Abstract/Summary

Politicians, strategists and environmental campaigners are increasingly concerned about the potential for climate change to create major systemic risks with extreme – and controversially existential – consequences. These systemic risks may be triggered not only by the direct physical impacts of climate change – on heatwaves, floods, fires and drought – but also by the effects of ecosystem changes generated by climate change. However, there have so far been very few robust analyses of systemic risks under different future emissions pathways. Moreover, whilst there have been several studies of direct physical risks, there are very few studies into ecosystem changes in terms directly relevant to human systems. This is partly because ecosystems are inherently difficult to model because they are based on complex inter-relationships, and partly because most studies have concentrated on indicators relevant to ecosystems in themselves. This report presents a review of the evidence available to support the robust assessment of the potential for ecosystem changes to trigger regional and global systemic risks. Such a robust assessment must involve a blend of quantitative information on relevant indicators calculated under different emissions pathways with expert judgment on how changes in exposure and vulnerability translate impacts into systemic risk. Ecosystem changes have the potential to generate regional and global systemic risk both through changes occurring over large areas and through changes occurring in particularly sensitive locations. Information on the effects of ecosystem changes should therefore be incorporated into this approach in two ways: using relevant high-level global-domain indicators combined with expert judgment on implications for human systems, and using expert judgment to identify critical sensitive locations and use locally-relevant indicators to infer impacts on ecosystems and systemic risks.