Land-Cover Trends in the Mojave Basin and 

Range Ecoregion

By Benjamin M. Sleeter and Christian G. Raumann

This report documents the rates and causes of late-20th century land-cover change in 

the Mojave Basin and Range ecoregion as part of the U.S. Geological Survey’s National 

Land-Cover Trends project.

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2006–5098
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reproduce any copyrighted materials contained within this report.

This report and any updates to it are available online at

http://pubs.usgs.gov/sir/2006/5098/

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

U.S. Department of the Interior

P. Lynn Scarlett, Acting Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

Cataloging-in-publication data are on file with the Library of Congress (URL http://www.loc.gov/).

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

endorsement of the U.S. Government.

Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, April 25, 2006

Text edited by Peter H. Stauffer

Layout and design by Susan Mayfield
iii

Contents

Abstract...........................................................................................................................................................1

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

Background.....................................................................................................................................................1

Ecoregion description..........................................................................................................................1

Relation of environmental characteristics and land cover ...........................................................4

Methods..................................................................................................................................................5

Results .............................................................................................................................................................6

Estimated gross area change.............................................................................................................6

Net change by land-cover type..........................................................................................................6

Common land-cover conversions ......................................................................................................7

Temporal component of change.......................................................................................................11

Verification....................................................................................................................................................11

Summary........................................................................................................................................................13

References....................................................................................................................................................13

Appendix 1. Land-cover classes and definitions used in the Land-Cover Trends project ..............15

Figures

1. Location map of Mojave Basin and Range Ecoregion ........................................................................2

2. Map showing Federal land ownership in the Mojave Basin and Range Ecoregion and surrounding area ................................................................................................................................3

3. Map showing National Land Cover Data (NLCD) in the study area and sample block 

selections.......................................................................................................................................5

4. Detailed maps of land-cover change in sample blocks #14-1009 (near Palmdale, 

California) and #14-555 (near Henderson, Nevada)........................................................... 8–9

5. Photograph of disturbed land at Fort Irwin National Training Center.............................................10

6. Graph of population trends in counties of the Mojave Basin and Range ecoregion ...................12

7. Graph of population trends for major cities within the Mojave Basin and 

Range Ecoregion.........................................................................................................................12

Tables

1. Characteristics of Landsat data sets used in the analysis of land-cover change..........................6

2. Normalized estimated annual land-cover change rates by time interval ........................................7

3. Percent total land area by land cover class .........................................................................................7

4. Areas of common land-cover conversions by time interval...............................................................7

5. Population change of selected cities in the western Mojave Basin and Range Ecoregion.........9

6. Precision of change estimates..............................................................................................................11
Land-Cover Trends in the Mojave Basin and 

Range Ecoregion

By Benjamin M. Sleeter and Christian G. Raumann

Abstract 

The U.S. Geological Survey’s Land-Cover Trends Project 

aims to estimate the rates of contemporary land-cover change 

within the conterminous United States between 1972 and 2000. 

A random sampling approach was used to select a representative sample of 10-km by 10-km sample blocks and to estimate 

change within +/−1 percent at an 85-percent confidence interval 

(Stehman and others, 2003; Loveland and others, 2002). Landsat Multispectral Scanner, Thematic Mapper, and Enhanced 

Thematic Mapper Plus data were used, and each 60-m pixel 

was assigned to one of 11 distinct land-cover classes based 

upon a modified Anderson classification system. Upon completion of land-cover change mapping for five dates, land-cover 

change statistics were generated and analyzed. This paper 

presents estimates for the Mojave Basin and Range ecoregion 

located in the southwestern United States. Our research suggests 

land-cover change within the Mojave to be relatively rare and 

highly localized. The primary shift in land cover is unidirectional, with natural desert grass/shrubland being converted to 

development. We estimate that more than 1,300 km2 have been 

converted since 1973 and that the conversion is being largely 

driven by economic and recreational opportunities provided by 

the Mojave ecoregion. The time interval with the highest rate 

of change was 1986 to 1992, in which the rate was 0.21 percent 

(321.9 km2) per year total change.

Introduction

The Mojave Basin and Range ecoregion (Omernik, 1987; 

Environmental Protection Agency, 1999) covers much of 

the Southern California desert, southern Nevada, and small 

portions of western Arizona and southwestern Utah (fig.1). 

The majority of the ecoregion (hereafter, the terms “Mojave 

ecoregion” or “ecoregion” will be used interchangeably) consists of undisturbed lands fragmented only by widely spaced 

road and highway development. With a combined population 

of 769,303 (U.S. Census Bureau, 2001), Las Vegas and the 

surrounding cities of Henderson and North Las Vegas form 

the major urban center and the main contributor to the ongoing population increase within the ecoregion. The cities of 

Palmdale and Lancaster, located along the western edge of the 

ecoregion, form the second largest urban area and have a combined population of more than 200,000 residents (U.S. Census 

Bureau, 2001). Recreation is a major activity in the ecoregion, 

because people are drawn to locations such as Death Valley 

National Park, Mojave National Preserve, open-access Bureau 

of Land Management (BLM) lands, Lake Mead National Recreation Area, and the city of Las Vegas. Despite the increasing 

population, active military training operations, and demands 

for recreation, there is a paucity of quantitative contemporary 

information on land-cover change for the Mojave ecoregion.

Historical satellite imagery, which has been widely available since the early 1970s, provides a consistent imagery base 

for comparative study of land-cover change. This study used 

methods developed by the U.S. Geological Survey Land-Cover 

Trends Project (Loveland and others, 2002), which implements 

a probability sampling technique and archived satellite imagery 

to map and quantify contemporary land-cover change for the 

84 U.S. Environmental Protection Agency Level III ecoregions 

(Omernik, 1987). Estimates of area and rates of change have 

been computed for the Mojave ecoregion on the basis of visual 

interpretation and subsequent postclassification comparison of 

five dates of imagery between 1973 and 2000 for 40 sample 

blocks, each 10 km by 10 km (see fig.2). A modified Anderson 

classification scheme (Anderson and others, 1976) was used to 

group land cover into 11 discrete classes.

This paper provides a description and discussion of 

land-cover change in the Mojave Basin and Range ecoregion. 

Two fundamental issues associated with land-cover change are 

addressed: (1) what are the spatial and temporal dimensions 

of land-use and land-cover change and (2) what are the local 

to global driving forces of land-use and land-cover change? 

A description of the Mojave ecoregion, historical land-cover 

trends and issues, and an analysis of contemporary land-cover 

change are included in this paper. 

