Current estimates of population resilience are not robust to the longer-term impacts of directional environmental shifts

Abstract

Natural systems worldwide are exposed to gradual changes imposed by directional environmental shifts, known as ramp disturbances. However, contemporary assessments of population resilience focus on the resistance and recovery of systems following one-off (i.e., pulse) disturbances. Thus, our current perception of demographic resilience overlooks the potential impacts of the cumulative effects of ramp disturbances on population dynamics. Simulating 50-year ramp disturbance scenarios upon the survival and fecundity dynamics of 511 populations across 344 species, we illustrate non-linear patterns in how directional environmental shifts will reshape the resilience of natural populations. Accordingly, existing estimates of population resilience are not robust against a backdrop of ongoing and continuous environmental change. Instead, we demonstrate the need to quantify how the relative partitioning of energetic resources across survival vs. fecundity informs population resilience. Our findings challenge the use of well-established approaches in forecasting population resilience to ongoing global change.