Land-Cover Trends of the Central Basin and Range 

Ecoregion

By Christopher E. Soulard

Scientific Investigations Report 2006-5288

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, October 18, 2006

Text edited by James W. Hendley II

Layout and design by Judy Weathers

U.S. Geological Survey, Reston, Virginia: 2006

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FRONT COVER

Field photo of sagebrush plant community. Sagebrush makes up more than one third of the vegetation in the Central 

Basin and Range ecoregion.
iii

The U.S. Geological Survey (USGS) Land Cover Trends research project is focused on 

understanding the amounts, rates, trends, causes, and implications of contemporary land-use 

and land-cover (LU/LC) change in the United States. This project is supported by the USGS 

Geographic Analysis and Monitoring Program in collaboration with the U.S. Environmental 

Protection Agency (EPA) and the National Aeronautics and Space Administration (NASA).

LU/LC change is a pervasive process that modifies landscape characteristics and affects 

a broad range of socioeconomic, biologic, and hydrologic systems. Understanding the impacts 

and feedbacks of LU/LC change on environmental systems requires an understanding of the 

rates, patterns, and driving forces of past, present, and future LU/LC change. The objectives of 

the Land Cover Trends project are to (1) determine and describe the amount, rates, and trends 

of contemporary LU/LC change by ecoregion for the period 1973-2000 for the conterminous 

United States, (2) document the causes, driving forces, and implications of change, and (3) synthesize individual ecoregion results into a national assessment of LU/LC change. 

The Land Cover Trends research team includes staff from the USGS National Center 

for Earth Resources Observation and Science (EROS), Rocky Mountain Geographic Science 

Center, Eastern Geographic Science Center, Mid-Continent Geographic Science Center, and the 

Western Geographic Science Center. Other partners include researchers at South Dakota State 

University, University of Southern Mississippi, and State University of New York College of 

Environmental Science and Forestry.

Foreword
iv 

Contents

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

Introduction.....................................................................................................................................................1

Study Area..............................................................................................................................................1

Historical Overview of Land Use and Land Cover (Pre-1973)........................................................2

Methods...........................................................................................................................................................3

Results .............................................................................................................................................................3

Footprint of Change.............................................................................................................................3

Normalized Annual Change ................................................................................................................3

Class Area and Change .......................................................................................................................3

Common Conversions...........................................................................................................................3

Temporal Change Characteristics......................................................................................................4

Change Precision..................................................................................................................................4

Discussion.......................................................................................................................................................4

Fire ..........................................................................................................................................................4

Agricultural Conversions.....................................................................................................................5

Water Conversions ...............................................................................................................................6

Development..........................................................................................................................................6

Mining ....................................................................................................................................................6

Conclusion.......................................................................................................................................................7

References......................................................................................................................................................7

Appendix. Definitions of Land Use and Land Cover.................................................................................9

Figures

1. Location map of the Central Basin and Range Ecoregion ................................................................10

2. Graphic illustrating interrelationship between land use, invasive plants, and fire ......................11

3. Graph illustrating average annual rates of change ..........................................................................12

4. Graph illustrating gross change by class over the study period .....................................................13

5. Example of nonmechanically disturbed classification......................................................................14

6. Comparison between two fire databases............................................................................................15

7. Field photos of agricultural land in the study area.............................................................................16 

8. Comparison between two development databases. .........................................................................16 

9. Field photos of waste facility and downstream drainage in the study area..................................17 

10. Field photos illustrating different elements of mining in the study area. .....................................18

Tables

1. Percent total land area by class over the study period ....................................................................19

2. Most common land-cover conversions over the study period ........................................................19

3. Average annual gains and losses by class .........................................................................................20

4. Gross change and margin of error by period......................................................................................20
Land-Cover Trends of the Central Basin and Range Ecoregion

By Christopher E. Soulard

Introduction

This report presents an assessment of land-use/land-cover 

(LU/LC) change in the Central Basin and Range ecoregion 

(fig. 1) for the period 1973-2000. The Central Basin and Range 

ecoregion is one of 84 Level-III ecoregions as defined by the 

Environmental Protection Agency (EPA, 1999, Omernik, 1987). 

Ecoregions have served as a spatial framework for environmental resource management and to denote areas that contain a geographically distinct assemblage of biotic and abiotic phenomena 

including geology, physiography, vegetation, climate, soils, 

land use, wildlife, and hydrology. The established Land Cover 

Trends methodology generates estimates of LU/LC change 

using a probability sampling approach and change-detection 

analysis of thematic land-cover images derived from Landsat 

satellite imagery.

Study Area

The Central Basin and Range Level III ecoregion is 

similar, yet distinct from the extent of the hydrographic Great 

Basin (Grayson, 1993). Most of the region is located in Nevada 

(65.4 percent) and Utah (25.1 percent), but small segments are 

also located in Idaho (5.6 percent), California (3.7 percent), 

and Oregon (0.2 percent). In all, the Central Basin and Range 

ecoregion (CBARE) encompasses 343,169 km2 of land bordered on the west by the Sierra Nevada Mountains, on the east 

by the Wasatch Mountains, on the north by the Northern Basin 

and Snake River Plain, and on the south by the Mojave Desert 

and Colorado Plateau (fig. 1). Basin and Range topography 

characterizes the CBARE: wide desert valleys bordered by parallel mountain ranges generally oriented north-south. There are 

more than 33 peaks within the CBARE with summits higher 

than 3,000 meters, but valleys in the region are also high, most 

with elevations above 1,200 meters (Grayson, 1993). The Great 

Basin desert, which is encompassed within the CBARE, is one 

of the four biologically defined deserts in North America in 

addition to the Mojave, Sonoran, and Chihuahuan (Grayson, 

1993). The Great Basin has the coldest climate of these deserts.

The CBARE’s high elevation and location between mountain ranges influences regional climate. The Sierra Nevada 

produces a rain shadow effect that blocks moisture from the 

Pacific Ocean, whereas the Rocky Mountains create a barrier 

effect that restricts moisture from the Gulf of Mexico (Rogers, 1982). Moisture that manages to reach the CBARE tends 

to precipitate as rain and snow in higher elevations, primarily over the region’s long, parallel mountains (Brussard and 

others, 1998). Ultimately, any precipitation that falls within 

the CBARE fails to drain either to the Atlantic Ocean or to 

the Pacific Ocean (thus the term basin). Instead, precipitation 

drains to ephemeral or saline lakes via streams, or disappears 

via evaporation and/or absorption into the soil (Grayson, 1993). 

