[obol] bird extinctions

[DJLauten and KACastelein]

Published on Tuesday, July 4, 2006 by the San Francisco Chronicle
Where Are All the Birds?
Startling New Figures on Rate of Extinctions Say 12% of Species to be in 
Peril by 2100
by Jane Kay


The world's birds are disappearing in greater numbers than previously 
calculated, and the number of extinctions will grow even more 
dramatically by the end of the century, according to a grim study 
published today in the journal Proceedings of the National Academy of 
Sciences.

The study, the most thorough analysis of global bird species, says 12 
percent of existing species -- about 1,250 -- are threatened with 
extinction by 2100.

Up until now, scientists had documented the extinction of about 130 bird 
species since the year 1500. But the study's authors -- from Stanford 
University, Duke University and the Missouri Botanical Garden in St. 
Louis -- say the more accurate estimate is about 500 extinctions out of 
more than 10,000 known bird species. That would be about one extinction 
per year over the last 500 years.

And that rate is 100 times higher than what was considered natural 
before human influence, the study said.

Over time, humans have cleared land for agriculture and other uses. 
They've hunted birds for food and sport. And they introduced other 
dangers, such as non-native birds, rats, snakes and diseases. 
Predictions of increased extinctions over the next century are based on 
these continuing threats as well as anticipated habitat loss linked to 
global warming.

Scientists say the decline of both the diversity and abundance of birds 
portends problems for the planet. Birds play a part in seed dispersal, 
plant pollination and insect control.

Critically endangered birds -- including the California condor and about 
12 Hawaiian species -- are seen as most at risk of extinction.

The new study's extinction calculations include previously unknown bird 
species only discovered as fossilized remains as well as bird species 
missing for scores of years but never officially declared extinct. It 
also takes into account species wiped out by humans before modern 
scientific description began in the mid-1700s.

Local species may have disappeared without a trace, and the more fragile 
small bird species "may easily have gone extinct without leaving a 
record,'' the study says.

"The extinctions all have to do with people in one way or another,'' 
said Peter Raven, president of the Missouri Botanical Garden, one of the 
world's three major botanical gardens. Raven began studying plant and 
animal extinctions 40 years ago at Stanford University.

The predominant threat to species now is habitat destruction, the study 
said. Brazil, where habitat loss has been severe, has 89 species at risk 
of extinction, including 13 species identified since 1980, according to 
BirdLife International, a British nonprofit registry of bird species.

Many scientists, including Harvard University entomologist E.O. Wilson, 
believe that Earth is in the middle of a mass extinction comparable to 
the one 65 million years ago that wiped out two-thirds of land species, 
including the dinosaurs.

"That's about the magnitude of what we expect to see during the 21st 
century,'' Raven said.

Since 1975, there have been 20 extinctions of wild species, six of which 
involve species that now survive only in captivity.

Conservation efforts have spared an additional 25 species from 
extinction, the study said.

In a separate study scheduled for publication, Stuart Butchart, global 
species program coordinator for BirdLife International, and colleague 
Alison Stattersfield also credit modern conservation efforts for saving 
two dozen bird species.

The Butchart group released a paper last month that also increased 
former extinction numbers. It also added that many missing species, such 
as the hooded seedeater of central Brazil, haven't been seen since the 
1800s but haven't been declared extinct by the IUCN, also called the 
World Conservation Union.

At the California Academy of Sciences, the curator of birds and mammals, 
Jack Dumbacher, said the new extinction estimates are disturbing.

"Birds are an important component of our ecosystem. They keep mice and 
rats in control and eat insects that attack crops. They are food for 
other organisms and create habitat for other organisms. They disperse 
seeds and pollen. There are cases on islands when birds go extinct that 
the trees also go extinct,'' Dumbacher said.

He spoke of birds' tremendous economic value, not only as protectors of 
crops but also as sources of meat, eggs and fiber. Bird watching is a 
multimillion dollar industry of tours, magazines, books and nature-based 
travel.

"That's the way a lot of people learn about wildlife,'' he said.

In addition to Raven, authors of the new study include Stuart Pimm, Duke 
University professor of conservation ecology; and Paul Ehrlich, 
president of the Center for Conservation Biology and Bing Professor of 
Population Studies at Stanford University.

Gone since 1500

About 500 of the planet's bird species have become extinct since about 
1500, according to a study published today. That includes many species 
of birds from what is now the United States. Here are some of the 
country's now-extinct birds and where they once lived:

     Passenger pigeon, east of the Great Plains; last captive bird died 
in 1914 in the Cincinnati Zoo

     Carolina parakeet, Eastern United States; last captive bird died in 
1918 at the Cincinnati Zoo

     Santa Barbara song sparrow, Santa Barbara Island; last observed in 1967

     Labrador duck, Northeastern United States; last specimen collected 
in 1875

     Black mamo, Hawaii; last specimen collected 1907

     Source: World Conservation Union

Email to: jkay at sfchronicle.com.

© 2006 San Francisco Chronicle

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