The disappearing Chesapeake?

chesapeake_swamp.jpgThe National Wildlife Federation has just released an important new report “Sea-Level Rise and Coastal Habitats of the Chesapeake Bay“, which provides the most detailed and comprehensive view yet of the likely impacts of climate change on specific habitats within the Chesapeake Bay region. The full report , as well as a 12-page summary are available here.

Among the highlghts:

“Coastal habitats in the Chesapeake Bay region will be dramatically altered if sea levels rise globally about two feet by the end of the century, which is at the low end of what is predicted if global warming pollution remains unaddressed. Under this scenario, the region would lose:

  • More than 167,000 acres of undeveloped dry land
  • 58% of beaches along ocean coasts
  • 69% of estuarine beaches along the bay
  • 161,000 acres of brackish marsh
  • More than half of the region’s important tidal swamp

These important wetland habitats would be replaced in part by over 266,000 acres (415.6 square miles) of newly open water and 50,000 acres of saltmarsh.”

I participated in the press conference to summarize the likely effects on wildlife and ecosystems of the Chesapeake Bay. The story was reported by the Baltimore Sun, the Richmond Times-Dispatch, and the Daily Press, among others.

Here are the points I made:

There’s now strong international consensus among scientists that climate change is real, and already happening. But most previous research has focused on very broad continental scales. The new report by the NWF is important because it shows in unprecedented detail how climate change is affecting our local Chesapeake Bay region.

The bottom line is that this is not a future threat. Rising temperatures and sea levels are already changing distributions, life cycles, and interactions of key animals and plants in our area. And those changes are disrupting important ecosystem services that coastal communities depend on—fisheries, water quality, shoreline protection.

The life cycles of animals and plants are closely tied to temperature, which determines when they emerge from dormant stages, reproduce, start seasonal migrations, and so on. For example, recruitment of commercially important fish and shellfish is highly sensitive to variation in both temperature and rainfall patterns. Springtime in the Chesapeake is starting about three weeks earlier now than it did in 1960. And the summers are getting hotter. In the Chesapeake, we may be in danger of losing more northerly species such as winter flounder and softshell clams.

blue_crab.JPGOne serious concern involves how changing climate affects “foundation species”, that is, key species that support entire ecosystems. One of these is eelgrass, an underwater plant that forms dense meadows throughout Chesapeake Bay and is a critical nursery habitat for young fish and shellfish, including blue crabs, rockfish, and speckled trout, among others.

Eelgrass is highly vulnerable to climate change, first because it’s near the southern end of its distribution in the Bay and thus already near the highest temperatures it can tolerate, and second because it’s already stressed from poor water quality. We got a preview of this in summer 2005 when we had record high water temperatures throughout the mid-Atlantic region. Eelgrass was wiped out in a matter of weeks from large areas of the Bay, and still hasn’t returned to some.

A few more hot summers like 2005 could give eelgrass the one-two punch that knocks it out for good. That would be bad for the animals it supports and for the coastal communities that depend on them.

Another set of threatened foundation species are the plants that support wetlands such as brackish marshes. These are important in literally holding the land together by trapping sediments to make soil. Roughly two thirds of the Chesapeake region’s commercial fishes depend on coastal marshes for nursery and spawning grounds, and these are highly sensitive to both habitat quality and climate.

blackwater_heron.jpgChesapeake wetlands have been declining fast in recent decades. The classic example is the Blackwater National Wildlife Refuge in Maryland, which has been called the “Everglades of the North” because of its great abundance and diversity of wildlife, including the largest population of bald eagles north of Florida.

Blackwater illustrates well how climate change interacts with other stresses. Over the last seventy years, it’s lost a third of its marsh area to sea level rise, sinking of the land, and overgrazing by nutria, an alien rodent. The nutria is currently kept from spreading north largely by its intolerance of cold winters, and there’s real concern that it could spread as winters warm.

Finally, an important impact of climate change is that it alters interactions between species that respond differently to changes, with important implications for food chains and ecosystems. One important case involves the oyster disease Dermo, which proliferates in warmer waters. Starting in the mid-1980s, Dermo spread rapidly up the East Coast from Chesapeake Bay during a series of unusually mild winters and is now found up through Maine, with major consequences for the oyster industry.

These changes have fundamental consequences for coastal ecosystems, economies, and ways of life.

About Emmett Duffy

I am a Natural Patriot and an ecologist with expertise in biodiversity and its importance to human society. My day job is Professor of Marine Science at the College of William and Mary in Virginia.
This entry was posted in Biodiversity, Biophilia, Oceans, Science, Sustainability and tagged . Bookmark the permalink.

One Response to The disappearing Chesapeake?

  1. Jeff says:

    That’s a real shame, the Chesapeake Bay area is one of the most beautiful areas in the whole country. Hopefully we can help to slow down the climate change, or at least resolve some of the issues that become of it.