By Ben Chou, Natural Resources Defense Council
The devastating effects of water pollution are on full display this summer. The Gulf of Mexico’s “dead zone”, which is an oxygen-poor area off the Gulf Coast, is the largest ever measured since record-keeping began more than 30 years ago. In fact, this year’s dead zone is as large as New Jersey! And forecasts predict that Lake Erie’s annual algal bloom, a toxic soup of blue-green algae that is dangerous to humans and wildlife, could be larger than average this year. Excess phosphorous and nitrogen in waterways are to blame for these problems.
But if it looks bad now, recent research in Science suggests that thanks to heavier and more rainfall from climate change, the worst is yet to come. Without acting to reduce carbon emissions or polluted runoff, nitrogen loading in rivers will increase by nearly 20 percent within the continental U.S. by the end of the century. In regions that historically have struggled with nutrient pollution—like the Northeast, upper Mississippi River basin, and the Great Lakes—nitrogen loading could increase by as much as 28 percent.
Excess fertilizer, rich in nutrients like phosphorus and nitrogen, is the main culprit behind these longstanding water quality problems. When it rains, nutrients from agricultural fields and lawns are washed into rivers and streams and transported either to lakes or the ocean. While farms are a major source of excess nutrients, nutrients also can come from inadequate sewage treatment. Nutrients fuel the growth of algae that eventually decompose and deplete oxygen in the water. This loss of oxygen effectively suffocates fish, shrimp, and other wildlife and makes large aquatic areas uninhabitable.
Algal “blooms” also can produce toxins that harm humans and wildlife. In August 2014, harmful algal blooms in Lake Erie temporarily shut down the water supply for 400,000 people in Toledo, Ohio. Residents were told not to ingest any water as it could cause vomiting, diarrhea, and liver damage.
To counteract the increased loading due to climate change-induced precipitation changes, nitrogen inputs must be reduced dramatically. According to the Science research article, a 33 percent reduction in nitrogen inputs will be necessary to counteract the 19 percent increase in nitrogen loading in the continental U.S.
Reducing nutrient pollution across an entire watershed is no small feat. However, farmers can decrease runoff from their fields by improving soil health, which reduces the need for synthetic fertilizers. Planting cover crops—crops that keep the soil covered and provide a supply of nutrients—and using diverse crop rotations can make soil more fertile while also improving water quality. Healthier soil holds more nutrients and filters water, reducing polluted runoff. In fact, the Union of Concerned Scientists recently found that a more diverse cropping rotation that includes cover crops increases crop yields, maintains profitability, and reduces runoff as well as the use of herbicides and nitrogen fertilizers.
These soil health building-practices also provide many other benefits. They can help farmers prepare for extreme weather and reduce crop losses by allowing soil to act as a sponge, storing excess water during flooding and retaining moisture during drought. Healthier soil also can help in the fight against climate change by sequestering the carbon that is leading to hotter temperatures and changing precipitation patterns.
While more extreme weather has dire consequences for farmers and our waterways, solutions are readily at hand. Federal crop insurance can be reformed to both eliminate barriers and provide incentives for farmers to build healthy soil by planting cover crops and adopting more diverse crop rotations. These time-tested approaches will not only benefit farmers but also will be a key tool for cleaning up our waterways.