Dealing with Climate Change
Because extreme events, whether they are from floods, droughts, or heat waves, will have large effects on fish and other delta populations, the adequacy of restoration actions and population models need to be considered in the context of increasing frequency and intensity of events. For example, if the frequency of extended hot dry summers increases, the frequency of year class failures would increase and the probability of extirpation of several salmon runs would increase. However, projecting the impacts of a changing frequency of extreme events is difficult. Current life-cycle models (e.g., Holmes 2001, Hinrichsen 2002, 2009, Lessard et al. 2010) assume that the pattern of demographic variability in the population is stable into the future. With climate change this assumption is violated, as described by Thompson et al. (2011). Furthermore, models are sensitive to choices of parameters characterizing future trends and so those not validated with data should be used with caution (Hulme 2005). In spite of these limitations, models linking climate variability and fish ecology are essentially the only way to project future impacts of climate change on fish (Jackson et al. 2009). However, those models need to be tested by careful monitoring; some effects of climate change on fish can be tested experimentally.
Information on climate science shapes public opinion regarding climate change, and the studies have much to contribute to the adaptive management of the Central Valley. While individuals typically form opinions either by learning from experience or from descriptions, experiential learning is the most compelling. However, when climate change is gradual, it has not been very noticeable to the public (Weber 2010). However, extreme events and resulting fishery closures are directly experienced by the public and noticed, although the public will not necessarily notice a connection between extreme events and long-term change. Yet if the climate predictions are correct, frequent extreme events will increase the need for Central Valley water resources by both the ecosystem and the public. In this case, managers may be asked to consider hard choices that are more in the context of triage than rehabilitation (e.g., CASCaDE 2010, Hanak et al. 2011, SPUR 2011). While such a scenario may not come to fruition, the committee encourages continued critical and comprehensive studies of the full range of future possibilities and how to adapt to climate change. Indeed, the committee recommends this kind of approach to delta issues in general.
In the future, effects of climate change will increase the need for Central Valley water resources by both the ecosystem and the public and induce even more competition among them. In developing alternative scenarios for the implementation of water management measures, it will be necessary to consider a larger variability in water supply and potential impacts on the ecosystem.