A team led by Michigan Technological University researcher Jared Wolfe is the first to uncover why long-lived rainforest birds are declining in an untouched environment historically considered a stable refuge. Their findings are alarming.
The results of the team's 27-year study, "Climate change aggravates bird mortality in pristine tropical forests," were recently published in Science Advances. They reveal that rising temperatures and decreasing rainfall have played a key role in drastically reduced survival rates in dozens of bird species — in some individual species by as much as 50%.
"This study signals an emerging crisis for birds in one of the world's most biodiverse regions."
"Our results provide the first evidence linking climate change, manifested through increasingly severe dry seasons, with decreased annual survival from a community of lowland understory tropical birds," said Wolfe, an assistant professor of wildlife ecology in Michigan Tech's College of Forest Resources and Environmental Science.
Researchers analyzed 4,264 annual bird captures over the 27-year period, covering 29 study species at 20 different sites in the Amazon rainforest from May through October from 1985 to 2012. They predicted that a 1-degree Celsius (1.8 degrees fahrenheit) increase in average dry-season temperature led to an estimated 63% reduction in survival rates across the entire understory bird community.
Wolfe said the need to understand how climate change is eroding diversity in pristine forests is urgent. Equally urgent is finding out what characteristics present in the landscape can help forests overcome climate challenges and thrive. The other key piece of the solution is formulating policies designed to safeguard resilient forests. "These are essential steps toward ensuring the persistence of vulnerable tropical bird communities into the 22nd century," Wolfe said.
Long-term datasets focused on measuring the impacts of climate change on bird demographics are scarce. That's also reason for concern, said Wolfe.
"We fear that the loss of birds at our study site is not unique and represents a larger pattern of diminished avian survival across the Neotropics. The research underscores the need to identify climate change refugia within the Amazon and other Neotropical regions to safeguard biodiversity."
Wolfe said more research is required to pinpoint the exact causes of bird mortality.
For example, it's important to know whether birds are perishing due to decreased food resources, thermoregulatory stress or a combination of both. Understanding all of the factors in play will allow for effective management plans that can help save at-risk bird populations. "The study calls for focused conservation efforts to protect vulnerable species as climate pressures increase," he said.
Hope is the Thing with Feathers
In light of such discouraging data, it's natural to wonder if many bird species someday will only be available to view in digital formats that allow us to remember them. But Wolfe and others are not complacent. A co-founder of the Biodiversity Initiative, Wolfe has often said that the goal of his research is not to document the end of species but rather to find the root causes of population declines and create solutions that result in recovery. That approach is leading to bold yet practical experiments, like cooling Upper Peninsula mines in order to create healthy habitats for bats — and irrigating the understory of the Amazon rainforest.
"These findings challenge the assumption that intact tropical rainforests are resilient to climate change. These birds serve as sentinels of climate change and broader disruptions to the whole ecosystem that we find inside these rainforests."
Wolfe is working with other researchers on irrigating a section of the understory in Brazil, piping water from a nearby reservoir. The National Science Foundation-funded project, in its early phase, includes team members David Luther at George Mason University and Cintia Cornelius Frische of Federal University of Amazonas in Manaus in Brazil.
"What we're trying to do is understand how birds respond to this artificial irrigation," said Wolfe. "We're trying to mimic the precipitation regimes of 40 or 50 years ago. Hopefully we can identify those microclimatic conditions that support abundant and healthy bird communities."
Explore the rainforest irrigation project on Michigan Tech YouTube.
Michigan Technological University is a public research university founded in 1885 in Houghton, Michigan, and is home to nearly 7,500 students from more than 60 countries around the world. Consistently ranked among the best universities in the country for return on investment, Michigan’s flagship technological university offers more than 120 undergraduate and graduate degree programs in science and technology, engineering, computing, forestry, business, health professions, humanities, mathematics, social sciences, and the arts. The rural campus is situated just miles from Lake Superior in Michigan's Upper Peninsula, offering year-round opportunities for outdoor adventure.
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