Assessing biodiversity hotspots below the species-level in Canada using designatable units

Abstract

The biodiversity hotspot approach is commonly used to identify key regions of conservation priority based on species richness and uniqueness. Like other countries, Canada uses below species-level conservation units, called Designatable Units (DUs), for assessing extinction risk on a case-by-case basis. Researchers have yet to investigate conservation unit hotspots below the species level, despite the potential benefits to optimize the impact of conservation strategies. Across taxa, we: (i) identified at-risk DU hotspots, eco-geographic regions in Canada with a disproportionate number of at-risk DUs relative to species richness; and (ii) compared at-risk DU hotspots using two sets of eco-geographic maps adopted by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). DU richness counts were based on COSEWIC assessed species and hence biased towards at-risk DUs; species richness values were obtained from the International Union for Conservation of Nature (IUCN) Red List. At-risk DU hotspots were consistently found in the Pacific and Great Lakes regions. A positive correlation was observed between at-risk DUs and species richness using both eco-geographic maps, but important regional nuances were also detected, i.e., hotspots were not always found in regions of high species richness. Moreover, there were 3.45 at-risk DUs for every at-risk species across all taxa, providing greater resolution for refining conservation prioritization across regions. For Canada, the at-risk DU hotspot approach permits the identification of regions with a high number of at-risk DUs relative to species richness, enabling the targeting of multiple DUs and taxa in one management plan. More generally, these results emphasize the importance of incorporating below species-level metrics into conservation decisions to better account for different components of biodiversity and extinction risk.