ENVIRONMENT: Global Warming Threatens Migratory Birds

By Jim Lobe Reprint | | Print |

Jim Lobe

WASHINGTON, Sep 19 1996 (IPS) - Like the canary taken down into the coal mines to warn miners of methane gas, migratory birds are telling humans that the earth’s climate is changing, according to a report released here Thursday by the World Wildlife Fund (WWF).

And, like that unfortunate canary, migratory birds are far more threatened by the dangers posed by changes in the world’s climate than the humans around them, according to the report, titled, ‘Interrupted Flight: Climate Change Impacts and Bird Migration.’

“Global warming will undoubtedly wreak havoc with the migration cycle of many bird species,” according to Adam Markham, author of the new report which calls for governments to commit themselves to strict limits on the emission of carbon dioxide and other “greenhouse gases.”

The report, part of a WWF campaign on global climate change, comes amid growing concern over the impact of global warming on human populations and health, even as oil and gas companies and some oil-producing states insist that there is still no conclusive proof that the burning of fossil fuels contributes to the phenomenon.

According to most climatologists and atmospheric scientists, such emissions are expected to warm the earth’s surface by as much as 3.5 degrees Fahrenheit by the end of the next century.

In a major policy change in July, the administration of U.S. President Bill Clinton announced that it will seek a binding treaty to reduce greenhouse gas emissions at an international conference in Tokyo late next year. Until then, Washington had supported a 1992 accord that set non-binding targets for reducing emissions.

Most industrialised countries, including the United States, have failed to meet those targets which is why Washington is now calling for mandatory reductions.

Migratory bird species are especially vulnerable to climate change, because of both the enormous distances they travel — in some cases, tens of thousands of kms — and the variety of sensitive habitats on which they rely, according to the report.

The greatest current threat to migratory birds is the loss of habitat due to human activity, including the destruction of forests, drainage of wetlands, water pollution, and the development of coastal areas, the report says.

But global warming now looms as an even greater threat, because it may affect “their chances for survival on every leg of their migratory journey — at the breeding grounds, at the wintering grounds, and at the stops in between.”

“The effect of global warming on bird migrations is like a family setting out on a cross-country road trip only to discover that all of the gas stations, hotels, and restaurants are closed,” says Markham, who directs the WWF’s Global Climate Change Campaign. “You wouldn’t get too far and you might not even survive.”

Already, scientists and birdwatchers are reporting changes in bird migrating patterns, much as one recent study of a butterfly, the Edith’s Checkspot, found that its migrating range had shifted 150 kms to the north over the last century as average temperatures rose by about one degree Fahrenheit.

“The birds are likely moving now, but their habitat is not,” says Dr. Jeff Price, director of the American Bird Conservancy’s Important Bird Area.

The specific climate-related threats faced by the birds include rises in sea level and coastal flooding; changes in the timing of the seasons; and drier weather in certain regions, according to the report.

Coastal wetlands are among the ecosystems that are most vulnerable to climate change, according to the report. Tidal deltas, sandy beaches, barrier islands, mudflats, salt marshes, mangroves, and lagoons all provide rich feeding grounds for migratory shorebirds, providing them with the nutrients they need to cover great distances.

During the last century, sea level has risen by between 10 and 25 cms, and the rate of rise is expected to be two to five times that over the next 100 years. Apart from the flooding of coastal areas, sea-level rise can destroy coastal freshwater systems, according to the report.

The result is rapid changes in the vegetation and animal life of these sensitive coastal areas in such a short span of time that the birds have no opportunity to adjust their diet, according to the report.

Global warming is already affecting the timing of bird migrations, the report says. In the United States, for example, species of spring migrants are arriving earlier in the Upper Michigan Peninsula than before — at the rate of about one day for every ten years — and scientists and birdwatchers report similar phenomena elsewhere.

That could be catastrophic for species such as the Red Knot, Ruddy Turnstone and Sanderling which rely on the eggs of millions of horseshoe crabs that emerge from the Atlantic Ocean into the Delaware Bay on their journey northwards. But climate change may cause the birds to arrive earlier, before the crabs, whose life- cycle is not geared to temperature change, hatch.

Inland, too, warming could have disastrous effects on migrating birds, especially as the climate in some areas becomes drier. These include the Great Plains of North America, the Mediterranean Basin, and parts of southern Africa.

Of greatest concern is the Arctic tundra, summer home to many species of shorebirds. The Western Arctic has just experienced its warmest decade on record. Disappearance of the tundra, which would result from the melting of its permafrost, would threaten species such as the Snow Goose and the Sanderling.

In addition to the Arctic, the report identifies 14 major wetlands frequented by migratory birds as those most threatened by climate change, ranging from the Great Salt Lake to Tierra del Fuego in the Americas and from the Solway Firth in the British Isles to the Zambezi Valley in southern Africa.

The wetlands of the Mediterranean, the Chesapeake and Delaware bays of the eastern United States, the Coppename River of Suriname, the Banc d’Anguin off Mauritania, the Sunderbans mangroves of Bangladesh and India, and the deltas and estuaries of the Mekong and Yangtze rivers are also critical bird areas under greatest threat from global warning, according to the report.