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468 assessment of climate change in the southwest united statesTable 20.1 Research needs and strategies associated with themes in the Assessment ofClimate Change in the Southwest United States (Continued)Uncertainty theme Research need Research strategyFew scientific studies have consideredfuture projections of climateand hydrologic extremes. Even fewerhave focused on regional extremes.Lack of studies increases uncertaintywith regard to common claims thatthe magnitudes and frequencies ofsome extremes will increase.Definition of the most impactbasedindicators of environmentalextremes that are relevantto society. The necessary crosssectorrelationships are still intheir infancy.Define extremes by first understandingtheir impacts in key sectors. Spur andnurture close collaborations betweenscience and the public-private policysectors, in order to define policy andimpact-relevant extremes.ECOSYSTEMS (CHAPTER 8)Despite the clear responses of thedistributions of some species toclimate, the relationship betweenchanges in climate and recentchanges in the geographic distributionof species is highly uncertain.Considerable uncertainty remainson how species and the communitiesand ecosystems they form willrespond to projected changes inclimate.Most projections of current or futuredistributions of species are based ontheir current climatic niches, whichunrealistically assume that nichesare static and uniform.Local jurisdictions vary considerablyin their technical expertise andcapacity to conduct effective coastalland use management.Projections of the effects ofclimate variability on geographicranges, accounting for multiplefactors affecting species persistenceand distribution.Species range projections thataccount for uncertainties dueto climate projections that falloutside the ranges of data usedto build the models.COASTAL (CHAPTER 9)Improved understanding ofpersistent adaptation barriersthat inhibit preparedness andactive implementation of climatechangeadaptation in coastalCalifornia.Projections that take into account species’environmental stress tolerances, andability to adapt. Consideration of environmentalchange, land-use change, andmanagement interventions. Elucidationof mechanisms of change in the interactionsamong factors such as climate variationand species fitness. Re-estimation ofthe probabilities of persistence of species.Knowledge gaps may be partly filledby identification of biotic and abioticdrivers of genetic change and selection,identifying which traits (or combinationsof traits) will be targets of this selection,and determining how genetic change andphenotypic plasticity affect selection ofpotentially correlated traits.Develop robust methods for accountingfor changing niche delineations. Characterizationof uncertainties associatedwith extrapolations beyond observationsused in constructing niche definitions.Estimating likely temporal and spatialchanges in these drivers, given multiplescenarios of climate change.Social science and communicationresearch aimed at characterizing adaptationbarriers. Definition and developmentof best practices for buildingcapacity for implementation of alternativeland-use management practices.