This dry climate and rugged topography proves too harsh 

for many plant and animal species; however, genetic adaptations to these conditions have led to reasonably high species 

richness within the CBARE. Furthermore, the significant 

variation between valleys and peaks has created a variety of 

habitat niches, which has in turn led to many small, isolated 

populations of genetically unique plant and animal species 

throughout the region. According to Grayson (1993), more 

than 600 species of vertebrates live in the floristic Great Basin, 

which has a similar areal footprint to the CBARE. Sixty-three 

of these species have been identified as species of conservation concern due to contracting natural habitats (for example, 

Centrocerus urophasianus, Vulpes macrotis, Dipodomys ordii, 

and Phyrnosoma platyrhinos) (Rowland and others,1997, 

Wisdom and others, 2003).

Ultimately, climate, elevation, soil type, and many 

anthropogenic variables greatly influence the diversity and 

distribution of shrubland, grassland, and woodland communities in the CBARE. For instance, the moisture and temperature 

variability between the mountains and valleys of the CBARE 

contributes to the vegetation gradation from shrubland to 

woodland as elevation increases. Lower valleys and playas, 

which have saline soils and great temperature fluctuations, are 

predominantly vegetated by scattered Iodine brush (Allenrolfea occidentalis), saltbrush (Atriplex canescens), saltgrass 

(Distichlis spicata), shadscale (Atriplex confertilfolia), and 

other drought tolerant shrubs (Rogers, 1982). The soil salinity 

and lack of moisture in this zone is not very conducive to most 

agriculture; however, livestock grazing and grain farming have 

historically contributed to a decline in the already scattered 

vegetation (Billings, 1951).

The drop in soil salinity and increase in moisture as elevation increases leads to a transition to sagebrush (Artemisia) 

and grasses just above the shadscale zone. This expanse, called 

the sagebrush zone, constitutes the largest amount of land in 

the CBARE (38.7 percent) and is dominated by big sagebrush 

(Artemisia tridentata) shrubland (Brussard and others, 1998). 
 Land-Cover Trends of the Central Basin and Range Ecoregion

Introduced annual grasses such as cheatgrass (Bromus tectorum) and halogeton (Halogeton glomeratus) also characterize 

this zone, although native bunchgrasses once thrived amongst 

sagebrush. Historical fire suppression, adjusted fire frequency 

following the introduction of annual grasses, and widespread 

livestock grazing have contributed to contraction of the sagebrush zone (Eiswerth and others, 2006). According to Noss 

and others (1995), 99 percent of the sagebrush-grass zone has 

been damaged by livestock, with major damage in 30 percent 

of the zone.

The subalpine woodlands on the mountain slopes above 

the sagebrush zone (~1,500 meters) are dominated by pinyon 

pine (Pinus edulis) and juniper communities (for example, 

Juniperus communis, Juniperus occidentalis, and Juniperus 

osteosperma). This zone of dense vegetation, made possible 

by thermal inversions and increased precipitation, is important 

to a wide variety of isolated animals that rely on this vegetation interface for survival (for example, Eutamias plameri) 

(Brussard and others, 1998).

Public lands are 76.4 percent of the CBARE, with 59.4 

percent managed by the Bureau of Land Management (BLM). 

Other public land managers include the U.S. Forest Service 

(USFS) and the National Park Service (NPS). USFS manages 

10.8 percent of the CBARE, including the Humboldt-Toiyabe 

National Forest and the Inyo National Forest. Great Basin 

National Park and part of Death Valley National Park are the 

only NPS holdings in the CBARE. Department of Defense 

(DOD) lands also are a large part of the Federal holdings in 

the CBARE (3.9 percent), the largest being Nellis Air Force 

Base (National Atlas of the United States, 2005). 

Public land management, military activities, and local 

government administration account for a large part of the 

CBARE’s economy. Other leading economic sectors include 

mining and agriculture, both of which have a rich history in 

the region. The mining sector is dominated by metal mining (for example, gold, copper, and nickel), but nonmetallic mineral (for example, gravel) and fossil fuel extraction 

also account for a significant number of operational mining 

establishments (County Business Patterns, 1997). Agricultural 

production can be primarily characterized by cattle and hay 

production; however, there are measurable contributions from 

sheep, alfalfa, and barley production to the agricultural sector 

(USDA, 2005). The economy is rounded off by manufacturing, which is encapsulated by the processing of these raw mining and agricultural materials, and the service sector, which 

is growing along with a burgeoning retirement community 

in the CBARE (Bureau of Economic Analysis, 2000). While 

mining and agricultural activities are dispersed throughout 

the CBARE, the remaining sectors of the economy tend to be 

concentrated in and around the municipalities of the region. 

The largest concentrations of population in the CBARE 

are along the eastern and western borders of the region. 

The eastern regional boundary encompasses the greater Salt 

Lake area, whereas the Reno-Sparks-Interstate 395 expanse 

composes the western regional boundary. In 2000, the largest cities in terms of population were Salt Lake City, Utah 

(pop. 181,743), Reno, Nevada (pop. 180,480), West Valley, 

Utah (pop. 108,896), Provo, Utah (pop. 105,166), and 33 

other cities with populations greater than 10,000 people 

(National Atlas of the United States, 2005). Overall, the 

CBARE has a total population around 2.5 million (U.S. Census Bureau, 2000). 

Historical Overview of Land Use and Land Cover 

(Pre-1973)

European habitation of the CBARE began in the 

late 1700s, and ushered in an era of intense natural-resource 

extraction. This shift in land use-intensity marked the change 

from a time when people reacted to environmental change to 

a time when the “environment [primarily] react[ed] to human 

influence” (Grayson, 1993). Early European immigrants 

engaged in mineral mining (gold, silver, and copper), livestock 

grazing, and timber harvesting (Rogers, 1982, University of 

Nevada Reno, 1999). Between 1860 and 1890, the regional 

mineral industry flourished via the Comstock Lode, a large 

silver and gold deposit found east of Mount Davidson, 

Nevada. This spike resulted in more intense resource 

exploration and the rise of many boomtown developments 

across the landscape, such as Goldfield and Tonopah 

(University of Nevada Reno, 1999). Massive tailing piles and 

the plethora of ghost towns scattered throughout the CBARE 

today provide a snapshot of this moment in history. 

