Climate Change Is so Clingy

Hey, Tarzan, your vines are messing with our carbon storage.

Tropical forests hold a lot of carbon—about a third of all the carbon stored on land. Think of forests as giant sponges that suck up carbon dioxide from the atmosphere and store it for hundreds of years. When a tree dies, that carbon is slowly released back into the environment.

But not every plant in the jungle is pulling its own weight in terms of carbon storage, says a study published this week in the Proceedings of the National Academy of Sciences. Vines called lianas—think Tarzan—root themselves in forest soil and wrap around trees as they climb toward the canopy. Since trees support most of the lineas’ weight, the vines can expend more energy producing leaves than woody tissues.

Unlike the thick-trunked, long-lived trees they cling to, lianas keep most of their carbon in their leaves, which provide only short-term climate benefits. Leaves die, fall to the ground, and decompose, releasing much of their carbon load back into air.

These vines can hinder a tree’s growth and often contribute to its death. According to coauthor Stefan Schnitzer, a biology professor at Marquette University and research associate at the Smithsonian Institute for Tropical Research, when it comes to carbon storage, people have assumed it doesn’t matter whether it’s 100 big, old-growth trees or 500 thin-stemmed vines—the prevailing thinking has been that all plants within the ecosystem chip in. But what this research suggests is that lianas don’t compensate for how much carbon a tree can store once they kill it off.

In a 60-year-old secondary rainforest in Panama, the researchers experimented on 16 large plots. In half of them, they cut away all the vine; in the other eight, they left the lianas alone. After three years, they compared the two groups and found that the lianas had reduced the carbon-holding potential of their plots by 76 percent each year.

Lianas aren’t all bad, though. They’re a natural part of these ecosystems, and in some cases, they give a little structural support back to trees. They also serve as an arboreal highway for animals, such as ants, lizards, sloths, monkeys, and lemurs.

What’s worrisome is that lianas are becoming more abundant in tropical forests—a surge possibly driven by climate change, drought, or other factors. A positive feedback loop where a changing climate brings more vines and more vines release more and more of the forest’s carbon into the atmosphere has the potential to turn into quite a death grip.

This article was originally published on onEarth, which is no longer in publication. onEarth was founded in 1979 as the Amicus Journal, an independent magazine of thought and opinion on the environment. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. This article is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the article was originally published by and link to the original; the article cannot be edited (beyond simple things such grammar); you can’t resell the article in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select articles individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our articles.

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