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We’re Living in the Tropics

When it comes to climate change, we live on a tropical planet, we just don’t realize it

Finally, it seems, the world’s warmer climates – so often overlooked when it comes to the impact of climate change – shared the spotlight in a high-profile analysis of the earth’s steadily rising temperatures.

The tropics, not the poles, will experience unprecedented climates first and in the very near future, according to a study published Oct. 9 in Nature which drew headlines around the world. The concern, researchers explained, is that because tropical species exist in such narrow temperature ranges – unlike trees and plants in colder climates – even modest warming can have dire ramifications.

What might have come as news to many environmental journalists has long been conventional wisdom to Yadvinder Malhi, a professor of ecosystem science at Oxford University and one of the world’s leading tropical biologists.

In London in May, at the behest of Charles, the Prince of Wales, Malhi helped draft the St. James Palace Memorandum on Tropical Forest Science, which aims to promote strategies to protect tropical forests around the world. And in August, he helped lead the 10th annual meeting of the Andes Biodiversity and Ecosystem Research Group in Pisac, Peru, where he has joined an international team in studying the cloud and rain forests in the Amazon basin of southern Peru for more than a decade.

“There’s a lot of attention paid to the poles, and what’s happening there is alarming,” Malhi said during a wide-ranging interview in Pisac. “But what’s happening in the tropics is probably as important and alarming for a number of reasons.

“Firstly, the size of processes is very large. The productivity, the flow of carbon, the shear intensity of the metabolism of the tropics is so immense that it can affect things hugely. But the tropics are also the center of global diversity. Two-thirds to three-quarters of species live in the tropics. So what happens in the tropics determines what happens to the earth’s biodiversity. The fact is, we live on a tropical planet; we just don’t realize it because so many of us live in the colder latitudes.”

The eastern slope of the Andes in southern Peru has proved to be an ideal laboratory for Malhi and other biologists in the Andes Group to study climate change in the tropics. Species diversity is staggering. On a single Andean slope, starting at 13,000 feet above the treeline and dropping down to sea level in dense rain forests, there are more species of trees, plants, birds and insects than on the entire eastern seaboard of the United States, from the arboreal forests of Maine to the coral reefs of the Florida Keys.

Yadvinder Malhi presents his findings to Peruvian environmental officials in Lima in August.

Yadvinder Malhi presents his findings to Peruvian environmental officials in Lima in August. Photograph by Justin Catanoso

“When we started the Andes Group (in 2003), we were interested in how a warming world impacted the tropics,” Malhi said. “This was to be a great experiment in how different temperatures affected the functioning of the forests. And it was a different way of approaching the question than in a lab with seedlings or with computer models.”

In establishing a series of research plots down the spine of an Andean ridge in the Kosnipata Valley, Malhi and his colleagues from the U.K, United States and Peru could observe how nature was warming and cooling ecosystems as a whole. By studying remote, pristine forests, they could also see how those ecosystems have been responding to rising temperatures.

Two American biologists, Ken Feeley of Florida International University, and Miles Silman of Wake Forest University, established for the first time in a 2010 study that tropical species are on the move as a result of climate change. Trees are migrating upslope as they reproduce in search of cooler temperatures more suitable to their viability. That adaptability is good, except for this: temperatures are rising faster than many tree and plant species appear able to keep up. With temperatures predicted to exceed levels never before seen on earth in just the next 50 to 75 years, mass species depopulations and extinctions are seen as a distinct possibility.

In talking at length with Malhi, it becomes clear that he balances his deep understanding of forest mechanics and global ecology against so many grim findings and predictions connected to climate change. While patterns and trends are being established, he finds hope in the remaining unknowns.

“While there are worst-case scenarios, there are many other scenarios that are far from that worst case,” he said. “We still need to understand how to identify which scenario we’re heading toward. We still don’t have a complete understanding of how a tree responds to a few degrees of warming. Does it adapt to that warming? Does it evolve? Is it a major problem? These are some of the questions we need to get at.”

Refusing to lose sight of the forest for the trees, Malhi is quick to connect the viability of tropical forests to global temperature and weather, which are among the main reasons why the impact of climate change on the tropics demands far greater attention.

“The circulation of moisture in the atmosphere is driven by the engines in the tropics and rain forests,” Malhi said. “How clouds rise up in the tropics, which is influenced by the trees and patterns underneath, powers the entire global circulation. That’s why changes in rainfall in the Amazon feed forward to changes in rainfall in North America and Europe and in Central Asia.”

Those are just a few of the environmental services that tropical forests provide the planet, Malhi said, along with absorbing and storing greenhouse gases in their trunks, limbs and roots. Protecting their health and vitality is crucial to any international strategy to address the impacts of climate change.

“We need not despair that this change is going on,” he said, “but rather understand what the change is, what are the opportunities for ecosystems, and what are the threats. Nature is dynamic. It’s always changing and responding. We need to better understand the nature of that response and do our best to support it.”

Justin Catanoso is a freelance journalist based in Greensboro, N.C. His reporting on climate change is supported by the Pulitzer Center on Crisis Reporting in Washington, D.C.