Framing
Synthetic fertilizers and livestock waste are the largest sources of excess nitrogen and phosphorus in the environment. High levels of nitrogen and phosphorus loading can lead to local water pollution, eutrophication, dead zones, and biodiversity loss. Nitrous oxide (N2O), a potent greenhouse gas, is also released by agriculture and industry. In 2009, the Planetary Boundaries framework identified thresholds for biogeochemical flows of nitrogen and phosphorus that are already surpassed due to human activity, posing serious risks to ecological stability. Subsequent research on Planetary Boundaries reaffirms that nitrogen and phosphorus loading is still among the most severely transgressed boundaries. In California, fertilizers enable the state's enormous agricultural productivity. Yet, roughly half the nitrogen applied every year isn't absorbed by crops and ends up polluting the state's air and water. To capture global and local environmental impacts, we assessed nitrogen leached in the state as well as consumption-based eutrophication potential. Eutrophication describes how chemical compounds, primarily nitrogen and phosphorus, impact water bodies by stimulating plant growth or algal blooms, leading to oxygen depletion and toxins that can be harmful to humans and other species.
Policy spotlight
* The California State Water Resources Control Board, along with nine Regional Water Quality Control Boards, is responsible for developing and enforcing Total Maximum Daily Loads (TMDLs) for water bodies identified as impaired, as mandated by Section 303(d) of the federal Clean Water Act. * The Sustainable Groundwater Management Act (SGMA) of 2014. Although primarily focused on sustainable groundwater use, SGMA mandates that Groundwater Sustainability Agencies (GSAs) also monitor water quality issues related to nutrient loading.
Justice lens
* Nitrogen pollution, particularly nitrates (NO3) from synthetic fertilizer and livestock manure, disproportionately impact disadvantaged communities in agricultural regions such as the San Joaquin Valley. * Research shows that California contributes substantially more nutrient loading than its per capita fair share to stay within planetary boundaries, which has implications for global environmental justice.
Source & citation
Content on this page draws from The California Doughnut Snapshot and Report, used under CC-BY 4.0.
Aritza, A. and Kraus-Polk, J. et al. (2025). The California Doughnut Snapshot and Report. Zenodo. https://doi.org/10.5281/zenodo.17540639