Humans Wipe Out Pacific Island Birds in Mass Extinction Event, Killing Hundreds of Species
Only a few thousand years ago, a wide variety of birds flourished on the numerous islands scattered throughout the Pacific Ocean. Yet when humans began to colonize these remote locations, the diversity quickly plummeted, leaving the islands with only a few species of these birds. So what exactly happened? Researchers have found that the most recently colonized places on Earth suffered a mass extinction event.
Although scientists were aware that many landbird species, ones that don't perch, died out after the first arrival of people on these islands, they were not sure exactly how many ceased to exist. Estimates ranged from 800 to 2,000 different species that disappeared once humans began hunting them. The main reason for these greatly differering estimates is that the fossil record available is somewhat spotty.
"Relatively few fossils have been collected from a lot of the islands that have been studied," said Richard Duncan, one of the researchers, in an interview with io9. Because fossils are only preserved in certain types of sites, it's difficult to locate these "specialized habitats." Thus, researchers have little to work with when it comes to estimating species loss.
Humans first arrived on the Pacific Ocean islands about 3,500 years ago, settling in locations such as Fiji and the Marianas. About 700 years ago, they spread out fully to the more remote islands, such as Hawai'i and Rapa Nui. The flightless birds that made their homes on these islands didn't stand a chance against hunting and habitat loss.
In order to find out exactly how many bird species were lost, though, Duncan and his colleagues used available data in order to refine extinction estimates. They focused on nonpasserine landbirds, which are much better preserved in the fossil record due to their larger bones. In particular, they looked at the extinction question as a "mark-recapture" problem. This method is used by ecologists to estimate the size of an animal population by capturing and tagging a portion of the population.
After performing calculations for a total of 41 Pacific Islands, the researchers found that a staggering two-thirds of nonpasserine landbird populations on the islands died off after the arrival of people. In other words, 983 species of birds became extinct--not including seabird and passerine bird extinctions.
"If we take into account all the other islands in the tropical Pacific, as well as seabirds and songbirds, the total extinction toll is likely to have been around 1,300 species," said Tim Blackburn, one of the researchers, in an interview with RedOrbit.
The study shows how much of an impact people can have on species, and reveals that massive rate of extinction that can occur if precautions aren't taken.
"To put it in context: This is probably the largest extinction event we've witnessed that was caused by humans," said Duncan in an interview with io9.
The findings are published in the Proceedings of the National Academy of Sciences.