Assessment of Predicted Changes in Landuse and Climate on Fish Habitat Conditions in the Arid Southwest United States

Anthropogenic demands on the freshwaters of southwest United States have substantially altered these systems and  predictions of climatic and land use changes over the next 50 – 100 years indicate increasing temperatures, decreasing rainfall volume, and temporal shifts in rainfall patterns.  The objective of this study was to assess potential impacts to fish habitats in the Lower Colorado River Basin (LCRB).  Current species distributions for native (n=16) and non-native (n=21) fish species were modeled using locations recorded between 1980 – 2009.  We used multivariate adaptive regression splines to calculate a probability of presence using  metrics describing averages and variability of current climate and land use conditions.  For future timesteps (2040, 2085) we calculated those metrics using projected land use and downscaled datasets for climate.   Based on the 2085 timestep, mean probability of occurrence for both native and non-native species showed greater declines in distribution than increases suggesting reductions in suitable habitat.  An evaluation of change in predicted distribution for cold water non-natives showed greater declines than expansion.  Among warm-water species, native fishes had greater declines than the non-native species with both demonstrating similar increases.  Successful conservation and management plans for fisheries and their aquatic habitat will benefit from forecasts of future environmental change to ecosystems as a result of changing climate and land use.