Background 

Ecoregion Description

The Mojave Basin and Range ecoregion as defined by 

Omernik (1987) is located in the southwestern United States 

and covers a total area of 130,742 km2. It includes portions of 

California (58.5% of the ecoregion), Nevada (29.4%), Arizona 
(11.7%), and Utah (0.4%)(fig. 1). Counties partly within the 

ecoregion boundary include San Bernardino, Riverside, Los 

Angeles, Inyo, and Kern Counties in California; Clark, Lincoln, 

Nye, and Esmeralda Counties in Nevada; Mohave and Coconino 

Counties in Arizona; and Washington County in Utah. 

The majority of the ecoregion consists of the Mojave 

Desert, but the northern extent of the ecoregion crosses into 

the southwestern edge of the Basin and Range geomorphic 

province. As its name indicates, the Mojave Basin and Range 

ecoregion is characterized by basin and range topography, 

with numerous distinct fault-bounded mountain ranges skirted 

by bajadas and separated by relatively flat and often expansive 

alluvial valley floors. A remarkable amount of vertical topographic relief results from this geology. 

Low annual precipitation and high summer temperatures 

are characteristic throughout the ecoregion. Average annual 

precipitation varies between 50 and 250 mm in the valleys and 

is as much as 625 mm in the mountain ranges. Precipitation is 

spread out fairly evenly over the year and falls mostly as rain. 

However, some snow does regularly fall at higher elevations 

in the winter and early spring. Average annual temperatures 

generally range between 16 and 24oC but are as low as 10oC 

Nye County

San Bernardino County

Inyo County

Mohave

County

Lincoln County

Clark County

Kern County

Riverside County

Tulare County

Yavapai County

Fresno County

Los Angeles

County

Esmeralda County

Mono

County

Iron County

La Paz

County

Washington

County

Mineral County White Pine

County

Coconino

County

Millard

County

Madera

County

Beaver

County

Tuolumne

County

Orange

County

Mariposa

County

San Diego

County

CALIFORNIA

NEVADA

ARIZONA

UTAH

Needles

Kingman

Hesperia

Yucca Valley

Twentynine Palms

Palmdale

Mesquite

Lancaster

Henderson

Ridgecrest

Boulder City

Bullhead

City

California City

North Las Vegas Las Vegas

Victorville

Barstow

Adelanto

Apple Valley

Pacific Ocean 0 50 100 KILOMETERS

0 25 50 MILES

Figure 1. Location map of the Mojave Basin and Range ecoregion (shaded area). The ecoregion is in the southwestern 

United States and includes land in California, Nevada, Arizona, and Utah. The area studied in this project covers 

approximately 130,000 km2.

 Land-Cover Trends in the Mojave Basin and Range Ecoregion
in the mountains (Natural Resources Conservation Service, 

1981). As a result of the harsh regional climatic conditions, 

this ecoregion is quite fragile and recovers slowly from anthropogenic disturbances (Hunter and others, 2003).

The largest landowner in the Mojave Basin and Range 

ecoregion is the Federal Government. Designated Federal 

lands in the ecoregion make up roughly 81 percent of the total 

land area (fig. 2). The Bureau of Land Management (BLM) 

controls almost half of the land in the ecoregion (44.7%). 

The National Park Service (NPS) manages 20 percent, with 

the largest holdings being Death Valley National Park, Lake 

Mead National Recreation Area, Joshua Tree National Park, 

and Mojave National Preserve. A portion of Grand Canyon 

National Park also lies on the eastern boundary of the ecoregion. The Department of Defense (DOD) is another major 

holder and user of lands in the ecoregion at 15 percent of the 

total area. Major military facilities, which in turn support the 

local economies of a number of towns and small cities, include 

China Lake Naval Air Weapons Station, Fort Irwin National 

Training Center, Nellis Air Force Base, Edwards Air Force 

Base, Marine Corps Air-Ground Combat Center TwentyNine Palms, and the Marine Corps Logistics Base at Nebo. 

Figure 2. Federal land ownership in the Mojave Basin and Range ecoregion and surrounding area. The Bureau of Land 

Management is the largest land holder; other lands are held and managed by the National Park Service, Department 

of Defense, Bureau of Reclamation, Bureau of Indian Affairs, and the U.S. Forest Service. Ecoregion names are in red, 

boundaries in black. Boxes are the forty sample blocks analyzed in this project.

Nellis AFB

Nevada 

Test Site

Nellis AFB

National

Wildlife

Range

Death

Valley

National

Park

China Lake

NAWS

Fort Irwin

National Training

Center

Toiyabe

National

Forest

Moapa

River

Lake Mead

National

Recreation

Area

Hualapai Indian

Reservation

Mojave

National

Preserve

29 Palms

Edwards AFB

Havasu

National

Wildlife

Refuge

Joshua Tree

National Park

MOJAVE BASIN

AND RANGE

CENTRAL BASIN

AND RANGE

SONORAN DESERT

CENTRAL AND 

SOUTHERN

CHAPARRAL AND

OAK WOODLANDS

SIERRA 

NEVADA

MOUNTAINS

ARIZONA/

NEW MEXICO

PLATEAU

COLORADO

PLATEAU

CALIF.

CENTRAL

VALLEY

SOUTHERN CALIF. MOUNTAINS

Bureau of Indian Affairs

Bureau of Land Management

Bureau of Reclamation

Department of Defense

Forest Service

Fish and Wildlife Service

National Park Service

Other

FEDERAL AGENCY

0 50 100 KILOMETERS

0 25 50 MILES Pacific Ocean

Background 
The Department of Energy’s (DOE) Nevada Test Site on the 

northeastern boundary of the ecoregion makes up 1.5 percent 

of total lands.

Urban development is generally limited throughout the 

ecoregion, mostly because of harsh environmental conditions 

and a lack of adequate resources and infrastructure. However, 

significant development has and continues to take place in the 

Las Vegas, Nevada, area and in California along the southwestern edge of the ecoregion in the cities of Lancaster and 

Palmdale. Almost all of the modern communities in the ecoregion have originated along lines of transportation, whether 

these were railroads, highways, pack animal trails, or even 

navigable rivers (Bard, 1972). 

Las Vegas, along with the surrounding cities of North 

Las Vegas, Henderson, and Boulder City, is the dominant 

urban center in the ecoregion. McCarran International Airport, 

which serves the Las Vegas area, is the eighth busiest airport 

in the world, and nearby Lake Mead has more than 10 million 

visitors a year. Vacation resorts, golf courses, and other tourist 

attractions draw large numbers of visitors to the area. The 

gaming and tourism industry is dependent on the continued 

influx of visitors, easy access to the area, and a local population capable of sustaining these industries. This local population is moving further away from the city centers, resulting in 

the need for continued infrastructure development. 

The southwestern edge of the ecoregion is occupied by 

several cities, with Lancaster, Palmdale, Victorville, and Barstow 

being the largest. The congested urban landscape of Los Angeles 

and western San Bernardino County is forcing development 

to move along transportation corridors that lead through the 

physiographic boundary of the San Gabriel and San Bernardino 

Mountains (Southern California Mountains ecoregion) into the 

western Mojave Desert. In many cases, people are willing to 

commute long distances to work in order to take advantage of 

more affordable housing in suburban neighborhoods located in 

the desert, contributing to urban growth in the region.

