Predicting decay in functional diversity in plant communities under future climates

Joshua Sean Lee , William K Cornwell, Lina Teckentrup, James Brazill-Boast, Rachael V. Gallagher

Climate change is expected to cause widespread shifts in the composition of plant communities. However, the extent to which these changes will alter the composition and diversity of plant functional traits is less clear. Here, we assess how climate change may reshape the functional diversity of 32,996 plant communities by combining data on their traits and realised climatic niches with future climate projections. We find that under projected climates for the decade centred on 2070, up to a third of species will experience conditions outside of their current realised climatic niches. Yet, on average, the loss of these species from communities represented a potential decay in functional diversity of 9.5%, indicating some functional redundancy. We found weak evidence that patterns of species replacement, which are contingent on their realised climate niches, resulted in increased loss of functional diversity compared with random removal. Patterns of relative functional decay (i.e., projected loss of functional diversity relative to species loss under future climate) were distinct between woody and non-woody species, with woody species being at higher risk of declines in functional diversity, particularly in alpine and woodland communities. These results highlight the importance of integrating additional metrics, such as functional diversity and functional decay, into conservation and restoration planning to prioritise elements of biodiversity that help explain vulnerability to climate change. Using this dimension of biodiversity can help conservation practitioners identify areas vulnerable to climate change, inform management actions, and prioritise the planting of key growth forms to restore ecosystem function and identity.