Warming seen as peril to bay birds Chesapeake put among 15 habitats in the most danger

Orioles might flee north

Conservation group notes rising seas, changes in seasons

September 20, 1996|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

WASHINGTON -- An international conservation organization says the Chesapeake and Delaware bays are among 15 "critical" migratory bird habitats around the world most threatened by global warming.

The World Wildlife Fund, in a report summarizing recent scientific research, says rising sea levels, changes in the timing of the seasons and drier weather in some locations have begun to alter breeding grounds and food availability, and could change them faster than some migratory birds can adapt.

Higher temperatures could even threaten to force the Baltimore oriole to Canada.

Jeff Price of the American Bird Conservancy said the oriole, which winters in Mexico and summers throughout the eastern United States, is already declining in Louisiana.

"It may be because it's too warm," he said, "but it also could be too many cats." If the cause is a change in climate, computer models suggest, the oriole will flee north from most of its current range -- including Baltimore -- in 50 to 75 years.

In any case, said World Wildlife Federation spokesman Lee Poston, "the first impacts of climate change can already be seen" in loss of habitat and inundation of coastal wetlands like those on the Chesapeake.

One-third of the marshes at the Blackwater National Wildlife Refuge on the Eastern Shore has been lost to rising seas levels and rapid erosion in the past 50 years, said Stephen P. Leatherman of the University of Maryland's Laboratory for Coastal Research. "Nobody knows quite how to stop it," he said.

Earlier springs around the world and longer summers in the Arctic could explain preliminary evidence of delays in the migration of the red knot, a species that refuels on the Delaware Bay.

If the flocks miss the emergence of certain insects and the bay's rich but brief bounty of horseshoe crab eggs, said Brian Harrington of the Manomet Observatory in Massachusetts, their migrations could fail and their numbers could plummet. Of 26 species of New World shorebirds studied, he said, 16 are in decline.

Poston said said such threats should encourage governments to reach binding agreements to reduce the combustion of fossil fuels, which release so-called greenhouse gases -- principally carbon dioxide -- into the atmosphere and contribute to global warming.

The Clinton administration has said that it will negotiate some form of "realistic" binding agreement on limiting such emissions. Prior U.S. policy called for voluntary limits.

Poston said individuals, too, should adjust their habits to minimize consumption of fossil fuels and to protect the habitats of migratory birds from urbanization.

Scientists generally agree that carbon dioxide levels have been rising since the 19th century and that global average temperatures have risen faster in this century than can be readily explained by natural processes. Last year was the warmest ever recorded.

Sea levels have risen an average of 6 inches worldwide in the past century, 70 percent of the world's beaches are eroding, and glaciers in many areas are in fast retreat.

In December, the United Nations' Intergovernmental Panel on Climate Change endorsed a consensus of 2,500 climate experts that there is a "discernible human influence" on global climate change.

But there is less agreement among scientists on how significant the human factor is and what natural processes might be at work to moderate the impact of man's activities.

Price said yesterday that "most species may be able to adjust" to global warming but that "we are likely to lose species" whose habitats are lost to rapid environmental changes.

"Whether that matters is a value judgment," he said.

The other 13 most-threatened migratory bird habitats include the Great Salt Lake, an important migratory stopover and breeding site threatened by evaporation and slackening rains; and the Arctic, which is experiencing earlier springs, shrinking permafrost and changes in vegetation.

Also included were wetlands around the Mediterranean; the Coppename River in Suriname and Tierra del Fuego, both in South America; the Wash and the Solway Firth, both wetlands in the United Kingdom; the Waddenzee in the Netherlands; and the Banc d'Arguin and the Zambezi Valley in Africa.

Wetlands in Bangladesh, India, Vietnam and China that are critical to migratory birds also were listed as threatened by flooding, erosion, rising sea levels and storms expected as a result of global warming.

Pub Date: 9/20/96

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