Other notable urbanized areas in the ecoregion, apart 

from those previously described, are Ridgecrest, California, 

which supports China Lake Naval Weapons Station, and the 

cities along or near the Colorado River in the south, including 

Needles, California, and Bullhead City and Kingman, Arizona.

Relation of Environmental Characteristics 

and Land Cover

Both climatic and topographic extremes contribute to the 

sparseness of vegetation within the ecoregion. However, these 

environmental conditions also promote species diversity, and the 

ecoregion is home to approximately 2,000 plant species, of which 

150 are introduced and 500 are endemic (Rowlands and others, 

1982). According to the National Land Cover Data Set from 

1992 (Vogelmann and others, 2001), the predominant land-cover 

type in the ecoregion is desert shrub/grassland, which covers 

approximately 86 percent of the ecoregion (fig. 3). The dominant 

shrub species throughout the ecoregion is creosote (Larrea tridentata), which is found up to elevations of about 1,375 m. Near 

the northernmost boundary of the ecoregion, creosote begins to 

disappear due to cooler winter temperatures, and big sagebrush 

(Artemisia tridentata) becomes more common. Other common plant species include white bursage (Ambrosia dumosa), 

Mormon tea (Ephedra sp.), Joshua Tree (Yucca brevifolia), and 

cactus. Pinyon-juniper woodland is found at higher elevations, 

consisting of single-leaf pinyon pines (Pinus monophylla) and 

Utah junipers (Juniperus osteosperma) (Little, 1971).

Many dry lakes forming playa deposits occur throughout 

the ecoregion. Large and actively migrating sand dunes are 

scattered throughout the ecoregion, as are geologically old and 

young volcanic features, such as cinder cones, domes, and lava 

flows. The dominant soils in the ecoregion are Orthents, Psamments, Fluvents, Orthids, and Argids, which generally have 

low moisture retention and high moisture evaporation rates 

(Natural Resources Conservation Service, 1981). The intermittent Mojave River is the major drainage in the ecoregion and 

has been subject to floods during nearly all recorded El Niño 

years (Hereford and Webb, 1997). Although very little surface 

water exists naturally within the ecoregion, a great deal of 

water moves through the ecoregion by way of the Colorado 

River Aqueduct. Furthermore, the small amounts of naturally 

existing surface water are subject to strict management. Most 

notably, the Mojave River has undergone much channeling and 

diversion throughout the time of settlement of the ecoregion 

(Mouat and others, 1998).

The ecoregion has historically supported human-related 

activities, such as military training, livestock grazing, aqueduct 

rights-of-way, mining, recreation, and agriculture, all of which 

have some level of effect on the desert landscape (Lovich and 

Bainbridge, 1999). Agriculture, although not extensive in the 

ecoregion, does occur locally along the Colorado and Mojave 

Rivers and west of Edwards Air Force Base and Lancaster. 

Grazing takes place primarily on BLM lands and is a controversial practice within the ecoregion, partly because of its 

impacts on land cover, including alteration of vegetation cover 

and composition as well as soil compaction (Mouat and others, 1998). Abundant geological resources have allowed for 

the development of extractive mining for a variety of minerals, 

resulting in the accumulation of tailings and modifications to 

fragile dry lake ecosystems.

Natural vegetation of the Mojave Basin and Range 

ecoregion is subjected to numerous types of anthropogenic 

alterations. The introduction of livestock for grazing (Bentley, 

1898), off-highway vehicle use (Webb and Wilshire, 1983), 

urbanization and associated activities (Reible and others, 1982, 

Walsh and Hoffer, 1991), and military use (Lathrop, 1983, 

Prose and others, 1987, Prose and Wilshire, 2000, Steiger and 

Webb, 2000) all contribute to the loss of vegetated lands. These 

impacts, when combined with the harsh environmental characteristics, result in a landscape slow to recover from disturbance.

The most widespread recreational activity in the ecoregion is off-highway vehicle (OHV) use, which began to rise 

dramatically around 1960 (Bard, 1972). OHV use in the 

ecoregion was initially minimally regulated, with large areas 

 Land-Cover Trends in the Mojave Basin and Range Ecoregion
open to unlimited use (Sheridan, 1979). However, because of 

the detrimental effects of OHV use on desert soils, air quality, 

vegetative cover, biodiversity, and specifically the Desert Tortoise (Gopherus agassizii), OHV use became a concern among 

those interested in the health of this desert ecosystem (Westec 

Services, 1978). As a result, land managers have implemented 

programs that limit and monitor OHV use while still providing 

ample designated areas for OHV recreation. In California, the 

Off-Highway Motor Vehicle Recreation Program was created 

in 1971 by the State Legislature and is operated by the State 

Department of Parks and Recreation. At the Federal level, the 

BLM has instituted the National Management Strategy on 

Motorized OHV Use in an effort to accommodate growing 

OHV use on public lands.

Methods

Forty sample blocks, each 10 km on a side, were randomly 

selected (see fig. 2) for analysis using Land Cover Trends sampling design protocols (Stehman and others, 2003; Loveland and 

others, 2002). The forty sample blocks selected (1,304 blocks 

make up the entire ecoregion) represent approximately 3 percent 

of the entire ecoregion area and are used to detect change at 

an 85 percent confidence interval +/− 1 percent. The sampling 

Figure 3. National Land Cover Data Set (NLCD) with sample block selections for the Mojave Basin and Range ecoregion. The 

dominate land-cover type in the ecoregion is grass/shrubland. Ecoregion names are in red, boundaries in black.

Pacific Ocean

(!

(!

CALIFORNIA

NEVADA

ARIZONA

UTAH

Palmdale

Las Vegas

Ridgecrest

Barstow

Twentynine

Palms

Needles

MOJAVE BASIN

AND RANGE

CENTRAL BASIN

AND RANGE

SONORAN DESERT

CENTRAL AND 

SOUTHERN

CHAPARRAL AND

OAK WOODLANDS

SIERRA 

NEVADA

MOUNTAINS

ARIZONA/

NEW MEXICO

PLATEAU

COLORADO

PLATEAU

CALIF.

