Flight of the oriole Global warming: Bird migration, survival linked to worldwide curbs on greenhouse gases.


THE BALTIMORE ORIOLE evicted from Maryland's woodlands by the ravages of global warming? Sounds like a story from the supermarket tabloids, but it is the latest warning from the World Wildlife Fund about the catastrophic climatic and habitat changes in store for the planet if man-made greenhouse gases go unchecked.

The immediate cause for such alarm is an effort to persuade the U.S. and other nations to agree to binding international limits on the burning of fossil fuels that produce carbon dioxide, which accumulates in the upper atmosphere and traps heat that warms the Earth. The U.S. and other nations supported voluntary reductions of emissions in 1992 but current treaty negotiations favor mandatory limits because the non-binding accord didn't work.

Hotter, drier weather is shrinking coastlines as the sea level rises. It also is changing the timing of seasons, environmental alterations that threaten the migration of birds around the world, the wildlife organization says. The Chesapeake Bay and the Delaware Bay are among 15 critical migratory bird habitats in the world that are most threatened by global warming's effects on breeding grounds and food supply.

While scientists are uncertain how much the changing weather is to blame for reported declines in worldwide bird sightings, the problem is that migratory species may be lost long before the direct impact can be definitively proven. Many species are adapting, with earlier egg laying and migration, but the change may be happening too rapidly for others.

Computer models suggest climatic change is a principal factor in forcing birds such as the oriole farther north for the summer. Accelerating loss of wetlands, earlier onset of the spring season, warmer global temperatures and higher sea levels are factors that underpin the wildlife group's conclusions.

There is consensus that carbon dioxide levels and global temperatures have been rising since the last century, causing environmental change. The debate is over the human contribution, from auto pollution to coal-burning power plants, to this process. Industrial nations and developing nations are split on the binding controls needed and the enormous costs involved. These weighty, comprehensive decisions may seem all too remote, but the possible fate of high-flying songbirds helps to bring the issue down to earth.

Pub Date: 10/13/96

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