Declines in seed-dispersing animal species impede plants’ ability to adapt to changing climate

Declines in seed-dispersing animal species – upon which half of all plant species rely – have significantly reduced the ability of plants to adapt to climate change by limiting plants’ ability to migrate into new ranges, according to a new study. The findings highlight the dynamic plant-animal mutualisms that support ecosystem functioning and illustrate a worrying feedback between biodiversity loss and the ongoing climate crisis. Seed dispersal is one of the most widespread mutualistic functions provided by vertebrates. Under climate change, many plant populations may need to migrate rapidly to track their shifting climatic niches. Thus, the ongoing mutualistic interactions between plants and animals will likely influence whether certain plant species persist and spread. However, these interactions are threatened by ongoing declines in animal populations. While the effects of defaunation on plant resilience at local scales have been evaluated, the global magnitude of potential impacts remains unknown. To address this important knowledge gap, Evan Fricke and colleagues assembled data from more than 400 seed dispersal networks worldwide and developed trait-based models to predict changes in seed dispersal due to declines in seed-dispersing animal species. They found that current seed dispersal function has steeply declined from its natural level, with declines particularly widespread outside the tropics. Fricke et al. estimate that past loss in mammal and bird species has already reduced the capacity of plants to track climate change by 60% globally. The results, say the authors, underscore the need to not only promote habitat connectivity to maximize the potential of current seed dispersers, but also the need to support recovery of large-bodied animals to increase the resilience of vegetation communities under climate change.