CENTRAL

VALLEY

SOUTHERN CALIF. MOUNTAINS

Water

Developed

Mechanical Disturbed

Mining

Natural Barren

Forest

Grass/Shrubland

Agriculture

Wetland

Non-Mechanical

Disturbed

LEGEND

0 50 100KILOMETERS

0 25 50MILES

Background 
design was random, as was the selection of sample blocks by 

various interpreters to reduce interpretative bias. A modified 

Anderson classification system (Anderson and others, 1976) 

was used to partition land cover into 11 distinct classes (appendix 1) using manual interpretation methods. Landsat Thematic 

Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and 

Multispectral Scanner (MSS) images, along with ancillary data 

such as topographic maps and aerial photographs, were used 

to derive land-cover and land-cover-change images for each 

sample block selected for analysis (table 1). Upon completion of 

sample block interpretations, postclassification comparison was 

used to generate land-cover change statistics for the ecoregion 

based on the assumption of a representative sample. A more 

comprehensive review of the land-cover trends methodology 

can be found in Loveland and others (2002).

Results

Estimated Gross Area Change

Results show land-cover change between our thematic 

classes (see appendix 1) to be relatively rare and highly localized. Total land-area change from 1973 to 2000 is estimated at 

2.6 percent (3,390 km2). The most common change observed 

was the conversion of an estimated 1,426 km2 of the grass/

shrubland class to the developed class. An additional 651 km2

of grass/shrubland was lost to mechanical disturbance and 

345 km2 to mining activities. In addition, it is estimated that 

340 km2 of forest transitioned to mechanically disturbed, and 

205 km2 are estimated to have transitioned from a mechanically disturbed state to developed. 

The urbanization process is represented by the conversion 

of natural-cover and mechanically disturbed cover types to the 

developed class. Urbanization is the dominate land-cover transition occurring in the ecoregion, and it follows a unidirectional 

pattern, terminating in the development of the desert landscape. 

In most instances, urbanization is represented by the direct 

transition of grass/shrublands to the developed class. However, 

in some cases the mechanically disturbed phase of urbanization was captured and reflects anthropogenic alterations such as 

scraping, leveling, and clearing of vegetation and soils. 

Although land-cover change in the ecoregion is rare as a 

percent of total ecoregion area, the total area of the ecoregion 

converted to development is significant. Developed lands 

increased by 1,695 km2 from 1973 to 2000, in addition to an 

increase of 423 km2 in mining land. The increase of development can be largely attributed to population growth in both the 

Las Vegas metropolitan area and the suburban areas of Lancaster and Palmdale along the western edge of the ecoregion. 

A substantial shift has occurred in mining-related activities as the ecoregion has shifted away from precious-metal 

and ore extraction to increased surface and aggregate mining 

for infrastructure construction uses. Most of the active mining 

operations observed in the sample blocks were arranged within 

close proximity of existing developed areas or an interstate 

highway expansion project.

Military training activities have contributed in a substantial way to our disturbance estimates. For example, one 

sample block located at Fort Irwin National Training Center 

experienced high amounts of disturbance due to its location 

in an area of the facility where tank and other vehicle training 

activities are particularly intense. The intense nature of this 

land use combined with the fragility of the desert landscape 

results in a slow recovery rate (Lovich and Bainbridge, 1999, 

Steiger and Webb, 2000, Prose and Wilshire, 2000) and thus 

the persistence of the mechanical disturbance classification. 

In addition to estimates of area changed, average annual 

rates of change were estimated by dividing the area changed 

per temporal interval by the number of years in the interval. 

Undoubtedly change is not evenly distributed across each year 

within a temporal interval. However, because the temporal sampling intervals are not equal in length (either six, seven, or eight 

years), for purposes of temporal comparison it is useful to compare average annual rates. After normalization, the 1986 to 1992 

interval remained the period with the most change (table 2).

Net Change by Land-Cover Type

As anticipated, the grass/shrubland class experienced the 

most change of any class, decreasing from 89.3 percent to 87.4 

percent between 1973 and 2000 (-1.9%; 2,347 km2). Between 

1986 and 1992 the grass/shrubland class lost 0.9 percent 

(1,173 km2). Other significant changes were in the developed 

Temporal

Center Point Sensor Source Processed

Resolution Projection

1973 MSS NALC 60m UTM

1980 MSS New Acquisition 60m UTM

1986 MSS NALC 60m UTM

1992 MSS, TM NALC, MRLC 60m, 30m UTM, Albers

2000 ETM+ MRLC 30m Albers

Table 1. Characteristics of Landsat data sets used in the analysis of land-cover change.

[MSS: Multispectral Scanner; TM: Thematic Mapper; ETM+: Enhanced Thematic Mapper Plus; NALC: North American Landscape Characterization Program; MRLC: Multi-Resolution Land Characteristics; UTM: Universal Transverse Mercator; Albers: 

Albers Conical Equal Area]

 Land-Cover Trends in the Mojave Basin and Range Ecoregion
Time Interval Change (%) Annual area change (km2)

1973 to 1980 0.07 96.4

1980 to 1986 0.08 103.2

1986 to 1992 0.21 323.9

1992 to 2000 0.08 140.1

Land cover 1973 1980 1986 1992 2000

Water 0.89 0.91 0.91 0.85 0.87

Developed 1.50 1.79 1.98 2.59 2.78

Mech. Disturbed 0.12 0.09 0.16 0.47 0.71

Mine/Quarry 1.07 1.13 1.25 1.36 1.38

Natural Barren 4.73 4.73 4.70 4.68 4.68

Forest 1.97 1.96 1.93 1.92 1.67

Grassland/Shrub 89.25 88.93 88.61 87.55 87.36

Agriculture 0.23 0.21 0.22 0.22 0.27

Wetlands 0.25 0.23 0.23 0.37 0.28

1973 to 1980

Area (km2) Conversion Area (km2) Conversion Area (km2) Conversion Area (km2) Conversion

1980 to 1986 1986 to 1992 1992 to 2000

314 Grass/Shrub to 

Developed

202 Grass/Shrub to 

Developed

751 Grass/Shrub to 

Developed

324 Forest to Mech. 

Disturbed

90 Grass/Shrub to 

Mining

115 Grass/Shrub to 

Mech. Disturbed

435 Grass/Shrub to 

Mech. Disturbed

160 Grass/Shrub to 

Developed

52 Mech. Disturbed 

to Developed

110 Grass/Shrub to 

Mining

125 Water to Wetland 89 Mech. Disturbed 

to Developed

51.9 Wetland to Water 49 Natural Barren to 

Mining

110 Grass/Shrub to 

Mining

82 Wetland to 

Agriculture

Table 2. Normalized estimated annual land-cover change rates by time interval.

[Because time intervals are not of equal length, estimated annual change is calculated by dividing total change in a time interval by the number of years in the time interval.]

Table 3. Percent total land area by land-cover class at different times.

[The grassland/shrub class shows a steady decline while the developed class increases in each time interval, revealing urbanization as being the major land-cover conversion associated with the ecoregion.]

class, which had an increase of 1.3 percent (1,695 km2), and 

the mechanically disturbed class at +0.5 percent (652 km2). All 

other land-cover classes remained fairly stable throughout the 

study period (table 3).

