Journal: Conservation Letters

Abstract:

Global threat-extinction risk networks illustrating the top 10 threats to threatened species. Networks illustrate the number of threatened species of (A) mammals, (B) reptiles, (C) birds, (D), amphibians, (E) ray-finned fishes (actinopterygians), and (F) cartilaginous fishes (chondrichthians) on the IUCN Red List that are impacted by each threat. Each node in the network is either an extinction risk category
or threat class, and the size of the node, or length of each section around the circle, represents the number of species within that node. Widths of lines joining each extinction risk category and threat class (node) represent the number of threatened species (links or edges) affected by each threat, within each extinction risk category. NT = near threatened, VU = vulnerable, EN = endangered, CR = critically endangered, EW = extinct in the wild, and EX = extinct.

Species afflicted by multiple threats are thought to face greater extinction risk. However, it is not known whether multiple threats operate antagonistically, additively, or synergistically, or whether they vary across different taxonomic and spatial scales. We addressed these questions by analyzing threats to 10,378 species in six vertebrate classes at global and regional spatial scales using network analysis. The total number of threats was a poor predictor of extinction risk, and particular combinations of threats did not predict extinction risk in the same way at different spatial scales. The exception was cartilaginous fishes, which faced increased extinction risk with increasing numbers of threats. Except for cartilaginous fishes, our findings indicate that species facing more threats than others do not face a higher risk of extinction and suggest that effective conservation will require more investment in identifying how threats and different ecosystem stressors operate together at local scales.

Reference: Greenville A. C., Newsome T. M., Wardle G. M., Dickman C. R., Ripple W. J. & Murray B. R. (2020). Simultaneously operating threats cannot predict extinction risk. Conservation Letters. doi.org/10.1111/conl.12758