Of the 1.9 billion acres of land in the continental United States, nearly 1.6 billion is used for livestock, forests and crops, in that order. The rest is occupied by urban areas, wetlands, parks, wildlife refuges and other domains. But that’s just a snapshot. How the nation’s land is used will inevitably change in the coming decades, driven by forces that range from the personal (income growth and changing diets) to the agricultural (yield and productivity changes) to the global (trade policy, population growth, climate change). Land-use changes will ultimately impact indicators of the land’s ability to support humans and other species, including biodiversity, water availability, carbon storage capacity and ecosystem health. These measures could spike or dip in short order when compounding forces and stressors create tipping points that lead to massive conversions of land from one use to another (e.g. farmland to forest or vice versa).
To project future trends and tipping points in continental U.S. land-use change requires a deep understanding of the forces that drive it, how those forces interact, and how these interactions will likely impact the allocation of land for different purposes. To that end, researchers at the MIT Joint Program on the Science and Policy of Global Change are applying an emerging scientific discipline called multi-sector dynamics (MSD), which models the interactions and interdependencies among human and natural systems, and the resilience of these systems to compounding forces and stressors.
In a study appearing in the journal iScience, the researchers use MSD to project future U.S. continental land-use change between now and 2050 under three scenarios: business-as-usual, based on conventional analyses of agricultural development over this period; high-pressure, in which combined stressors on land-use are maximized, and low-pressure, in which these stressors are minimized. The MSD-oriented model used in the study—an 18-region, global economic model expanded to include links to natural resources, including energy and land resources—represents the complex, interwoven, dynamic relationships among domestic and global demographics, climate, agriculture markets and economic systems.
Under all three scenarios, the researchers project that over the next three decades there will likely be no tipping points leading to rapid deforestation or abandonment of agricultural land in the continental U.S. Their projections show that historic trends for this region—small, gradual declines in cropland and increases in grassland and natural forest cover—accelerate under the high-pressure scenario and dissipate under the low-pressure scenario.
“While recent studies present a wide range of estimates for future global and regional land use in the continental U.S., our projections show trends in land use that remain consistent regardless of the intensity of societal pressures on the land,” says Angelo Gurgel, a research scientist at the MIT Joint Program and lead author of the study. “From a multi-sector dynamic perspective, we see no clear tipping points for land-use-change in this area throughout the next three decades.”
The study also projects that under the low- and high-pressure scenarios, the most pronounced impacts of land-use change over this period occur in the agriculture sector, with substantial changes in livestock production, agrichemical use and associated emissions of nitrous oxide, methane and carbon dioxide.
This research was funded primarily by the U.S. Department of Energy Office of Science.
Photo: Cow herd in Door County, Wisconsin (Source: Flickr Elvis Kennedy)