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- Maricruz MaGowan
Office of Environmental Information
What are the trends in land use and their effects on human health and the environment?
Land use represents the economic and cultural activities that are practiced at a place, such as agricultural, residential, industrial, mining, and recreational uses. Land use changes occur constantly and at many scales, and can have specific and cumulative effects on air and water quality, watershed function, generation of waste, extent and quality of wildlife habitat, climate, and human health. Land use differs from land cover in that some uses are not always physically obvious (e.g., land used for producing timber but not harvested for many years or land used for grazing but without animals will not be visible). Public and private lands frequently represent very different uses. Urban development seldom occurs on public lands, while private lands are infrequently protected for wilderness uses.
EPA is concerned about the use of land because of the potential effects of land use and its byproducts on the environment. For example, land development creates impervious surfaces through construction of roads, parking lots, and other structures. Impervious surfaces contribute to nonpoint source water pollution by limiting the capacity of soils to filter runoff. Impervious surface areas also affect peak flow and water volume, which heighten erosion potential and affect habitat and water quality. Increased storm water runoff from impervious surfaces can deliver more pollutants to water bodies that residents may rely on for drinking and recreation.9 Storm runoff from urban and suburban areas contains dirt, oils from road surfaces, nutrients from fertilizers, and various toxic compounds. Point source discharges from industrial and municipal wastewater treatment facilities can contribute toxic compounds and heated water. Impervious surfaces also affect ground water aquifer recharge.
Some land development patterns, in particular dispersed growth such as “suburbanization,” can contribute to a variety of environmental concerns. For example, increased air pollution due to increased vehicle use can result in increased concentrations of certain air pollutants in developed areas that may exacerbate human health problems such as asthma.10 Another potential effect of land development is the formation of “heat islands,” or domes of warmer air over urban and suburban areas, caused by the loss of trees and shrubs and the absorption of more heat by pavement, buildings, and other sources. Heat islands can affect local, regional, and global climate, as well as air quality.11
Agricultural land uses can affect the quality of water and watersheds. The types of crops planted, tillage practices, and various irrigation practices can limit the amount of water available for other uses. Livestock grazing in riparian zones can change landscape conditions by reducing stream bank vegetation and increasing water temperatures, sedimentation, and nutrient levels. Runoff from pesticides, fertilizers, and nutrients from animal manure can also degrade water quality. Additionally, agricultural land uses may result in loss of native habitats or increased wind erosion and dust, exposing humans to particulate matter and various chemicals.12
Some land uses can accelerate or exacerbate the spread of invasive species. Certain land use practices, such as overgrazing, land conversion, fertilization, and the use of agricultural chemicals, can enhance the growth of invasive plants.13 These plants can alter fish and wildlife habitat, contribute to decreases in biodiversity, and create health risks to livestock and humans. Introduction of invasive species on agricultural lands can reduce water quality and water availability for native fish and wildlife species.
Research is beginning to elucidate the connections between land use changes and infectious disease. For example, fragmentation of forest habitat into smaller patches separated by agricultural activities or developed land increases the “edge effect” and promotes the interaction among pathogens, vectors, and hosts.14
In some cases, changes in land use may have positive effects, such as increasing habitat as a result of deliberate habitat restoration measures; and reclamation of lands for urban/suburban development as a result of cleanup of previously contaminated land.