Meghan Hodges
The Chesapeake Bay, the largest estuary in the United States, is facing significant pollution challenges. Excessive nutrients, particularly nitrogen and phosphorus, are the primary contributors to the poor health of the bay and its waterways. These nutrients originate from various sources, including wastewater treatment plants, agricultural and urban runoff, and air pollution. While there have been efforts to reduce pollution, such as the implementation of the Clean Water Act and state initiatives, the bay continues to be impaired by low oxygen levels and pollution that threaten aquatic life. Population growth, agricultural practices, and climate change are also exacerbating the pollution issues in the Chesapeake Bay.
| Characteristics | Values |
|---|---|
| Major contributors to pollution | Nitrogen, phosphorus, and sediment |
| Nitrogen sources | Wastewater treatment plants, urban, suburban, and agricultural runoff, air pollution, septic tank discharges, fertilizers, and lawn fertilizers |
| Phosphorus sources | Wastewater treatment plants, urban, suburban, and agricultural runoff, fertilizers |
| Sediment sources | Urban landscapes, agricultural operations, and stormwater runoff |
| Impact of pollution | Reduced levels of oxygen, killing off fish, crabs, oysters, and other aquatic life |
| Population growth impact | Increased hard surfaces, leading to more polluted stormwater runoff |
| Climate change impact | Increased precipitation, resulting in more nutrient-laden runoff |
| Chesapeake Bay watershed impact | Affects 17 million people across six states, including Pennsylvania, which supplies about half of the bay's freshwater flow |
| Cleanup efforts | Chesapeake Bay Program's computer models, Penn State's initiatives, and the federal Clean Water Act (CWA) |
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What You'll Learn
Nitrogen, phosphorus, and sediment pollution
Wastewater treatment plants are a significant source of nitrogen and phosphorus pollution in the Bay. In 2005, new permit processes were implemented to limit the amount of nutrients these plants could release into the water. As a result, nitrogen loads from these plants have declined by 57% since 1985, while phosphorus loads have declined by 75%.
Urban, suburban, and agricultural runoff is another major source of nitrogen and phosphorus pollution. This includes lawn fertilizers, septic systems, and livestock manure. Agricultural runoff is the largest source of nutrient and sediment pollution, contributing approximately 60% of the nitrogen and 45% of the phosphorus in the Bay. Implementing conservation measures on farms is a cost-effective way to reduce pollution in the Bay.
Air pollution is also a significant contributor to nitrogen pollution in the Bay, accounting for about one-third of the total nitrogen load. This includes emissions from cars, trucks, industries, and gas-powered lawn tools. By reducing vehicle emissions and conserving energy, it is possible to lower the amount of nitrogen entering the Bay through air pollution.
Sediment pollution, caused by tiny particles of dirt, sand, and clay floating in the water, can turn the water cloudy, blocking sunlight from reaching aquatic grasses. It can also smother bottom-dwelling species when it settles to the bottom. The Chesapeake Bay Program has set goals to reduce nitrogen, phosphorus, and sediment pollution, with a target of implementing 100% of practices to achieve these reductions by 2025.
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Agricultural pollution
Agriculture is a significant contributor to the pollution of the Chesapeake Bay. While only about 23% of the 64,000-square-mile Chesapeake watershed is farmland, agricultural practices are the source of 58% of the sediment pollution, 58% of the phosphorus, and 42% of the nitrogen that reaches the Bay.
Nitrogen, phosphorus, and sediment are the three major contributors to the poor health of the Chesapeake Bay. High levels of nitrogen and phosphorus fuel unnaturally high levels of algae growth in the water, blocking sunlight from reaching underwater grasses and depleting the water's oxygen levels as the algae are decomposed by bacteria. Too much sediment turns the water cloudy, also blocking sunlight from reaching aquatic grasses, and can smother bottom-dwelling species such as oysters.
Excessive amounts of nitrogen and phosphorus come from fertilizers, wastewater, septic tank discharges, air pollution, and runoff from farms, cities, and suburbs. While nutrients are a natural part of the Chesapeake Bay ecosystem, they have become far more abundant due to human activity. As forest and wetland plants that would usually absorb nutrients have been removed to accommodate a growing population, nutrient pollution to the Bay has increased.
Agricultural practices such as conventional farming leave operations vulnerable to the effects of climate change, with extreme storms leading to floods that wash away soil and fertilizers, carrying pollution into waterways. Eroded topsoil also decreases water retention, making farms more vulnerable to drought and reducing farm yield and economic viability.
However, there are signs of improvement. Farmers are increasingly adopting practices that reduce polluted runoff, such as no-till and cover crop conservation methods. It is estimated that widespread use of these practices could reduce the amount of nitrogen pollution entering the Bay from nonpoint sources by up to 60%. The Chesapeake Bay Program has also been measuring improvements, announcing in 2016 that inputs of nitrogen, sediment, and phosphorus had dropped by 8%, 7%, and 20% respectively since 2009.
To further lower nutrient pollution, the Chesapeake Bay Program has set a goal of achieving a 67% reduction in phosphorus and a 57% reduction in nitrogen by 2025 through its Watershed Implementation Plans.
