Humans May Have Driven Twice as Many Bird Species to Extinction as Previously Thought

Statistical modeling of undiscovered extinctions suggests 1,430 bird species have disappeared during modern human history

illustration of birds in a forest
This A.I.-generated illustration shows what some of the undiscovered extinct birds might have looked like. U.K. Center for Ecology & Hydrology

Humans have likely driven 1,430 bird species to extinction—twice as many as previously estimated, according to new research.

Scientists used statistical modeling to calculate the total number of bird extinctions that have occurred during modern human history. In addition to known extinctions, the model also factored in undiscovered, or “dark,” extinctions of species that disappeared before humans could identify them.

Based on the new estimates, published Tuesday in the journal Nature Communications, scientists now estimate nearly 12 percent of bird species have died out since the Late Pleistocene around 130,000 years ago.

Humans were likely responsible for the demise of most of those species, especially on islands, where animals are especially vulnerable to intervention. When humans first set foot on isolated lands such as the Azores, Hawaii and Tonga, they brought with them invasive rats, pigs, dogs or other animals that outcompeted birds for food or raided their nests. Across the planet, people doomed birds through deforestation, overhunting and fire.

Scientists know about bird species that have gone extinct since the 1500s, when written observational records began. But to learn about birds that lived or died before that, they have to rely on fossils. This gives scientists an incomplete picture, because birds have hollow, lightweight bones that disintegrate easily. Avian skeletons are only preserved as fossils under “extraordinary circumstances,” per the American Museum of Natural History.

Previous estimates, based on written records and the few fossils that exist, have suggested around 640 bird species have gone extinct since the Late Pleistocene. But researchers suspected the number was actually much higher because of gaps in the fossil record.

“We know we have lost iconic birds like the dodo, but we wanted to get a better estimate of the bird extinctions we didn’t know about,” says study co-author Rob Cooke, an ecological modeler at the U.K. Center for Ecology and Hydrology, to the Guardian’s Sophie Kevany.

The team created a computer model to estimate the true number of bird extinctions. In addition to the 640 known extinctions, their model suggested an additional 790 previously unknown species had also disappeared. Only about 50 of those birds would have gone extinct naturally, the scientists say, and humans were responsible for killing off the rest, according to a statement.

“The sobering thing is that this estimate could actually be conservative,” says Jamie Wood, an ecologist at the University of Adelaide in Australia who was not involved in the research, to Nature News’ Gemma Conroy.

Humans were particularly damaging to birds in the Pacific—this region alone accounts for an estimated 61 percent of the total avian extinctions and 70 percent of the “undiscovered” ones, per the study. When 14th-century explorers arrived at sites like Hawaii and the Cook Islands in the eastern Pacific, they contributed to the demise of about 570 species—which is nearly 100 times the rate of natural extinction, according to the scientists.

The loss of so many birds is troubling in its own right. But these extinctions also likely had “cascading harmful effects on ecosystems,” since birds play a vital role in pollination and seed dispersal, says study co-author Søren Faurby, a biologist at the University of Gothenburg in Sweden, in the statement.

“These historic extinctions have major implications for the current biodiversity crisis,” he adds. “We will have lost a lot of plants and animals that depended on these species for survival.”

Today’s birds face new human-caused threats—including climate change and pollution. In North America alone, an estimated 2.9 billion individual birds have disappeared since 1970—a steep population decline of roughly 29 percent, or more than one in four birds.

Additionally, previous modeling research from the team predicts an additional 700 bird species could go extinct within the next few hundred years, unless humans change their behavior.

“Whether or not further bird species will go extinct is up to us,” says Cooke in the statement. “Recent conservation has saved some species, and we must now increase efforts to protect birds.”

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