Manure happens: Unintended consequences of nourishing over seven billion human omnivores


Eric A. Davidson
Professor and Director, Appalachian Laboratory
University of Maryland Center for Environmental Science

Humans have profoundly altered the global nitrogen cycle in an effort to feed over 7 billion people. Humanity has disrupted the nitrogen cycle even more than the carbon cycle, leading to widespread effects on ecosystems, biodiversity, human health, and climate. There have been important successes in reducing nitrogen emissions to the atmosphere by industrial and transportation sectors, and this has improved air quality.

Effective solutions for reducing nitrogen losses from agriculture to groundwater and surface waters have also been identified, although considerable political, social, and economic impediments to their adoption remain. At the same time, demand for food is growing. One effort to integrate and frame socioeconomic and ecological challenges is the Sustainable Agricultural Matrix, which is a collection of quantifiable indicators from environmental, social, and economic dimensions, selected according to criteria of sustainability, data availability, data quality, and the potential to evaluate trade-offs at national scales.