Modeled Historical Land Use and Land Cover for the Conterminous United States
The landscape of the conterminous United States has changed dramatically since the start of the 20th century, with agriculture, urban expansion, forestry, and other anthropogenic land uses altering the land’s surface across vast swaths of the country. Landscape change has direct effects on many natural processes, including carbon and biogeochemical cycles, hydrology, biodiversity, and climate. Understanding how the landscape has changed in the past helps scientists to understand what the impacts were on climate, ecological and societal processes, and it informs efforts to mitigate any potential negative impacts of landscape change in the future.
Consistent, regional- to global-scale satellite observations began in 1972 with the launch of Landsat 1 (originally named Earth Resources Technology Satellite 1). The first maps of historical landscape change based on these data were not created until 1992, and the only prior LULC mapping for the United States is a 1970s era map created by the USGS using an interpretation of aerial photography. Modeling approaches are often used to produce projections of future landscape change, but these methodologies have rarely been used to model and reconstruct historical landscapes. To fill the need for consistent, thematically and spatially detailed maps of historical LULC change, the USGS used a modeling approach to create historical annual maps for the conterminous United States going back to 1938.
The modeling of historical landscape change was based on well-quantified historical data sources documenting anthropogenic land-use change, including satellite-based landscape observations going back to 1973, databases on historical changes in agricultural land use and extent, population and urban change, wetland loss, reservoir construction dates, and other historical data sources. The USGS’ Forecasting Scenarios of Land-use Change (FORE-SCE) model was used to create spatially explicit historical maps from 1938 to 1992 for the conterminous U.S. at a 250-meter spatial resolution, representing 14 thematic classes (see figure for example).
These data represent the first spatially explicit, thematically detailed LULC data available for the entire conterminous United States for dates prior to availability of data from the Landsat series of satellites. The results closely mimic rates of changes measured by numerous historical data sources. Researchers can use LULC data from this historical period to reveal connections between LULC change and a variety of ecological and societal phenomenon. Additionally, this data can be used in combination with a previously produced suite of landscape projections from 1992 through 2100, to better understand the potential future consequences of LULC change.
The modeled historical data from this study, as well as multiple projections of future landscape change, are freely available for download and use at https://www.usgs.gov/core-science-systems/eros/lulc. The paper, "Modeled historical land use and land cover for the conterminous United States", was published in the Journal of Land Use Science.