دانلود رایگان مقاله تغییرات پیش بینی آب و هوا در فضای ماهی آب شیرین

Abstract

The implications of climate change for terrestrial and aquatic taxa are for their dispersal pole-wards and/ or to higher altitudes as they track their climate niches. Here, bioclimatic models are developed to predict how projected climate change scenarios for a northern temperate region (Great Britain) shift the climate spaces (i.e. areas of suitable thermal habitat) for 12 freshwater fishes of the Salmonidae, Percidae, Esocidae and Cyprinidae families. Climate envelope models developed in Biomod2 used the current species' distributions and their relationships with current climatic variables, and projected these onto the BCC-CSM1-1 and HadGEM2-AO climate change scenarios (low and high emissions, 2050 and 2070) in full and no dispersal scenarios. Substantial contractions in climate spaces were predicted for native salmonid fishes, with decreases of up to 78% for Atlantic salmon Salmo salar, with these largely unchanged between the dispersal scenarios. Conversely, for the majority of cyprinid fishes, expansions were predicted, including into northern regions where they are current not present biogeographically. Only under the no dispersal scenarios did their predicted distributions remain the same as their current distributions. For all non-salmonid species, the most important climate variables in the model predictions related to temperature; for salmonids, they were a combination of temperature and shifts in annual mean precipitation. As these predictions suggest that there is potential for considerable alterations to the climate spaces of freshwater fishes in Great Britain during this century then regulatory and mitigation conservation actions should be undertaken to minimise these.

4. Discussion

Building bioclimate models for a range of freshwater fishes in Great Britain under current and future climate scenarios predicted that the climate space of each species would shift, with centroid displacement always in a north-westerly direction. Predictions revealed that even under low emission climate change scenarios and the two dispersal scenarios, alterations in climate space were generally consistent at the family level, with constriction for the freshwater life-stages of native salmonid fishes and a large increase in the climate space of most cyprinid species, including the non-native C. carpio, other than under the no dispersal scenario when their distribution would be unchanged. Across all the modelled fishes, annual mean temperature was the most important variable in the ensemble model predictions. There was, however, some inter-family variability across the importance of the climatic variables, with a combination of annual mean precipitation and temperature variables being most important for the two salmonid species. For all other modelled species, temperature variables were most important, with their combined importance to the ensemble models being a minimum of 92%. The limitation of the modelling architecture to the use of only two dispersal scenarios limited the distribution predictions to scenarios of no dispersal and full dispersal. It is highly probable that some dispersal within and between some catchments of species will occur naturally and/or by anthropogenic means (Conti et al., 2015). This is thus a limitation of the method used and so it is recommended that future work incorporates the ability of freshwater fish to disperse in relation to hydrological connectivity and the changes in their environments. The modelling approach was based on bioclimatic variables, using the assumption that the influence of climate on the biology and ecology of the fishes was the key determinant of their distribution pattern (Woodward and Beerling, 1997; Hampe, 2004).