The potential future impact of climate warming and other human activities on the productive capacity of Canada's lake fisheries: a meta-model.

A simple meta-model was used to examine how climate warming and stresses due to other human activities might affect the productive capacity of fisheries in all of Canada's lakes. Recent estimates of lake resource characteristics by secondary watershed and area size-class provided the basis for the model. Potential fishery productivity was estimated using a variant of the Schlesinger and Regier (1982) model which had lake mean depth, total dissolved solids concentration, and mean annual air temperature as inputs. A business-as-usual climate change scenario (SRES A2) was used to estimate worst case future temperature increases (4.5-8.3°C by the 2080s). The stress index from Chu et al. (2003) was used as a proxy for the impact on fisheries of other human activities. Projected populations for the SRES A2 scenario were used to scale future stress index levels. Potential biotic responses to warming were represented in two ways; the first as potential biotic displacement of currently dominant species when temperature rose beyond their preferred range and the second as potential biotic adaptation of other species, particularly in species rich areas, replacing displaced species. Potential productive capacity of fisheries in all Canadian lakes was 361,000 tonnes for the baseline climate norms period of 1961-1990. Climate warming increased productivity by 80.7% in the 2080s but stress reduced levels by 19.4% in the norms period and held the increase to 10.3% in the 2080s. Biotic displacement alone resulted in large decreases in productivity, by 65.2% in the 2080s and, when stress was added, by 79.5%. Biotic adaptation largely offset displacement. Applying stress and both biotic responses productivity was reduced by 31.4% in the 2080s from the unstressed norms baseline or 12% with stress added. Further investigations are needed to better establish the likely extent of stress impacts and potential biotic responses to climate warming in Canada's lakes. [ABSTRACT FROM AUTHOR]