The surface of the earth is a mosaic of natural and cultural landscapes. Each patch forms part of a diverse, yet interconnected set of landscapes ranging from relatively pristine natural ecosystems to completely human-dominated urban and industrial areas. The mosaic is not static, but shifts due to changes from human activities and natural phenomena. Changes to the surface of the earth from weathering, fire, glaciations, and other natural events have always occurred.
Since the appearance of humans on the earth, natural landscapes have routinely been converted to human-dominated areas for cultivation, occupation, and other economic activity. The scale of landscape change ranges from local (conversion of a farm into a suburb) to regional (conversion of tall grass prairie ecosystems to agriculture) to global (climate change). Climate change is widely recognized as having the potential to profoundly transform both ecological and cultural landscapes.
Increasing interest in understanding landscape changes has led to the emergence of a new field of study: land change science. Land change scientists treat the complex dynamics of land cover and land use as a coupled human-environment system and develop new concepts, approaches, and tools for improved understanding and management of land resources. (Turner et al., 2007)
The Land Change Science Program
The Land Change Science (LCS) Program is focused on understanding the types, rates, causes, and consequences of land change. LCS scientists conduct studies of the land cover and disturbance histories of the United States and overseas areas to determine the reasons for and the impacts of land-surface change. They seek to answer questions such as "What kinds of changes are occurring and why?", and "What are the impacts of these changes on the land for environment and society?" Recording any type of land change requires the characterization of land features at two or more times. However, a long term, scientific perspective of land change requires continued, periodic monitoring of the land surface.
LCS researchers at USGS actively monitor and investigate several key aspects of land change, including:
Land Use and Land Cover — LCS staff develop and maintain the National Land Cover Database (NLCD), the standard land cover map and database for the nation. Other scientists study long-term changes in land cover associated with climate variability, fire disturbance, and changes in management activities, such as intensifying biofuel development and irrigated agriculture. Landsat satellite imagery is a major source of information for land cover and land use analysis.
Carbon — LCS staff lead a major national assessment, called LandCarbon, to identify and quantify biological stocks of carbon and the fluxes of carbon between terrestrial, aquatic, and atmospheric pools. This rigorous assessment involves complex biogeochemical modeling based on land cover data at fine spatial resolutions over very large regions. The assessment creates a starting point for future land management decision-making. Globally, LCS has a leadership role in SilvaCarbon, an effort to connect forest carbon sequestration experts in the USGS and other organizations with scientists in developing countries who are responsible for quantifying their nation's forest biomass carbon stocks and fluxes.
Ecosystems and Their Benefits — Ecosystems provide goods (food, fiber, water, fuel, etc.) and services (flood control, water provision, maintenance of soil fertility, pollination, etc.) that are crucial for human welfare. By providing such vital functions, ecosystems become a key focus of scientific investigation. To document changes in ecosystem extent and function, it is important to know what ecosystems are found on the landscape, where they are located, and how well they are functioning. LCS scientists participate in national and global ecosystem mapping to identify and delineate these ecosystems, research their production of goods and services, and develop methods to assess their economic and social values. LCS scientists also conduct research on incorporating this information into management planning and ecological restoration (e.g. Chesapeake Bay Ecosystem) decisions.
Risk and Vulnerability — The objective of LCS risk and vulnerability studies is to develop quantitative, qualitative, and geospatial methods and decision support tools that characterize and communicate the vulnerability of both human communities and natural ecosystems to natural hazards. Research approaches include assessing both episodic hazards (tsunami, earthquakes, volcanoes, wildfires) and longer term hazards (coastal erosion, sea level rise).
Land Change Science Tools and Approaches
All of the above studies rely on an applied geographic approach to emphasize and then correlate location, spatial relationships, and regional characteristics. LCS scientists use remotely sensed imagery, geographic information systems (GIS) and global positioning systems (GPS) to analyze and integrate data. A variety of image types (optical, radar, lidar, multispectral) are used with a range of spatial resolutions. LCS scientists also use quantitative models to characterize land surface features, develop possible scenarios of future conditions, and conduct integrative, holistic assessments of land cover change. In addition, LCS scientists are developing decision-support tools that incorporate scientific information in resource allocation decisions.
For additional information about the program: Land Change Science Information Sheet (5.8 Mb, PDF)