Effect of extreme sea surface temperature events on the demography of an age-structured albatross population

International audienceClimate changes include concurrent changes in environmental mean, varianceand extremes, and it is challenging to understand their respectiveimpact on wild populations, especially when contrasted age-dependentresponses to climate occur. We assessed how changes in mean and standarddeviation of sea surface temperature (SST), frequency and magnitude ofwarm SST extreme climatic events (ECE) influenced the stochastic populationgrowth rate log(ls) and age structure of a black-browed albatrosspopulation. For changes in SST around historical levels observed since1982, changes in standard deviation had a larger (threefold) and negativeimpact on log(ls) compared to changes in mean. By contrast, the meanhad a positive impact on log(ls). The historical SST mean was lower thanthe optimal SST value for which log(ls) was maximized. Thus, a largerenvironmental mean increased the occurrence of SST close to this optimumthat buffered the negative effect of ECE. This ‘climate safety margin’(i.e. difference between optimal and historical climatic conditions) and thespecific shape of the population growth rate response to climate for a speciesdetermine how ECE affect the population. For a wider range in SST, both themean and standard deviation had negative impact on log(ls), with changesin the mean having a greater effect than the standard deviation. Furthermore,around SST historical levels increases in either mean or standard deviation ofthe SST distribution led to a younger population, with potentially importantconservation implications for black-browed albatrosses.This article is part of the themed issue ‘Behavioural, ecological andevolutionary responses to extreme climatic events’