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We know what species might be lost, but not how their loss will impact ecosystems...
For decades, conservation research has focused on understanding which species are likely to go extinct. For example, lists like the IUCN Red List combined spatial, demographic, functional, and abundance data to estimate the "extinction risk" of species around the world. However, despite a near-complete understanding of the risks facing Earth's vertebrates, we lack similar information on how the loss of these species threatens Earth's ecosystems.
To address this knowledge gap, we used a bunch of species loss scenarios in Canada to try and understand how the potential loss of imperiled species would impact ecosystems across Canada. We were particularly interested in whether species richness, which has been long thought to "insure" ecosystems against species loss, will buffer or mediate the potential impacts of these future extinctions?
To assess the impact of species loss on ecosystems, we used metrics of functional and interaction diversity - which together aim to represent the integrity of an ecological system. Declines in these metrics can indicate impending ecosystem collapse and they are often used in vulnerability assessments. Specifically, we first calculated functional and interaction diversity for complete species assemblages before removing species based on extinction risk and assessing resulting declines (see right).
We found that:
1) Despite harbouring far fewer species at risk, northern ecosystems are disproportionately vulnerable, whereby the loss of imperilled taxa could result in up to 25% and 20% declines in functional and interaction diversity, respectively.
2) Surprisingly, despite high species richness, some southern ecosystems containing high numbers of imperilled taxa were also vulnerable, indicating that richness alone is likely insufficient at predicting community vulnerability to species loss.
What does this mean for conservation in Canada?
Our findings demonstrate the need to account for future species loss when evaluating the vulnerability of Earth's ecosystems and highlight the importance of conserving species at risk, specifically in northern communities where they potentially play outsized roles in structuring and maintaining the integrity of ecosystems.
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