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How Tropical Vines Could Be Impacting The Pace Of Climate Change

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Stefan Schnitzer
Vines are outcompeting tropical trees on Barro Colorado Island.

Marquette University biologist Stefan Schnitzer spends months at a time at his lab on Barro Colorado Island in Panama. Amidst the fauna and flora, the island is home to dozens of woody vine species, or liana.

“And what’s happening now is that the forests are changing enough that they (lianas) seem to be thriving when many trees are not,” Schnitzer says.

Trees are important not simply to a balanced tropical forest ecosystem, they are vital to the planet. “What we want from these forests is that they pull the carbon into the tree trunk for a thousand years,” he says.

Schnitzer says 95 percent of carbon in tropical rainforests is in tree trunks and soils, and the majority of that being in the trunk of trees.

His team is chronicling a shift in the tropical forest - vines are stopping the trees from growing and increasing tree mortality. This is bad, he says, because more carbon is getting into the air.

Credit Sergio Estrada-Villegas
Member of Schnitzer's team cutting liana.

In 2007, Schnitzer’s team launched a census on a 125-acre plot focusing on 65,000 individual vines. “And the reason we need so many individuals is because there are 180 species, and we’re finding new ones. And you have to have enough replication where you can notice a clear trend of change,” Schnitzer says.

This allows his team to determine which vine species are increasing, and which are decreasing.

“Some people would view that carbon storage in tropical forests is a zero sum game. If one plant out-competes it just takes its carbon and carbon stays fairly stable over time, so who cares if there’s plant A or plant B,” he says. However, Schnitzer’s team is learning that this assumption is false.

Lianas don’t take up nearly the amount of carbon dioxide trees do, and as a result: “These tropical rain forests seem to be pulling up less carbon and storing less carbon over time,” Schnitzer says.

He hopes his research will increase the understanding of how tropical forests work and how they are changing.

Credit Stefan Schnitzer
liana competition experiments - which thrive, which don't - in a shade-house.

“This research is also showing some of the changes that are happening over a very short period of time,” Schnitzer adds. “ It’s not as stable as we thought it was. These forests are changing rapidly and that has huge ramifications for climate change and is feeding back into climate change.”

Yet, he says, “Tropical forests may still be able to save us.”

Schnitzer calls it a simple formula: “We need to increase carbon [storage] and decrease carbon sources. If we do that, I think we can start to reverse these changes in the climate. It may take 50 years to do, but that’s along the time scale that got us into this mess.”

Credit Susan Bence / Milwaukee Public Radio
Milwaukee Public Radio
Stefan Schnitzer, second from right, with his Marquette University lab team.

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Susan Bence entered broadcasting in an untraditional way. After years of avid public radio listening, Susan returned to school and earned a bachelor's degree in Journalism from the University of Wisconsin Milwaukee. She interned for WUWM News and worked with theLake Effect team, before being hired full-time as a WUWM News reporter / producer.