By the end of the century one in 10 species of birds in the world will be extinct and a further 15 per cent will be on the brink, according to one of the largest studies of avian biodiversity. It is estimated just over 1 per cent of bird species have become extinct in the past 500 years but habitat loss, disease and climate change will accelerate that tenfold in the next 100 years.
Stanford University in California found that the loss of birds will not only have an impact on other wildlife but could also increase the risk of disease hitting the human population. The report cites the recent decline of three species of Indian vulture, caused by the widespread use of a veterinary drug by local cattle farmers. The decline led to an explosion in the population of feral dogs feeding off dead cows, leading to 30,000 cases of human rabies a year.
"Our projections indicate that, by 2100, up to 14 per cent of species may be extinct and one in four may be functionally extinct, that is critically endangered or extinct in the wild," said Cagan Sekercioglu, who led researchers in the study. Functionally extent means that the genetic integrity of the species is so badly damaged (genetic inbreeding will occur), that even with intensive conservation attempts it will die out. "Even though only 1.3 per cent of bird species have gone extinct since 1500, the global number of individual birds is estimated to have experienced a 20 to 25 per cent reduction during the same period," he said.
A total of 11,046 species of plants and animals are threatened, facing a high risk of extinction in the near future, in almost all cases as a result of human activities. This includes 24 percent (one in four) of mammal species and 12 percent (one in eight) of bird species. The total number of threatened animal species has increased from 5,205 to 5,435. Indonesia, India, Brazil and China are among the countries with the most threatened mammals and birds, while plant species are declining rapidly in South and Central America, Central and West Africa, and Southeast Asia. Habitat loss and degradation affect 89 percent of all threatened birds, 83 percent of mammals, and 91 percent of threatened plants assessed. Habitats with the highest number of threatened mammals and birds are lowland and mountain tropical rainforest. Freshwater habitats are extremely vulnerable with many threatened fish, reptile, amphibian and invertebrate species.
"Given the momentum of climate change, widespread habitat loss and increasing numbers of invasive species, avian declines and extinctions are predicted to continue unabated in the near future," he added. The study involved analysis of all 9787 species of birds alive today, and of the 129 species that have gone extinct recently, to produce one of the most comprehensive databases ever compiled into the state of one class of animals.
Using a computer forecast, based on present rates of decline, the researchers found that just over one in four species is now prone to extinction and 6.5 per cent are "functionally extinct". A quarter of fruit-eaters and omnivores are in danger, along with a third of herbivores, fish-eaters and scavengers. In the worst-case scenario put forward in the study, published in the journal Proceedings of the National Academy of Sciences, the researchers predict that threatened bird species will increase by 1 per cent each decade.
"These assumptions are conservative, since it is estimated that every year natural habitats and dependent vertebrate populations decrease by an average of 1.1 per cent," the study said. Gretchen Daily, a member of the research team, said it might be difficult to imagine how the loss of a particular species of bird can cause an outbreak of human disease. "Yet consider the case of the passenger pigeon. Its loss is thought to have made Lyme's disease the huge problem it is today. "When passenger pigeons were abundant and they used to occur in unimaginably large flocks of hundreds of millions of birds, the acorns on which they specialised would have been too scarce to support the large populations of deer mice, the main reservoir of Lyme's disease, that thrive on them today," said Professor Daily
Auks are a common group of marine birds comprising 22 species, and include guillemots and puffins. The largest species, the Great Auk, became extinct in 1844. Auks are weak fliers, (the Great Auk was completely flightless), but excellent underwater swimmers. When submerged, they propel themselves with their wings, steering with the feet. The legs are near the tail, giving the birds an upright posture on land, like that of a penguin. Living auks weigh from 90 grams to 1 kg. The Great Auk weighed 5 kg. Auks apparently originated near the Bering Sea, and presently occur in the North Pacific, North Atlantic, and Arctic Oceans. The Great Auk inhabited temperate and subarctic waters (Northern Britain, Iceland, Greenland, and Newfoundland), moving further south in winter. Except during the breeding season, auks live in the open sea. The diet of auks consists principally of fish, but also includes many other types of marine organisms. Most auk species breed in large colonies, choosing coastal cliff ledges, crevices, and burrows for their nests. Males and females share the task of incubating the one or two eggs, a process which requires four to six weeks. Depending on the species, the chicks remain in the nest for a period of two to fifty days.
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