Extinction

More than a third of native California bird species could vanish from a wide swath of their current range by the end of the 21st century because of global warming, according to a new study by Audubon California.

Three Australian caves have yielded a treasure trove of fossils of ancient kangaroos, marsupial lions and giant lizards that roamed the outback for hundreds of thousands of years. These so-called megafauna went extinct about 45,000 years ago, shortly after humans arrived on the continent. Researchers, writing in Thursday's issue of the journal Nature, suggest that the extinction was the result of the human use of fire for hunting -- and not climate change, as some scientists have suggested.

Paleontologists have long assumed that intensive hunting by humans led to the extinction of the woolly mammoths about 12,000 years ago, but new genetic analysis indicates that inbreeding and loss of genetic variability was the cause. Paleontologists Ian Barnes of the University of London and Adrian Lister of University College London and their colleagues studied mitochondrial DNA samples from 96 bone, tooth and ivory specimens collected primarily in Alaska and Siberia.

A game of asteroid billiards may have set in motion the chain of events that wiped out the dinosaurs 65 million years ago, a team of researchers announced this week. According to the Czech-American team, the giant rock that hit Earth was probably a fragment from a collision in the asteroid belt about 100 million years earlier.

A rare European leech seems to be headed toward extinction as global warming dries out its Austrian forest home, scientists reported this week in the journal Naturwissenschaften. Researchers at German and Austrian universities found only one juvenile leech in birch forests near Graz, Austria, in searches from 2001 to 2005. Scientists had found 20 in the same forests in the 1960s. A five-degree rise in average summer temperatures since the 1960s dried out the forests where leeches lived.

The success story of the Pacific gray whales' full recovery from near-extinction is wrong, according to a new genetic analysis that pegs the current population at only one-third to one-fifth of historical levels. By examining subtle variations in DNA taken from 42 modern whales, scientists have concluded that between 78,500 and 117,700 gray whales lived before the heyday of commercial whaling in the 19th and 20th centuries.

British scientists have eliminated one potential explanation for the Neanderthals' extinction 26,000 to 32,000 years ago. Using a core sample of ocean sediment drilled from Venezuela's Cariaco Basin, researchers from the University of Leeds concluded that there were no significant changes in climate during the period. That leaves elimination of the Neanderthals by modern humans as the most likely explanation, they reported Thursday in the journal Nature.

One of the world's 7,000 distinct languages disappears every 14 days, an extinction rate exceeding that of birds, mammals or plants, researchers said Tuesday. At least 20% of the world's languages are in imminent danger of becoming extinct as their last speakers die off, compared with about 18% of mammals, 8% of plants and 5% of birds. The extinction of a language translates into a loss of knowledge, said K.

Climate change may cause as many as 30% of all land-bird species to become extinct by 2100 because food will become scarce as temperatures increase, according to a Stanford University study. Rising temperatures will limit the availability of plants and animals that serve as food for birds, according to the study, published this week in the journal Conservation Biology.

Bluefin tuna risk being fished to extinction in the Northeast Atlantic and Mediterranean Sea, a conservation group warned, appealing for an immediate ban on catches. The World Wide Fund for Nature said catches were running at 40% above the legal quota. It said boats from Libya, Turkey and European Union nations led by France were responsible for most of the illegal and unregulated catches.