Assessing extinction risks under the combined effects of climate change and human disturbance through the analysis of life-history plasticity

Plastic responses of species to unprecedented conditions and increased variability caused by climate change (CC) and anthropogenic disturbances are expected to play a major role determining populations’ extinction risk. We developed a method for assessing CC effects on population dynamics based on analyzing plastic life history responses to weather conditions within an ensemble forecasting framework. The method is illustrated using two threatened cactus species with contrasting distribution ranges. Demographic models were parameterized using 5 years of field data, from which the relationship between life-history traits and rainfall and temperature was estimated. These functions were used in Integral Projection Models to predict population growth under CC scenarios and different anthropogenic disturbance regimes. Both species were affected by CC and its interaction with disturbance. The most widespread species was less affected by CC, suggesting that past selection on plasticity allows it to survive under variable conditions. Managing disturbance appropriately lessened the impact of CC. Some directives for conservation under CC were identified based on projected elasticity values. Our procedure for modeling population dynamics as a function of climate may be used for designing management plans for conservation or sustainable use aimed at important plant sizes or life-history traits, predicting potential distributions, and identifying viable populations.