However, not all of the towns that arose in the mid-1800s 

experienced a bust after the mines were exhausted and silver 

prices dropped. Some of the mining cities in the western 

CBARE (for example, Reno and Carson City) prospered 

from a steady stream of gold and silver strikes coupled with 

the businesses that came along with the Pony Express and 

transcontinental railroad. In the early 20th century, these towns 

experienced another boom following the legalization of casino 

gambling in Nevada. Cities that were not entirely dependant 

on mining, such as Great Salt Lake City (now Salt Lake City), 

relied on agricultural production as an economic staple in their 

early stages of urbanization. During World War II, military 

installations helped invigorate the economies of Salt Lake City 

and its neighboring communities following the Great Depression (Launius, 2004). 

The westward expansion of railroads in the late 1860s 

brought more settlers, more intense land use, and ultimately 

led to the introduction or many invasive species in the 

CBARE (Trimble, 1989). The most notable of these invasive 

species is cheatgrass (Bromus tectorum), which was introduced by settlers intending to feed domestic livestock by 

filling areas left void by native plants (Pellant and others, 

2004). Cheatgrass and other introduced annuals not only outcompeted native bunchgrasses, but also altered the CBARE’s 

fire regime. In areas that previously burned about every 30 to 

70 years, the introduction of cheatgrass increased fire-return 

intervals to less than 10 years (Pellant and others, 2004). 

In turn, this led to a significant decline in native sagebrush. 
Results   

The agricultural industry intensified the problem for native 

plants between 1930 and 1960, when vast areas were tilled 

and seeded with crested wheatgrass (Agropyron desertorum)

for livestock, and herbicides were applied to kill native brush 

varieties (Trimble, 1989). The Sagebrush Rebellion, which 

was based on reducing Federal influence in state lands, began 

soon thereafter and spurred changes in state laws towards 

local control. These changes led to considerable range 

improvements in the 1980s, which were challenged by many 

conservation groups (Pellant and others, 2004). Despite the 

recent shift in public land management towards sagebrush 

conservation, the interplay between native-plant decline, 

cheatgrass expansion, and fire continues to be a trend in the 

CBARE today (fig. 2). 

Methods

Our interpretation team estimated the amount and rates of 

LU/LC change in the CBARE ecoregion using a stratified random sample of 36 100-km2 (10-km by 10-km) blocks allocated 

across the ecoregion (fig. 1). We manually interpreted up to 

11 classes of LU/LC (appendix) from five dates (1973, 1980, 

1986, 1992, and 2000) of archived Landsat Multispectral 

Scanner (MSS), Thematic Mapper (TM), and Enhanced Thematic Mapper Plus (ETM+) satellite imagery using a 60-meter 

minimum mapping unit (MMU). In addition to manual interpretation techniques, we used historical aerial photographs, 

topographic maps, and various ancillary data sources to aid in 

image interpretation. Our LU/LC mapping effort yielded five 

individual dates and four discrete periods for analysis. We then 

used post-classification comparison of the five dates of thematic LU/LC data for each sample block to generate estimates 

of LU/LC change for the entire CBARE along with corresponding margins of error at an 85 percent confidence level. A 

full explanation of Land Cover Trends project methodology is 

provided by Loveland and others (2002).

Results

The section that follows illustrates the results of the post 

classification comparison applied to the five core dates (1973, 

1980, 1986, 1992, and 2000) over 36 100 km2 sample blocks 

within the CBARE. Sampling results have been scaled up to 

the entire CBARE and are reported thusly.

Footprint of Change

Between 1973 and 2000, the footprint of LU/LC change 

in the CBARE was 1.45 percent, or 4,978 km2. This change 

can be interpreted as the amount of the CBARE that experienced change at least once within the study period (and does 

not account for the frequency of change in any given location). This overall spatial change translates to 4,370 km2 that 

changed in one period, 442 km2 that changed in two periods, 

and 166 km2 that changed in three periods. 

Normalized Annual Change

The normalized annual rate of LU/LC change in the 

CBARE from 1973 to 2000 was 0.06 percent/year. This means 

that the region averaged 0.06 percent (206 km2) of change 

each year in the 27-year study period. However, change was 

not consistent throughout the study period, but varied greatly 

between each of the four periods. As a matter of fact, the 

CBARE experienced a growing rate of change from 1973 

to 2000 (fig. 3). Between 1973 and 1980, the annual rate of 

change in the CBARE was 0.03 percent/year, while the annual 

rate of change increased to 0.06 percent/year from 1980 to 

1986 and 1986 to 1992. The final period, which spanned from 

1992 to 2000, experienced an increased rate of change from 

the preceding periods, up to 0.10 percent/year.

Class Area and Change

Our results illustrate the dominance of four of the eleven 

LU/LC classes in the CBARE in 2000: grassland/shrubland 

(75.38 percent), forest (15.26 percent), natural barren (3.88 

percent), and agriculture (2.91 percent). Although the remaining seven classes cumulatively made up the remaining 2.55 

percent of the CBARE landscape in 2000, each of these 

classes made up less than 1 percent of the ecoregion (table 

1). Between 1973 and 2000, the LU/LC types that experienced a measurable net change in relation to the total CBARE 

area include (in descending order) grassland/shrubland (0.57 

percent decrease), nonmechanical disturbed (0.55 percent 

increase), forest (0.30 percent decrease), developed (0.19 

percent increase), water (0.15 percent increase), mining (0.14 

percent increase), and wetland (0.14 percent decrease). However, net change is not necessarily the best indicator of within 

class variability for those classes experiencing spatio-temporal 

fluctuations (fig. 4). For instance, agriculture may have only 

experienced a net loss of 0.03 percent from 1973 to 2000, but 

agricultural lands experienced 0.26 percent gross change in the 

CBARE in the same period. 

Common Conversions

The “from-to” information afforded by a post classification comparison allowed us to identify LU/LC class conversions and rank these conversions according to their magnitude. 

