Posted on 27-3-2003

Bird Populations Plummet Under Weight of Humanity
By J.R. Pegg

WASHINGTON, DC, March 24, 2003 (ENS) - Bird species today face a wave of extinction not seen on Earth since the dinosaurs died out some 65 million years ago, according to a new report from the Worldwatch Institute.

Pressures from a human population of more than 6.2 billion have put about 12 percent of the world's 9,800 bird species at risk of extinction, the report finds, and species across the globe are showing increasing signs of distress.

This potential extinction wave has implications beyond the immediate fate of these bird species, says the author of the report, titled "Winged Messengers: The Decline of Birds."

Declining bird populations mark the "unraveling of delicate natural balances," said author Howard Youth.

Bird extinctions already far exceed the natural rate of loss, according to the report, with 103 extinctions occurring since 1800.

Island bird species have been, and continue to be, at particular risk of extinction at the hands of humans - 93 percent of bird extinctions recorded since 1500 have occurred on islands.

But now many species that reside on mainlands across the world face a long list of threats, including habitat loss, invasive species, chemicals, hunting, fishing and climate change.

Species face varying threats across the world based on local conditions, Youth said, but he found "there was a familiar rhythm to declines and dangers."

Habitat loss stands as the single greatest overall threat to bird species. Some 25 percent of the world's known bird species occur only within ranges of less than 50,000 square kilometers, and many of these now only have small pockets of natural habitat remaining.

Deforestation has jeopardized 85 percent of the world's most threatened species. Tropical species have in particular felt the brunt of deforestation. Replacement of natural forests with plantation monoculture does little to revive threatened species, Youth said.

Loss of wetlands and grasslands is wiping out critical habitat for many species, in particular migrating species that depend on these areas for food and shelter along their migratory paths.

Habitat loss often brings additional threats from human development, such as roads, power lines and communication towers. An estimated 40 million birds are killed in the United States each year by communication towers.

Some 25 percent of threatened bird species are at risk because of non-native species, including snakes, rats, cats, plants and insects.

This threat cannot be underestimated. The brown tree snake, for example, wiped out 12 of Guam's 14 land bird species by the 1980s, after less than 40 years on the island.

House cats and feral cats have quite a history of decimating bird species. These animals have contributed to the extinction of 22 bird species, and they kill an estimated one billion birds annually just within the United States.

Some insects threaten birds directly, such as the yellow crazy ant in Australia, and some indirectly, such as mosquitoes carrying the West Nile virus.

And the diverse array of songbirds on the Hawaiian Islands, Youth explained, face "a cocktail of threats" including introduced pathogens transmitted by non-native mosquitoes.

The impact on the native birds is increased because non-native bird species on the islands are largely immune to these pathogens and  promote their transmission.

Seabird species have been impacted by oil spills and face a serious threat from expanded use of pesticides, which kill millions of birds on water and on land.

Longline fishing has contributed to the 23 species of seabirds that are at risk, as has illegal hunting.

A third of the world's parrot species are threatened with extinction because people desire them as pets.

Climate change is a new and emerging threat to bird species, according to the report. How this threat will evolve is still uncertain, Youth said, but there is definite concern about the impacts to coastal habitat.

In addition, some migrating species, those that travel long distances as well as those that migrate shorter distances, seem to be responding to climate change by arriving earlier on nesting grounds, Youth explained. This could have implications for the long term stability of some populations, he said.

For example, some long distance migrants have arrived back at their traditional places at the traditional times to find that the insect populations they usually feast on have "already peaked due to accelerations brought on by warming temperatures."

Still, Youth finds some cause for optimism, including the potential of the trend toward protecting biodiversity for ecotourism.

He notes that successful conservation efforts are increasingly relying on critical partnerships between conservationists and local communities that take into account, the land, water resources, the local people and economy.

The rise of organic farming and sustainable agriculture, such as shade grown coffee, are other promising trends that are helping conservation efforts in developing countries.

"The actions needed to ensure a secure future for birds are the very same ones needed to achieve a sustainable human future," says Youth.

"Wildlife conservation must be worked into and be compatible with rural, suburban, and urban planning efforts that improve the prospects of the world's poor while making our cities and industries safer for all living beings," he says.

The author suggests a renewed focus on trying to prevent more species from falling into risky situations, and he maintains that enforcement of existing international laws and agreements would "go a long way toward saving the world's remaining bird diversity."

There is another key resource conservationists must use more to their advantage, Youth said, and that is the increasing number of bird watchers throughout the world.

Millions of people worldwide take time to watch and document birds in their communities, and this provides science with a growing pool of information about the status of bird species and their habitats.

This is vital for scientists because their understanding of bird species is far from comprehensive for many birds, especially species within Africa, Asia and the New World tropics.

There are still unknown bird species, as evidenced by the 2001 discovery of an owl in the island nation of Sri Lanka, the first new species found there in 132 years.

"Birds provide us with food, inspiration, a link to nature, and an alert system for detecting environmental ills," Youth concluded. "But today, this feathered resource is in great need of human attention."

"Winged Messengers: The Decline of Birds" is available from Worldwatch Institute at: www.worldwatch.org/pubs/paper/165/