Effect of extreme sea surface temperature events on the demography of an age-structured albatross population
Résumé
Climate changes include concurrent changes in environmental mean, variance
and extremes, and it is challenging to understand their respective
impact on wild populations, especially when contrasted age-dependent
responses to climate occur. We assessed how changes in mean and standard
deviation of sea surface temperature (SST), frequency and magnitude of
warm SST extreme climatic events (ECE) influenced the stochastic population
growth rate log(ls) and age structure of a black-browed albatross
population. For changes in SST around historical levels observed since
1982, changes in standard deviation had a larger (threefold) and negative
impact on log(ls) compared to changes in mean. By contrast, the mean
had a positive impact on log(ls). The historical SST mean was lower than
the optimal SST value for which log(ls) was maximized. Thus, a larger
environmental mean increased the occurrence of SST close to this optimum
that buffered the negative effect of ECE. This ‘climate safety margin’
(i.e. difference between optimal and historical climatic conditions) and the
specific shape of the population growth rate response to climate for a species
determine how ECE affect the population. For a wider range in SST, both the
mean and standard deviation had negative impact on log(ls), with changes
in the mean having a greater effect than the standard deviation. Furthermore,
around SST historical levels increases in either mean or standard deviation of
the SST distribution led to a younger population, with potentially important
conservation implications for black-browed albatrosses.
This article is part of the themed issue ‘Behavioural, ecological and
evolutionary responses to extreme climatic events’.