Increasing importance of climate change and other threats to at-risk species in Canada

Abstract

In a previous analysis, six major threats to at-risk species in Canada were quantified: habitat loss, introduced species, over-exploitation, pollution, native species interactions, and natural causes (O. Venter et al. 2006. Bioscience, 56(11): 903–910). Because of rapid environmental change in Canada and an enhanced understanding of the drivers of species endangerment, we updated the 2005 analysis and tested for changes in threats up until the end of 2018. We also expanded the scope to acknowledge climate change as a seventh major threat to species, given its increasing importance for reshaping biological communities. Using information on the COSEWIC (Committee on the Status of Endangered Wildlife in Canada) website, we scored the threats for each of 814 species. Habitat loss remained the most important anthropogenic threat to Canada’s at-risk species, affecting 82% of species, followed by over-exploitation (47%), introduced species (46%), and pollution (35%). Climate change was the least important threat, affecting only 13% of species. However, report writers used less certain language when talking about climate change compared with other threats, so when we included cases where climate change was listed as a probable or future cause, climate change was the fourth most important anthropogenic threat, affecting some 38% of species. The prevalence of threat categories was broadly similar to those for the United States and IUCN listed species. The taxa most affected by climate change included lichens (77%), birds (63%), marine mammals (60%), and Arctic species of all taxa (79%), whereas vascular plants (23%), marine fishes (24%), arthropods (27%), and non-Arctic species (35%) were least affected. A paired analysis of the 188 species with two or more reports indicated that any mention of climate change as a threat increased from 12% to 50% in 10 years. Other anthropogenic threats that have increased significantly over time in the paired analysis included introduced species, over-exploitation, and pollution. Our analysis suggests that threats are changing rapidly over time, emphasizing the need to monitor future trends of all threats, including climate change.