Land change happens in the course of human civilization. Since prehistoric times, people have indelibly changed the land to advance human goals — by clearing fields and forests, damming rivers, filling in swamps, and building cities. Over time, the surface of the earth has been transformed into a patchwork mosaic of natural and cultural landscapes across the globe. Land change is tightly intertwined with multiple issues of past, present, and future land-use practices, weather patterns, soil and carbon dynamics, and climate change.

The National Research Council of the National Academy of Sciences has identified the understanding of land-use dynamics as a critical component for assessments of ecosystem health and diversity, economic development and policy, technology issues, human population size and distribution, and overall human health. Further, the Intergovernmental Panel on Climate Change’s Third Assessment Report has cited the lack of scientific understanding about the response of ecological, social, and economic systems to the combined effects of climate change and land-use and land-cover change as a key uncertainty in determining societal vulnerabilities and predicting both regional and global impacts of climate change.

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Toward a deeper understanding of land change

Land-change studies attempt to explain the “what, where, when, how, and why” of changes to the vegetation and to the use of the land. Land-change research is aimed specifically at measuring where change is occurring (and where it is not occurring); which land-use and land-cover classes are changing (and what they are changing to); how much land is changing (and how fast); and what social, economic, and biophysical forces drive the measured changes. The goal is not only to understand the scope of change but also to provide the information base necessary to evaluate, predict, and manage the consequences of change.

One such study is the Land Cover Trends project, a long-term USGS research investigation that focused on analyzing the rates, trends, causes, and consequences of contemporary U.S. land use and land cover change. Field work for the project took place from 1999 to 2009. Analysis and presentation of the collected data is still being conducted as part of the USGS Land Change Research Project.

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USGS Professional Paper 1794, a planned four-volume series on the status and trends of the Nation’s land use and land cover between 1973 and 2000, will form the first comprehensive assessment of land-cover change across the conterminous United States. This national study is the culmination of nearly 10 years of research and development by the U.S. Geological Survey, with support from the U.S. Environmental Protection Agency and the National Aeronautics and Space Administration, as well as university collaborators. The first volume, Status and trends of land change in the Western United States — 1973 to 2000, was published as Professional Paper (PP) 1794-A in 2012.

Great Plains: somewhat changed, still great

USGS scientists recently published the second volume of the series, Status and trends of land change in the Great Plains of the United States—1973 to 2000. The authors relied principally on Landsat satellite imagery —the longest continuous and consistent dataset of synoptic Earth observations — to characterize changes in 11 primary land-use and land-cover classes spanning four time periods between 1973 and 2000 across carefully defined ecological regions in the Montana, North Dakota, South Dakota, Wyoming, Minnesota, Iowa, Missouri, Nebraska, Colorado, Kansas, Oklahoma, New Mexico, and Texas.

Following an overview of land change observed across the entire Great Plains, the remaining chapters of the study present summaries of change for each of the 17 Great Plains ecoregions. Using field photographs, sample-based statistics, and comparisons with other assessments, these summaries document the rates, types, total extent, and drivers of late 20th century land-use/land-cover change.

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Overall, an estimated 8.4 percent (186,616 km2) of land cover in the Great Plains ecoregions changed at least once between 1973 and 2000. However, the overall amount of change varied substantially across the 17 Great Plains ecoregions. Numerous different, and often complex, interactions between an ecoregion’s socioeconomic drivers and its biological and physical characteristics have produced widespread regional and temporal variability of land change.

The ecoregion that experienced the highest amount of change was the Northwestern Glaciated Plains Ecoregion (located in northern Montana, northwestern and central North Dakota and central South Dakota, and northern Nebraska), at 14.1 percent. The ecoregion that experienced the lowest amount of change was the Lake Agassiz Plain Ecoregion (located mostly in eastern North Dakota and northwestern Minnesota) at 1.5 percent.

Agriculture and grassland/shrubland, the two dominant land-cover classes, underwent a substantial shift over the 27-year study period. Most of the Great Plains ecoregions experienced an overall decline in agricultural land, which was facilitated by the policies and incentives of the Conservation Reserve Program. The decline followed an earlier period of agricultural expansion between 1973 and 1980 that occurred at the expense of grassland/shrubland.

Trends on the horizon

“People and their use of the land are interrelated in complex ways,” acting USGS director Suzette Kimball wrote in the foreword to the Great Plains volume (PP 1794-B). “… the effects of land-use and land-over change can have a huge impact on their quality of life, on the goods and services that they can expect from the land, and on the hazards that they may face.” The remaining volumes of the series — PP 1794-C, Midwest-South Central U.S.; and PP 1794-D, Eastern U.S — are slated for publication by the end of 2015 and during the first half of 2016, respectively.

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Land cover trends project

Status and Trends of Land Change in the Western United States—1973 to 2000

Status and trends of land change in the Great Plains of the United States—1973 to 2000

USGS Land Change Science