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11/18/20081Grappling the ecological impacts of global warming on terrestrial systems: top-down drivers to species level-responsesHow will the impacts of climate change be distributed across species, habitats, and continents? •What do we mean by impact?– Range shifts (area, altitude, latitude)– Extinction probabilitiesDemographic impacts (fitness)–Demographic impacts (fitness)– Community Impacts (cohesion)– Ecosystem Impacts (services, integrity)• Direct vs. Indirect Impacts–Direct (ex.: ∆ in temp -> ∆ in performance)– Indirect (ex. ∆ in temp -> ∆ in herbivory, predation, competition, disease -> ∆ in performanceOutline• Looking at Impacts in different waysI. Climate – envelope (niche modeling)II. Response vs. ImpactIII.Physiology and ClimateIV. Positive feedbacks and ecosystem fxnsScientists Predict Widespread Extinction by Global WarmingNEW YORK, THURSDAY, JANUARY 8, 2004V. Range dynamics, climate, and the evolution of vagilityVI. Community impacts• Climate envel• What is the climate range where an organism lives now?• Where will those conditions occur at Dryopteris dialataI. Climate – envelope (niche modeling)future date?• Often:–dispersal fxn modifies range– Impact on species = area ∆• Benefits:– Species-specific fxns widely applicable Thomas et al 2004: 1537% of species “committed to extinction” by I. Climate – envelope (niche modeling)•Thomas et al 2004: 15-37% of species committed to extinction” by 2100–Range ∆ and extinction risk clearly related• Assumptions and limitations– All individuals have identical sensitivity to temp change– All individuals adapted to all temp. within species range– No adaptive shifts in temp. tolerance– Dispersal assumed perfect– Difficult to generalizeTemperature change:Two questions:1) What is changing, and where? 2) Does change = impact?II. Response vs. ImpactA2 emissions – warming in °C by 2100“…we expect changes to be concentratedin areas where temperature changes are largest(that is, at higher latitudes and altitudes) and forchanges to be less evident elsewhere.”Root, Price, Hall, Schneider, Rosenzweig & PoundsNature 200311/18/20082What is changing, and where? Phenology – the timing of nature - is changing (Parmesan 2007)II. Response vs. ImpactLarger responses are seen at higher latitudePied flycatchers are not “keeping up” with the change in their food supplyDoes change = impact?An example from the NetherlandsBoth et al 2006dateEarly lateII. Response vs. ImpactLarger changes in phenology can cause greater impact to slow responding organismsSpring TempLaying dEEarly latelow high•Pied flycatches feed caterpillars to young•# of young fledged depends on caterpillar abundance•Caterpillar abunmdance is changingDoes change = impact?Observed response to Some problems with this approach to estimate impactsII. Response vs. Impact•Observed response to climate ∆ are not typically good measures of fitness ∆• What is easy to measure is not always most valuable• Sampling biasPredicting sensitivity to temperature changeOrganisms have highest fitness near temperatures they experience most often, and fitness declines as temperatures deviate from temperature optimaIII. Physiology and ClimatePopulations which experience more variation in temperature should be physiologically adapted to a wider range of temperatures- Pianka 1966, 78, Janzen 1967, Slobodkin and Sanders 1969, Pielou 1975pp…and thus have lower sensitivity to changing climates fitnessgeneralist specialistWhen temperatures change, generalists fare better than specialistsIII. Physiology and ClimateTemperatureTemperatureRelative -10 0 10 20 30 400. temperature variability is low near the equatorIII. Physiology and ClimateSeasonality (σ mean monthly temp) in ºCInsects (Frazier et al. 2006)-10 0 10 20 30 400. rates (r)• 38 Insect taxa from 42S to 52NInsect fitness in a warmer world-CTmaxopt2σpT-Texp2optToptT-T1-2for T ≤ Topt for T > ToptP(T)=Clavigralla shadabi -BeninIII. Physiology and Climate60S 40S 20S 0 20N 40N 60N10010203040-10 0 10 20 30 400. (°C)CTminCTmaxToptRelative Gro42S to 52N• Population growthmeasured at multiple temperatures in each taxaAcyrthosiphon pisum- EnglandC.s. A.p.JT10-10 0 10 20 30 400. shadabip. growth (r)• Calculate current pop. growth (r) by integration under each growth curve, using current climate (w/ annual and diurnal variation) (Wcurrent)• Project climate 100 years (A2) and calculate pop growth again pop. growth)CTmaxToptThabCTminImpact (W100–Wcurrent)Unlikely to benefit tropical ectotherms as much as temperate ectotherms –ability to acclimate to new Insect fitness in a warmer worldIII. Physiology and Climate-10 0 10 20 30 400. 40S 20S 0 20N 40N 60N60S 40S 20S 0 20N 40N 60N-0.3-0.2-0.10.0CTmaxCTminToptAcyrthosiphon pisumTemperature (°C)Relative popand calculate pop. growth again (W100)• W100-Wcurrent= Impact (∆ in pop. growth)Impact (∆ in p∆TC.s. A.p.ability to acclimate to new temperatures is also a function of history with temperature change000.10.20.3pop. growth)Kurtz et al. 2008 NatureMountain Pine Beetle expansionLizard decline in Costa Rica Linked to climate change through reduced tree productivityIII. Physiology and ClimateIV. Positive Feedbacks60S 40S 20S 0 20N 40N 60N-0.3-0.2-0.10.0Impact (∆ in pDensity (per 100 m2)Whitfield et al., 2007 PNASPositive Feedback: 270 megatonnes (Mt) carbon released from an area the size of Montana from 2000-2020, Forests move from carbon sink to carbon source.Carbon and Soil - Permafrost, Peatlands and warming: a potential positive feedback driven by biologyIV. Positive Feedbacksmore carbon in soils than in the atmosphereIf warming increases decomposition, increased CO2 and methane (positive feedback)If increases in plant productivity are greater than increases in decomposition, more carbon would be trapped in soils (negative feedback)Outline• Looking at Impacts in different waysI. Climate – envelope (niche modeling)II. Response vs. ImpactIII.Physiology and ClimateIV. Positive feedbacks and ecosystem fxnsScientists Predict Widespread Extinction by Global WarmingNEW YORK, THURSDAY, JANUARY 8, 2004V. Range dynamics, climate, and the evolution of vagilityVI. Community impactsOutline• Looking at Impacts in different waysI.

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