Response diversity and resilience in freshwater ecosystem responses to climate change

Background/Question/Methods

Most assessments of the ecological responses to climate change are uniformly pessimistic about what the future holds for ecosystem processes and the services provided to people. Most published work on climate impacts on ecosystems has emphasized that freshwater systems are especially sensitive to changing climate, and that all change is bad news. Further, little attention has been paid to developing strategies for dealing with inevitable climate-driven changes to ecosystems in ways that will maintain some of the structural features and services that humans currently value. We used 5 decades of data on the zooplankton and fish communities from lakes in Bristol Bay, Alaska, to evaluate ecological responses to the substantial regional warming that has occurred in the last century. In addition to evaluating the direction of ecological responses to warming climate, we assessed the variation in responses, and how these patterns emerged at different spatial and temporal scales.

Results/Conclusions

Our analyses demonstrate that ecological responses to climate change are strongly scale-dependent. At coarse spatial and temporal scales, freshwater productivity has increased over the last 5 decades in response to regional warming in southwest Alaska. Concomitant with these increases in freshwater productivity has been a distinct increase in anadromous salmon production that is partially a response to enhanced growing conditions for juveniles in freshwater ecosystems. At finer spatial and temporal scales, there is considerable diversity in the responses of individual taxa and in individual populations to regional climate warming. This response diversity has made these ecosystems far more resilient to climate warming than if they had been dominated by taxa and populations with coherent responses to climate change. Thus, developing policy that maintains and protects ecological heterogeneity in ecosystems is likely an important strategy for dealing with ongoing climate change.