How climate “pressures” and “pulses” affect Magellanic penguins

Climate change will reshape ecosystems around the world through two types of climate events: short-term extreme events – such as a heat wave – and long-term changes, such as a change in ocean currents. Environmentalists call short-term events “pulses” and long-term changes “pressures.”

Presses and legumes will likely have different effects on animal species. But how? And how will the animals react? Answering these questions is not an easy task because individual events can have radically divergent impacts on an animal species. Yet understanding the effects of presses and legumes is essential as environmental advocates and policymakers attempt to preserve ecosystems and safeguard biodiversity.

Researchers from the University of Washington have discovered the impact of different pressures and impulses on Magellanic penguins – a migratory marine predator – over nearly four decades at their largest historic breeding site in Punta Tombo, Argentina. In an article published the week of January 9 in the Proceedings of the National Academy of Sciences, the team from the UW’s Center for Ecosystem Sentinels reports that while individual pressures and drives impacted penguins in various ways, both were equally important to the future survival of the penguin population . They also found that these types of climate changes, taken together, lead to an overall population decline at that particular site.

“We found that penguin survival does not depend solely – or even largely – on one or a few climatic effects,” said lead author TJ Clark-Wolf, a postdoctoral researcher in biology at the UW and scientist at the center. “Instead, many different pressures and impulses impact penguin reproduction and survival over time.”

The study analyzed data collected at Punta Tombo from 1982 to 2019 by co-author Dee Boersma, founder of the Center for Ecosystem Sentinels and a UW biology professor, and colleagues. The data includes:

• survival and reproductive success of nearly 54,000 penguins at the site, which is historically where hundreds of thousands of Magellanic penguins come to breed each summer
• climatic conditions during each breeding season
• ocean conditions off Punta Tombo, where adults feed during the breeding season and bring food back to the nest to feed their chicks
• ocean conditions off the coast of South America, where adults and juveniles feed during their migration outside of the breeding season

Rain soaks the down of a Magellanic chick, left, which is still too young to have the waterproof plumage of its parent, right. Photo by Dee Boersma/UW Center for Ecosystem Sentinels

Clark-Wolf and lead author Briana Abrahms, assistant professor of biology at the UW, integrated these data into an integrated population model that analyzed the effects of separate pressures and drives on the survival of Magellanic penguins in the over time. They found that different climate effects had distinct impacts on the Punta Tombo population. For example, heat waves – a climate pulse – have a detrimental effect on the population by killing both adults and chicks, as illustrated by a single-day heat wave in 2019 in Punta Tombo that killed more than 350 penguins. Climatic pressure and increased rainfall at the site have also negatively impacted the population, as storms during the breeding season kill chicks from exposure.

The gradual weakening of the plume of silt expelled into the ocean by the Río de la Plata, the second largest river basin in South America, is one of the factors that has had a positive impact on penguin survival. This pressure impacts penguins’ winter feeding waters off the coasts of northern Argentina, Uruguay and Brazil. Previous research by Ginger Rebstock, co-author of the new study and a research scientist at the UW, indicated that a weaker plume could allow penguins, especially females, to catch enough food each winter and to return to the breeding site in peak season. condition.

But the positive effects of a weakened plume could not offset the negative effects of other climate events in Punta Tombo, which over nearly four decades has become hotter and wetter. The number of breeding pairs at the site has declined from a peak of around 400,000 in the early 1980s to around 150,000 in 2019.

“This colony will be 100 years old in 2024, but we completed another field study at the end of October in Punta Tombo and its numbers continue to decline,” Boersma said. “The penguins tend to move north to be closer to their food.”

Studies have found that Magellanic penguins establish other breeding sites further north on the South American coast in search of better feeding opportunities.

A summer scene at the Magellanic penguin colony at Punta Tombo in Argentina. Photo by Dee Boersma/UW Center for Ecosystem Sentinels

Understanding how these presses and legumes shape this population is crucial to informing conservation efforts, the researchers said.

“For conservation to be most effective, we need to know where, when and how to use our limited resources,” Abrahms said. “The information generated by this study tells us which climate effects we should worry about and which we should not worry about – and therefore can help us focus on the measures we know will have a positive impact.”

The decades of faithfully collected data at Punta Tombo allowed the team to examine the effects of long-term climate change and extreme events in combination and, therefore, better predict the impact of climate on this population over time. ‘future. They say it’s this same approach that can help conservationists and scientists understand how climate change will shape other long-lived animal species in our warming planet.

Thanks to the University of Washington for this news.