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June 6, 2022

Chesapeake Bay Program — by Jake Solyst — June 6, 2022

"By 1950, the Chesapeake region had changed dramatically due the influx of people moving to the area. The watershed experienced massive deforestation, expansion of farmland and the growth of suburbs and cities. With all that change came an increase in stressors to local waterways—particularly nitrogen pollution—which continues to be one of the biggest impediments to restoring the Bay.

Nitrogen enters the water from sources like fertilizers, animal waste, wastewater, urban runoff and atmospheric deposition, which is when nitrogen in the air comes back down with precipitation or air particles. When found in too high amounts, nitrogen causes excessive algae growth, which blocks sunlight from reaching underwater plants. When the algae decomposes, it removes oxygen from the water which creates dead zones. Efforts to reduce nitrogen runoff is an ongoing battle as each jurisdiction in the Chesapeake Bay watershed has a limit on the amount of nitrogen that can enter their waters and flow into the Bay.

In 2021, U.S. Geological Survey (USGS) researchers working with Chesapeake Bay Program scientists released an award-winning report that explores 100 years of nitrogen pollution. The report provides a unique, long-term perspective of the major drivers of nitrogen pollution—including climate change, hydrology, atmospheric deposition, land use, agriculture, developed areas and wastewater—from 1950 up to 2012, when the study started. The team then forecasted data out to 2050, resulting in a 100-year timeline of nitrogen pollution. . ."

Annual nitrogen loads exported to the Chesapeake Bay by source
Annual nitrogen loads exported to the Chesapeake Bay by source, 1950–2050. Fertilizer and manure are combined into a single agricultural source for the modeled time period. After 2010, the two future agricultural scenarios represent (1) increased intensity of both crop and animal agriculture, and (2) decreased intensity of both crop and animal agriculture (figure OV.S1). Only the future scenario for constant wastewater treatment technology is shown (Hopple and others, 2020, 2021) Nitrogen in the Chesapeake Bay watershed—A century of change, 1950–2050