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Air pollution
There are four main sources of air pollution in the Chesapeake Bay region: stationary and area sources, mobile sources, agricultural sources, and natural sources. Stationary sources, such as power plants, chemical facilities, and manufacturing facilities, are large, consistent sources of pollution with fixed locations. Area sources, like dry cleaners and gas stations, are smaller but often clustered together. Mobile sources of pollution include cars, trucks, and other vehicles, which emit pollutants directly into the air as they move. Agricultural sources of air pollution come from farms, contributing nutrients and sediment pollution to the Bay.
Nitrogen oxides (NOx) and ammonia are two of the most significant airborne pollutants affecting the Chesapeake Bay. These pollutants are produced by vehicles, power plants, and other sources burning fossil fuels like gas, coal, or oil. Excess nitrogen fuels the growth of algae blooms, which block sunlight from reaching underwater grasses and create low-oxygen "dead zones" that harm marine life. Atmospheric deposition of nitrogen accounts for about one-third of the total nitrogen loads in the Bay, with direct deposition onto the tidal surface waters estimated at 6 to 8 percent.
Other chemical contaminants in the air that impact the Bay include mercury, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). Mercury is released into the air when coal, oil, natural gas, and hazardous materials are burned, and it can reach toxic levels in the tissue of fish and shellfish. PCBs and PAHs are released during the burning of fossil fuels, and while PCBs are banned in the US, they persist in the environment. Sulfur dioxide (SO2) emissions, another pollutant, contribute to acid rain and damage the growth of plants that sustain the Bay's ecosystem.
Reducing air pollution is crucial to improving the health of the Chesapeake Bay. Maintaining and protecting forests that absorb airborne pollutants, enacting regulations to reduce emissions, and promoting clean air efforts are all essential strategies. Individuals can also play a role by driving less, carpooling, and advocating for stricter air-quality standards.
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Population growth
The Chesapeake Bay watershed is home to over 18.5 million people, and this number is expected to surpass 20 million by 2040. The rapid rate of population growth has raised concerns over the sustainability of the plants, animals, and people in the region. As more people move into the area, forests, farms, and other landscapes are being converted into subdivisions, shopping centers, and parking lots. This development results in more hard surfaces, increasing polluted stormwater runoff.
With a growing population comes an increase in wastewater from homes, schools, businesses, farms, and industrial facilities. Wastewater treatment plants are used to treat this water before releasing it back into the environment. However, these plants can fail due to outdated technology or being overwhelmed by the volume of wastewater. When this happens, nutrient and sediment pollution are released into the waterways, further degrading the health of the bay.
Agricultural intensification and development are projected to continue, and climate change impacts on nutrients are expected to accelerate. Population growth will also lead to an increase in nutrient pollution from wastewater treatment plants, as the amount of nutrients from these plants is expected to rise. Therefore, future nutrient reductions must come from controlling runoff from farms and developed lands, which are significant sources of pollution.
To mitigate the effects of population growth, low-impact development techniques can be implemented. This includes the use of rain gardens, porous pavement, and green roofs to reduce pollution from developed areas. Additionally, practices such as reducing stormwater runoff and redirecting it away from paved surfaces can help lower the impact of population growth on the bay's health.
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Climate change
Chesapeake Bay is the largest estuary in the United States, spanning 64,000 square miles and encompassing six states and the District of Columbia. It is an ecologically and economically significant region, supporting a diverse ecosystem and industries such as commercial and recreational fishing, tourism, and boating. However, human activities and climate change have severely impacted the bay, threatening its health and sustainability.
The impacts of climate change are evident in the Chesapeake Bay region, with inhabited islands like Smith Island and Tangier Island already facing the threat of rising sea levels, and previously inhabited islands completely submerged. The Chesapeake Bay Foundation's property in Annapolis, Maryland, has also lost several dozen acres of pine forest to rising waters in recent decades.
To mitigate the effects of climate change and protect the Chesapeake Bay, controlling emissions of greenhouse gases is crucial. Additionally, improving water quality and implementing erosion prevention tactics, such as living shorelines, can help buffer the bay against the most harmful consequences of climate change. The Chesapeake Bay Program and the National Wildlife Federation are actively working to address these issues, restore the bay, and support the region's communities and wildlife.
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Frequently asked questions
Nitrogen, phosphorus, and sediment are the three main contributors to the poor health of Chesapeake Bay. These nutrients enter the bay from wastewater treatment plants, urban and agricultural runoff, and air pollution.
Nitrogen and phosphorus cause unnaturally high levels of algae growth in the water, blocking sunlight from reaching underwater grasses and robbing the water of oxygen, making it uninhabitable for aquatic life. Sediment clouds the water, smothers vegetation and insects, and settles at the bottom, suffocating bottom-dwelling species like oysters.
The federal Clean Water Act (CWA) requires states to identify and list polluted waterways. Under the CWA, the Environmental Protection Agency (EPA) sets limits on pollutants. In 2010, the EPA set limits on nitrogen, phosphorus, and sediment pollution for the Chesapeake Bay watershed. States are responsible for creating and implementing plans to achieve these limits by 2025.
Individuals can help by reducing the amount of pollution that runs off their property. This includes installing a green roof or rain garden, using porous surfaces, and redirecting home downspouts onto grass or gravel. People can also reduce air pollution by walking, biking, or taking public transportation, and using electric lawn mowers and yard tools.
