. Scientific Frontline: Human-driven extinction of birds much greater than previously known

Wednesday, December 27, 2023

Human-driven extinction of birds much greater than previously known

The dodo was endemic to the island of Mauritius. It could not fly and was exterminated by man during the 17th century.
Image Credit: German Rojas

On many of the world's islands, bird species began to become extinct with the arrival of humans. In a new study involving researchers from the University of Gothenburg and Uppsala University, it is estimated that humans have contributed to the extinction of around 1,400 bird species – twice as high as previously thought.

Because the lightweight bones of birds break down quickly, few fossils are formed. In the past, when scientists had to rely on observations and fossils, it was estimated that 640 species of birds had become extinct during the lifetime of modern humans, 90 percent of them on islands inhabited by humans. Classic examples are the dodo on Mauritius and the great auk in the North Atlantic, which, like penguins, could not fly.

However, by using statistical modeling, scientists now dare to estimate that around 1,400 bird species have become extinct.

“This is twice as many species as those that have left fossils as evidence of their existence. “Virtually all of these species were wiped out directly or indirectly due to human activity,” says Søren Faurby, a researcher in Zoology at the University of Gothenburg and co-author of the study published in Nature Communications.

Comparison with New Zealand

Much of the study was conducted at the University of Gothenburg, where researcher Rob Cooke led the work. The study team based their modelled estimates on known extinctions and the range of relevant research in different regions compared to the situation in New Zealand. That country is the only place in the world where the pre-human bird fauna is thought to be fully known, with well-preserved remains of all the birds there.

“Our study shows that humans have rapidly devastated bird populations through habitat loss, overexploitation and the introduction of rats and domestic animals that raided the birds’ nests and competed with them for food,” says Rob Cooke, who now works at the UK Centre for Ecology & Hydrology (UKCEH).

Tobias Andermann, who leads the Biodiversity Data Lab (biodiversity.se) at UU, analyzed the data for this study together with lead author Cooke. For this purpose, Andermann developed a custom-built Bayesian statistical model to predict the expected number of extinct bird species for different island systems.

“This study was an interesting exercise in quantifying how many species of birds have likely vanished from islands without ever being recorded by science. It is a sad but important reminder that there is a huge but often overlooked human impact on the hidden part of biodiversity, referring to all those species for which we don’t have data and which can disappear without us ever noticing.”

Major consequences

An extinct bird is not just a lost species. It can also have an impact on ecosystems, the researchers say.

“The world may have lost key functions for seed dispersal and pollination. This has widespread and damaging effects on ecosystems, so in addition to the birds, we have probably lost many plants and animals that depended on these species for survival,” says Faurby.

The study reveals that the largest human-driven vertebrate extinction event occurred in the 14th century, when 570 bird species were lost after humans first arrived in the eastern Pacific, including Hawaii. A similar period of mass extinction probably occurred in the 8th century BC in the western Pacific Ocean and the Canary Islands, which were populated at that time. We are currently living in a third such period that started in the middle of the 18th century.

Habitat restoration

Previous research by the authors of the study suggests that we are at risk of losing a further 700 bird species over the next hundred years. “Whether or not more bird species become extinct is up to us. Recent efforts have saved some species and we now need to step up efforts to protect birds, with habitat restoration led by local people,” adds Cooke.

Published in journalNature Communications

Source/CreditUppsala University

Reference Number: zoo122723_01

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