Recent land cover change to agriculture in the Lake States, USA: Implications for natural lands loss and potential perennial cellulosic biomass production
The United States is undergoing massive agricultural expansion, which competes with lands potentially suited for bioenergy feedstocks and affects the integrity of natural ecosystems. We evaluate the magnitude and effects of recent agricultural expansion (2008-2013) in the U.S. Lake States (Minnesota, Wisconsin, Michigan). The exact extent and consequences of agricultural expansion that has occurred in the Lake States is unknown. Our basic question is, how have recent land cover patterns changed under current drivers, and how has this affected open, non-agricultural lands assumed available for cellulosic biomass production? The region is potentially suited for a diversity of bioenergy production systems, both grasses and woody biomass, due to the widespread forest economy in the north and agricultural economy in the south. We used GIS and the USDA annual Cropland Data Layer (CDL), national land cover data and other national datasets to calculate changes in the amount of row crop agriculture and the types of ecosystems being replaced.
Our results show that over 800,000 ha of non-agricultural open lands were already converted to agricultural uses between 2008 and 2013 in the Lake States, a loss of nearly 37%. The greatest relative changes occurred in the southern half that encompasses some of the most diverse cultivable lands in the country. Expansion of row crops (corn, soybean) was responsible for the majority of open land loss, determined using transition diagrams that reveal net changes. Perennial cellulosic feedstocks may have potential to reduce life-cycle greenhouse gas (GHG) emissions by offsetting fossil fuels and current grain ethanol. However, this potential depends on meeting a number of important criteria involving land cover change, including avoiding displacement of agricultural production, not reducing uncultivated natural lands that provide biodiversity habitat and other valued ecosystem services, and the carbon debt that accompanies displacing natural lands. Recent and prevailing crop insurance programs and incentives for grain ethanol production are driving conversion of idle and natural lands of all productivity classes to row crops, primarily corn, as well as closing the window for any opportunity to establish a sustainable cellulosic feedstock economy in the Lake States.