Mapping ecological vulnerability to recent climate change in Canada's Pacific marine ecosystems

Abstract Much knowledge is emerging about the past and potential effects of climate change on the unique and complex marine ecosystems of Canada's Pacific, including variations in the resilience, sensitivities, responsiveness, and non-stationarity of the biota. Such knowledge, however, is rarely synthesized or summarized with any overall integrated analyses that could guide the development of proactive planning for the effects of climate change. Regional and local planning of climate adaptation strategies, for example, requires an examination of ecological sensitivities and vulnerabilities at relevant spatial resolutions. We developed an illustrative example of a habitat-based ecological vulnerability assessment for the whole of Canada's Pacific marine area using existing spatial information from this region and from the California Current ecosystem. Potential climate impacts were calculated as the product of estimated exposure (E) of habitats to multiple dimensions of changing climate variables and expert-derived sensitivity (S) ratings of those habitats to changes in those climate variables. Vulnerability was then derived as the product of the estimated potential climate impacts in a location and the estimated cumulative impacts (CI) of non-climate stressors there, which we considered to be an inverse proxy of the adaptive capacity (AC) of the biota in those habitats. We found considerable spatial variability of potential climate impacts and vulnerability on the scales of the 12 Ecosections of Canada's Pacific, 25 habitat categories, and at finer scales. We produced maps of ecological vulnerability to climate change as an example output for use in spatially-oriented adaptation planning. Our initial assessment indicated that the Strait of Georgia in particular followed by Queen Charlotte Strait, Juan de Fuca Strait, Vancouver Island Shelf, and Johnstone Strait have relatively high vulnerabilities to climate change, in part due to concentrations of local stressors there. On a coast wide basis the habitats that were indicated as most vulnerable are shallow rocky reefs, seagrass habitats, kelp habitats, and deep rocky reefs. This approach for mapping vulnerability to climate change could be improved with finer scale climate data, additional climate variables, and stressor-habitat sensitivity estimates derived specifically for this system. We provide a stepwise manual for policy-makers, managers, or other practitioners to map ecological vulnerability to climate change in other marine settings.