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, 106 (6), 1844-7

Demographic Models and IPCC Climate Projections Predict the Decline of an Emperor Penguin Population

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Demographic Models and IPCC Climate Projections Predict the Decline of an Emperor Penguin Population

Stéphanie Jenouvrier et al. Proc Natl Acad Sci U S A.

Erratum in

  • Proc Natl Acad Sci U S A. 2009 Jul 7;106(27):11425

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 approximately 6,000 to approximately 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.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Stochastic growth rate (logλs) as a function of the frequency w and mean duration d of warm events (in years). It was calculated from a stochastic model with 2 states: normal and warm environmental conditions. The contour denotes logλs = 0. The frequency of warm events must satisfy d > . The dark area indicates impossible combinations of w and d.
Fig. 2.
Fig. 2.
Sea ice anomolies and warm events. (A) Proportional change in winter sea ice extent anomalies (SIEa) in Terre Adélie (sector 120°E-160°E), measured relative to the mean over the period 1982–2006, produced by 10 coupled IPCC climate models from 1900 to 2100 (for line colors, see legend). (B) Frequency of warm events calculated from the backward projections of SIEa for 10 IPCC climate models from 1900 to 2006 (color lines) and calculated from SIEa satellite observations from 1979 to 2006 (black line) as a function of the threshold defining a warm event. The frequency of warm events experienced by emperor penguin between 1952 and 2006 is 0.18, and is represented by the dotted line. (C) Frequency of warm events from 1900 to 2100 calculated from the SIEa produced by 10 IPCC climate models with the most conservative warm event threshold of −0.15. The dotted black line represent wt calculated from the sequence of warm and normal events define by the observed regime shift from 1952 to 2006.
Fig. 3.
Fig. 3.
Quasi-extinction and population projection. (A) Probability of quasi-extinction (a decline of 95% or more) of the emperor penguin population in Terre Adélie by 2100, as a function of the warm event thresholds. The distribution of warm event thresholds calculated from Fig. 2B for the 10 IPCC models is represented by the gray bars, and warm event threshold calculated from Fig. 2B for the satellite observation by the vertical dotted line. The probability of quasi-extinction varied from 0.36 to 0.84 over the range of likely thresholds [−0.15; 0.07]. (B) Observations and projections of the emperor penguin population. The thick dark line is the observed number of breeding pairs. The thick orange line from 1962 to 2000 is the projected number of breeding pairs based on the observed sequence of warm events. The thick red line from 2005 to 2100 is the median of 10,000 stochastic projections based on the forecasts of SIEa produced by the 10 IPCC models. To give a sense of the variability in these projections, 30 projections from 2005 to 2100 (three for each climate model) are shown; line colors as in Fig. 2.

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