Fact Sheet 2007–3030

April 2007

Geographic Analysis and Monitoring Program

In 1913, Miami, Florida, was a small settlement along the banks of the Miami River. Today, the city and its surrounding landscape have been 

utterly transformed. Buildings stand where woodlands once grew. Networks of streets and highways have replaced wetlands. The city’s population has burgeoned from a few thousand to nearly 400,000 (fig. 1). In 2000, Miami and its neighboring municipalities ranked as the Nation’s 

6th largest metropolitan area, having grown over 23 percent from 1990 to 2000.

How significant are such changes to the landscape? What impact do they have on natural ecosystems, climate, resources, and human health? 

How do changes in one location affect other parts of a region, an entire country, or the rest of the world? How do landscape change and 

human-induced factors, such as population growth, interact to influence the risk and vulnerability of communities to hazard events? What can 

we learn from past land-surface changes that will enable us to better predict and handle changes in the future?

The U.S. Geological Survey’s (USGS’s) Geographic and Analysis Monitoring (GAM) Program answers these and other vital questions about 

land-surface change.

Figure 1.  These two photographs of the same location in Miami, taken in 1913 and 1997, exemplify how dramatically urban expansion can alter the 

landscape, ecosystems, and the human environment over time. (Photos courtesy of Historical Museum of Southern Florida, left; South Florida Water 

Management District, right.)

U.S. Department of the Interior

U.S. Geological Survey Printed on recycled paper

A Changing Planet

The surface of the Earth is changing rapidly, 

at local, regional, national, and global scales, 

with significant repercussions for people, the 

economy, and the environment. Some changes 

have natural causes, such as wildland fires or 

hurricanes, while other changes on the land, 

such as resource extraction, agricultural practices, and urban growth, are human-induced 

processes. There are other types of changes 

that are a combination of natural and humaninduced factors; landslides and floods, for 

example, are fundamentally natural processes 

that are often intensified or accelerated by 

human land use practices. Whatever their 

cause, land-surface changes can have profound environmental and economic impacts.

Changes in land use and land cover are also 

important contributors to climate change 

because the land and the atmosphere are 

intricately linked through the exchange of 

gases, the radiation balance of the land surface, wind behavior, and many other factors. 

At the same time, some changes in the land 

surface can impartially record the impacts of 

climate change.

Cumulatively, land-surface changes at the 

local level have the potential to impact global 

climate and threaten the sustainability of natural systems worldwide. They can also affect 

human health and the health of ecosystems, 

influence vulnerability to floods and fires, 

interfere with biogeochemical cycles, and 

threaten biodiversity.

Focus of GAM Research

The goal of the GAM Program is to contribute 

to an understanding of the Nation’s urgent 

environmental, natural resource, and economic challenges. The program assesses the 

Earth’s land cover at a range of spatial and 

temporal scales to better understand the causes 

and consequences of land cover change.

Land cover—the biophysical pattern of natural vegetation, agriculture, and urban areas—

is the product of both natural processes and 

human influences. While human modification of land cover is an inevitable aspect of 

modern society, human-induced changes in 

land cover have important implications for 

both society and the environment. Land cover 

provides an indication of the availability and 

quality of natural resources, as well as a historical record of resource use. Consequently, 

comprehensive information about land cover 

is essential in a wide variety of investigations, 

such as assessing climate change, evaluating 

ecosystem status and health, understanding 

spatial patterns of biodiversity, and informing land use planning and land-management 

policy.

The GAM Program conducts long-term studies of the land cover and disturbance histories 

of the United States and selected overseas 

areas in order to determine the reasons for 

and the impacts of land-surface change. GAM 

research activities seek to answer four fundamental questions:

1. What kinds of changes are occurring and 

why?

2. What are the impacts of these changes?

3. How do these impacts, in turn, further 

influence the land surface?

4. How can GAM research findings best be 

used for making decisions in resource 

use and allocation, as well as in reducing 

risk and vulnerability to natural hazards?
The Range of GAM Science 

Investigations

The GAM Program is responsible for two 

continuing national projects: the National 

Land Cover Database (NLCD) and the Land 

Cover Status and Trends Reports. These longterm compilations of land cover conditions 

provide the foundation of USGS land-surface monitoring efforts, as well as those of 

numerous governmental and nongovernmental 

organizations. The results of these projects 

are necessary components of any regional or 

national environmental assessment.