Common Land-Cover Conversions

The main story of change in the Mojave Basin and Range 

ecoregion is urbanization of the desert landscape as reflected 

by our mapped conversion of grass/shrubland to developed 

land. However, the driving forces of land-cover change are not 

uniform across the ecoregion and tend to vary at a local scale.

The four most common conversions for each time 

interval, presented in table 4, support urbanization being the 

major process driving land-cover change in the ecoregion. 

Grass/shrublands converting to developed is one of the top 

two changes by area in each temporal interval and is the top 

change in three of those intervals. In addition, grass/shrublands converting to mechanical disturbance and grass/shrublands converting to mining are also present in each of the 

Table 4. Areas of common land-cover conversions by time interval.

[Grassland/shrub to developed (urbanization) is the top conversion in the first three time intervals and the second most common conversion 

in the final time interval.]

Results 
four time intervals. These changes are commonly associated 

with urbanization.

Clark County, Nevada, and its largest city, Las Vegas, 

represent one of the fastest growing regions in the country 

(U.S. Census Bureau, 2001). The rapid growth of Las Vegas 

and the surrounding cities such as Henderson can be attributed 

to the development of this area as a world-famous tourist destination made popular primarily by the ever-apparent gaming 

industry. Numerous megaresort-style hotel casinos have been 

built since the 1970s and have attracted millions of visitors 

annually. The large influx of tourism within Clark County in 

the past 30 years has necessitated the development of infrastructure, housing, and jobs to support the tourist industry. 

This development has resulted in the rapid conversion of the 

natural desert landscape to urban land uses.

Helping this rise in tourism, a modern interstate highway 

system facilitates the movement of people from large populated areas such as Phoenix, Arizona, and the Los Angeles 

metropolitan area to the Las Vegas area. Furthermore, many 

recreation activities exist in the Las Vegas area that attract 

more visitors and increase the demand for infrastructure. 

Hoover Dam, Lake Mead, and the Grand Canyon are all 

close to Las Vegas and offer a wide range of recreational and 

cultural activities. These recreational opportunities in addition 

to a low cost of living and abundant affordable housing contribute to the Las Vegas area being a desirable place to live, 

which in turn has contributed to the increased development of 

the Las Vegas area.

Of the 19 sample blocks that experienced some amount 

of change (47.5% of all sample blocks), 63 percent experienced a transition to developed. The distribution of these 

changed blocks across the ecoregion generally follows transportation corridors, with the highest change blocks occurring 

closest to established urban areas. This is evidenced in blocks 

#14-555 and #14-1009. The most frequent conversions in each 

interval generally involved the grass/shrubland and developed 

classes, with mining and mechanical disturbance as associated changes. Examples from sample-block interpretations are 

presented in figure 4.

In contrast to areas in the eastern portion of the ecoregion, where tourism is the primary driver of change, the western Mojave ecoregion is characterized by a number of smaller 

1973 1980 1986 1992 2000

1973-1980 1980-1986 1986-1992 1992-2000

DEVELOPED MECHANICAL DISTURBANCE MINING GRASSLAND/SHRUB AGRICULTURE

A

Figure 4. Two selected sample blocks illustrating urbanization taking place in the Mojave Basin and Range ecoregion. The top row of 

images is actual satellite data used to map land-cover change in each time interval. The second row of images is mapped land-cover 

for each time interval. The third set of images shows areas of change (in green) between successive image dates. A, Sample block 

#14-1009 located near Palmdale, California. B, Sample block #14-555 located near Henderson, Nevada.

 Land-Cover Trends in the Mojave Basin and Range Ecoregion
City Population

(2000)

Population change

(1990–2000)

Palmdale 116,670 +50.9%

Lancaster 118,718 +20.6%

Victorville 64,029 +26.9%

Table 5. Population change of selected cities in the western 

Mojave Basin and Range ecoregion

1973 1980 1986 1992 2000

1973-1980 1980-1986 1986-1992 1992-2000

DEVELOPED MECHANICAL DISTURBANCE MINING NATURAL BARREN GRASSLAND/SHRUB FOREST WATER

B

urban areas serving as either bedroom communities to the Los 

Angeles metropolitan area or in direct support of local military 

installations. The cities of Lancaster (population 118,718; U.S. 

Census Bureau, 2001) and Palmdale (population 116,670; 

U.S. Census Bureau, 2001) have experienced high rates of 

population change since 1990 as a result of migration from the 

crowded Los Angeles Basin (table 5)( U.S. Census Bureau, 

2001). Many of the residents of urban areas in the western 

Mojave ecoregion commute to the Los Angeles area for work 

while enjoying the thriving recreation-based economy of the 

desert communities (Hunter and others, 2003). 

Other settlements of relatively substantial size in the 

western Mojave ecoregion include Victorville (population 

64,029), Ridgecrest (population 24,927), and Barstow (population 21,119) (U.S. Census Bureau, 2001). The proximity of 

these rapidly growing communities to local military installations suggests the central role military operations may play in 

local economies (Hunter and others, 2003). For example, the 

three previously listed cities are located adjacent to Edwards 

Air Force Base, China Lake Naval Weapons Center, and Fort 

Irwin National Training Center, respectively. Military training activities, since the end of the Cold War and the terrorist 

attacks of 11 September 2001, have shifted to desert warfare 

scenarios. Given new and future military training requirements, it is reasonable to expect communities colocated with 

military installations in the ecoregion will continue to grow 

and evolve, resulting in the alteration and development of an 

increasing amount of desert lands.

Land ownership is another driving force of land-cover 

change. As previously noted, the Federal Government owns 

a large percentage of lands within the ecoregion, the largest 

landholder being the BLM. The NPS and DOD are also major 

Figure 4.—Continued.

Results 
public-land holders (fig 2). Each of these three agencies manages public lands to meet various distinct goals and objectives. 

For instance, BLM lands are often open for public use and 

recreation as seen in the popularity of OHV activities (Lovich 

and Bainbridge, 1999). In most cases, OHV disturbances, such 

as single vehicle tracks, were not detected in image interpretations because of the coarseness of the minimum mapping unit 

(60 m2) and are therefore not described by the change estimates. However, image interpretations identified several large 

staging areas where relatively large areas of grass/shrubland 

have gradually been stripped of vegetation. Continued use 

of these areas has resulted in soil compaction, preventing the 

re-establishment of vegetation. The growth of OHV activity 

in the ecoregion can be largely attributed to the open-access 

policy of the BLM and the close proximity of these lands to 

major urban areas (Sheridan, 1979).