Table 2 illustrates the most frequent conversions from 1973 

to 2000 in the CBARE. The two most prominent conversions 

reflect the natural or nonmechanical disturbance of natural 

land-cover by fire. Cumulatively, the effect of nonmechanical disturbance on grassland, shrubland, and forest resulted 
 Land-Cover Trends of the Central Basin and Range Ecoregion

in 1,872 km2 of vegetated land-cover loss. The transition to 

and from agriculture and to and from water represent other 

common conversions in the CBARE. Prominent shifts in 

agricultural lands include a 527 km2 conversion from grassland/shrubland to agriculture and a 503 km2 from agriculture 

to grassland/shrubland. Similarly, the water class experienced a variety of conversions within the CBARE: a 602 km2 

conversion from wetland to water, a 255 km2 conversion from 

water to grassland/shrubland, a 222 km2 conversion from 

grassland/shrubland to water, and a 178 km2 conversion from 

water to wetland (note: water conversions account for shifts 

in both natural and manmade water bodies). Ultimately, these 

agricultural and water conversions illustrate the shifting landuse dynamics across the region. The types of conversions that 

were predominantly unidirectional and permanent include 

changes from the grassland/shrubland class to both developed 

(538 km2) and mining lands (526 km2).

Temporal Change Characteristics

Throughout the 27-year study period, we measured 

substantial temporal variability in certain LU/LC classes in 

the CBARE. Table 3 illustrates these fluctuating conversion 

rates. In terms of land-use fluctuations, agriculture, water, and 

mining all experienced measurable within and between period 

fluctuations from 1973 to 2000. Between 1973 and 1980, 

the agricultural class averaged a net annual increase of 48.6 

km2/year. During the next two periods, CBARE agriculture 

averaged an annual decline of 16.4 km2/year (1980-1986) and 

66.1 km2/year (1986-1992). During the final period from 1992 

to 2000, the rate of agricultural conversions increased to +8.4 

km2/year. 

Temporal fluctuations in the water class within periods 

were not as significant as the agricultural class, but between 

period fluctuations ranged a great deal. From 1973 to 2000, 

the rate of water conversions averaged a 6.2 km2/year decline, 

but conversions increased to +151.6 km2/year from 1980 to 

1986. Average water conversions declined by 53.5 km2/year 

for the period from 1986 to 1992, and only declined by 3.4 

km2/year from 1992 to 2000. 

Whereas the agricultural and water class averaged major 

temporal change fluctuations, the mining class followed a general growth trend with the exception of one period. In the first 

period (1973-1980), mining increased annually by a rate of 

4.8 km2/year. However, the second period from 1980 to 1986 

averaged a 1.5 km2/year decline. During the final two periods, 

the rate of mining then increased to an average of 19.7 km2/yr 

from 1986 to 1992 and 44 km2/year from 1992 to 2000.

Many of the aforementioned fluctuations in land use 

(along with less variable instances of land use) inversely influenced land-cover in the CBARE. Because grassland/shrubland 

was the dominant land-cover in the region (75.4 percent), 

shifts in anthropogenic land use tended to influence this class 

the most, thus accounting for the considerable within and 

between period variability. The grassland/shrubland class averaged an annual decline of 50 km2/year from 1973 to 1980 and 

a decline of 48.5 km2/year in the period from 1980 to 1986. 

During the third period (1986-1992), grassland/shrubland 

averaged an annual increase of 25.7 km2/year, which was 

consistent with the drop in agriculture and water in the same 

period. In the final period (1992-2000), grassland/shrubland 

declined by 183.2 km2/year, predominantly attributable to an 

increase in the nonmechanically disturbed class (fire). 

Change Precision

LU/LC change estimates for each of the four time periods 

(1973-1980, 1980-1986, 1986-1992, and 1992-2000) are 

stated by a margin of error at an 85 percent confidence interval 

(table 4). Each period had a very low margin of error, well 

within the Land Cover Trends project precision standard of 

detecting change at +/- one percent at an 85 percent confidence. However, these small errors are directly related to the 

small amount of gross change across the CBARE.

Discussion

The minimal amount of LU/LC change measured in the 

CBARE between 1973 and 2000 has been primarily influenced by 

natural forces. The harsh climate, infertile soils, and lack of viable 

resources have historically impeded human land-use change in the 

region (Brussard and others, 1998, Pellant and others, 2004, and 

Chambers and others, 2004). These factors continue to minimize 

anthropogenic change in the region, despite a variety of drivers 

encouraging change. The following section details the predominant changes in the CBARE from 1973 to 2000.

Fire

We found the most significant change in the CBARE 

from 1973 to 2000 to be a conversion to the nonmechanically 

disturbed class, entirely from fire. The total amount of change 

due to fire totaled 1,872 km2, 1,005 km2 from forest to nonmechanically disturbed, and 867 km2 from grassland/shrubland 

to nonmechanically disturbed (fig. 5). These changes, which 

all occurred from 1992 to 2000, translate to 0.55 percent of 

change in the CBARE’s land area.

In order to evaluate our results for the conversions to the 

nonmechanical disturbance class, we compared all detected 

instances of fire with a geospatial dataset of fire perimeters 

developed by the USGS SAGEMAP Program (SAGEMAP). 

The SAGEMAP fire database, which was composed using 

486 different files on Great Basin fire history, contains regions 

(polygons) representing fire perimeters between 1870 and 

2003 (Finn and others, 2004). Each of the fires captured in our 

sampling were consistent with fire locations from the SAGEMAP region coverage; however, we did not detect all of the 

instances of fire within the SAGEMAP dataset in our sample 
Discussion 

blocks. The characteristics of each dataset may account for 

this discrepancy. For example, our ability to map fire is highly 

dependant upon factors such as burn area, fire severity, and 

fire ignition date (given our imagery resolution and temporal 

design parameters). The SAGEMAP fire database has a suite 

of its own characteristics that may account for this discrepancy, such as the inconsistency of data combined to form the 

large database. Despite differences in the total area burned 

in each time period, the CBARE’s trend towards increased 

fire frequency identified in our research is consistent with the 

SAGEMAP trend from 1973 to 2000 (fig. 6). 

The instances of nonmechanical disturbance within the 

CBARE over the study period are attributed exclusively to 

fire. Much like the remainder of the West, fire regimes are a 

normal phenomenon that accompanies arid climates and an 

abundance of dry fuel sources. However, fire regimes have 

changed significantly within the region since Eurasian settlement in the late 1800s, ultimately contributing to the loss of 

sagebrush plant communities (Miller and others, 2001). Most 

notably, livestock grazing and adoption of fire suppression 

in the CBARE have played a role in the expansion of juniper 

woodlands (for example, Juniperus communis, Juniperus occidentalis, and Juniperus osteosperma) from upland slopes into 

sagebrush communities (for example, Artemisia tridentata, 

Artemisia cana, and Artemisia arbuscula). Prescribed burns 

have been applied as a method to control juniper expansion, 

but prescribed fires tend to raise levels of nitrogen for 2 to 3 

months following a fire. 

