Modeling the future of a charismatic bird
July 30, 2014 |
Emperor penguins, the large, charismatic birds known from their
frequent film and TV appearances, are in danger. A collaborative
research project is drawing attention to the impending plight of the
emperors. By 2100, according to a new study, their numbers will have
fallen by around 19% and will continue to decline, qualifying the
species for endangered status.
Emperor penguin communities entirely ring the continent
of Antarctica. Of the 45 known colonies, only one has been extensively
studied for decades, and most of the others have never been visited by
humans, nor are they likely to be. Emperors live on sea ice off the
coast of the continent, and the amount of ice plays a major role in
determining the health of a colony. Too much ice and the penguins have a
long, debilitating walk to the sea and food; too little ice and the
colony is more exposed and vulnerable to predation.
A colony of emperor penguins at Australia's Snow Hill Island, October 2009. (Photo by Jenny Varley, Wikimedia Commons.)
Stéphanie Jenouvrier (Woods Hole Oceanographic
Institution) is an expert on penguin life, and she wanted to project the
size of emperor populations into the future as Earth’s climate warms.
The problem, she says, was her “limited background on climate science.”
Meanwhile, at NCAR, senior scientist Marika Holland is a climate
scientist with a longstanding specialty in modeling sea ice changes,
although she has never been to Antarctica and has never seen an emperor
penguin.
Aware of Holland’s previous work, Jenouvrier contacted
her and Julienne Stroeve at the University of Colorado’s Cooperative
Institute for Research in Environmental Sciences. The three of them
collaborated on preliminary studies published in 2009. Jenouvrier
received a fellowship from CIRES and worked in Boulder for almost a
year, collaborating closely with Holland, Stroeve, Mark Serreze at the
CIRES National Snow and Ice Data Center, and other scientists on a
follow-up study, published in 2012, and on their most extensive update,
recently published in Nature Climate Change.
The biologists used long-term data from the one
well-studied emperor colony, off the coast of Terre Adélie, to estimate
the relationship between sea ice and rates of breeding success and
survival of chicks. They used the record of penguin population and sea
ice concentrations at Terre Adélie to estimate vital rates
(births/deaths) and population dynamics at each colony.
Learning each other’s languages: biology and climate
The next challenge was to project sea ice changes over the rest of the 21st
century and relate that to the health of each penguin community. Sea
ice off Antarctica does not behave uniformly: although the total area of
sea ice around the continent has increased somewhat in recent years,
the trends vary by region during the course of a year and over longer
periods. Sea ice must therefore be studied in the relatively small
segments that host individual colonies, in order to assess the viability
of penguin populations. At first, says Holland, the biologists and
climate modelers spoke two different languages, which was “a bit of a
barrier.” The frequent interchanges during Jenouvrier’s year in Boulder
helped bridge that gap, she adds.
The sea ice scientists began with a group of 20 or so
climate models and settled on a widely used midrange scenario of
emissions produced for the Intergovernmental Panel on Climate Change
called SRES A1B.
Once the penguin population models and sea ice change models were set,
climate projections were fed into the penguin population models. Due to
inherent uncertainties in the models, Jenouvrier ran tens of thousands
of computer simulations to achieve the results that the team published.
They found that sea ice will generally decline and its
variability will increase by the end of this century. As a result, the
simulations indicate that emperor populations will increase by around
10% through midcentury, but then decline to 19% below current levels by
2100. One group of 7 colonies facing the Ross Sea will still be
non-threatened by that time, although with a reduced population. On the
other side of the continent, facing the Indian Ocean and Weddell Sea, 10
colonies will face quasi-extinction. Most of the rest will qualify as
endangered.
The collaborative nature of a study like this, Holland
says, allows the expertise of NCAR scientists to inform such other
fields as biology and economics to better understand the global system.
The researchers conclude that the emperor penguin is “fully deserving of
Endangered status due to climate change, and can act as an iconic
example of a new global conservation paradigm for species threatened by
future climate change.”
| WriterHarvey Leifert ContactDavid Hosansky, NCAR & UCAR Communications Collaborating institutionsNational Center for Atmospheric Research University of Amsterdam University College London University of Colorado/Cooperative Institute for Research in Environmental Sciences University of La Rochelle Woods Hole Oceanographic Institution FundersAlexander von Humboldt Foundation European Research Council Grayce B. Kerr Fund National Oceanic and Atmospheric Administration National Science Foundation Penzance Endowed Fund in Support of Assistant Scientists Woods Hole Oceanographic Institution |
Dive deeper
Stéphanie Jenouvrier, Marika Holland, Julienne Stroeve, Mark Serreze, Christophe Barbraud, Henri Weimerskirch and Hal Caswell, Projected continent-wide declines of the emperor penguin under climate change, Nature Climate Change (2014), doi:10.1038/nclimate2280In Graphic Terms
Annual mean change of sea ice concentrations (SIC) between the twentieth and twenty-first centuries and conservation status of emperor penguin colonies by 2100. SIC projections were obtained from a subset of atmosphere-ocean general circulation models. Dot numbers refer to each colony evaluated, with dot color showing conservation status (red = quasi-extinct, orange = endangered, yellow = vulnerable, green = not threatened). (Figure 1 from Jenouvrier et al., Projected continent-wide declines of the emperor penguin under climate change, doi:10.1038/nclimate2280; image courtesy Nature Climate Change.)
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