Land use and Land cover change in the conterminous United States from 1973 to 2000

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This article is part of the Fall 2014 issue of the Earth Science Matters Newsetter. 

 

Land Use Land Change (LULC) management often leads to changes that compromise human needs and ecosystem functioning. These LULC changes have been shown to have impacts at the local to global scale, directly affecting the cycling of chemicals and nutrients (e.g. carbon), functioning of ecosystems, water quality, and climate and weather systems. For example, LULC changes have been shown to alter the regional carbon budgets of forested ecosystems, resulting in increased flux of CO2 to the atmosphere. 

Despite broad acceptance in the scientific community of LULC change as a significant cause of environmental change, there has been a lack of integrated studies conducted at sufficient spatial, temporal, and thematic scales needed to comprehensively characterize LULC change at the national scale. A recent USGS CLU R&D study used nearly 30 years of Landsat satellite observations to measure spatial and temporal patterns of LULC changes in the conterminous United States. 

The study divided the nation into 84 conterminous ecoregions and used a random sampling approach that included 2688 sample sites imaged by Landsat over five periods (see figure). This methodology enabled the direct comparison of estimates of change in LULC across time periods and ecoregions. The researchers found that LULC is a pervasive and variable phenomenon with considerable geographic and temporal variability. For example, the southeast and northwest have undergone almost continuous change while southwest deserts have been relatively stable. The most dynamic regions are those in which environmental conditions such as climate, soils, and topography are suitable for productive and relatively intensive resource-based land uses, such as urbanization, cultivation, and timber extraction. 

Satellite image showing the growth of Las Vegas.

Decades of consistent data from Landsat help scientists monitor the growth of urban areas in a world where more than half of the population lives in cities. For example, Las Vegas, Nevada, one of the fastest growing metropolitan areas in the United States, has seen its population expand from 273,000 in 1972 to 2,204,079 in 2017.

(Public domain.)

The findings from this research provide important baseline data on LULC change by ecoregion over time, which can be used to assess the impacts on other environmental processes such as assessing regional water quantity and quality, analyzing the health of ecosystems and critical habitat needed by imperiled species, and the cycling of energy between the ocean, land and sea.

This paper, published in Global Environmental Change in 2013, can be found at: https://pubs.er.usgs.gov/publication/70074779

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