Albatrosses hooked in the wind of change.

Marine megafauna, a key component of ocean condition and functioning (1), is increasingly threatened by direct exploitation, incidental capture of nontarget species or bycatch, competition for forage fish by fisheries, pollution, and rapid ongoing climate change (2, 3). Seabirds are particularly at risk and their conservation status has deteriorated faster over recent decades (4). Currently, 31% of the world’s seabird species are listed as threatened on the International Union for the Conservation of Nature’s Red List and 45% of the species of albatrosses, petrels, and shearwaters are threatened (5). However, assessing seabird population status and trends, and proposing management actions require a good understanding of these threats and a quantification of their relative and combined impacts on demography and population dynamics. Although several studies have investigated the effect of individual environmental factors on seabird demographics, most only examined part of the demographic components, few investigated the additive effects of several environmental actors, and even fewer used a multiple species and comparative approach. In PNAS, Pardo et al. (6) address this gap by analyzing nearly all demographic rates (immigration and emigration rates are very challenging to estimate from single-site studies and were not estimated), and by identifying demographic, climate, and anthropogenic drivers of population growth rates, the rate at which the number of individuals in a population increases in a given time period expressed as a fraction of the initial population, of three sympatric albatross species since the early 1980s. The comparative approach and the results presented by Pardo et al. (6) significantly expand our view of ecological processes governing seabird populations and suggest the possibility of a new form of fisheries mitigation. Several statistical methods exist to describe and explain demographic processes in populations (the demographic paradigm) and to quantify the impact of environmental factors on demographics (the ecological paradigm). Pardo et al. (6) used the more processoriented approach based on estimation and analysis of demographic parameters, such as survival or breeding probabilities, assessment of the effect of environmental factors on these parameters, and joint modeling of these parameters using matrix population models (7, 8). Using high-quality data from ringed individuals collected over five decades as part of a remarkable long-term monitoring program of albatrosses on Bird Island, South Georgia, Southern Ocean, Pardo et al. (6) are able to disentangle the relative and additive influences of fisheries and climate on the population dynamics of albatrosses, including their effects on juvenile and immature classes. Estimating juvenile and immature survival is challenging in such long-lived species where individuals remain continuously at sea during their early life (9). By doing so, the effects of environmental drivers on population dynamics were examined over the entire life cycle, which, together with the wealth of information assembled, including at-sea distribution data to inform spatial exposure of individuals to environmental conditions, constitutes a particular strength of the Pardo et al. (6) study. A full understanding of the effects of environmental drivers on the dynamics of wild populations requires estimating the relative contribution of each demographic rate to the observed changes in population growth rate. Pardo et al. (6) estimate these contributions and show that adult survival was, in average, the largest contributor in all species, but the contributions of the other demographic rates differed between species. Juvenile survival and recruitment were the second most important contributors for the wandering albatross Diomedea exulans, whereas for the gray-headed Thalassarche chrysostoma and blackbrowed albatrosses Thalassarche melanophris it was breeding success. Pardo et al. (6) then show that exposure to longline fisheries negatively affected adult survival for two of the three species, which given the extreme sensitivity of population growth rate to adult survival in these long-lived marine species, resulted in alarming population declines (from ∼43% to ∼65%) since the 1980s. Although positive effects of fisheries were foundon somebreeding parameters, their influence