Chesapeake Bay

The Chesapeake Bay is the largest estuary in the United States. It runs north-south from the mouth of the Susquehanna River to the Atlantic Ocean. It is one of the most productive estuaries in the world, with over 3,600 species of animals and plants. The bay provides vitally important habitats for wildlife, lots of recreational opportunities for people, and is an important fishery upon which both people and wildlife depend.


The Chesapeake Bay watershed includes parts of six states and is home to some 17 million people, including the cities of Washington, D.C., and Baltimore, Maryland. The watershed's many rivers provide people with not only drinking water, but also places for fishing, boating, and birding opportunities. Its wetlands are also sites for boating, along with bird-watching and waterfowl hunting.

The bay itself is popular for boating and recreational fishing. The Chesapeake's commercial fishery is worth billions of dollars and includes blue crabs, rockfish, menhaden, and eastern oysters. The bay also includes two of the biggest East Coast commercial ports—Baltimore and Hampton Roads.


The Chesapeake Bay is a very large and complex ecosystem with many kinds of wildlife habitats, including forests, wetlands, rivers, and the bay estuary itself. The bay supports over 3,600 species of plant and animal life, including more than 300 fish species and 2,700 plant types.

The waters of the bay are a mix of saltwater and freshwater. Saltwater comes into the bay from the Atlantic Ocean and freshwater enters through rivers and streams, as well as through underground water flows called groundwater. Many of the bay's wildlife, including the blue crab and waterfowl, depend on underwater bay grasses that grow in the shallow waters.

Around 350 varieties of fish live in the bay, including some that prefer freshwater, such as the pumpkinseed; some that are migratory, such as the summer flounder; and some that move between freshwater and saltwater, such as the American shad. Four kinds of sea turtles come to lower reaches of the bay: the loggerhead, Kemp's ridley, leatherback, and green sea turtle.

Hundreds of invertebrates, like the blue crab and the oyster, and other less edible but important species such as the horseshoe crab, also call the bay home. Oysters, once very populous in the bay, have greatly declined. Oysters filter and clean water, and their loss has affected the water quality of the bay and the health of other species.

Different birds inhabit the bay during different times of the year, from raptors such as bald eagles and ospreys, to waterfowl like swans and ducks, and migratory birds like sanderlings and ruby-throated hummingbirds. The region's beaches support some of the largest populations of shorebirds in the Western Hemisphere, such as the red knot and piping plover. For waterfowl, the Chesapeake is a major stopover site and wintering ground along the Atlantic Flyway. Every year, one million waterfowl winter in the Chesapeake Bay region.

Threats & Conservation

Land Use and Pollution

The millions of people living in the Chesapeake Bay watershed have made their imprint upon its lands and waters. About 55 percent of the watershed is forest, while the rest has been converted by people for agricultural (30 percent) and suburban and urban uses (9 percent). These land use changes have impacts on the bay.

One of the bay's biggest problems is too many nutrients in the water. Excess nutrients come from many sources, including treated wastewater, runoff from agricultural areas, runoff from suburban areas such as lawn and garden fertilizers and septic systems, and even air pollution.

Although it may not sound like a bad thing, too many nutrients can cause a lot of problems in the bay. Phosphorus and nitrogen are limiting factors for plants. With the addition of runoff nutrients, algae plants have nothing to keep them in check, so they grow into giant blooms. Algae blooms blocks sunlight that underwater bay grasses need to survive. Many bay species depend on grasses for food and protection. Algae blooms also take oxygen from the water that species like crabs and oysters need to survive.

Forests and wetlands can serve as a sink for excess nutrients—absorbing them before they reach the bay. But in urban and suburban areas around the Chesapeake Bay, many of the forests and wetlands have been removed. A hundred acres of forest habitat in the bay watershed are lost each day due primarily to development.

The watershed is covered with too much pavement and other hard surfaces that water cannot run through, such as roads, rooftops, sidewalks, and parking lots (also called "impervious surfaces"). These hard surfaces make up 21 percent of all urban lands in the bay watershed. Not only do they contribute to the excess nutrients (by making it easier for nutrients to be picked up by rain), they also have their own set of problems. Water that falls on these surfaces cannot be slowly absorbed into the ground to replenish area groundwater, but instead flows quickly into streams and rivers, causing erosion, or directly into storm sewers, causing flooding.

Climate Change

Climate change threatens to not only exacerbate many of the environmental threats already facing the Chesapeake Bay, it is also causing a rise in sea level that is eating away the diverse estuaries and wildlife habitat. The Chesapeake Bay is our nation's largest estuary and sustains more than 3,600 species of plants, fish, and animals. If climate change continues unabated, projected rising sea levels will significantly reshape the region's coastal landscape, threatening waterfowl hunting and recreational saltwater fishing in Virginia and Maryland.

With its expansive coastline, low-lying topography, and growing coastal population, the Chesapeake Bay region is among the places in the nation most vulnerable to sea level rise. Average sea levels in the Chesapeake Bay have been rising. Many places along the bay have seen a one-foot increase in relative sea level rise over the 20th century, six inches due to climate change and another six inches due to naturally subsiding coastal lands—a factor that places the Chesapeake Bay region at particular risk. Already, at least 13 islands in the bay have disappeared entirely, and many more are at risk of being lost soon. Sea level rise in the Chesapeake Bay region could reach 17 to 28 inches above 1990 levels by 2095.