Elevated soil nitrogen levels contribute to another problem that plagues the CBARE. Invasive cheatgrass is favored in 

high-nitrogen conditions over native plants and increases fire 

frequency in the CBARE by providing a dense and continuous source of fuel that extends the fire season (Pyke, 2002). 

Frequent fires not only eliminate native sagebrush in the 

short term from pure destruction, but the competitiveness and 

prolific seed production of cheatgrass also allows it to reestablish before sagebrush after wildfires occur (Keeley, 2006, 

Pellant and others, 2004). Cheatgrass has ultimately created 

a positive feedback mechanism that favors frequent fires and 

early reestablishment in previously occupied landscapes. Fire 

records indicate a doubling of fires between 1988 and 1999 

(Pyke, 2002). The complex nature of vegetation preservation 

and fire management in the CBARE continues to perplex land 

managers, who hope to restore sagebrush communities in a 

self-sustainable manner. 

Increased fire frequency in the CBARE has a wide range 

of potential consequences beyond the effect on native vegetation. Much of the wildlife that depends on this vegetated 

landscape may become more vulnerable due to loss of habitat 

following a fire, but certain species such as the Great Basin 

pocket mouse (Perognathus parvus) benefit from rapid seed 

dispersal during post-fire plant succession (Brandt and others, 

1994). Fire also threatens human communities and jeopardizes 

traditional ranging practices in the region (USGS, 2003). 

These potential impacts on human and natural systems require 

a better understanding of the interrelationship between vegetation expansion and fire trends. Although our project design 

does not lend itself to mapping changes between grassland and 

shrubland communities, our research can be used in conjunction with existing data on cheatgrass expansion to better 

understand the interrelationship between vegetation expansion 

and fire in the CBARE. 

Agricultural Conversions

Although the statistics reflect a small net change (103 

km2 decrease) in the agriculture class over the 27-year study 

period, the total amount of change to and from the agricultural 

class was quite significant (892 km2). This gross change illustrates the shift in agricultural use across the CBARE. The poor 

soil quality and low rainfall across the CBARE makes water accessibility a major obstacle to farmers in the region. Our interpretations and field work suggest that agricultural lands more 

dependent on water (excluding rangeland) tend to be located 

near riparian segments and/or springs. The locations of other 

irrigation dependent agricultural lands across the CBARE are 

dictated by shifts in ground-water pumping and water diversion practices. Water diversions along the Carson, Humboldt, 

Truckee, and Walker Rivers have shifted to accommodate 

irrigation demand, municipal water demand, and government 

mandated water conservation. These shifts have spread agricultural land use into certain areas, and eliminated agriculture 

in areas that previously thrived. According to the U.S. Department of Agriculture (2005), areas of stimulated agricultural 

use in the CBARE have experienced growth in alfalfa and beef 

production (fig. 7).

However, shifting water allocations only account for a 

portion of the agricultural variability measured in the CBARE. 

The northeastern portion of the CBARE, which has the greatest 

concentration of agricultural land in the ecoregion, has experienced a steady decline in agriculture since the adoption of the 

Conservation Reserve Program (CRP) in 1985 (USDA, 2005). 

The CRP, which was created to offset agricultural erosion and 

preserve wildlife habitat, is a voluntary program that offers 

rental payments and cost-sharing support to farmers willing 

to halt agricultural production on their land for 10 to 15 years. 

With growing enrollment in the CRP in recent years, we expect 

this decline in agriculture to persist into the future.

The potential impacts of these changes in agricultural land 

use on the environment can be negative or positive in nature. 

According to the U.S. General Accounting Office (1993), water 

diversions, agricultural development, and livestock grazing 

are the major causes of riparian vegetation degradation. The 

conversion from natural wetlands and riparian (or spring fed) 

meadows to agriculture alters the ecological and physical 

properties of riparian areas, thus degrading ecosystems vital to 

the fitness of many vertebrates and invertebrates. This degradation is manifested as livestock trampling of native vegetation 

and lowered water tables caused by agricultural and municipal 

diversions (Brussard and others, 1998). However, irrigation 

water diversions to areas such as the Smith and Mason Valleys 
 Land-Cover Trends of the Central Basin and Range Ecoregion

may have created artificial habitats conducive to biological 

diversity (Brussard and others, 1998). Moreover, land being 

conserved through CRP enrollment has provided a way to 

reduce the aforementioned degradation to natural vegetation.

Water Conversions

Between 1973 and 2000, we also detected a measurable change to and from the water class, which is a result of 

shifting hydrologic regimes in the area generated by regional 

irrigation demand, municipal water demand, and government 

mandated water conservation. We estimated 1,257 km2 of 

gross change in the water class: 602 km2 of land converted 

to water and 655 km2 of land that converted from water to 

another class. Many of the reservoirs in the CBARE have 

experienced surface level fluctuations between 1972 and 2000 

(for example, Walker Lake). Although the literature indicates 

a generally dry climatic trend from 1973 to 2000 (rainfall: 4.9 

inches/year), many of the lakes in the western CBARE have 

nearly zero inflows due to agricultural diversions, which is 

the primary factor contributing to the drop in lake levels in the 

western CBARE (Thomas, 1995).

Water fluctuations are both a cause and effect of many 

issues in the region. Water diversions may support municipal 

and agricultural growth in the CBARE, but the decline of water 

resources has caused a clear problem concerning regional fauna 

that rely on water and riparian vegetation. The significant drop 

in many reservoirs in CBARE in the 20th century has not only 

endangered fish populations (for example, cui cui (Chasmistes 

cujas), tui chub (Gila bicolor), and Lahontan cutthroat trout 

(Oncorhynchus clarki henshawi)) but also the migratory birds 

that depend on these fish for survival (Brussard and others, 

1998, USGS, 2003). In the Walker Lake area alone, agricultural 

water diversions along the Walker River have contributed to a 

rapid drop in lake level, which has increased the concentration 

of total dissolved solids and jeopardized the health of fish and 

invertebrate populations (Koch and others 1979). Declining fish 

populations also translate to a decline in recreational fishing 

and the elimination of a cultural asset of the Northern Pauite 

Indians (Brussard and others, 1998, USGS, 2003). 

