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 (Venter et al. 2006). 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 (http://www.cosewic.ca/index.php/en-ca/), 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 to 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.

A framework for mapping cumulative threats and its application to Canada

“…Considering the threats that affect biodiversity most globally (Maxwell et al 2016) and within Canada (Woo-Durand et al 2020), I sought to develop a human footprint map incorporating threats with the most up to date layers. Although I did address parts of the three 'big killers' for global biodiversity -Over-exploitation with logging, Agricultural Activity and Urban Development (Maxwell et al 2016), I was unable to include introduced species that affect 46% of Canada's "at-risk" species and many aspects of habitat loss and overexploitation (Woo-Durand et al 2020). Even though habitat loss from seismic lines and recreation trails could be seen with high resolution imagery in my validation plots, there were no national spatial datasets that could be applied.…”

“…COSEWIC identified that species classified as "at-risk" in Canada are most commonly affected by the threat of habitat loss, affecting over 80% of species included (Venter et al 2006;Woo-Durand et al 2020). I mapped nine threats that directly contributed to habitat loss for the Canadian human footprint to help address the threat that most commonly affects Canadian biodiversity "at-risk".…”

“…With my product the incorporations of the above threats occur with the inclusion of crop land, forestry, built environments and pasture land layers, all of which fall within the top six mean human footprint scores for Canada. With Canada's "at-risk" species facing more than one threat (Woo-Durand et al 2020), the utility of the Canadian human footprint, which includes the threats that are most affecting biodiversity (Maxwell et al 2016), is an important tool for conservation planning and the mitigation of such threats.…”

“…These should be a priority for future improvements to my work. There were also threats affecting terrestrial endangered species in Canada, such as extreme weather and introduced species, that I was unable to incorporate in the human footprint (Venter et al 2006;Woo-Durand et al 2020). My product only included terrestrial anthropogenic threats, so it is important to note that threats to the aquatic ecosystems were not included.…”

“…Woo-Durand et al(2020)analysed threats to 820 species identified as "at-risk" in Canada by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). They found that the number of threats affecting each species has increased significantly from an average of 2.5 to an average of 3.5 threats between 1999 and 2018, showing the need to map threats in Canada cumulatively and not in isolation(Venter et al 2006;Woo-Durand et al 2020). Nevertheless, no cumulative threat map covers the entirety of Canada.…”