The DOD has a significantly different mandate pertaining to its land ownership and management policies. The 

DOD manages vast areas of the ecoregion for the purpose of 

conducting military training activities (see fig. 2). The largest 

of these facilities entirely within the ecoregion is Fort Irwin 

National Training Center (2,369 km2). Fort Irwin is used for 

desert warfare training, including live-fire exercises. Tracked 

and wheeled vehicles operate throughout the facility and can 

have a major impact on the health and composition of desert 

flora and fauna (Prose and Wilshire, 2000). Recent studies 

have estimated that several hundred years will be needed for 

desert soils and vegetation to recover once exposed to these 

intensive land-use practices (Prose and Wilshire, 2000, Steiger 

and Webb, 2000). This phenomenon was observed with sample block #14-712 (fig. 5). The sample block is located in the 

eastern portion of Fort Irwin and was heavily used for tracked 

and wheeled vehicle operations training. Evidence of this use 

includes compacted and rutted soils, low shrub density, and 

stunted growth of creosote and other vegetation.

Unlike the BLM and DOD, the NPS attempts to preserve 

natural desert lands while promoting low-impact public recreation such as camping, hiking, and sightseeing. The largest holding of the NPS within the ecoregion is Death Valley National 

Park (12,759 km2). Other NPS areas include Mojave National 

Preserve and Joshua Tree National Park. With the exception of 

small tourism-supporting development such as visitor centers, 

boardwalks, campgrounds, hiking trails, and unimproved roads, 

no land cover changes were detected in NPS lands, further illustrating the significant role land ownership plays regarding the 

spatial distribution of contemporary land-cover change. 

The only period in which the change from grass/shrubland 

to developed was not the leading transition was from 1992 to 

2000. The most common transition during this temporal interval was the conversion of 324 km2

 of forest to the mechanically disturbed class. This can be attributed to the cutting 

and removal of exotic and invasive saltcedar (or tamarisk, 

Tamarix ramossissima). Substantial forest clearing of these 

trees in sampled riparian areas was identified in this study. 

The recognition of varying degrees of environmental damage is driving the clearing of saltcedar-dominated forestland 

detected from 1992 to 2000. There is widespread recognition 

that saltcedar, which grows as shrubs and medium-size trees 

Figure 5. Photograph of 

mechanical disturbance 

observed at sample block 

#14-712 at Fort Irwin 

National Training Center, 

the site of intensive military 

training including livefire exercises. The view 

is looking west towards 

“Alpha-Bravo Pass.”

10 Land-Cover Trends in the Mojave Basin and Range Ecoregion
mostly in riparian areas, is undesirable from the standpoint of 

maintaining vigorous native ecosystems. As a result, saltcedar 

is included on the California Exotic Pest Plant Council’s list of 

exotic pest plants of greatest ecological concern (Lovich and de 

Gouvenain, 1998). Saltcedar competes with and replaces native 

plant communities, degrades wildlife habitat, alters stream 

morphology, uses large amounts of groundwater, increases fire 

frequency, reduces recreational and agricultural usage, and 

reduces biodiversity. Many managed areas within the ecoregion, such as the Havasu National Wildlife Refuge, implement 

programs to remove saltcedar and revegetate mechanically 

treated areas with native species in efforts to alleviate these 

consequences. However, mechanical treatment of saltcedar 

stands is not without potentially devastating consequences. The 

southwestern willow flycatcher (Epidonax trailii extimus) has 

begun nesting in saltcedar, causing great concern among biologists that biological control of saltcedar may reduce flycatcher 

populations (DeLoach and others, 2000).

The conversion of 34 km2 of wetlands to water from 1973 

to 1980, 125 km2 of water to wetlands from 1986 to 1992, 

and 28 km2 of wetlands to water from 1992 to 2000 can be 

attributed to fluctuations of surface water levels in marshlands. 

Wetland-to-water and water-to-wetland land-cover conversions 

are relatively local changes, because approximately 81 percent 

of all Mojave ecoregion wetlands occur along the Colorado, 

Virgin, and Muddy rivers upstream of and flowing into Lake 

Mead and along the lower Colorado River downstream from 

Lake Mead. This localization of wetland distribution is illustrated by 53 percent of all ecoregion wetlands occurring within 

a 7-km buffer along a 40-km stretch of the lower Colorado 

River near Needles, California. Furthermore, these changes are 

dictated by a combination of environmental and managerial 

driving forces. Large wetland areas, such as Topock Marsh (16 

km2) near Needles and part of the Havasu National Wildlife 

Refuge, depend on water diversions from the Colorado River. 

As a result, these areas are subject to fluctuations in flow 

based on annual variations in water availability as well as metropolitan water needs in coordination and consideration of the 

best water levels for waterfowl and shorebird habitat (Lower 

Colorado River Multi-Species Conservation Program, 2004).

Temporal Component of Change

Results indicate that land-cover change is fairly consistent over time, with the exception of a substantial increase in 

the amount of urbanization occurring between 1986 and 1992. 

The normalized average annual rate for all land-cover changes 

is estimated at 0.07 to 0.08 percent for all time periods with 

the exception of the 1986 to 1992 (0.21%/year). Change estimates also show no shift in the dominant type of land-cover 

change, urbanization remaining the primary change observed 

during all temporal intervals.

It is presumed that favorable economic conditions during 

the mid-1980s, combined with rapid construction farther away 

from the Los Angeles Basin, served to make the 1986 to 1992 

the most dynamic in terms of land-cover change. Many new 

megaresort casinos were developed during this time, resulting in more jobs and economic opportunity for the Las Vegas 

region. Between 1980 and 1990, Clark County added more 

than a quarter of a million residents. The Palmdale and Lancaster region of the western Mojave also experienced a spike 

in growth again because of a favorable economic landscape 

and the availability of relatively inexpensive housing still 

within commuting range of greater Los Angeles. 

Verification

Verification of land-cover change results for the Mojave 

ecoregion is divided into two parts: (1) how well the sample 

blocks represented the ecoregion and (2) how accurately image 

interpretations identified and described land-cover dynamics. 

The sampling methodology used was developed to achieve 

greater statistical precision on smaller areas of land when 

compared to mapping change in the entire ecoregion while also 

being more cost effective than wall-to-wall mapping (Stehman 

and others, 2003). The statistical formula used to determine the 

number of sample blocks needed for the ecoregion was based on 

the project-established standard of detecting change within +/− 1 

percent at an 85-percent confidence interval (that is, the accuracy 

of interpretation) (Stehman and others, 2003, Loveland and others, 2002). Change estimates with a margin of error greater than 

1 percent were the result of higher than expected variability in 

the spatial distribution of change, such as rare events or clumped 

and clustered change (Loveland and others, 2002). 

The interpretations of Mojave Basin and Range landcover change indicate that the 40 samples used to estimate 

rates of land-cover change for the ecoregion result in standard error limits within our goal of mapping change at +/− 1 

percent at an 85-percent confidence interval (table 6). The 

1986 to 1992 period had the highest error margin at +/− 0.94 

percent and was the period with the most amount of change 

(1.27%), while the 1980 to 1986 period had the lowest margin 

of error (+/− 0.24%) and was the period with the least amount 

of change at 0.46 percent.

