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Sunday, May 19, 2024

An Atlas Reveals Climate Change Is Pushing Birds Further North

This story originally appeared in The Guardian and is part of the Climate Desk collaboration.

Europe’s breeding bird populations have shifted on average 1 kilometer north every year for the past three decades, likely driven by the climate crisis, according to one of the world’s largest citizen science projects on biodiversity.

The European Breeding Bird Atlas 2 (EBBA2) provides the most detailed picture yet of the distribution of the continent’s birds, after 120,000 volunteers and field-workers surveyed 11 million square kilometers, from the Azores in the west to the Russian Urals in the east.

The book documents changes in the range of Europe’s 539 native bird species in the 30 years since the first EBBA, which was published in 1997 but was based on observations from the 1980s. It shows that since the first study, each population can be found around 28 kilometers further north.

Mediterranean species such as the European bee-eater and little egret are now reaching the UK, France, and the Netherlands, mainly due to milder winters. Eurasian bitterns, pied avocets, and red kites have also expanded their range, probably in response to better protection of habitats coupled with laws banning persecution.

Overall, 35 percent of birds increased their breeding range, and 25 percent contracted their breeding range. (As for the rest, either they did not show any change or the trend is unknown.) Forest birds and those protected by international legislation have generally expanded their range, while farmland birds occupy a smaller total area.

Generally, if a species is present in more areas it is less likely to go extinct, but it could be spreading out because of habitat deterioration, and not because the population has increased. “The results are confirmation that the major driving forces are climate change and land-use change. At the same time, the situation is really very complex, and that’s why we will provide this data set for further exploration and investigation,” said Petr Voříšek from the Czech Society for Ornithology.

Iván Ramírez, senior head of conservation at BirdLife Europe and Central Asia, said: “Those birds that have been legally protected have been doing better than those which are not protected. This is a really important message within the European Union. We have one of the oldest policies—the Birds Directive—and we can prove that it works.” Birds protected by the Bern Convention, such as white-tailed eagles, are also doing better.

As the climate warms, forests are stretching into boreal and Arctic regions. In parts of northern Europe, there has also been tree planting (mainly for wood and paper) and land abandonment (specifically in Mediterranean areas), which have damaged farmland birds but benefited many woodland species such as woodpeckers and warblers.

Alpine species are also losing out as scrubby trees and vegetation colonize higher mountain slopes, shrinking the range of mountain grassland specialists such as wall creepers and water pipits.

Generally, farmland birds are big losers, suffering overall declines in population and reduced distribution because agricultural intensification means there is less food, such as insects and residue from harvesting. A report titled "State of Nature in the EU 2013-2018" showed 80 percent of key habitats were in poor or bad condition, and intensive farming is a major driver of decline. The UK’s farmland birds have declined by 55 percent since 1970.

If birds are forced into new habitats on the edge of their range, this can also put them under stress, particularly migratory species such as swifts and swallows, where small changes in timing have considerable implications. “Birds are optimized machines,” said Ramírez. “They have been learning for generations and millennia how to do these migrations. They have genetically been designed to do a migration of x kilometers. If you’re putting x plus 10 or 15 kilometers, you are putting them under stress.”

The data also showed an increase in nonnative species. One in 10 breeding bird species is nonnative (57 in total), and 39 of these arrived in the past 30 years, including the ring-necked parakeet, monk parakeet, and Egyptian goose, which are all likely to be expanding their territories.

Ramírez said this is caused by the “perfect storm”—an increase in the wildlife trade, climate change making European habitats more suitable for exotic birds, and an abundance of food in urban areas. Taken together, invasive species are one of the top five drivers of biodiversity decline globally, but the researchers did not look at whether these particular species were negatively impacting native populations.

There has only been one known bird extinction in Europe in the past 30 years—the common button quail—but if trends continue, there are likely to be many more in the next 30 years, said Ramírez. Populations will decline in suboptimal habitats until they reach a limit, beyond which they collapse. “What the science tells me, and what I’ve seen after 20 years working on birds, is that every single time we publish a new report, the overall state of birds is always declining. This hasn’t changed since the '70s, when the Birds Directive started, and nothing makes me believe that this is going to change,” he said.

The book is being released by the European Bird Census Council (EBCC) and was put together by a network of partners in 48 countries using data collected between 2013 and 2017. “This is by far the widest and best coverage of all species of birds that we have in our region … International cooperation has enabled us to survey every single square in the region to a very fine detail,” said Ramírez.

To create the data, Europe was carved up into squares measuring 50 by 50 kilometers. Bird enthusiasts (mainly volunteers) from around the world recorded what birds were breeding within that space.

Ornithologists will now be able to use this data to work out why these population changes are occurring, which should in turn form the bedrock of policy. “This atlas shows, in unprecedented detail, how bird populations are changing across Europe,” said RSPB’s principal conservation scientist, Mark Eaton.

“Predictably, there are winners and losers. We can see how some species, such as black-winged stilts and cattle egrets, have expanded across the continent rapidly and have begun to colonize UK wetlands. In contrast, we can see ranges shrinking as species of northern Europe feel the impact of climate change, and species such as the dotterel are dwindling in numbers and range in northern Britain,” he said.

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