Humans have wiped out more birds than thought

Humans have wiped out more birds than thought

All of these birds have been gone for a long time: This AI-generated image shows what some of the bird species that were extinct in prehistoric times may have looked like. © UKCEH

The dodo was just one of many: humans have wiped out more bird species throughout history than long thought, a study reveals. According to this, more than 1,400 bird species have become extinct due to our influence in the last 130,000 years - at least. This is the largest human-caused vertebrate extinction in history, as the researchers report. Almost everywhere, the arrival of humans in new areas has resulted in the disappearance of bird species - and bird deaths continue.

Whether through hunting, the theft of eggs or the destruction of habitats: Since the beginning of human history, humans have been interfering with nature and thus becoming an acute threat to many animals. Our Stone Age ancestors could have played a decisive role in the extinction of many large herbivores in North America, but also Australia. And many birds also disappeared forever when humans arrived in new areas or on islands.

Look back into the past

“So far we knew from observations and fossils that 640 bird species have become extinct due to humans - 90 percent of them on islands,” says co-author Manuel Steinbauer from the University of Bayreuth. The spectrum ranges from the iconic dodo in Mauritius to the great auk in the North Atlantic to the lesser-known St. Helena giant hop. The problem, however, is that while the extinction of many birds since the year 1500 has been reasonably well documented, our knowledge of the fate of more distant extinctions is based almost exclusively on fossils. But such fossils are rarely available because light bird bones decompose over time. As a result, the true extent of global human-caused extinction is difficult to discern.

To shed more light on human extinctions of bird species, Steinbauer, first author Rob Cooke from the University of Gothenburg and their colleagues developed statistical models to extrapolate known data into the past. The study team based its models on information about known extinctions and the extent of research in specific regions. The latter influences the number of fossils of extinct bird species discovered so far and thus also the completeness of the data. Through the analyses, the researchers were able to estimate the “true” number of bird species that have been extinct by humans since the Late Pleistocene, around 130,000 years ago.

Traces of extinction since the Stone Age

The result: Cooke and his colleagues determined that around 1,430 bird species have become extinct due to human influence since the late Pleistocene - this corresponds to around eleven percent of all bird species and is therefore the largest human-caused vertebrate extinction in history. “However, based on the model results, we estimate that the actual number is slightly more than twice as high,” explains Steinbauer. Many of the bird species that were extinct in prehistoric times are no longer even known today. “Our study shows that human influence on bird diversity was far greater than previously thought,” says Cooke. “Many species became extinct before written records and left no trace – they have been erased from natural history.”

The causes of the extinction of bird species are diverse: “Humans have rapidly destroyed bird populations through habitat destruction, overexploitation, and the introduction of rats, pigs, and dogs, which raided the birds’ nests and competed with them for food,” Cooke reports. Larger waves of extinction occurred especially when our ancestors settled in new areas or islands, such as when humans arrived on the Pacific and Atlantic islands around 3,000 years ago. But the emergence of sea travel and global maritime trade from the 14th century also contributed significantly to the extinction of many birds.

And bird deaths continue: especially since the 18th century, in addition to increasing deforestation and the spread of invasive species, birds have also been exposed to human-caused threats from climate change, intensive agriculture and pollution. The International Union for Conservation of Nature (IUCN) estimates that up to 700 more bird species could become extinct in the next hundred years. “Against the background of the current extinction of species, it is now important for us to understand how the loss of a species and the associated loss of an ecological function affects the interaction in ecological systems,” says Steinbauer. “An extinction always has an impact on the entire ecosystem.”

Source: University of Bayreuth; Specialist article: Nature Communications, doi: 10.1038/s41467-023-43445-2

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