Delaware Bay: As sea level rises, Delaware Bay's marshes—which provide valuable habitat for waterfowl and nursery ground for fish—will be inundated with greater frequency. In Delaware Bay, a 27.2-inch rise in sea-level would mean a 92 percent decline in brackish marsh, a three-fold increase in saltmarsh, and a 13 percent increase in open water. In some areas, the marshes will be able to migrate inland, allowing continued viability of the habitat, however it will contribute to a loss of nearly 41,000 acres of undeveloped dry land. In total, 41 percent of marshes are predicted to be lost across the region by 2100. In addition to supporting many waterfowl species, these coastal marshes are important nursery and spawning grounds for multiple fish species, including Atlantic menhaden, bluefish, flounder, spot, mullet, croaker, and rockfish.

Maryland Shore: The considerable low-lying marshes and dry lands of the Eastern Maryland Shore region are at risk from sea-level rise over the next century. Along the Maryland Shore, a 27.2-inch rise in sea-level would mean a 47 percent decline in brackish marsh, a 38 percent decline of its tidal swamp, and all but 32 acres of tidal flat. The brackish marsh habitat of Kent Island and the Eastern Neck Island National Wildlife Refuge are especially at risk of inundation. As the soil saturates, freshwater swamps will expand by about 20 percent across the region.

Blackwater National Wildlife Refuge: This refuge is a crown jewel among Chesapeake Bay's treasured places. Unfortunately, it could be largely underwater by 2100. Dramatic habitat losses are predicted for the refuge and surrounding areas, where global sea-level rise is compounded by high rates of land subsidence due to groundwater withdrawal for agriculture and relatively lower rates of natural accretion in marshes.

The site is predicted to lose over 90 percent of its tidal fresh marsh, tidal swamp and brackish marsh, which are converted to saltmarsh and—ultimately—open water.

The loss of brackish marsh could be particularly harmful to species that have adapted to these habitats, including rockfish and white perch, as well as anadromous species such as herring and shad, which use brackish marsh habitat as they transition between their freshwater and saltwater life cycles.

Similarly, the loss of tidal fresh marshes could affect minnows, carp, sunfish, crappie and bass, which depend on these habitats for shelter, food, and spawning.

Virginia's Eastern Shore: Virginia's Eastern Shore faces a dramatic loss of estuarine and ocean beaches. By 2025, estuarine beach is projected to decline by 52 percent and ocean beach by 26 percent. By 2100, more than 80 percent of these beaches could disappear and be converted to open water. Like other regions around the bay, the peninsula is projected to lose more than half of its brackish marsh by 2050, with a nearly complete loss by 2100.

The extremely rare sea-level fens are also at risk. Located upland of wide, ocean-side tidal marshes on the upper east side of the peninsula, these habitats are comprised entirely of open, freshwater wetlands whose primary water source is groundwater. Only certain types of plants and animals can thrive in the fens, including the ten-angled pipewort, carnivorous sundew, bladderwort, elfin skimmer dragonfly, and eastern mud turtle.

Upper Tidewater Region: The extensive tidal swamp, brackish marsh, and tidal flat habitats of the Upper Tidewater Region could undergo major shifts due to climate change. If sea level rises 27.2 inches this century, the region would face a 30 percent decline in tidal swamp, an 85 percent decline in the area of brackish marsh, and a 76 percent decline in tidal flats. In addition, Plum Tree Island National Wildlife Refuge, home to many species of migratory waterfowl, would largely disappear.

At the same time, that amount of sea level rise is projected to cause a 33 percent expansion of freshwater swamp area, which includes both forested and scrub-shrub habitat, with notable expansion into the undeveloped dry land along Mobjack Bay. Overall, the area of undeveloped dry land across this site declines by 17 percent, or 45,611 acres.

Lower Tidewater Region: The Lower Tidewater Region, including the cities of Norfolk and Virginia Beach, has extensive urban development surrounded by agricultural and conservation lands.

Nearly 20 percent of undeveloped dry land at this site is at risk of inundation, mostly as rivers widen and transitional marsh and saltmarsh expand. While these undeveloped lands provide opportunities for habitats to migrate inland, pressure to develop some of these lands will likely increase because human population in this part of Virginia is projected to grow considerably in the coming decades. Proactive measures to identify and protect lands where habitats can migrate will be critically important. In addition, the region is projected to face a 79 percent loss of ocean beach by 2100, without extensive beach re-nourishment.

Tangier Sound: The sound is home to some of the bay's larger islands--including Smith, Deal, and Tangier--the majority of which could be gone by 2100. Towns on the mainland, like Crisfield, will also see surrounding wetlands disappear and undeveloped dry land inundated by rising seas.

Thousands of acres of brackish marsh in this region will be converted to salt marsh and open water, possibly ravaging lucrative commercial and recreational fisheries that depend on healthy marshes. The critical seagrass beds in this area are also at significant risk from sea-level rise and increased deposition of sediments from the Blackwater area to the north.

Our Work in the Chesapeake Bay

The Mid-Atlantic region is defined by one unifying feature: water. In 2009, we helped launch the Choose Clean Water Coalition to advocate for restoring the thousands of streams and rivers flowing to the Chesapeake Bay. The coalition brings together more than 200 organizations from Pennsylvania, New York, Maryland, Delaware, Virginia, West Virginia, and the District of Columbia to advocate for clean water. (Read more about our work in the bay.)


Chesapeake Bay Program
Chesapeake Mid-Atlantic Regional Center, National Wildlife Federation
National Park Service Chesapeake Bay Office
National Oceanic and Atmospheric Administration Chesapeake Bay Office

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Where We Work

More than one-third of U.S. fish and wildlife species are at risk of extinction in the coming decades. We're on the ground in seven regions across the country, collaborating with 52 state and territory affiliates to reverse the crisis and ensure wildlife thrive.

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Regional Centers and Affiliates