Simultaneously operating threats cannot predict extinction risk

Aaron C Greenville,Brad R Murray,William J Ripple,Thomas M Newsome,Glenda M Wardle,Chris R Dickman

doi:10.1111/conl.12758

Aaron C Greenville, Brad R Murray + Show 4 more

Open Access

https://doi.org/10.1111/conl.12758

Copy DOI

Abstract

AbstractSpecies 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.

Highlights

To help resolve the Earths’ biodiversity crisis (Ceballos et al, 2015; Pimm et al, 2014), there is an urgent need to understand which species are at greatest risk of extinction, which regions they occupy, and why levels of risk vary
Contrary to expectation, the weighted mean number of shared threats was a poor predictor of extinction risk for five of the six vertebrate classes (Figure 1a–e)
The IUCN Red List dataset is often used for regional and global assessments, and our interrogation of it here at these scales failed to confirm that species affected by more threats than others face a higher risk of extinction

Summary

Introduction

To help resolve the Earths’ biodiversity crisis (Ceballos et al, 2015; Pimm et al, 2014), there is an urgent need to understand which species are at greatest risk of extinction, which regions they occupy, and why levels of risk vary. Moilanen, & Di Minin, 2017) and identify threat “hotspots” at global and regional scales to prioritize conservation efforts (Brooks et al, 2006; Moran & Kanemoto, 2017). It is not known whether species afflicted by multiple threats have an elevated risk of extinction, or whether multiple threats operate antagonistically, additively, or synergistically at different spatial scales. Identifying which combinations of threats are associated with elevated extinction risk should allow more effective conservation planning and decision-making (Brook, Sodhi, & Bradshaw, 2008)

Methods

Results

Discussion

Conclusion