions across the conterminous United States. For each 

sample block, five dates of Landsat imagery were interpreted 

in order to map land use and land cover, using a classification 

system that consists of 11 general land-cover classes (see 

appendix 3, entitled “Land-Cover Classification System Used 

in ‘Status and Trends of Land Change’ Study”). The resulting 

land-cover data for each sample block were used to determine 

change for four time periods, and sample-block data were used 

to calculate change estimates for each ecoregion. 

Sampling Strategy

In this study, a sampling strategy was used as a costefficient method for characterizing land-cover change in an 

area as large as the conterminous United States. The study 

used a stratified random sample of 2,688 square blocks 

(fig. 1); a random sample of these blocks was independently 

selected for each ecoregion analyzed. Because the study used 

a probability sample, the estimates of land-use/land-cover 

change that are derived can be considered as categorically 

representative of the population (Kish, 1987). 

The size of each sample block in this study, as well as 

the sampling density (that is, the number of sample blocks 

analyzed per ecoregion), was based on a compromise between 

two conflicting objectives: (1) estimating change in landcover area, and (2) estimating change in landscape pattern. 

Larger numbers of smaller sample blocks would result in 

more precise estimates of change in land-cover area, whereas 

smaller numbers of larger sample blocks would be more 

desirable for characterizing landscape pattern. 

Size of Samples

In the initial study design, a 20 × 20 km (400 km2) 

sample-block size was used, and nine ecoregions were 

analyzed, each analysis consisting of 9 to 11 sample blocks. 

On the basis of results from these initial ecoregion analyses, 

a decision was made to use a higher density of smaller (10 

× 10 km; 100 km2) sample blocks for the remainder of the 

ecoregion analyses in order to maximize the precision of the 

land-cover change estimates.

Sampling Density

The sampling density was determined by both the project 

requirements for precision in the change estimates and the 

expected characteristics of change within the ecoregion 

being studied. As precision requirements increase, so must 

the sampling density. Similarly, a greater sampling density is 

required when areas of change are expected to be less evenly 

distributed throughout an ecoregion.

In this study, the target precision level was to map gross 

overall change to within a ±1% margin of error at an 85% 

confidence level for each ecoregion. On the basis of this target 

precision level and the expected characteristics of change 

within all 84 ecoregions in the conterminous United States, 

it was determined that between 25 and 48 of the 10 × 10 

km sample blocks per ecoregion would likely be needed to 

adequately characterize overall change in each ecoregion.

Implementation of the Sampling Strategy

The sampling strategy outlined above was fairly 

straightforward to implement. A regular grid of 10 × 10 km 

(or, in a few cases, 20 × 20 km) sample blocks was overlain on 

an ecoregion map of the conterminous United States. Blocks 

whose centers fell within the boundaries of an ecoregion were 

highlighted as potentially valid sample blocks for that ecoregion 

and then were assigned a unique numerical value from 1 to N. 

A random number generator was then used to select sample 

blocks, one at a time, until the desired number was reached. 

Thus, each sample block within an ecoregion had an equal 

probability of being included in the final sample analysis. 

Although the number of sample blocks selected and 

analyzed was based on both the target precision level and 

the expected characteristics of change within the ecoregion, 

unexpected heterogeneity in the distribution of change 

could still result in the estimates of change having levels of 

precision that are lower than desired. Should this occur, the 

sampling strategy allowed for the selection and interpretation 

of additional sample blocks. The inclusion of these reserve 

blocks allowed the analysis to achieve change estimates that 

have acceptable levels of precision. In actuality, for various 

reasons, no reserve blocks were implemented. 

Geographic Framework

A central premise of the study design was the use of a 

geographic framework to provide regional land-cover change 

estimates. Geographers have long used regional frameworks 

because they capture the essence and potential of the 

landscape without masking the roles of environmental, social, 

and economic forces (Turner and Meyer, 1991). This “Status 

and Trends of Land Change” study chose to use ecoregions, 

as originally defined by Omernik (1987) and later modified 
Appendix 4. Methodology Used in “Status and Trends of Land Change” Study 175

by the U.S. Environmental Protection Agency (1999), as the 

framework from which to tell the regional story of change. 

