U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3077

June 2011

RESEARCH AT THE USGS WESTERN GEOGRAPHIC SCIENCE CENTER

S

Mapping Perennial Vegetation Cover in the Mojave Desert

cientists with the U.S. Geological 

Survey’s Western Geographic 

Science Center have recently created 

a regional map of perennial vegetation cover for the Mojave Desert. The 

scientists used existing field data collected for a variety of previous studies 

and satellite data available for free 

through USGS archives to create a 

calibrated model of percent vegetation 

cover, an important attribute of desert 

ecosystems. This map is being used 

to inform ongoing scientific investigations and land-management efforts, 

including endangered species habitat 

mapping and vulnerability and recoverability studies of desert landscapes 

in the arid Southwest.

The Mojave Desert encompasses approximately 48,000 square miles of arid landscape 

in southern Nevada, western Arizona, southwestern Utah, and southeastern California. 

More than a million people live in this desert, 

which includes Las Vegas, Nevada, one of 

the fastest growing cities in the southwestern 

United States. The Mojave Desert is also 

within a day’s drive for 40 million people 

The Mojave Desert is home to more than a million people. Because of intensive human land uses, land and resource managers routinely make decisions that allow for economic, recreational, and military use, while striving 

to maintain a healthy desert ecosystem. Total cover of perennial vegetation (plants that live for more than 2 years) 

is an important measure of desert ecosystem health and, as shown in this photograph, is typically sparse, low, 

and shrubby in the Mojave. (USGS photo by Robert H. Webb.)

who live in southern California and central 

Arizona. Lands in the Mojave Desert are managed by a patchwork of entities, including four 

national park units, six major military training 

bases, and the Bureau of Land Management 

(BLM), which manages vast tracks of land in 

the region. Because of intensive human land 

uses, land and resource managers routinely 

make decisions that allow for economic, recreational, and military use, while 

striving to maintain a healthy 

desert ecosystem.

Total cover of perennial vegetation (plants that live for more 

than 2 years) can be considered 

the single most important attribute of desert ecosystems. 

Routinely measured in the field 

using standardized methods, 

perennial cover affects a number 

of important ecosystem processes, including soil-moisture

availability, potential evapotranspiration 

(evaporation and plant transpiration from the 

land surface to atmosphere), stability of biological soil crusts, wind and water erosion potential, and wildlife habitat. Perennial cover in 

the Mojave Desert fluctuates between decades 

with climatic variability, making this cover a 

key indicator of ecosystem health.

Scientists with the U.S. Geological Survey’s 

Western Geographic Science Center (WGSC) 

have created a regional map of perennial vegetation cover for the Mojave Desert to better 

understand the role of perennial vegetation in 

desert ecosystem health, habitat mapping, dust 

mitigation, and related studies. Regional mapping of ecological attributes, such as perennial 

vegetation, forms a crucial component of 

informed natural-resource management. However, such mapping can be difficult, especially 

in areas with large tracts of remote terrain, like 

the Mojave Desert. WGSC scientists derived 

perennial vegetation cover by coupling Moderate Resolution Imaging Spectroradiometer 

(MODIS) Enhanced Vegetation Index (EVI) 

satellite data with vegetation-transect data 

collected in the field. MODIS-EVI data are 

available for free through the USGS Glovis 

This map shows the Mojave Desert ecoregion (green) and the Mojave National Preserve (yellow). Black dots show 

locations of measured vegetation transects used by researchers with the USGS Western Geographic Science Center 

to calibrate MODIS-EVI, Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI), 

satellite “greenness” data so that it could be used to produce a regional map of perennial vegetation cover.

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UTAH

ARIZ

NEV

CALIF

Phoenix

Las Vegas

Los Angeles

100 MILES

100 KILOMETERS

0

0

N

EXPLANATION

Transect

Location

Mojave

Desert

Urban

Areas

Mojave

National

Preserve
0

0

100 MILES

100 KILOMETERS

N

EVI Profiles for 2001. Profile colors 

correspond to color of field location points 

in the map below. 