Development

The CBARE has remained one of the least developed 

areas in the United States, but our research indicates a trend 

towards rapid development. Between 1973 and 2000, we 

detected a 43 percent growth in development across the 

CBARE, most of which occurred along Interstate-80, Interstate-15, and U.S. Highway-395. This translates to 649 km2 

(0.2 percent of the CBARE) of land converted to development, 

mostly from grassland/shrubland (538 km2). We also noticed 

an increasing trend in development throughout the 27-year 

study period. Ultimately, this growth can be attributed to the 

emigration of people from Pacific states seeking out gaming, 

recreation, and tourist opportunities, as well as the appeal of 

tax incentives (no income tax in Nevada). In recent history, the 

CBARE’s service economy has become far more appealing to 

emigrants than the tradition resource-based economy (Starrs 

and others, 1996). 

These growth trends are consistent with housing unit 

statistics gathered by the U.S. Census Bureau since 1980 

(Geolytics, 2004). The only detectable discrepancy between 

each of these datasets is the slightly larger growth in housing 

units (54.6 percent increase) compared to our rate of development (41.1 percent increase) from 1980 to 2000 (fig. 8). 

This difference may be attributable to the low development 

density and high percentage of mobile homes in the region, 

two factors that present a problem when trying to map development using a 60-meter mapping unit. The U.S. Census 

Bureau’s definition of a housing unit may also account for 

the small discrepancy in growth rates. According to the 

U.S. Census Bureau (2000), a housing unit can be any place 

intended for occupancy as separate living quarters, including individual apartments or single rooms. This distinction 

causes difficulties in comparing housing unit counts to the 

instances of development identified in our study, as one 

structure can account for a wide range of housing units. 

Much like agricultural waste, municipal waste from 

development poses a threat to wildlife in the CBARE (fig. 

9). Additionally, development creates landscapes that are not 

used by most native species. Finally, growing regional development leads to an increase in resource consumption, such as 

municipal and agricultural water demand. Local population 

growth is directly related to regional demand for raw materials. Therefore, development often dictates how other land useclasses change throughout time and is partially responsible 

for any of the potential implications affiliated with water and 

mineral resource use. 

Mining

Like the growth of development in the ecoregion, growth 

in regional mining comprises a small segment of the LU/LC 

in the CBARE, but has grown considerably throughout the 27-

year study period. Although the change in mining only reflects 

a 0.1 percent change in the CBARE’s land area from 1973 

to 2000, regional mining has increased by 158 percent (498 

km2) throughout the study period. However, we found that the 

growth in mining has not been consistent between 1973 and 

2000. For example, we observed a net decrease in mining from 

1980 to 1986, followed by a 35 percent increase from 1986 to 

1992 and a 77 percent increase from 1992 to 2000. 

Fluctuations in mining production tend to occur with 

fluctuations in the price of gold and government regulation 

(Nevada is the third largest gold producer in the world), which 

dictate mining plans and the rate of exploration activity in the 

CBARE (Moyer, 2004). The mining growth in the final two 

periods can be attributed to the rapid investment in mining 
References   

plants, equipment, and exploration since 1980, totaling over 

$10 billion in Nevada alone (University of Nevada Reno, 

1999) (fig. 10). 

One of the most significant implications of mining in the 

CBARE is the long-term contamination of lands inhabited 

by wildlife and humans. The effect of historical mining in 

the region is well-documented and continues to be a problem 

(Lechler and others, 1997, Shevenell, 2000). For example, 

a large portion of the Carson River is designated as an EPA 

Superfund Site due to the mercury contamination while mining 

gold and silver during the Comstock Lode (1860-1890). Recent 

gold mining also poses an environmental threat. For example, 

a large number of migratory birds were killed from the mid1980s through the early 1990s from cyanide contamination 

at Nevada gold mines (USGS, 2003). Other species directly 

impacted by toxin contamination include many bat species that 

roost in old mine shafts and fish populations located in areas of 

water contamination (Brussard and others, 1998). The bioaccumulation of mining-related toxins in the food chain also has 

potential implications on other wildlife and humans.

Conclusion

Contemporary land-use/land-cover change has been very 

minimal throughout the CBARE. However, the results of our 

analysis indicate that these landscape changes resulting from 

increased fire frequency, rising demand for water and mineral resources, and growing highway development can have 

far-reaching consequences despite the small spatial extent of 

change. Although wildlife has proven to be resilient to anthropogenic land use, the loss of natural vegetation due to the 

aforementioned changes has both eliminated and polluted ecosystems utilized by endangered species such as the sage grouse 

(Centrocercus urophasianus). Moreover, certain trends such as 

increased fire frequency in the CBARE have the potential to 

harm human populations as well. The growth of human populations in the Reno-Sparks and Salt Lake City-Odgen metro 

areas will likely dictate the rate of future land-use conversions 

in the CBARE, either encouraging public land management 

agencies to preserve natural vegetation or continuing with 

current resource extraction practices. These findings can be 

used in conjunction with existing literature to explore how and 

to what extent current land-use/land-cover trends will impact 

the CBARE into the future and may provide insights into how 

policy change may change current landscape conditions.

References

Anderson, J.P., 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, 28p.

Billings, W.D., 1951, Vegetational zonation in the Great Basin of 

western North America: International Union of Biological Sciences, Series B, no. 9.

Brandt, C.A., and Rickard, W.H., 1994, Alien taxa in the North 

American shrub-steppe four decades after cessation of livestock 

grazing and cultivation agriculture: Biological Conservation, v. 

62, no. 2, p. 95-105.

Brussard, P.F., Charlet, D.A., Dobkin, D.S., Ball, L.C., 

Bishop, K.A., Britten, H.B., Fleishman, E., Fleury, S.C., 

Jenni, T., Kennedy, T.B., Mullen, C.O., Peacock, M.M., 

Prusso, D., Reed, M., Riley, L., Rust, R.W., Simpkin, 

J.L., Vinyard, G., Yandell, U.G., Marlow, R., and Charlet, 

D.A., 1998, Great Basin-Mojave Desert Region, in Mac, 

M.J., Opler, P.A., Puckett Haeker, C.E., and Doran, P.D., 

eds., Status and trends of the nation’s biological resources: 

Reno, Nevada, U.S. Geological Survey, v. 2 [http://biology.usgs.gov/s+t/SNT/noframe/gb150.htm (last accessed 

February 2, 2006)].