Ecoregions were chosen as the unit of analysis because 

(1) they provide a means to localize estimates of the rates 

and driving forces of change, (2) they were developed by 

synthesizing information on a wide variety of factors (for 

example, climate, geology, physiography, soils, vegetation, 

hydrology, and human influences) and, therefore, should 

reflect both current land-use and land-cover types and future 

change trajectories, and (3) they provide a framework that can 

be extended globally. 

Landsat Data

Landsat satellite imagery was the primary source of 

data used for detecting land-cover change in this study. Data 

from the Landsat Multispectral Scanner (MSS), Thematic 

Mapper (TM), and Enhanced Thematic Mapper Plus (ETM+) 

instruments were acquired from the Landsat data archive: 

Landsat MSS datasets are available from late-1972 through 

late-1992; Landsat TM data are available from 1982 to the 

present; and Landsat ETM+ data are available from 1999 to the 

present. Each of these products provided a consistent, synoptic, 

multispectral view of the land surface from which land cover 

could be interpreted for the period between 1972 and 2000. To 

analyze trends in land-use/land-cover change throughout this 

period, five target study dates spaced at semiregular intervals 

(1973, 1980, 1986, 1992, and 2000) were selected. Landsat 

imagery corresponding to each 10 × 10 km (or 20 × 20 km) 

sample block was extracted from full Landsat scenes, resulting 

in five dates of satellite imagery for each sample block. To 

reduce expenses, the initial data-acquisition strategy was to 

use existing geoprocessed Landsat datasets as the primary 

input data source. Four of the five dates of Landsat MSS, 

TM, and ETM+ data were available in a geocoded format as 

a result of processing done for two previous projects: (1) the 

North American Landscape Characterization (NALC) project 

produced 1973, 1986, and 1992 geocoded Landsat MSS datasets 

for the conterminous United States and Mexico (Lunetta and 

others, 1998), and (2) the 1992 TM and 2000 ETM+ data 

came from the Multiresolution Landscape Characterization 

initiative (Loveland and Shaw, 1996). New 1980 Landsat MSS 

acquisitions were obtained in order to maintain the six- to eightyear interval between the five target dates. 

The Landsat MSS, TM, and ETM+ scenes obtained 

were previously georeferenced to root-mean-square error of 1 

pixel or less but to differing map projections. For this study, 

all scenes were translated to a common Albers equal-area 

projection. Most of the NALC MSS data had also been terraincorrected, but approximately one-third of the NALC data 

(path and rows) had been processed before the implementation 

of terrain-correction techniques. However, this was not 

considered a problem because the early NALC scenes were 

located primarily in areas with negligible terrain variability.

Ancillary Data

Additional ancillary data were acquired to aid 

interpreters in delineating land use and land cover from 

the Landsat data. For example, aerial photography was 

acquired for each sample block to provide a high-resolution 

data source to help with difficult interpretations. The 

National Aerial Photography Program (NAPP) generally 

provided one or two dates of color-infrared (CIR) and 

(or) black-and-white aerial photographs from 1987 to the 

present. The National High Altitude Photograph (NHAP) 

Program generally provided one date of CIR and (or) 

black-and-white aerial photographs between 1980 and 

1986. Although the Landsat imagery was always used 

as the source material for delineating land use and land 

cover, these higher resolution aerial photographs were 

invaluable for assisting in the interpretation of the imagery. 

Topographic maps, census data, other electronic sources 

of aerial photographs (for example, Google Earth), and 

digital raster graphics were among the other sources of 

information that interpreters found useful when processing 

the data.

Land-Cover Classification Scheme

The analysis of land use and land cover change during 

the 1973 to 2000 study period was based on classifications 

of land cover for the five target dates mentioned previously. 

The classification system used consists of the following 11 

general land-cover classes: water, developed, mechanically 

disturbed, mining, barren, forest, grassland/shrubland, 

agriculture, wetland, nonmechanically disturbed, and ice/

snow. See appendix 3, entitled “Land-Cover Classification 

System Used in ‘Status and Trends of Land Change’ 

Study,” for definitions of these 11 classifications.

Two primary factors affected the design of the 

classification system. The first factor was recognizing that 

the use of moderate-resolution Landsat imagery would 

necessitate a land-cover classification system that was fairly 

general in order to achieve high interpretation accuracy 

and consistency. The ability to identify and map land cover 

would be limited both by the technical specifications of 

the Landsat MSS, TM, and ETM sensors and by the local 

and regional landscape characteristics that affect the form 

and contrast visible in satellite imagery. This would be 

especially true when interpreting Landsat MSS data. 

