Vulnerability to climate change increases with trophic level in terrestrial organisms

The resilience of ecosystem function under global climate change is governed by individual species vulnerabilities and the functional groups they contribute to (e.g. decomposition, primary production, pollination, primary, secondary and tertiary consumption). Yet it remains unclear whether species that contribute to different functional groups, which un-derpin ecosystem function, differ in their vulnerability to climate change. We used existing upper thermal limit data across a range of terrestrial species (N = 1701) to calculate species warming margins (degrees distance between a spe-cies upper thermal limit and the maximum environmental temperature they inhabit), as a metric of climate change vul-nerability. We examined whether species that comprise different functional groups exhibit differential vulnerability to climate change, and if vulnerability trends change across geographic space while considering evolutionary history. Pri-mary producers had the broadest warming margins across the globe (mu = 18.72 degrees C) and tertiary consumers had the narrowest warming margins (mu = 9.64 degrees C), where vulnerability tended to increase with trophic level. Warming mar-gins had a nonlinear relationship (second-degree polynomial) with absolute latitude, where warming margins were narrowest at about 33 degrees, and were broader at lower and higher absolute latitudes. Evolutionary history explained sig-nificant variation in species warming margins, as did the methodology used to estimate species upper thermal limits. We investigated if variation in body mass across the trophic levels could explain why higher trophic level organisms had narrower warming margins than lower trophic level organisms, however, we did not find support for this hypoth-esis. This study provides a critical first step in linking individual species vulnerabilities with whole ecosystem re-sponses to climate change.

Automated summary

The resilience of ecosystem function under global climate change is influenced by individual species vulnerabilities and their contributions to functional groups. This study investigated the vulnerability of different functional groups to climate change using upper thermal limit data of terrestrial species. The results showed that vulnerability varied among functional groups and changed across geographic space.