Humans caused extinction of some 1,430 bird species: Study

Recent research suggests that human activities have led to the extinction of approximately 1,430 bird species, more than double the number previously estimated. This information, derived from mathematical models and published in the journal Nature Communication, highlights the significant impact of human-induced global extinctions.

Humans caused many island bird extinctions

Previously, fossil records and observations indicated that about 600 bird species have gone extinct since the end of the Pleistocene era, when human expansion began. Notably, 90 percent of these extinctions occurred on islands inhabited by humans.

Extinct species range from well-known examples like the Mauritius dodo and the North Atlantic great auk, to lesser-known species from the Canary and Balearic Islands, such as the unicolored oystercatcher and the Trias greenfinch, and the Ibiza rail, respectively.

However, the recent study and its developed statistical models suggest that the actual number of lost species is over double the previous estimate, with about 1,430 species, or roughly 11 per cent of all current bird species, having gone extinct. This finding underscores the profound effect humans have had on bird biodiversity.

Not long ago, numerous islands around the world were untouched havens of natural beauty. However, human arrival in remote locations like Hawaii, Tonga, the Azores, as well as the Canary and Balearic Islands, led to significant and long-lasting impacts. These included deforestation, overhunting, and the introduction of invasive species, resulting in the extinction of many bird species on these islands.

Fossil scarcity obscures true extinction extent

The loss of these bird species has been recorded since the 1500s. Prior to that, our understanding of species’ fate was primarily based on fossil evidence, but many sites remain undiscovered. Without these fossils, the true extent of extinctions is largely unknown, leading to a patchy understanding across different regions of the world.

A research team, including members from the UK Center for Ecology and Hydrology (UKCEH) and CREAF, has employed statistical models to estimate the number of bird extinctions that might have gone undiscovered throughout modern human history, dating back to the late Pleistocene era about 130,000 years ago.

The team used known extinction data and extrapolated it to estimate the potential number of additional species that could have gone extinct if research efforts were as extensive as those conducted in New Zealand. This country is unique in that it’s believed to have a complete record of its bird species prior to human arrival, thanks to well-preserved remains of all the birds that once inhabited it.

Reasons for the extinction

UKCEH modeller Rob Cooke stated, "Habitat degradation, overexploitation, and the introduction of rats, pigs, and dogs which prey on bird nests, rapidly devastated bird populations on islands where no predators existed prior to that. Many bird species have gone extinct before any written records of them were made, leaving no trace behind."

Ferran Sayol, a researcher at CREAF and co-author of the study, adds that the historical extinctions might cause significant impact on the functioning of ecosystems. He explains that the "world didn't just lose a large number of unique bird species, but also the key functions these birds were responsible for. He states, as an example, that the loss in seed dispersal or pollination can create harmful knock-on effects on other species and the entire ecosystem."

Three major mass extinctions 

The scientists reveal that their study has shown some of the most significant human-driven vertebrate extinction events in history. First, they cite the one that occurred during the 14th century in the Eastern Pacific (including the Hawaiian Islands). People's arrival led to the loss of an estimated 570 species of birds, almost 100 times the rate of natural extinction.

Secondly, people mainly drove the events in the 9th century BC by arriving in the Western Pacific, including the Fiji Islands. Finally, they highlight that the extinction event we are currently experiencing began in the mid-18th century.

Since then, in addition to increased deforestation and the spread of invasive species, birds have had to face additional human-driven threats such as climate change, intensive agriculture and pollution. Experts predict that this ongoing crisis could surpass the 14th century extinction event, as we risk losing up to 700 additional bird species in the next few hundred years.

Ferran Sayol concludes: "Despite the tragedy that the loss of species represents, hope still exists. The most recent conservation efforts have yielded successful results, rescuing species like the Mauritius kestrel and the California condor from extinction. We have the chance to increase our efforts to protect many bird habitats and prevent additional extinctions, thereby preserving the proper functioning of ecosystems."

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