Bureau of Economic Analysis, 2000, Bureau of Economic 

Analysis Regional Economic Information System [http://

www.bea.gov/bea/regional/data.htm (last accessed October 

15, 2006)].

Chambers, J.C., and Miller, J.R., 2004, Great Basin riparian 

areas; ecology, management, and restoration: Society for 

Ecological Restoration International: Washington, D.C., 

Island Press, 303p.

County Business Patterns, 1997, University of Virginia, Geospatial and Statistical Data Center [http://fisher.lib.virginia.

edu/collections/stats/cbp/ (last accessed October 15, 2006)].

Eiswerth, M.E., and Shonkwiler, J.S., 2006, Examining 

post-wildfire reseeding on arid rangeland: A multivariate 

tobit modelling approach: Ecological Modeling, v. 192, p. 

286-298.

Environmental Protection Agency, 1999, Level III Ecoregions of the Continental United States: Corvallis, Oregon, 

U.S. Environmental Protection Agency, National Health 

and Environmental Effects Research Laboratory, scale 

1:7,500,000.

Finn, S.P., Hanser, S.E., Meinke, C.W., and Smith, A., 2004, 

The Great Western Fire Map (<=2003) [http://sagemap.

wr.usgs.gov/ftp/regional/USGS/Fires_WNA.zip (last 

accessed July 7, 2005)].

GeoLytics, Inc., 2004, Housing Unit Database 1980-2000 

Block Group Data: East Brunswick, New Jersey, GeoLytics, 

Inc.

Grayson, D.K., 1993, The desert’s past; a natural prehistory of 

the Great Basin: Washington, D.C., Smithsonian Institution 

Press, 356 p.
 Land-Cover Trends of the Central Basin and Range Ecoregion

Keeley, J.E., 2006, Fire management impacts on invasive 

plants species in the Western United States: Conservation 

Biology, v. 20, p. 375-384.

Koch, D.L., Cooper, J.J., Lider, E.L., Jacobson, R.L., and 

Spencer, R.J., 1979, Investigations of Walker Lake, Nevada; 

dynamic ecological relationships: Reno, Nevada, Bioresources Center, Desert Research Institute, University of 

Nevada at Reno, 189 p.

Launius, R.D., 2004, History to Go, Utah History Encyclopedia, State of Utah [http://historytogo.utah.gov/utah_chapters/from_war_to_war/worldwar2inutah.html (last accessed 

May 25, 2006)].

Lechler, P.J., Miller, J.R., Hsu, L.C., and Desilets, M.O., 1997, 

Mercury mobility at the Carson River Superfund Site, westcentral Nevada, USA; Interpretation of mercury speciation 

data in mill tailings, soils, and sediments: Journal of Geochemical Exploration, v. 58, p. 259-267.

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. 1091-99.

Miller, R., Baisan, C., Rose, J., and Pacioretty, D., 2001, Preand post-settlement fire regime in mountain big sagebrush 

steppe and aspen: the northwestern Great Basin: Corvallis, 

Oregon, National Interagency Fire Center.

Moyer, L.A., 2004, Mining activity in Nevada, 1851-1995: 

U.S. Geological Survey Open File Report 2004-1244 [http://

pubs.usgs.gov/of/2004/1244/ (last accessed July 14, 2006)].

National Atlas of the United States, 2005, Cities and Towns 

of the United States [http://www.nationalatlas.gov/atlasftp.

html#citiesx (last accessed October 15, 2006)].

National Atlas of the United States, 2005, Federal Lands of 

the United States [http://www.nationalatlas.gov/atlasftp.

html#fedlanp (last accessed October 15, 2006)].

Noss, R.F., LaRoe, E.T., III, and Scott, J.M., 1995, Endangered ecosystems of the United States; a preliminary assessment of loss and degradation: National Biological Service 

Biological Report 28, 58 p.

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

States: Annals of the Association of American Geographers, 

v. 77, p. 118-125.

Pellant, M., Abbey, B., and Karl, S., 2004, Restoring the Great 

Basin Desert, U.S.A.; integrating science, management, and 

people: Environmental Modeling and Assessment, v. 99, p. 

169-179.

Pyke, D.A., 2002, Born of fire-restoring sagebrush steppe: 

U.S. Geological Survey Forest and Rangeland Ecosystem 

Science Center, Fact Sheet 126-02, 2 p.

Rogers, G.F., 1982, Then and now: a photographic history of 

vegetation change in the central Great Basin desert: Salt 

Lake City, Utah, University of Utah Press.

Rowland, M.M., Wisdom, M.J., Suring, L.H., and Meinke, 

C.W., 2006, Greater sage-grouse as an umbrella species for 

sagebrush-associated vertebrates: Biological Conservation, 

v. 129, p. 323-335.

Shevenell, L., 2000, Water quality in pit lakes in disseminated 

gold deposits compared to two natural, terminal lakes in 

Nevada: Environmental Geology, v. 39, no. 7, p. 807-815.

Starrs, P.L., and Wright, J.B., 1996, Great Basin growth 

and the withering of California’s pacific idyll: The 

Geographical Review, v. 85, no. 4, p. 417-435.

Thomas, J., 1995, Water budget and salinity of Walker Lake, 

western Nevada: U.S. Geological Survey Fact Sheet 

115-95, 4 p.

Trimble, S., 1989, The Sagebrush Ocean: A Natural History of 

the Great Basin: Reno, Nevada, University of Nevada Press.

U.S. Census Bureau, 2000, Glossary of Decennial Census 

terms and acronyms [http://www.census.gov/main/www/

glossary.html (last accessed January 14, 2006)].

U.S. Census Bureau, 2000, American Fact Finder [http://fact

finder.census.gov/home/saff/main.html?_lang=en (last 

accessed January 14, 2006)].

U.S. Department of Agriculture, 2005, National Agricultural 

Statistical Service (NASS): United States Department 

of Agriculture, National Agricultural Statistics Service, 

Research and Development Division, Geospatial Information Branch [http://www.nass.usda.gov/ last accessed 

October 13, 2006)].

U.S. General Accounting Office, 1993, Livestock grazing on 

western riparian areas: Gaithersburg, Maryland, 44 p.

U.S. Geological Survey, 2003, Biological science in the Great 

Basin: Seattle, Washington, U.S. Geological Survey Forest 

and Rangeland Ecosystem Science Center, Western Region 

Briefing Paper, 2 p.

