Mapping Agricultural Land-Use Change in the U.S. 2008-2012

Abstract:

Cultivation of corn and soybeans in the United States reached record levels following the biofuels boom of the late 2000s. Debate churns about whether expansion of these crops caused conversion of carbon-rich natural ecosystems or instead replaced other crops on existing fields. Here we describe a novel trajectory-based methodology for analyzing satellite-derived land cover products that enables integration of all available and intermediate-year data to improve consistency across data sources, time, and geographic boundaries. Using this approach, we track crop-specific expansion pathways across the conterminous U.S., 2008-2012, and identify the types, amount, and locations of all land converted to and from cropland.

We find total cropland area increased by a net of 3 million acres over the study period, with gross land conversion to cropland 2.5 times greater than net expansion. Grasslands were the source of 77% of all new cropland, and we estimate 1.6 million acres (22%) were virgin grasslands that had not been previously planted or plowed. Corn was the most common crop planted directly on new land, as well as the largest indirect contributor to change through its displacement of other crops. Results identify holes in federal policies including improper enforcement of the Renewable Fuels Standard and insufficient coverage of recent Farm Bill provisions, suggesting current implementations of federal policies are likely insufficient to protect remaining grassland habitat.