To verify image interpretations of land-cover change we 

focused on the developed land-cover type. Conversion to developed is the dominant change we documented, and we assume 

its verified performance is parallel to the other mapped conversions. To confirm this, we accessed the U.S. Bureau of Census 

data that documents the acres of new development. Although 

Change

Interval Change Avg. AnnualChange 85% CI

1973-1980 0.52% 0.07% +/- 0.279%

1980-1986 0.46% 0.08% +/- 0.246%

1986-1992 1.27% 0.21% +/- 0.940%

1992-2000 0.64% 0.08% +/- 0.476%

Table 6. Precision of change estimates.

Verification 11
there is no definitive data source that can be used to measure the 

true accuracy of our change estimate, the U.S. Census provides 

a highly accurate source of data to compare change in the 

developed classification. However, census data are not without 

limitations. For this project, county-level census data could not 

be relied upon to validate change estimates because of the size 

and arrangement of counties that make up the ecoregion. For 

example, San Bernardino County has a vast majority of its area 

within the ecoregion, but a majority of its population resides in 

the small area outside of the ecoregion. The use of finer census 

units such as tracts and block groups is difficult because as 

population changes over time, boundary locations change and 

single reporting units are divided into multiple units.

Clark County, Nevada, has been one of the fastest 

growing counties in the country (fig. 6) and provides a good 

proxy for the estimation of change in developed land cover. 

The cities of Las Vegas, North Las Vegas, and Henderson are 

within both Clark County and the Mojave ecoregion and have 

undergone rapid urbanization since 1970. This corresponds 

with our estimates that conversion of the vegetated landscape 

to urban uses is the leading type of land-cover change occurring in the ecoregion. 

Year

Number of persons added in previous ten years

523,364

210,994

441,298

189,799

278,372

835,082

LAND COVER TRENDS

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Inyo County

San Bernardino County

Clark County

Esmeralda County

Population (thousands)

0

50

100

150

200

250

300

350

400

450

500

15

30

45

60

75

90

105

120

135

150

1965 1970 1975 1980 1985

Year

1990 1995 2000 2005 2010

7 years 6 years 6 years 8 years

0.08% 0.07% 0.21% 0.08%

Victorville

Lancaster

Palmdale

Western Mojave

Henderson

North Las Vegas

Las Vegas

Eastern Mojave

55 km2/ year

41 km2/ year

131 km2/ year

31 km2/ year

Avg. annual change 

to Developed

Figure 6. Population trends in counties of the Mojave Basin and Range ecoregion. Data are number of persons 

added to each county based on U.S. Census. San Bernardino County, California, and Clark County, Nevada, 

have experienced the most growth of any counties in the ecoregion, adding more than 175,000 persons in each 

decade since 1980. The time period studied in the Land Cover Trends Project is indicated.

Figure 7. Population trends for major cities within the Mojave Basin and Range ecoregion. The gray bars and the area 

and percent figures show average annual increase in the developed category during the four time intervals studied.

12  Land-Cover Trends in the Mojave Basin and Range Ecoregion
To further verify estimates of land-cover change, citylevel population data were used. Cities in the ecoregion with a 

2000 census population greater than 20,000 were selected for 

comparison. It is reasonable to conclude that changes in population of major urban areas in the ecoregion would correspond 

to our estimates of change in the developed class. Figure 7 

plots the population trend of the six largest cities in the ecoregion and shows the estimated average annual increase in the 

developed class. A relatively large amount of grass/shrublands 

was converted to developed lands between 1986 and 1992 (131 

km2/year) and this corresponds to a general spike in population trends of major cities during this same period. However, 

it should be noted that in the final time interval (1992-2000) 

our change estimates appear to contradict the city population 

data. In this interval we see the largest population numbers for 

the six cities used for comparison, while our study estimates 

urbanization to be at its lowest during this interval. This could 

in part be due to a lag between the urbanization process and 

the time it takes to populate new developments.

Summary

Land-cover change estimates for the Mojave Basin and 

Range ecoregion were derived by using a probabilistic random 

sampling approach (Stehman and others, 2003, Loveland and 

others, 2002) and mapping land-cover change for five dates 

and four temporal intervals at a 60-m minimum mapping unit 

(Loveland and others, 2002). Forty 10-km by 10-km sample 

blocks were selected, and land-cover change was mapped for 

each time interval in each block using a modified Anderson 

classification scheme (appendix 1).

Our results reveal that land-cover change between 

thematic classes in the Mojave is relatively rare and is 

highly localized. Urbanization is the primary type of change, 

although other human-use activities such as military training 

and recreation are significant contributors to change within the 

ecoregion. The most dynamic period observed was the 1986 

to 1992 interval, with 0.21 percent change per year. All of the 

other intervals remained relatively constant at less than 0.10 

percent change per year.

Land-cover change in the Mojave is most likely to occur 

at or near the edges of existing urban areas such as those found 

near Las Vegas, Nevada, and Palmdale and Lancaster, California. Other urban areas associated with military installations 

are also places where change is likely to occur, especially in 

the developed and grass/shrubland classes. However, change 

in more remote locations was not uncommon, as was seen in 

military training sites and isolated wetland regions. 

The key drivers of change include population growth, 

land ownership, and recreation opportunities. Population 

growth is occurring for various reasons in different parts of the 

ecoregion. The Las Vegas area has grown significantly since 

the early 1970s and is now one of the main vacation destinations in the country. To satisfy this demand, there has been a 

large increase in population to support the local gaming and 

tourism industry. Change in the western portion of the ecoregion is occurring for different reasons, as people seek outdoor 

recreation activities and affordable housing all within commuting distance to major metropolitan cities.

Federal land ownership appears to be a major driver as 

well. Various Federal government agencies operate under 

different mandates, thus impacting the landscape in various 

ways, as seen in the comparison of National Park Service and 

Department of Defense land holdings. The level and intensity 

of use allowed in designated lands appears to lead to increased 

disturbance when heavy use is allowed and/or required. 

Lands set aside for conservation, as is the case of many NPS 

holdings, generally appear less impacted by human use and 

disturbance. BLM lands range from low-intensity use to highintensity use and more disturbance is generally associated with 

areas of heavy off-highway vehicle activity.

References

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. 

Bard, R.C., 1972, Settlement patterns of the eastern Mojave Desert: Los Angeles, University of California, Ph.D. dissertation.

Bentley, H.L., 1898, Cattle ranges of the southwest; a history 

of the exhaustion of the pasturage and suggestions for its 

restoration: U.S. Department of Agriculture, Farmers Bulletin 72, p.1-31.