University of Nevada at Reno, 1999, Trends in the mining industry; Reno, Nevada, State of Nevada and Eureka 

County: University of Nevada at Reno, 4 p.

Wisdom, M.J., Suring, L.H., Rowland, M.M., Tausch, R.J., 

Miller, R.F., Schueck, L., Wolff Meinke, C., Knick, S.T., 

and Wales, B.C., 2003, A prototype regional assessment of 

habitats for species of conservation concern in the Great 

Basin Ecoregion and State of Nevada; chapter 5: La Grande, 

Oregon, USDA Forest Service, Pacific Northwest Research 

Station, Version 1.1, unpub. report on file.
Appendix   

Appendix. Definitions of Land Use and Land Cover

The following are the general land-cover definitions that 

will be used in the project. To the extent possible, the definitions are based on the original Anderson and others (1976) 

level I definitions so that land-cover data developed through 

the Land Cover Trends project are consistent with those 

produced through other programs and projects. A minimum 

mapping unit of 60 meters will used to determine land-cover.

Developed – Areas of intensive use with much of the land 

covered with structures (for example, high density residential, 

commercial, industrial, or transportation) or less intensive uses 

where the land-cover matrix includes both vegetation and structures (for example, low density residential, recreational facilities, 

cemeteries, or transportation and utility corridors), including any 

land functionally related to the developed or built-up activity.

Cropland and Pasture – Land in either a vegetated or 

unvegetated state used for the production of food and fiber. 

This includes cultivated and uncultivated croplands, hay lands, 

pasture, orchards, vineyards, and confined livestock operations. Note that forest plantations are considered as forests or 

woodlands regardless of the use of the wood products.

Forests and Woodland – Tree-covered land where the 

tree-cover density is greater than 10 percent. Note that cleared 

forest land (for example, clearcuts) will be mapped according to current cover (for example, disturbed or transitional, 

shrubland/grassland).

Shrubland/Grassland – Land predominately covered with 

grasses, forbs, or shrubs. The vegetated cover must be at least 10 

percent of the area.

Wetland – Lands where water saturation is the 

determining factor in soil characteristics, vegetation 

types, and animal communities. Wetlands are comprised of water and vegetated cover.

Water Bodies – Areas persistently covered with 

water, such as streams, canals, lakes, reservoirs, bays, or 

oceans.

Snow and Ice – Land where the accumulation of 

snow and ice does not completely melt during the summer period.

Natural Barren – Land comprised of natural 

occurrences of soils, sand, or rocks where less than 10 

percent of the area is vegetated.

Mined Lands – Areas with extractive mining 

activities that have a significant surface expression. 

This includes (to the extent that these features can be 

detected) mining buildings, quarry pits, overburden, 

leach, evaporative, tailing, or other related components.

Mechanical Disturbed or Transitional – Land in 

an altered unvegetated state that, due to disturbances by 

mechanical means, is in transition from one cover type 

to another. Mechanical disturbances including forest 

clear cutting, earthmoving, scraping, chaining, reservoir 

draw down, or other related human-induced changes.

Nonmechanical Disturbed or Transitional – Land 

in an altered unvegetated state that, due to disturbances 

by nonmechanical means, is in transition from cover 

type to another. Nonmechanical disturbances include 

wind, floods, fire, animals, and other related sources.
10 Land-Cover Trends of the Central Basin and Range Ecoregion

Figure 1. Central Basin and Range ecoregion. Information shown for the Central Basin and Range ecoregion 

includes land use/land cover from the 1992 National Land Cover Dataset and the 36 randomly selected 100 km2 

sample blocks.
Figures 11

Figure 2. Historical and present interrelationships between land use, invasive plants, and fire in 

the Central Basin and Range ecoregion (from Rogers, 1982).
12  Land-Cover Trends of the Central Basin and Range Ecoregion

Figure 3. Average annual rates of change by period for the Central Basin and Range ecoregion.
Figures 13

Figure 4. Gross change in land use/land cover for each of the four periods studied for the Central Basin and Range ecoregion. 

Illustrates within class fluctuations for each period.
14  Land-Cover Trends of the Central Basin and Range Ecoregion

1992 Landsat TM 2000 Landsat ETM+

1992 Land-Use/Land-Cover Data 2000 Land-Use/Land-Cover Data

Figure 5. An example of nonmechanically disturbed (NMD) in the period from 1992-2000. NMD, which is 

entirely attributable to fire in the Central Basin and Range ecoregion, is shown in the 2000 land-use/landcover data as purple.
Figures 15

Figure 6. Amount of area burned (km2) between 1973 and 2000. Comparison 

between U.S. Geological Survey SAGEMAP fire database and our results for the 

Central Basin and Range ecoregion.
16  Land-Cover Trends of the Central Basin and Range Ecoregion

Figure 7. Field photos illustrating instances of agriculture in the Central Basin and Range ecoregion. 

Upper left picture shows livestock grazing on rangeland, whereas lower right picture shows irrigated 

fields growing livestock feed.

Figure 8. Rate of development in the Central Basin and Range ecoregion between 1980 and 2000. Comparison 

between U.S. Census data and our results.
Figures 17

Figure 9. Hillside municipal waste facility and downhill stream drainage near Lockwood, 

Nevada.
18  Land-Cover Trends of the Central Basin and Range Ecoregion

Figure 10. Graphic showing the different elements of mining in the Central Basin and Range ecoregion. A, Gravel extraction site near 

Tooele, Utah; B, Piles of gravel aggregate awaiting transport; C, Mineral processing facility along Interstate 80 near Reno, Nevada; and 

D, an old tailing pile undergoing reestablishment of vegetation.

A B

C D
Tables 19

Table 2. Most common land-use/land-cover conversions throughout the 27-year study period for 

the Central Basin and Range ecoregion.

Table 1. Each thematic land-use/land-cover class for the five study dates, as a percentage of Central Basin and 

Range ecoregion area.

[

MD-mechanically disturbed, NB-natural barren, and NMD-nonmechanically disturbed]
20 Land-Cover Trends of the Central Basin and Range Ecoregion

Table 3. Average annual gains and losses by land-use/land-cover class for the Central Basin and Range ecoregion.

Table 4. Gross change and corresponding margin of error for each time 

period for the Central Basin and Range ecoregion.