Climate change has undisputable global effects on a wide variety of ecosystems and ecological community compositions. However, scientists have long pondered why certain communities are more resilient to its effects than others. In a new study led by the University of Helsinki covering almost all North American bird species, the experts examined community composition changes and diversity over half a century (1966-2016).
The analysis revealed that bird communities with higher species richness and a larger variety of functional properties changed less radically in their community composition due to climate change during the study period.
“For example, if a community contained birds of prey, insectivores, and seed-eaters rather than birds from just one feeding guild, it was better safeguarded against the negative impacts of climate change,” explained study lead author Emma-Liina Marjakangas, a community ecologist at Helsinki.
According to the scientists, community-level diversity functions as a buffer against negative climate change impacts, particularly during winter, the season that has shown the strongest warming patterns across the Northern Hemisphere. By contrast, biodiversity seems to have played a less significant role during the breeding season.
“Habitat and available food determine a species’ flexibility for changing its breeding and wintering areas. For example, grassland species have shifted their distributions northwards slower than forest passerines, such as the American robin, or habitat generalists, such as the mourning dove,” said study senior author Aleksi Lehikoinen, an expert in Ecology and Ornithology at the same university.
This phenomenon is likely caused by the fact that functionally diverse bird communities help maintaining ecosystems through plant seed dispersal, pest insect control, and even pollination. Since climate change frequently reshuffles the composition of these bird communities, it currently threatens their ability to provide these critical ecosystem services.
“Our results strengthen the understanding that biodiversity safeguards ecosystem functioning and that the biodiversity and climate crises need to be mitigated simultaneously to avoid multiplicative effects,” Marjakangas concluded.
The study is published in the journal Nature Scientific Reports.
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