A study shows that almost 12 per cent of bird species have become extinct and humans are often to blame
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A new study, by the UK Centre for Ecology & Hydrology (UKCEH) and published in Nature Communications, has revealed that humans have wiped out 1,430 bird species – nearly twice as many as previously thought. The vast majority of these bird extinctions occurred on remote islands which had previously had minimal or no contact with humans.
Although birds are one of the most studied animal groups, our knowledge of them only goes back a relatively short way. Most studies into bird extinctions only look back as far as about the 1500s, and that’s because there’s very little data on distribution any further back than that. But, by taking a different approach, this new study was able to head right back down through human history to the Late Pleistocene period, 130,000 years ago. By doing so, they were able to estimate that twice as many bird species had gone extinct than we had previously realised. And, the report authors say, the majority of bird species vanished from the Earth due to human interference.
Studying bird extinction rates so far back in time is not without its problems. Because of the lack of data, scientists normally rely on fossilised birds, but because bird bones are so lightweight, they often disintegrate over time, so fossilised birds are rare. This meant that to come up with these latest figures the study authors used statistical modelling in order to estimate how many bird species became extinct before the species in question were even known to science. To do this the team based their modelling on New Zealand, because this is the only part of the world where – thanks to an unusually exceptional fossil record – it’s believed we know all bird species that existed before the arrival of humans and so know exactly what percentage of the overall species count went extinct after humans arrived in New Zealand. Through these calculations the study authors were able to come up with the 1,430 figure.
The study also discovered that the greatest number of bird extinctions occurred on remote island groups where birds had no few natural predators and no concept that mankind was generally best avoided. So, when humans did arrive the local bird fauna was often easy to catch and eat. And those birds that didn’t succumb to hunters were instead killed by the cats, rats and dogs that invariably sailed alongside man or were wiped out through habitat loss. Easily the most famous such example of an island bird species quickly brought to extinction when it first encountered man is the dodo.
Lead author of the study, Dr Rob Cooke, an ecological modeller at UKCEH, commented: ‘Our study demonstrates there has been a far higher human impact on avian diversity than previously recognised. Humans have rapidly devastated bird populations via habitat loss, overexploitation and the introduction of rats, pigs and dogs that raided nests of birds and competed with them for food. We show that many species became extinct before written records and left no trace, lost from history’.
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