DeLoach, C.J., Carruthers, R.I., Lovich, J.E., Dudley, T.L., and 

Smith, S.D., 2000, Ecological interactions in the biological control of saltcedar (Tamarix spp.) in the United States; 

toward a new understanding, in Spencer, N. R., ed., Proceedings of the X International Symposium on Biological 

Control of Weeds, 4-14 Jul 1999: Bozeman, Montana State 

University, p. 819-873.

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, 1:7,500,000-

scale map.

Hereford, R., and Webb, R.H, 1997, How often does rainfall 

cause overland flow in the arid Mojave Desert? A study of 

reservoir deposits in Valjean Valley [abs.]: Quarterly San 

Bernardino County Museum Association, v. 44, p. 14.

Hunter, L.M., Gonzalez, M.de J., Stevenson, M., Karish, K.S., 

Toth, R., Edwards, T.C., Lilieholm, R.J., and Cablk, M., 

2003, Population and land use change in the California 

Mojave; natural habitat implications of alternative futures: 

Population Research and Policy Review, v. 22, p. 373-379.

Summary 13
Lathrop, E. W., 1983, The effect of vehicle use on desert 

vegetation, in Webb, R. H., and Wilshire, H. G., eds., 

Environmental effects of off-road vehicles; impacts and 

management in arid regions: New York, Springer-Verlag, p. 

154­-166.

Little, E.L., Jr., 1971, Atlas of United States trees; conifers 

and important hardwoods: U.S. Department of Agriculture 

Miscellaneous Publication 1146, v. 1, 9 p., 200 maps.

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. 1091-1095.

Lovich, J.E., and Bainbridge, D., 1999, Anthropogenic degradation of the southern California desert ecosystem and 

prospects for natural recovery and restoration: Environmental Management, v. 24, p. 309-326.

Lovich, J.E., and de Gouvenain, R.G., 1998, Saltcedar invasion in desert wetlands of the southwestern United States; 

ecological and political implications, in Majumdar, S. K., 

Miller, E. W., and Brenner, F. J., eds., Ecology of wetlands 

and associated systems: Pennsylvania Academy of Science, 

p. 447-467. 

Lower Colorado River Multi-Species Conservation Program, 

2004, Lower Colorado River Multi-Species Conservation 

Program, Habitat Conservation Plan, Final: Sacramento, 

California, Jones and Stokes, v. 2.

 Mouat, D.A., Kiester, R., and Baker, J., 1998, Analysis and 

assessment of impacts on biodiversity; a framework for 

environmental management on DoD Lands within the California Mojave Desert; a research plan: Corvallis, Oregon, 

U.S. Environmental Protection Agency, 61 p.

Natural Resources Conservation Service, 1981, Land resource 

regions and major land resource areas of the United States: 

USDA Agriculture Handbook 296, 156 p.

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

States: Annals of the Association of American Geographers, 

v. 77, p. 118-125.

Prose, D. V., and Wilshire, H. G., 2000, The lasting effects of 

tank maneuvers on desert soils and intershrub flora: U.S. 

Geological Survey Open File Report 00-512, 22 p.

Prose, D. V., Metzger, S. K., and Wilshire, H. G., 1987, Effects 

of substrate disturbance on secondary plant succession, 

Mojave Desert, California: Journal of Applied Ecology, v. 

24, p. 305-­313.

Reible, D. D., Ouimette, J. R., and Shair, F. H., 1982, Atmospheric transport of visibility degrading pollutants into 

California Mojave Desert: Atmospheric Environment, v. 

16(3), p. 599-­613.

Rowlands, P., Johnson, H., Ritter, E., and Endo, A., 1982, The 

Mojave Desert, in Bender, G.L., ed., Reference handbook 

on the deserts of North America: Westport, Connecticut, 

Greenwood Press, 594 p. 

Sheridan, D., 1979, Off-road vehicles on public land: Council 

on Environmental Quality, 84 p.

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, p. 517-529.

Steiger, J.W., and Webb, R.H, 2000, Recovery of perennial 

vegetation in the military target sites in the eastern Mojave 

Desert, Arizona: U.S. Geological Survey Water-Resources 

Investigations Report 00-355, 28 p.

U.S. Census Bureau, 2001, American Fact Finder [http://factfinder.census.gov/home/saff/main.html?_lang=en (accessed 

May 1, 2005)].

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.

Walsh, P.A., and Hoffer, T. E., 1991, The changing environment of a desert boomtown: The Science of the Total Environment, v. 105, p. 233-258.

Webb, R. H., and Wilshire, H. G., 1983, Environmental effects 

of off-road vehicles; impacts and management in arid 

regions: New York, Springer-Verlag, 534 p.

Westec Services, Inc., 1978, A history of land use in the 

California Desert Conservation Area: Riverside, California, prepared for Bureau of Land management, Desert 

Planning Staff.

14  Land-Cover Trends in the Mojave Basin and Range Ecoregion
Appendix 1. Land-Cover Classes and Definitions Used in the 

Land-Cover Trends Project.

Definitions used in this project are based on the original 

Anderson and others (1976) Level I definitions, so that the 

land-cover data developed are consistent with those produced through other projects. The spatial resolution of the 

trends database is 60 m2. Features with ground footprints 

less than the minimum mapping unit are not mapped. Our 

ability to identify and map these land-cover classes is limited by the technical specifications of Landsat MSS, TM, 

and ETM+ sensors and by the local and regional landscape 

characteristics that affect the form and contrast of landcover characteristics.

Water Areas persistently covered with water, such as 

streams, canals, lakes, reservoirs, bays, or oceans.

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.

Mechanically disturbed or transitional Land in an altered 

unvegetated state that, because of disturbances by mechanical means, is in transition from one cover type to another. 

Mechanical disturbances include forest clearcutting, earthmoving, scraping, chaining, reservoir drawdown, and other related 

human-induced changes.

Mining 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, tailings and leach, evaporative, or other related components.

Natural barren Land comprising natural occurrences of 

soils, sand, or rocks where less than 10 percent of the area is 

vegetated.

Forests and woodland Tree-covered land where the treecover density is greater than 10 percent. Note that cleared 

forest land (that is, clearcuts) will be mapped according to 

current cover (for example, disturbed or transitional, shrubland/grassland).

Shrubland/grassland Land dominantly covered with grasses, 

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

percent of the area. 

Cropland and pasture Land in either a vegetated or nonvegetated state used for the production of food or 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.

Wetland Lands where water saturation is the determining 

factor in soil characteristics, vegetation types, and animal 

communities. Wetlands comprise water and vegetated cover.

Nonmechanical disturbed or transitional Land in an altered 

nonvegetated state that, because of disturbances by nonmechanical means, is in transition from one cover type to another. 

Nonmechanical disturbances include wind, floods, fire, animals, and other related sources. 

Snow and ice Land where the accumulation of snow and ice 

does not completely melt during the summer period. 

Appendix 1 15