Nearly 17 million people live in the Chesapeake Bay watershed, and demographers estimate that the watershed's population is growing by about 157,000 residents per year. At this rate, the population will reach 20 million by 2030. A growing population creates issues that threaten the Bay ecosystem.
Land use changes
As people move to the area and development increases, land use in the watershed changes. New homes, businesses, and roads replace forests and fields. Lands that once absorbed rainfall have been transformed into impervious surfaces such as parking lots and roads that increase stormwater runoff—often full of sediment, excess nutrients, and chemical contaminants—flowing into the Bay and its tributaries.
Air pollution threatens the air we breathe and the land and water. Air and water pollution are intricately linked. Of particular concern to the Chesapeake region are airborne nitrogen and chemical contaminants such as mercury. These airborne pollutants come from large point sources like power plants and industrial facilities, vehicles, and agricultural sources. Airborne nitrogen increases the acidity of surface waters and soils, forms ground-level ozone, and contaminates drinking water. Chemical contaminants persist in the environment, moving through the food web in a process called bioaccumulation. This affects the growth and reproduction of both terrestrial and aquatic species.
Nitrogen and chemical contaminants pose threats to the Chesapeake Bay when they enter the Bay either by falling directly into the water or by falling onto the land and being carried into the water by stormwater runoff. Excess nutrients such as nitrogen and phosphorus—most of which come from agricultural sources such as fertilizer and manure—create algae blooms that prevent sunlight from reaching submerged aquatic vegetation, limiting growth of vital underwater Bay grasses. These excess nutrients also deplete dissolved oxygen, necessary for the survival of oysters, crabs, and other bottom-dwelling species in the Bay.
Excess sediments also contribute to the Bay's poor health. More than 18.7 billion pounds (8.5 billion kg) of sediment enter the Bay each year. Sediments come from the erosion of land and stream banks (watershed sources) and shoreline and nearshore areas (tidal sources). Too much sediment makes the water cloudy, which keeps sunlight from reaching underwater grasses; smothers oysters and other bottom-dwelling species; degrades streams; clogs ports and channels; and binds with pollutants, which then spread throughout the Bay.
The fishing industry is essential to the Chesapeake Bay character and economy. The Bay provides rich grounds for both commercial and recreational fisheries of the Chesapeake's signature species, including blue crabs, oysters, American shad, Atlantic menhaden, and striped bass. Overfishing, along with pollution, diseases, and other stressors, has affected the populations of many fish and shellfish in the Bay and, in cases like the American shad, contributed to closures of commercial fisheries in the Bay.
Plants and animals currently living and reproducing in a habitat outside their historic native range are considered "exotic." Exotic species become "invasive" when they negatively impact an ecosystem or species by encroaching on habitat and food sources. Introduced through a variety of means (some intentional, some not), invasive plants, insects, and diseases threaten all the habitats of the watershed. Invasive plants often grow and reproduce faster than native species, lowering the quality of available food and shelter for native species and out-competing native plants for habitat and pollinators.
The Bay Today
The Chesapeake region has begun to feel the effects of a changing climate, which has repercussions for the entire ecosystem. Over the last century, the average air temperature along the coastal margins of the Chesapeake Bay has warmed 1.4° F. Between 1950 and 2000 water temperatures rose about 2° F. These warmer air and water temperatures can change the plant and animal species in an area, contribute to expanding dead zones and algal blooms, and encourage the expansion of hardy invasive species such as nutria.
Much of the Chesapeake region is experiencing greater precipitation extremes and a 10 percent increase in average precipitation. The increasing precipitation and storm intensities will lead to greater volumes of runoff and associated toxic chemicals and nutrient pollution in Bay waters.
Water levels in the Bay have also risen, with nearly a foot of sea-level rise in some places. Many coastal marshes and small islands have already been lost to rising water, and more are at risk. These marshes provide important ecosystem functions by filtering pollution, protecting shorelines, and providing habitat. Sea-level rise will also affect salinity and distribution of freshwater in the estuary—and consequently the Bay's animals and plants.
Effects on waterfowl
Global warming poses a triple threat to waterfowl in the Chesapeake Bay. First, the summer breeding grounds of many of the Bay's migratory duck species are threatened. Many of these birds breed in the Prairie Pothole Region of south-central Canada and north-central United States, which has an abundance of small, shallow wetlands. With 50 percent of the nation's ducks coming from this area, it is the most important breeding ground for North America's migratory ducks. As the climate warms, these vital wetlands are expected to remain wet for shorter periods or dry up all together.
Effects on fish and shellfish
Researchers have linked the spread of new diseases and more frequent epidemics to global warming. In the Chesapeake, a new species of mycobacterium recently infected rockfish, and outbreaks are more common in other Bay fish as well. Diseases have decimated native oysters. Poor water quality, pollution, and habitat degradation are factors in these infections, but the stress of warmer water makes the species more vulnerable to disease.
Effects on submerged aquatic vegetation
Resource managers expect sea-level rise to have a direct effect on submerged aquatic vegetation in the Chesapeake Bay. As water depth increases, the sunlight available to the plants decreases, reducing their ability to photosynthesize. Higher water temperatures also affect underwater grasses. For example, higher water temperatures, in conjunction with turbidity and low-light conditions, have contributed to the decline of eelgrass in the last decade. Warmer water, in conjunction with turbidity and low-light conditions, kills the grasses. Some documentation indicates that grasses can recover when water conditions improve, but the trend towards further warming will have the opposite effect.
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Restoring the Bay
Today the Chesapeake Bay is in peril. We can see the results of human activities and natural events that affect the Bay's health and diversity. The Bay's ability to sustain life has diminished in visible and measurable ways. Key species have declined, threatening the sensitive ecosystem and the livelihoods of communities dependent on Bay harvests. Cutting forests to make way for development has destroyed natural protections for fragile shorelines, habitats, and water quality. The complex network of rivers and streams within the surrounding watershed carries pollution and heavy sediment loads downstream.
The Chesapeake Bay was the nation's first estuary targeted by the U.S. Congress for restoration and protection. In the 1970s Congress authorized a five-year study to analyze the rapid loss of wildlife and aquatic life that was devastating the Bay. The findings of this study led to creation of the Chesapeake Bay Program in 1983 to head the restoration of the Bay and its tributaries.
What you can do
You may think you have little impact on the Chesapeake Bay, but collectively the nearly 18 million people living in the Chesapeake watershed play a very significant role in the health of the Bay and its many tributaries. It will take the actions of all of us to successfully restore the Chesapeake. Simple everyday actions make a big difference if we each do our part to save the Bay.
Last updated: August 8, 2018