Climate change: Many birds cannot escape

Climate change: Many birds cannot escape

Birds in the mountains in particular have their limits when fleeing global warming. © Aleksi Lehikoinen

Rising temperatures are causing some species to migrate to cooler areas to survive. However, this is not always possible, as a study now shows. Accordingly, mountains and seas represent major obstacles for "fleeing" birds - especially in Europe. They influence the distance the animals cover and the direction in which they migrate. In the long term, these natural barriers could even lead to the extinction of some species because they remain in climatically unfavorable habitats.

When climate change corners species with rising temperatures, they basically have only three choices: adapt, migrate, or become extinct. It has been documented many times that some animal species have migrated north in search of cooler areas or have settled in higher-lying regions. But how natural barriers, such as seas or mountains, affect these migration movements is still largely unknown.

Many European Birds Are “Climate Refugees”

In a large-scale long-term study, researchers led by Emma-Liina Marjakangas from the University of Helsinki have now examined the migratory behavior of bird species across Europe. The extensive data sets of the European breeding bird atlases allowed the team to trace the migration movements of almost all European bird species. The earliest dates are between 1981 and 1989, the newest dates are between 2013 and 2017. This enabled Marjakangas and her colleagues to trace more than three decades of habitat displacement. They also examined the influence of natural obstacles such as mountains and coastlines.

The result: two thirds of all European bird species migrated to cooler areas between 1981 and 2017 and now live on average 100 kilometers further north or east than a few decades ago, as the researchers report. However, in some cases, the distance traveled appears to have been severely limited by natural barriers. “We already knew that some birds are not moving their habitat fast enough to continue living in climates that are right for them. Now we have part of the explanation for this phenomenon,” explains Marjakangas' colleague Laura Bosco, also from the University of Helsinki.

Natural barriers fuel extinctions

Accordingly, coastlines are a particular hindrance when it comes to "escape" to cooler areas. This was shown in the evaluated data by the fact that the distribution area of ​​the birds living near the coast had shifted by significantly fewer kilometers during the observation period than for birds far away from the coast. And this despite the fact that climate change is continuously heating up both habitats to a similar extent. In the long term, this means that coastal birds will find it difficult to escape the unfavorable climatic conditions and some of them may even become extinct. That would be a particularly bitter loss: "The bird life in coastal areas often consists of rare species," as Bosco explains.

The situation could be similar for highly specialized species in alpine habitats, such as the snow sparrow, the rock ptarmigan or the mountain pipit. Due to their adaptation to life at high altitudes, they find it difficult to leave the mountains and may therefore also fall victim to climate change. A look at the data confirms this fear: "The bird communities mostly moved along the directions with the smallest changes in altitude compared to their original location," reports the research team. Thus, birds adapted to mountain life have shifted their habitat minimally, if at all, despite unfavorable climatic changes.

Taken together, the data from the breeding bird atlases indicate that mountains and coastlines pose significantly greater obstacles to birds than previously thought. They make it difficult for the animals to "fly after" their ecological niche, which is constantly shifting as a result of climate change. But these new findings could now benefit the birds: "Our results have the potential to influence nature conservation policy in the face of climate change, for example through improved designation of a protected area network for biodiversity shifts, protection along climate change paths and ecological corridors and the identification of contemporary climate refuges". , so Marjakangas and her team.

Source: Swiss National Science Foundation; Specialist article: Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2213330120

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