Innovative applications of GAM research 

take place in many fields, including climatic 

and hydrologic variability, biogeochemical 

cycling, ecosystem health, natural hazards 

analyses (including disaster prediction, 

mitigation, and response), and wildfire science. These applications provide a basis for 

resource managers and the public to understand the dynamic nature of our 

landscape and to anticipate the 

consequences of the interplay 

between natural processes and 

human actions.

Analytical approaches to the 

geographic relationship of 

natural hazards and society (see 

fig. 2) enable GAM researchers 

to develop methods and processes, such as decision-support 

systems and economic models, 

that can facilitate the use of 

USGS science in public policy. 

By understanding the vulnerability and resilience of human and 

environmental systems in the context of place, 

geographic science can link assessments of 

potential hazards with the development of 

risk-reduction measures.

Societal

Risk of 

Disaster

Natural Hazard Vulnerable System

Knowledge of Potential Catastrophic Exposure, Sensitivity, and Resilience of:

and Chronic Physical Events:

Past Recurrence Intervals

Future Probability

Speed of Onset

Magnitude

Duration

Spatial Extent Ability, Resources, and (or) Willingness to:

Population and Cultural Assets

Economy

Development

Infrastructure and Critical Facilities

Natural Resources and Ecosystem

 Services

Mitigate

Prepare

Respond

Recover

Understanding Risk

Figure 2.  Diagram showing the combination of vulnerability and 

natural hazards to produce risk.

GAM Science Highlights

National Land Cover Database (NLCD)

Under the leadership of the USGS, the Federal 

interagency Multi-Resolution Land Characteristics Consortium develops the National Land 

Cover Database (NLCD 2001) for the Nation. 

Information contained in the massive database 

enables managers of public and private lands, 

urban planners, agricultural experts, and 

scientists with many different interests (for 

instance, climate change or invasive species) to identify critical characteristics of the 

land. Derived from Landsat satellite imagery, 

NLCD products include 21 classes of land 

cover, percent tree canopy, and degree of 

surface imperviousness in urban areas (fig. 3). 

Figure 3.  Outline of the contiguous United States with land cover data layers displayed. The NLCD 

contains multiple layers of precise data that can be built or deconstructed, merged with other types 

of data, and analyzed to answer vital questions about the Nation’s land resources. Illustrating how 

the data can be separated or combined, the graphic depicts various degrees of tree canopy in the 

West and urban imperviousness in the East. In the central States, 16 distinct classes of land cover are 

consolidated in a colorful mosaic.

The national consistency of NLCD information makes possible the sweeping, contextual 

analysis of national land perspectives, such 

as the Heinz Center’s State of the Nation’s 

Ecosystems and the Environmental Protection 

Agency’s Draft Report on the Environment.

Land Cover Status and Trends

Understanding the impacts and feedbacks of 

land use and land cover change on environmental systems requires an understanding of 

the rates, patterns, and driving forces of past, 

present, and future land use and land cover 

change. As the first comprehensive national 

land cover change analysis ever conducted, 

the goals of the Land Cover Trends Project are to document and understand how, 

where, when, and why the Nation’s land has 

changed, and thus provide a solid foundation 

of research for projecting future change and 

managing its consequences.

The objectives of the Land Cover Trends 

project are to (1) determine the amount, rates, 

and trends of contemporary land use and land 

cover change by ecoregion for the period 

1973 to 2000 for the conterminous United 

States, (2) document the driving forces and 

consequences of change, and (3) synthesize 

individual ecoregion results into a national 

assessment of land use and land cover change.

In the eastern States, GAM scientists have 

found that most land cover change has 

been associated with forest harvesting 

and regrowth, agricultural abandonment, 

and development (fig. 4). Data from these 

Figure 4.  Map showing the overall spatial 

change between 1973 and 2000 measured in the 

20 ecoregions of the eastern U.S. The amounts 

of change range from a low of 2.0 percent (light 

pink) in the Blue Ridge ecoregion to a high of 

24.9 percent (dark red) in the Southern Coastal 

Plain. Ecoregions with larger amounts of change 

typically have active forest harvesting and 

regrowth occurring.
observations indicate that in 20 of the eastern 

ecoregions, there has been steady deforestation over the past 30 years. This finding is 

important because of its relationship to water 

quality, species biodiversity, and climate.

