Biodiversity safeguards bird communities under a changing climate

A new study shows that North American bird communities containing functionally diverse species have changed less under climate change during the past 50 years than functionally simple communities.

Climate change has undisputable global effects on ecosystems and ecological community compositions, but why certain communities are better able to resist the effects of climate change than others remains unclear. In a recent scientific study covering nearly all North American bird species, researchers studied community composition changes and community diversity over half a century. Consistently, bird communities with higher species richness and a larger variety of functional properties changed less radically in their community composition following climate change.

– 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, highlights PhD Emma-Liina Marjakangas, the leading researcher of the study from University of Helsinki.

Community-level diversity works as a buffer against negative climate change impacts, especially during winter, i.e the season that has shown strongest climatic warming across the Northern Hemisphere. On the other hand, biodiversity played a smaller role during the breeding season. Indeed, earlier studies have shown that bird communities change faster during winter than summer, which explains this pattern.

– 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, explains Senior curator Aleksi Lehikoinen from the University of Helsinki.

Functionally diverse bird communities help maintain ecosystems via plant seed dispersal, pest insect control and even pollination of flowering plants. Climate change reshuffles the composition of these important bird communities and therefore threatens their ability to provide 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 emphasizes.

The study is based on a community science database from 1966–2016 covering all of North America, and it was published in the international journal Scientific Reports.