0

0 100 KILOMETERS

100 MILES

Relative EVI

Month 2001

50

50

Web site (http://glovis.usgs.gov/) and offer 

a regional view of the landscape at frequent 

time intervals (daily data that are composited 

over 16-day intervals), revealing the dynamic 

“greenness” of the landscape, which includes 

both annual and perennial vegetation that typically exhibit different annual greenness patterns. The field data were used to calibrate the 

MODIS-EVI data so that differences between 

these patterns could be used to produce a regional map of perennial vegetation cover.

To create a regional map of perennial vegetation cover for the Mojave Desert ecoregion, 

WGSC scientists (1) compiled preexisting U.S. 

Geological Survey (USGS), BLM, and Department of Defense field data that had been collected for a variety of unrelated studies using 

the same field techniques, (2) evaluated these 

data to determine how representative they are 

of 250-meter MODIS pixels by examining 

the complexity of the landscape in the vicinity 

of the field data points using finer-resolution 

Landsat Thematic Mapper satellite data, and 

(3) used stepwise-linear regression models 

and statistical methods to relate total perennial 

cover to the MODIS images. The resulting 

map shows percentage cover of perennial vegetation for the entire Mojave Desert ecoregion 

with an accuracy of greater than 80%.

This research demonstrates that existing 

field data, collected for various purposes, can 

be used effectively with remotely sensed data 

in modeling total perennial cover. The wealth 

of vegetation-cover data collected and compiled by USGS personnel over the past century 

in the Mojave Desert and other areas, as well 

as the wealth of satellite data available for free 

through the USGS, offer unparalleled opportunities for scientific investigations.

The Mojave Desert perennial-cover map is 

being used to inform several ongoing scientific 

investigations and land-management efforts 

related to the vulnerability and recoverability 

of desert landscapes. It is being used by USGS 

researchers in studies of dust emissions in the 

Mojave Desert and to model habitat of the 

Mojave Desert tortoise (Gopherus agassizii) 

(http://pubs.usgs.gov/of/2009/1102/).

The work of Western Geographic Science 

Center (WGSC) scientists mapping perennial 

vegetation cover in the Mojave Desert is only 

part of WGSC’s efforts to better understand 

the causes and consequences of land-cover 

change. WGSC is continuing productive collaborations with public land managers, tribal 

leaders, and local communities to help ensure 

that they have the crucial information they 

need to make informed decisions about ongoing and future land-use choices.

Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) satellite 16-day composite images, shown here for 2001, capture the dynamics 

of “greenness” in the Mojave National Preserve (black outline). Even in an area of sparse vegetation, changes in “greenness” are evident and provide information on 

vegetation type and density. USGS scientists coupled these images with field data to model perennial vegetation distribution in this arid landscape. 

This computer generated map shows percentage 

of perennial vegetation cover in the Mojave Desert 

ecoregion within the area of each 250-meter MODIS 

satellite pixel. USGS scientists calibrated the data 

used to create this image on a pixel-by-pixel basis 

to an overall accuracy of 80%. The resulting map is 

being used to inform ongoing scientific investigations and land-management efforts related to the 

vulnerability and recoverability of fragile desert 

landscapes in the arid Southwest.

Cynthia S. Wallace

Edited by James W. Hendley II

Graphics and layout by Judy Weathers

For more information, contact:

Cynthia S. Wallace

U.S. Geological Survey

520 N. Park Ave., MS 150

Tucson, AZ 85719

Tel. (520) 670-5589

cwallace@usgs.gov 

http://geography.wr.usgs.gov;

http://geography.wr.usgs.gov/science/mojave.html

This Fact Sheet and any updates to it 

are available at

http://pubs.usgs.gov/fs/2011/3077/

Dynamics of Mojave Desert Greeness