The second factor involved choosing land-cover 

classes that captured the land-cover changes of interest. 

Because the project’s interest was in land-use change, with 

land cover serving as a surrogate for land use, the decision 

was to use the Anderson Level I classes (Anderson and 

others, 1976) because they were designed as use surrogates. 

However, the Anderson system was selectively modified by 

adding two disturbance categories, mechanically disturbed 

(human induced) and nonmechanically disturbed (natural). 
176 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Manual Land-Cover Delineation

Land-cover delineation for each sample block began 

with the creation of a baseline reference land-cover dataset. 

The 1992 date usually was the starting point owing to the 

availability of the 30-m-resolution 1992 National Land Cover 

Data (NLCD) dataset (Vogelmann and others, 2001). The 

NLCD dataset provided a starting template after the more 

detailed NLCD classes were aggregated to match the general 

land-cover classification described above. 

The NLCD data first were manually edited on the 

computer screen, using on-screen interpretation methods, 

while using the 1992 Landsat TM data and the NAPP aerial 

photographs as interpretation aids. This cleanup procedure to 

improve the NLCD classification accuracy was carried out 

because the NLCD data were created using automated imageprocessing procedures, and they were not meant for use in 

local- or ecoregional-scale assessments. A minimum mapping 

unit of 60 × 60 meters was used for this study. Thus, features 

having ground footprints less than 60 m wide generally 

were not mapped, resulting in the exclusion of high-contrast 

features such as roads, which have a distinct spectral signature 

but have ground dimensions of less than 60 m.

To carry out the NLCD editing for a particular sample 

block, the analyst displayed the NLCD data alongside 

the 1992 Landsat TM data on the computer screen. These 

data sources, along with hard-copy prints of NAPP aerial 

photography roughly corresponding to the 1992 date, 

were visually inspected by the analyst to determine if any 

corrections were needed in the sample block. The analyst 

manually delineated polygons that consisted of contiguous 

blocks of specific land-cover classes. Each of these polygons 

was then given a code value that corresponded to the 

land-cover classes outlined in the classification scheme in 

appendix 3. The process continued until the entire sample 

block was manually inspected, mapped, and coded by the 

analyst.

To analyze change, land-cover classes for the 1973, 

1980, 1986, and 2000 study dates were backward- or forwardclassified using the 1992 land-cover dataset as the template. 

For example, creation of the 2000 land-cover product began 

by making an exact copy of the 1992 land-cover product. This 

copy served as a baseline for the 2000 land-cover product, 

in which identified changes between 1992 and 2000 were 

manually edited into the copied image. This baseline 2000 

land-cover product was displayed on screen, along with the 

1992 Landsat imagery and the 2000 Landsat imagery, allowing 

the analyst to pan through the entire area of the sample block 

while examining the 1992 and 2000 Landsat imagery and 

any relevant aerial photography for valid land-cover changes 

between the two study dates. Any identified land-cover 

changes were manually digitized on screen, and the land cover 

was recoded on the 2000 land-cover product. 

Upon completion of the 2000 land-cover product, the 

same procedures were used to create the 1986, 1980, and 1973 

land-cover products. This manual process eliminated errors 

that may occur between independently created land-cover 

products that are compared in a subsequent change analysis. 

Because only manually identified, delineated, and coded landcover changes were analyzed during this phase, classification 

errors were greatly reduced.

Statistical Analysis

The resulting land-cover data for each sample block 

was used in postclassification comparisons to determine 

change between study years (fig. 2). Sample blocks within 

each ecoregion were used to generate change statistics for 

all 84 ecoregions. These statistics were used to determine 

the predominant types of land-cover conversions occurring 

within each ecoregion, the estimated rates of change for these 

conversions, and whether these types and rates of change are 

constant or variable across time. The analysis of change also 

involved looking for spatial correlations between conversion 

types and selected socioeconomic and environmental factors, 

such as timber production, agricultural yields, precipitation 

amounts, population levels, proximity to urban development, 

and overall economic conditions, in order to improve the 

understanding of potential drivers of change.
Appendix 4. Methodology Used in “Status and Trends of Land Change” Study 177

