Demographic models and IPCC climate projections predict the decline of an emperor penguin population

Abstract

Studies have reported important effects of recent climate change on Antarctic species, but there has been to our knowledge no attempt to explicitly link those results to forecasted population responses to climate change. Antarctic sea ice extent (SIE) is projected to shrink as concentrations of atmospheric greenhouse gases (GHGs) increase, and emperor penguins ( Aptenodytes forsteri ) are extremely sensitive to these changes because they use sea ice as a breeding, foraging and molting habitat. We project emperor penguin population responses to future sea ice changes, using a stochastic population model that combines a unique long-term demographic dataset (1962–2005) from a colony in Terre Adélie, Antarctica and projections of SIE from General Circulation Models (GCM) of Earth's climate included in the most recent Intergovernmental Panel on Climate Change (IPCC) assessment report. We show that the increased frequency of warm events associated with projected decreases in SIE will reduce the population viability. The probability of quasi-extinction (a decline of 95% or more) is at least 36% by 2100. The median population size is projected to decline from ≈6,000 to ≈400 breeding pairs over this period. To avoid extinction, emperor penguins will have to adapt, migrate or change the timing of their growth stages. However, given the future projected increases in GHGs and its effect on Antarctic climate, evolution or migration seem unlikely for such long lived species at the remote southern end of the Earth.

Adélie penguin (Pygoscelis adeliae) survival rates and their relationship to environmental indices in the South Shetland Islands, Antarctica

“…Recent studies in seabirds have demonstrated how increased variance in survival rates due to environmental variability can drive population declines (Frederiksen et al 2008;Jenouvrier 2009). A hallmark of model predictions for future climate change in the Antarctic includes continued directional change, but also increases in climate variation and extreme events (Solomon et al 2007).…”

“…If such events cause the frequency of years with poor survival rates to increase, accelerated population decline may occur. This prediction can be tested with a demographic model of population dynamics (e.g., Jenouvrier et al 2009) and is the focus of the ongoing research.…”

“…The chosen variables covered a time span of 1982 through 2011 and included indices of large-scale atmospheric forcing (Southern Oscillation Index (SOI) and the Southern Annular Mode (SAM), a local index of physical habitat (sea ice extent) during the non-breeding season (March-November) in the WAP region, a regional index of sea ice extent for the non-breeding season across the entire Weddell Sea, and local measures of environmental conditions (spring temperatures and precipitation). These six environmental variables have been implicated previously as factors affecting Adélie population dynamics and survival throughout much of their breeding range (Forcada and Trathan 2009;Jenouvrier et al 2009), and we have selected them to examine their utility for explaining variation in survival rates in a northern breeding population studied here.…”

“…In particular, long-term data on Antarctic seabirds dependent on sea ice habitats, including emperor (Aptenodytes forsteri) and Adélie penguins (Pygoscelis adeliae), and snow petrels (Pagodroma nivea) suggest that variation in the seasonal duration and spatial extent of winter sea ice can be important drivers of population change (Croxall et al 2002;Jenouvrier et al 2005;Emmerson and Southwell 2011). Demographic models that link vital rates to environmental drivers (e.g., Jenouvrier et al 2009) and habitatassociation models (e.g., Ainley et al 2010) suggest that continued warming and loss of sea ice in Antarctica may hasten declines in the abundance of ice-obligate species.…”

Fitness implications of seasonal climate variation in Columbian ground squirrels

“…As climate change is expected to accelerate in the future (IPCC 2014), such explicit links are arguably more relevant in our establishing an ability to predict responses to climate change than broad‐scale phenotypic shifts (e.g., Jenouvrier et al. 2009; Ozgul et al. 2010).…”