Climate mitigation contributes more to population persistence than evolutionary adaptation in a long-lived seabird.

Evolutionary rescue-the process by which adaptive evolution prevents population extinction following environmental deterioration -is frequently proposed as a buffer against biodiversity loss under climate change, yet its capacity to alter future population trajectories is rarely assessed quantitatively. Most forecasts of evolutionary rescue rely on simplified demographic models, focus on a single adaptive trait, and explore hypothetical environmental scenarios rather than standardized climate pathways, neglecting uncertainty from demographic and internal climate variability. We developed a hyperstate eco-evolutionary population model coupled with large ensembles of climate projections from global climate models to test whether evolutionary adaptation or climate mitigation (through reduced greenhouse gas emissions) can prevent declines in a threatened seabird, the black-browed albatross. We parameterized this framework using three decades of demographic and phenotypic data, while propagating uncertainty from demographic processes and natural climate variability in climate projections. We modeled selection on morphological, behavioral, and phenological traits affecting different life-cycle components across climate scenarios. Across climate scenarios, evolution increased population size under stationary historical climates but failed to prevent decline under projected warming. Increasing heritability had little effect on extinction risk, whereas climate mitigation reduced extinction probability by approximately half. Evolutionary rescue occurred only under the most optimistic climate scenario when climate change directly strengthened selection on wing length, a trait affecting juvenile survival. Our results reveal limits to evolutionary rescue under environmental change.