70°

80°

80°

90°

90°

100°

100°

110°

110° 120°

45° 45°40° 40°35° 35°30° 30°

25° 25°

CANADA

MEXICO

0 200 400 600 MILES0 200 400 600 KILOMETERS

Total change

10 × 10 km20 × 20 km

, as

EXPLANATION

percent of ecoregion

0 – 4.14.2 – 7.57.6 – 14.414.5 – 33.8

Ecoregion boundary

Sample blocks

Figure 4.1. Map of ecoregions in conterminous United States, showing locations of 2,688 sample blocks that were used in “Status and Trends of Land Change” study 

(purple and blue squares indicate locations of 10 × 10 km and 20 × 20 km sample blocks, respectively). Also shown are amounts of total change in each ecoregion between 1973 and 2000, as percent of ecoregion
178 Status and Trends of Land Change in the Great Plains of the United States—1973 to 2000

Figure 4.2. Example of data compiled for each sample block, showing sample block 14-0555 (located near 

Henderson, Nevada, in Mojave Basin and Range Ecoregion, one of Western United States ecoregions). Left 

column is satellite imagery collected for each of five years analyzed in study (imagery sources for study years: 

1973, 1980, and 1986 are Landsat Multispectral Scanner (MSS) images; 1992 is Landsat Thematic Mapper 

(TM) image; 2000 is Landsat Enhanced Thematic Mapper (ETM) image). Center column is mapped land-use/

land-cover data for each study year. Right column shows areas that changed (green areas) in each of four 

time periods between study years; light- and dark-gray-shaded areas show areas of previous change and 

represent overall land-change footprint throughout study period.

 

1973–1980

1980–1986

1986–1992

1992–2000

Forest

Grassland/Shrubland

Mining

Water

Barren

Mechanically disturbed

Developed

Land-use/land-cover class

1973

Landsat images Mapped land-use/land-cover Areas of change

1980

1986

1992

2000
References Cited 179

References Cited

Anderson, J.R., Hardy, E.E., Roach, J.T., and Witmer, R.E., 

1976, A Land Use and Land Cover Classification System 

for Use with Remote Sensor Data: U.S. Geological Survey 

Professional Paper 964, 28 p., available at http://pubs.usgs.

gov/pp/0964/report.pdf.

Kish, L., 1987, Statistical Design for Research: New York, 

John Wiley & Sons, Inc., 296 p.

Loveland, T.R., and Shaw, D.M., 1996, Multiresolution land 

characterization—Building collaborative partnerships, 

in Scott, J.M., Tear, T.H., and Davis, F.W., eds., Gap 

Analysis—A landscape approach to biodiversity planning: 

Bethesda, Maryland, American Society for Photogrammetry 

and Remote Sensing, p. 17–25.

Loveland, T.R., Sohl, T.L., Stehman, S.V., Gallant, A.L., 

Sayler, K.L., and Napton, D.E., 2002, A strategy for 

estimating the rates of recent United States land cover 

changes: Photogrammetric Engineering and Remote 

Sensing, v. 68, no. 10, p. 1,091–1,099.

Lunetta, R.S., Lyon, J.G., Guindon, B., and Elvidge, C.D., 

1998, North American landscape characterization dataset 

development and data fusion issues: Photogrammetric 

Engineering and Remote Sensing, v. 64, no. 8, p. 821–829.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Turner, B.L., II, and Meyer, W.B., 1991, Land use and land 

cover in global environmental change—Considerations for 

study: International Social Science Journal, v. 130, 

p. 669–677.

U.S. Environmental Protection Agency, 1999, Level 

III Ecoregions of the continental United States: U.S. 

Environmental Protection Agency National Health 

and Environmental Effects Research Laboratory, scale 

1:7,500,000, available at ftp://ftp.epa.gov/wed/ecoregions/

us/Eco_Level_III_US.pdf.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.
Produced in the Menlo Park Publishing Service Center, Menlo Park, California

Manuscript approved for publication June 18, 2015

Edited by Taryn A. Lindquist and John S. Osias

Design and layout by Jeanne S. DiLeo and David R. Jones

ISSN 1044-9612 (print) 

ISSN 2330-7102 (online) 

Printed on recycled paper http://dx.doi.org/10.3133/pp1794B

I SBN 978- 1- 4113- 3934- 7

9 7 8 141 1 3 3 9 34 7