Global Impacts of Climate Change on Avian Functional Diversity

Abstract

Climate change is predicted to drive geographical range shifts in many taxa, leading to the formation of novel species assemblages and fluctuations in species richness worldwide. However, the effect of these changes on functional diversity is not yet fully understood, in part because comprehensive species-level trait data are generally lacking at global scales. Here we use morphometric and ecological trait data for 8269 terrestrial bird species to compare functional diversity (FD) of current and future bird assemblages under a medium emissions scenario. We show that future assemblages are likely to undergo substantial shifts in trait structure, with the direction and magnitude of these shifts varying with geographical location and trophic guild. Specifically, invertivore FD is projected to increase at higher latitudes with concurrent losses at mid-latitudes, reflecting poleward shifts in range, whereas frugivore FD is projected to fluctuate in many tropical regions with major declines in much of South America and New Guinea. We show that these projected changes in FD are generally greater than expected from changing species richness alone, indicating that projected FD changes are primarily driven by the loss or gain of functionally distinct species. Our findings suggest that climate change will drive continental-scale shifts in avian functional diversity, with potentially far-reaching implications for ecosystem functions and resilience.

AVONET: morphological, ecological and geographical data for all birds

“…Integrating functional perspectives may help make sense of the variation in species responses to change (Bender et al, 2019), enabling the development of more general and mechanistic models of current and future changes in distribution and diversity (Estrada et al, 2016). For instance because the morphological data in AVONET cover different aspects of species ecology, from movement (reflected in wing shape) to feeding (reflected in beak shape), these data can be used to parameterise global range shift models with morphological indices of dispersal and trophic niche structure respectively (Stewart et al, 2022). In addition, trait‐based analyses show promise in understanding and predicting the effects of environmental change on trophic interaction networks (Gravel et al, 2016; Schleuning et al, 2020), with implications for the conservation of key ecosystem processes regulated by birds, such as seed dispersal and pest control (Bregman et al, 2015, 2016).…”

“…For example, previous applications of trait-based indices of dispersal focused on avian sister species or individual clades (Kennedy et al, 2016;Pigot & Tobias, 2015) whereas the data are now available for global analyses (Sheard et al, 2020). Similarly, traitbased assessments of the impacts of global change on avian functional diversity have shifted focus from surveys of plots or transects (Bender et al, 2018;Bregman et al, 2015Bregman et al, , 2016 to the global scale (Sol et al, 2020;Stewart et al, 2022).…”

A bird in the hand: Global‐scale morphological trait datasets open new frontiers of ecology, evolution and ecosystem science

“…Cannon et al, 2019; Chapman et al, 2018; Trisos et al, 2014) to continental or global assemblages (e.g. Sol et al, 2020; Stewart et al, 2022).…”

“…Neate‐Clegg et al, 2021). Similarly, studies applying techniques developed in community ecology have begun to explore how the trait structure and functional diversity of bird assemblages are affected by climate change (Bender et al, 2019; Stewart et al, 2022), urbanisation (Sol et al, 2020), and agricultural expansion (Cannon et al, 2019; Chapman et al, 2018; Rurangwa et al, 2020). Using a trait‐based approach can also give important insights into functional turnover between system states.…”

Upscaling tropical restoration to deliver environmental benefits and socially equitable outcomes

“…For instance, seed dispersers foster natural regeneration 103 , yet in the Australian wet tropics, the median seed-dispersal distance of frugivorous birds, bats, and marsupials is projected to fall 38.7% by 2100 under worst-case climate scenarios 104 . Furthermore, strong predicted declines in functional diversity of avian frugivores under medium emissions scenarios renders dispersal-dependent restoration particularly vulnerable across South America, New Guinea, and southern Congo 105 , intensifying existing seed-dispersal limitation from contemporary defaunation 103 . Hence, restoration efforts need also to protect overhunted fauna, thereby assisting migration of impacted trees.…”