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Penguin census, completed from space, yields surprise

April 16, 2012
Courtesy of the National Science Foundation
and World Science staff

A new study us­ing sat­el­lite map­ping re­veals there are twice as many em­per­or pen­guins in Ant­arc­ti­ca as pre­vi­ously thought, sci­en­tists say.

“We are de­light­ed” with the find­ings, said ge­og­ra­pher Pe­ter Fretwell at Brit­ish Ant­arc­tic Sur­vey. “This is the first com­pre­hen­sive cen­sus of a spe­cies tak­en from space,” said Fretwell, who is the lead au­thor of the stu­dy, pub­lished this week in the re­search jour­nal PLoS One. “We counted 595,000 birds, which is al­most dou­ble the pre­vi­ous es­ti­mates of 270,000-350,000 birds.”

Em­per­or pen­guins with their ba­bies. (Cred­it: Paul Pon­ga­nis, US Nat'l Sci­ence Founda­tion )


Re­search­ers said the re­sults pro­vide key in­forma­t­ion for mon­i­tor­ing the im­pact of glob­al warm­ing on the icon­ic bird, which breeds in re­mote ar­eas that are hard to study be­cause they’re of­ten in­ac­ces­si­ble. Tem­per­a­tures in those re­gions fall as low as minus 58 de­grees Fahr­en­heit.

The sci­en­tists used high-res­o­lu­tion sat­el­lite im­ages to es­ti­mate the num­ber of pen­guins at each col­o­ny around the coast­line of Ant­arc­ti­ca. Us­ing a tech­nique called pan-sharpening to boost the im­age res­o­lu­tion, they were able to tell apart birds, ice, shad­ow and pen­guin poo, or gua­no. They then used ground counts and aer­i­al pho­tog­ra­phy to cal­i­brate the anal­y­sis.

On the ice, em­per­or pen­guins with their black and white plum­age stand out against the snow and col­o­nies are clearly vis­i­ble on sat­el­lite im­agery. This al­lowed the team to an­a­lyze 44 col­o­nies around the coast of Ant­arc­ti­ca, and sev­en pre­vi­ously un­known col­o­nies.

“The meth­ods we used are an enor­mous step for­ward in Ant­arc­tic ecol­o­gy be­cause we can con­duct re­search safely and ef­fi­ciently with lit­tle en­vi­ron­men­tal im­pact, and de­ter­mine es­ti­mates of an en­tire pen­guin popula­t­ion,” said co-au­thor Michelle LaRue from the Uni­vers­ity of Min­ne­so­ta. “We now have a cost-ef­fec­tive way to apply our meth­ods to oth­er poorly-understood spe­cies in the Ant­arc­tic, to strength­en on-going field re­search, and to pro­vide ac­cu­rate in­forma­t­ion for in­terna­t­ional con­serva­t­ion ef­forts.”

“Cur­rent re­search sug­gests that em­per­or pen­guin col­o­nies will be se­ri­ously af­fect­ed by cli­mate change. An ac­cu­rate continent-wide cen­sus that can be easily re­peat­ed on a reg­u­lar ba­sis will help us mon­i­tor more ac­cu­rately the im­pacts of fu­ture change,” added Brit­ish Ant­arc­tic Sur­vey bi­ol­o­gist Phil Trathan, anoth­er co-au­thor.

Sci­en­tists wor­ry that in some re­gions of Ant­arc­ti­ca, ear­li­er spring warm­ing is lead­ing to loss of sea ice hab­i­tat for em­per­or pen­guins, mak­ing their north­erly col­o­nies more vulnera­ble to fur­ther cli­mate change. The new cen­sus un­for­tu­nately does­n’t change that bas­ic out­look, Trathan said. “The ef­fects of warm­ing around Ant­arc­ti­ca are re­gion­al and un­even. In the fu­ture, we an­ti­cipate that the more south­erly col­o­nies should re­main, mak­ing these im­por­tant sites for fur­ther re­search and pro­tec­tion.”


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A new study using satellite mapping technology reveals there are twice as many emperor penguins in Antarctica than previously thought, scientists say. “We are delighted” with the findings, said geographer Peter Fretwell at British Antarctic Survey, lead author of the study, published this week in the research journal PLoS One. “This is the first comprehensive census of a species taken from space,” he said. “We counted 595,000 birds, which is almost double the previous estimates of 270,000-350,000 birds.” Researchers said the results provide key information for monitoring the impact of global warming on the iconic bird, which breeds in remote areas that are hard to study because they’re often inaccessible with temperatures as low as -58 degrees Fahrenheit. The scientists used high-resolution satellite images to estimate the number of penguins at each colony around the coastline of Antarctica. Using a technique called pan-sharpening to boost the image resolution, they were able to tell apart birds, ice, shadow and penguin poo, or guano. They then used ground counts and aerial photography to calibrate the analysis. On the ice, emperor penguins with their black and white plumage stand out against the snow and colonies are clearly visible on satellite imagery. This allowed the team to analyze 44 colonies around the coast of Antarctica, and seven previously unknown colonies. “The methods we used are an enormous step forward in Antarctic ecology because we can conduct research safely and efficiently with little environmental impact, and determine estimates of an entire penguin population,” said co-author Michelle LaRue from the University of Minnesota and funded by the U.S. National Science Foundation. “We now have a cost-effective way to apply our methods to other poorly-understood species in the Antarctic, to strengthen on-going field research, and to provide accurate information for international conservation efforts.” “Current research suggests that emperor penguin colonies will be seriously affected by climate change. An accurate continent-wide census that can be easily repeated on a regular basis will help us monitor more accurately the impacts of future change,” added British Antarctic Survey biologist Phil Trathan, another co-author. Scientists worry that in some regions of Antarctica, earlier spring warming is leading to loss of sea ice habitat for emperor penguins, making their northerly colonies more vulnerable to further climate change. The new census unfortunately doesn’t change that basic outlook, Trathan said. “The effects of warming around Antarctica are regional and uneven. In the future, we anticipate that the more southerly colonies should remain, making these important sites for further research and protection.”