Water Pollution Takeaways
Takeaways are key points detailed and referenced in the Water Pollution section
Nutrient Pollution
The largest water pollution problem is nutrient pollution – the excess of nitrogen and phosphorus in waterways. (Nutrient pollution also impacts air, land, and soil.)
Nutrient pollution causes eutrophication – the depletion of oxygen in waterways, which stresses or kills aquatic species and supports the growth of harmful algae and invasive plants.
The impacts of nutrient pollution include biodiversity loss, clean water scarcity, climate change, risks to human health, and extensive economic loss.
Nutrient pollution is viewed by many scientists as one of nine critical “planetary boundaries.” Both phosphorus and nitrogen outputs continue to surpass the suggested limits by wide margins, threatening long-term human survival.
Animal Ag and Nutrient Pollution
Agriculture is the primary driver of nutrient pollution, broadly estimated at ~75% of anthropogenic sources.
Animal ag makes up about two-thirds of agriculture’s contributions, and therefore about half of all nutrient pollution.
The concentration of large numbers of animals raised indoors or on feedlots leads to the accumulation of massive amounts of manure, a major source of nutrient pollution.
Excess chemical fertilizer application is the other primary source of nutrient pollution. Nearly half of all chemical fertilizers is used on crops for animal feed.
Animal Ag and U.S. Waterways
Nutrients are released into waterways through discharges from manure storage sites, the over-application of both chemical fertilizers and manure on croplands, and landscape modifications such as tile drainage.
Nitrogen from manure and chemical fertilizers is also released into the air as ammonia, much of it eventually returning to the earth and polluting waterways.
About half of the nation’s lakes, and more than 40% of rivers and streams are rated poor by the EPA for nitrogen and phosphorus levels.
Less than half of U.S. freshwater bodies are in good biological condition based on the number and diversity of fish, invertebrates, and other organisms; biological condition is strongly influenced by nutrient pollution.
Almost three-fourths of U.S. lakes are eutrophic. Less than one-third of rivers and streams have healthy biological communities. The 5-year average size of the Gulf of Mexico dead zone is ~4,300 square miles.
For decades, government agencies have failed to address nutrient pollution because of agricultural exceptionalism, the widely dispersed factory farm and cropland sources, and an unwillingness to acknowledge the insurmountable problems arising from the concentration and confinement of farmed animals.