Evaluating the impacts of alternative restoration and climate change scenarios on fish productivity in the Everglades

Background/Question/Methods

Climate change may have major implications for the effectiveness of regional restoration projects, such as those in the Everglades. Thus, it is important to assess our abilities to forecast how such changes will impact important faunal elements of the Everglades. Under a trophic hypothesis, a desired result of restored hydroperiods is to re-establish the abundance and spatial pattern of small fishes throughout the Everglades, which in turn are predicted to benefit higher trophic-level predators such as wading birds, reptiles, and larger fish. Our goal was to predict how fish productivity may respond to specific restoration alternatives and climate scenarios that include altered rainfall, increased temperature and evapotranspiration, and rising sea level. Using 10-year time series data (1996-2006), a logistic model to predict small fish densities based on the time between drying events was developed. At 137 sites, we calculated cumulative differences in fish densities predicted under different climate and restoration scenarios using rainfall observed over a 41-year time period (1965-2005).

Results/Conclusions

Despite using only a single independent variable, these logistic models were significant (P<0.001) and explained the majority of variation (60%-70%) in small fish density. Because of variation in landscape features and hydrology within different regions of the Everglades, logistic models were fit regionally. These results show that model parameters varied regionally, as did the predicted effects of various restoration scenarios. Fish densities were predicted to increase most drastically in Shark River Slough (25%– 33%) and Southern Marl Prairies (>60%).  However, the negative effects of climate scenarios influenced fish productivity at ecosystem wide extents.  In addition, sea level rise was predicted to increase saltwater intrusion in the southern most sites of the Everglades. Predictions based on most climate scenarios indicate decreased water depths and increased lengths of drying events will lead to decreased fish productivity throughout the Everglades, with potentially system wide affects on higher trophic-level fauna. Thus, restoration scenarios that restore sheet flows and hydroperiods throughout the Everglades will be critical to maintain the functioning of this system in a changing world.