A multi-trait approach for the identification and protection of European freshwater species that are potentially vulnerable to the impacts of climate change

We present a multi-trait approach to identify potentially vulnerable species of Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies), collectively referred to as EPT, to the impacts of climate change (CC). The "climate change vulnerability score" (CCVS) is an aggregation of six autecological traits that are known to be associated with vulnerability to CC: endemism, micro-endemism, temperature preference, altitudinal preference, stream zonation preference, and life history. We assigned a vulnerability score (0 - invulnerable to 6 - highly vulnerable to climate change) to 1940 EPT species and discussed the applicability of the index at three spatial scales: (1) continental (Europe), (2) state (the German Federal State of North Rhine-Westphalia) and (3) a river basin (the Ruhr River). We identified 157 EPT species (ca. 8%) as highly vulnerable to climate change (CCVS ≥ 4), including 95 species of caddisflies, 60 species of stoneflies and two species of mayflies. These are mostly found in France and Italy (52 species each), Spain and Slovenia (36 and 34, respectively), and Austria and Switzerland (30 species each), of which 95 are caddisflies, 60 stoneflies, and 2 mayflies. Using data collected in routine regional sampling we show that although no endemic EPTs were found in the German Federal State of North Rhine-Westphalia, eight species can still be identified as relatively vulnerable to CC (CCVS of 3). Almost all of these species are occurring in the 'mountainous' regions of the state (>200 m a.s.l.), the Sauerland and the Eifel. The upper reaches of the Ruhr catchment have been found to be relatively rich in vulnerable species, including several locally rare species. This index can assist conservationists to identify "hotspots" in terms of climate vulnerability and climate change refuge areas that can be considered for protection or the application of restoration measures at a local and regional scale. Nevertheless, not all species have complete autecological information, which hinders our ability to fully recognize the areas of priority. To further stabilize and enhance the applicability of this method, it is essential to fill these knowledge gaps in the future.