Since humans began to expand around the world, they have caused the extinction of more than 1,400 species of birds. The new figure represents double previous estimates and is the result of a study published this Tuesday in the journal Nature Communications. The equivalent of 12% of all bird species that exist today have already disappeared. This research gives a new dimension to both the magnitude of these extinctions (due to deforestation, mass hunting and the introduction of invasive species) and their implications for biodiversity.
The iconic dodo of Mauritius or the great auk are the symbols that remind us of the disappearance of birds, but there are much closer examples of extinct birds in the Canary and Balearic Islands: the unicolored oystercatcher, the Trias greenfinch and the Ibiza rail. are some of them. Because most known bird extinctions have occurred on islands, researchers took advantage of the fossil record to estimate how many species went extinct without documentation on Fiji, Hawaii, New Zealand, and other Western Pacific islands. Thus they calculated that 1,430 species of birds around the world have disappeared since the Late Pleistocene (beginning 126,000 years ago), and most of these extinctions have occurred in the last 11,700 years.
55% of them had not been discovered until now. Previous data had focused on well-documented disappearances, dating back just over 500 years. The team, made up of scientists from the Center for Ecology and Hydrology in the United Kingdom, the Center for Research in Ecology and Forest Applications (CREAF) in Spain and other universities in Sweden, Germany and Norway, considered that this approach could underestimate the magnitude. Since bird remains are more difficult to preserve and knowledge is very uneven in different parts of the world, some species may have become extinct before being recorded. For this reason, they incorporated statistical models to extrapolate the figure with existing data on fossil remains. Ferran Sayol, CREAF researcher and co-author of the study, explains that humans have driven more than one in nine bird species to extinction, with serious ecological and evolutionary and potentially irreversible consequences.
Birds perform different functions, such as seed dispersal by toucans, pollination by hummingbirds, or recycling nutrients from carrion by vultures. The disappearance of a bird species impacts each ecosystem differently, but “by losing their roles or functions, they cause cascading effects, for example, that a plant can no longer disperse its seeds or pollinate itself; and, therefore, it also becomes extinct,” explains Sayol.
Research has revealed some of the most massive human-driven extinctions in history. First, Sayol and his colleagues found that the largest wave of bird extinction is associated with human dispersal across the Eastern Pacific (including the Hawaiian Islands) during the 14th century, where they found extinction rates 80 times higher than previously thought. expected. Another massive one had occurred in the 9th century BC. C., driven by human dispersal in the Western Pacific. Researchers estimate that Pacific islands account for 61% of total bird extinctions; some emblematic, such as the high-billed crow and the Sinoto parrot.
Three major mass extinctions
Finally, they highlight that another great extinction has been occurring since 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. This crisis is expected to surpass the previous largest wave of extinction, as up to 700 bird species could disappear in the next hundreds of years.
Sayol explains that current rates of disappearance are 80 times faster than the natural rate of extinction, and although the levels of mass extinctions of the past have not yet been reached, the speed is much greater: “It is happening in a few hundred years what would normally happen in millions. If we continue at the current pace, we could reach that level.”
Ramón Martí, director of institutional development of the Spanish Ornithological Society, who has not participated in the study, considers that the figures found “reflect the severity of the human footprint on nature.” Furthermore, he details that in Spain there are 18 species classified as critically endangered. From SEO/Birdlife they have recently announced that in Spain around 60 million birds die every year due to human causes such as collisions with power lines, illegal captures, electrocution and accidents.
The authors highlight the need to intensify conservation efforts to avoid further losses in biodiversity, as the findings highlight the critical situation of birds globally and human responsibility in preserving diversity. Sayol hopes that by looking at the past and better understanding how many species have disappeared because of humans, “the necessary efforts will be made to save those that are still here.”
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