Ecosystem Performance and Climate 

Change

Land management is an important tool for 

controlling the levels of greenhouse gases 

in the atmosphere, a contributing factor to 

climate change. Whether land-based ecosystems remove carbon dioxide (CO2

) from the 

atmosphere (a sink) or contribute CO2

 to the 

atmosphere (a source) is influenced by the 

productivity of the land. GAM scientists use 

spatial data from remote sensing and other 

sources, coupled with integrating models, 

to quantify the carbon cycle performance of 

ecosystems (fig. 5).

Figure 5.  Ecosystem productivity of coniferous boreal forests in the Yukon River Basin, Alaska, in 2004. 

Elevation is shown (black = low, white = high) in nonconiferous areas and outside the Yukon Basin. 

Black lines outline where fires occurred after 1997, revealing underperformance.

Societal Vulnerability

Societal vulnerability to natural hazards is 

a function of how communities occupy and 

use hazard-prone land. To better understand 

community vulnerability, GAM researchers and their partners use spatial data from 

the National Land Cover Database (NLCD 

2001) and socioeconomic sources to quantify 

variations in land cover, human populations, and economies in relation to predicted 

hazard-prone land (fig. 6). This geographic 

information helps local, State, and Federal 

officials make informed and realistic decisions 

that strengthen community preparedness for, 

response to, and recovery from disasters. 

Developing and applying new approaches for 

understanding and communicating community 

vulnerability to natural hazards, including 

climate change, helps the Nation improve its 

ability to reduce risk and increase resilience.

Zone Subduction

Cascadia

Juan

de Fuca 

Tectonic

Plate North

American

Tectonic

Plate

Percent of

Developed Land in

Tsunami-Hazard Zone

17 - 42

42 - 100

0 - 5

5 - 17

California

Oregon

Washington

Figure 6.  Graphic image showing the regional 

extent of the Cascadia subduction zone and the 

coast that is vulnerable to tsunamis created 

by earthquakes in this zone. Based on NLCD 

2001 and tsunami-hazard data, the amount 

of developed land in hazard-prone areas 

varies considerably among Oregon coastal 

communities. GAM research successes in 

conveying the concept of societal vulnerability 

to the leaders of coastal communities in Oregon 

have led to formal interagency agreements with 

State agencies in Washington and Hawaii for 

similar research there.

Ecosystem Geography

Ecosystem management is a strategy for the 

integrated management of land, water, and living resources that promotes conservation and 

sustainable use in an equitable way. Ecosystems are widely recognized as fundamental 

components of biodiversity that need to be 

conserved and, in some cases, restored. GAM 

researchers have undertaken the classification and delineation of ecosystems for the 

conterminous United States at a scale that is 

appropriate for ecosystem management. GAM 

researchers use the biophysical characteristics 

of landform, surficial geology, bioclimate, 

and land cover to define and map ecosystems 

after determining sound methodologies for 

generating these core components (fig. 7). 

They also compile each biophysical component as a national data layer. The resulting 

geographic information database for ecosystems is available—as integrated composite 

ecological footprints or as separate core 

component data layers—to researchers and 

to land managers responsible for making science-based decisions.

USGS scientists have also developed a Global 

Data Toolset (GDT) that integrates Webaccessible analytical tools and data to analyze 

Figure 7.  Illustration of the data layers of 

biophysical components that can be combined in 

ecosystem databases.
For more information, please contact: 

Jonathan H. Smith, Ph.D., Program Coordinator 

U.S. Geological Survey, Geographic Analysis and Monitoring Program 

519 National Center 

12201 Sunrise Valley Dr. 

Reston, VA 20192

Phone: 703-648-4516 

Fax: 703-648-5542

E-mail: jhsmith@usgs.gov

Please visit the GAM Program Web site: http://gam.usgs.gov/ .

and display ecosystem information. The GDT supports landscape analyses at scales 

ranging from site-based projects, to regional studies, to global applications. The GDT 

provides new data and tools for monitoring key land variables at a global scale.

