Penguin declines linked to warming
Adélie penguins nest on rocky outcrops of the West Antarctic Peninsula and as glaciers retreat, the habitat increases. But the population is declining, and researchers at the University of Delaware believe it may be because it’s too warm.
The research team projects there could be a 30 percent decline of the bird colony by 2060 and a 60 percent drop by the turn of the century, based on a model that looks at long-term temperature shifts on the peninsula and correlates that over time to the size of the penguin population.
“It is only in recent decades that we know Adélie penguins population declines are associated with warming, which suggests that many regions of Antarctica have warmed too much and that further warming is no longer positive for the species,” said Megan Cimino, who earned her doctoral degree from the University of Delaware in May.
Cimino has done her research out of Palmer Station, reached by boat from the southern tip of South America. She and research adviser Matthew Oliver estimate penguin colonies near there have declined by at least 80 percent since the 1970s. Regionally, they observed most years with a warmer-than-normal sea-surface temperature.
Cimino was the lead author in a paper published in Scientific Reports and was joined in the research by Oliver, principal investigator on the project who is the Patricia and Charles Robertson Professor of Marine Science and Policy at the College of Earth, Ocean, and Environment; Heather J. Lynch, assistant professor in the Department of Ecology and Evolution at Stony Brook University; and Vincent S. Saba, a research fishery biologist with the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service.
Cimino previously looked at how annual climate variability impacted penguin populations in the region. She and others recognized that because some years are warmer or colder than others, the glaciers retreat and expand. During warmer periods, when the glaciers retreat, there are more of the bare rock habitats that Adélie penguins favor for nesting.
Her latest research takes a longer view look at the bird population.
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"The declining populations are associated with many years of ... climate warming" and that warming is likely associated with "warmer than normal sea surface temperatures," she said
The researchers aren't sure why the warming temperatures are causing the decline in population, but they believe it is connected to the warming signal they detected when they looked at years of temperature and population data to build a model that can project into the future. The West Antarctic Peninsula is one of the most rapidly warming areas on earth, she said.
Even with the decline, "it's not all doom and gloom," Cimino said. Thousands of miles away at the Ross Sea there is another population of Adélie penguins and that population seems stable, she said. The Cape Adare region of the Ross Sea is home to the earliest known penguin occupation and has the largest known Adélie penguin rookery in the world, CImino said.
The research goal with this project was to better understand the effects on climate change on Antarctic Adélie penguin colonies. The study builds on work that looked at shifting ecosystems on the southern-most continent. They tracked penguins and their habitats. The latest work used satellite data and global climate model projections to look at population trends now and into the future.
The research was supported by the NASA Biodiversity program and is based on satellite observations from 1981-2010 of sea surface temperature, sea ice and bare rock locations, presence-absence data of penguins from satellite imagery.
The scientists zeroed in on the period from 1981-2010 with novel or unusual climate during the Adélie penguin chick-rearing period. Using this data, they projected out what might happen to the population in the future.
One of the key advances over the last decade is our ability to find penguin colonies from space and, nearly as important, to determine which areas of Antarctica do not support penguin colonies, Lynch said. "Having both true presence and absence across a species’ global range is unique to this system, and opens up new avenues for modeling habitat suitability.”
Adélie penguins are already declining in the southern and northern Western Antarctic Peninsula and nearby islands, Cimino said.
The researchers believe that over time, the population will contract to the southern part of its range.
“Studies like this are important because they focus our attention on areas where a species is most vulnerable to change,” Cimino said. “The results can be used for management; they can have implications for other species that live in the area and for other ecosystem processes.”
Reach Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.