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Report on the Environment

Land Cover

What are the trends in land cover and their effects on human health and the environment?

Land cover — the surface components of land that are physically present and visible — provides a means to examine landscape patterns and characteristics. Patterns and landscape characteristics are important in understanding the extent, availability, and condition of lands; ecological system extent, structure, and condition; and the potential for dispersion and effects of chemicals and other pollutants in and on the environment. (Land cover represents a starting point from which a variety of monitoring activities can be performed. EPA considers land cover information to be critically important for a number of reasons, including the ability to assess nonpoint sources of pollution, to understand landscape variables for ecological analyses, to assess the behavior of chemicals, and to analyze the effects of air pollution.

Land cover, in its naturally occurring condition, integrates and reflects a given site’s climate, geology and soils, and available biota over a time span of decades or longer. Land cover can be affected on shorter time scales by naturally occurring disturbances (e.g., storms, floods, fires, volcanic eruptions, insects, landslides) and human activities. Land cover represents the results of both naturally occurring conditions and disturbances and human activities such as population change, industrial and urban development, deforestation or reforestation, water diversion, and road-building. Depending on one’s perspective, the changes wrought by natural processes and human activities can be perceived as improvements or degradations of the state of land cover.

Land cover is also important because it affects other environmental variables including water quality, watershed hydrology, habitat and species composition, climate, and carbon storage. Land cover influences the mass and energy exchanges between the surface and the atmosphere and thus influences weather and climate.5 Land cover is also a primary ingredient of ecological structure and function, with changes affecting species habitat and distribution. Land cover changes in watersheds can alter hydrologic regimes, runoff patterns, and flood buffering.6

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