Ecosystem Restoration—Chesapeake Bay

Excessive nutrients and sediments are the leading causes of impairment to the health 

of the Chesapeake Bay. Land uses and land-management practices throughout the 

64,000-square-mile Chesapeake Bay watershed contribute the majority of nutrients 

(nitrogen and phosphorus) to the estuary and are a major source of sediments in the 

upper Bay; therefore, managing land uses and changes to the land are the main activities needed to restore water quality in the Chesapeake.

In order to identify future environmental consequences of land change, eight- to tenyear forecasts of land change have been produced to establish nutrient and sediment 

reduction goals in the Chesapeake Bay watershed (fig. 8). Longer term forecasts 

of land change are needed given the rapid rate of urbanization and land change and 

evidence that increased nutrient loads from urban development may be impeding 

progress in reducing nutrients. USGS and its partners—Woods Hole Research Center, 

Shippensburg University, and the Maryland Department of Planning—are developing 

a model to forecast land changes in the bay watershed through the year 2030. USGS 

expertise in land change and water-quality modeling are key components of this effort. 

The land-change forecasts will be coupled with a watershed model to simulate future 

nutrient and sediment loads to the bay. This information will be used by State agencies 

and local governments to help make informed decisions concerning environmentally 

sound land use policies as a means of maintaining nutrient and sediment reductions.

Figure 8.  Map of Chesapeake Bay watershed showing highurban development pressure. Red areas denote lands under 

high development pressure—land that has experienced a 

significant increase in impervious surface and (or) residential 

housing over the 1990s. Areas within close driving proximity 

to the high-pressure areas are represented in orange as 

moderate-development pressure. All lands under lowdevelopment pressure are represented by their dominant land 

cover class (e.g., open water, nonforest, forest, or wetland).

Phenology

Phenology is the study of periodic plant and animal life-cycle events that are influenced by environmental changes, especially seasonal variations in temperature 

and precipitation driven by weather and climate. GAM scientists investigate the 

relationship of phenology to the abundance, diversity, and geographic distribution 

of organisms using time-series analysis of satellite imagery (fig. 9). With sufficient 

observations and understanding, phenology can be used as a predictor for important 

environmental processes and variables at local to global scales and could drive a variety of ecological forecast models.

Figure 9.  Map outline of North America showing trends 

in growing season greenness from 1982 to 2003, derived 

from satellite data. Areas in green depict regions that have 

increasing productivity during this period, primarily as a result 

of extended growing seasons, but also because of land use 

change. Red areas show a decline in productivity as a result 

of land use change, fires, and other factors. The new National 

Phenology Network will provide a means of connecting the 

satellite data to ground-based observations and will present 

a ready means of communicating some of the impacts of 

environmental change to citizens.

Scientific Collaboration and Contributions

The GAM Program collaborates with other USGS science programs, such as Status 

and Trends of Biological Resources, National Water-Quality Assessment, and National 

Biological Information Infrastructure. It contributes to Bureau initiatives, including 

the Southern California Multi-Hazards Demonstration Project, as well as disaster 

response and assessments, such as those for Hurricane Katrina and western wildfires. 

The GAM Program supports the research objectives of the U.S. Climate Change Science Program and is an active participant in international global science initiatives.

Program partners and customers include the scientific community, State and Federal 

agencies, and public organizations that make land-management decisions or influence and shape policy. The GAM Program works closely with stakeholders within 

the Department of the Interior bureaus that have land-management roles, such as the 

Bureau of Land Management, the National Parks Service, Fish and Wildlife Service, 

and the Bureau of Reclamation. Partners and customers also include other national 

agencies with research, regulatory, or land-management roles, such as the U.S. 

Environmental Protection Agency, the U.S. Forest Service, the National Oceanic and 

Atmospheric Administration, and the National Aeronautics and Space Administration. 

The program supports our Nation’s international efforts, working with the Department of State, the U.S. Agency for International Development, foreign governments, 

multinational organizations, and nongovernment organizations in analyzing land cover 

and conducting environmental analyses around the globe.

By Jon C. Campbell