Project to Eradicate Termites Reveals How Much Rainforests Need Them

A termite carrying larvae.
Photo: University of Liverpool / Natural History Museum

Homeowners tend to equate termites with property value apocalypse, but ecologically speaking, they’re more a force of stability than destruction. A new study points to how termites can help the rainforests they call home to weather droughts—which are expected to increase in frequency and intensity as climate change causes the tropics to heat up.

Termites are found across the tropics, where they feed on wood and dead leaves and build mounds that can sometimes be seen from space. Despite the wide-ranging influence of these ecological engineers, there’s been little research on how termites impact the ability of the forests they call home to withstand one of the biggest natural disturbances they face: drought.

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That’s an important knowledge gap, since climate change is already causing some rainforests to become drier, and cyclical events like El Niño can trigger drought across the tropical belt. These droughts come with global consequences: During the mega El Niño of 2015-2016, Earth’s tropical forests spewed an extra 2.5 billion tons of carbon into the air, something researchers attributed to the effects of warming and drying.

The scientists behind the new study didn’t set out to determine how wood-munching insects affect rainforests during dry spells. They just happened to have the opportunity when, shortly after launching a termite-removal experiment in Malaysian Borneo in 2014, the aforementioned El Niño-fueled drought hit. The researchers had already set up ~0.6 acre plots on which they had done their darndest to eliminate termites. Both during and after El Niño, they measured termite abundance as well as various indicators of ecosystem health on the plots, and compared the results to control plots featuring a full complement of termites.

“It’s just really really lucky that our experiment coincided with this massive ecological disturbance,” study co-lead author Hannah Griffiths of the University of Liverpool told Earther.

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The findings, published today in Science, suggest that, at least over the short term, termites can have a big impact on how forests handle drought. Termite activity spiked during El Niño, with the researchers recording twice as many insect encounters as they did during the post-drought period (in plots that hadn’t been termite-bombed, that is). While it isn’t immediately clear why, Griffiths suspects that dry weather makes it easier for the insects to burrow into the soil. It’s also possible that ants, a key termite predator, are suppressed during drought.

What’s more clear is that the uptick in termite activity was a good thing for the forest as a whole.

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Compared with the termite-eradicated plots, undisturbed forest plots featured greater levels of soil moisture throughout the drought, likely a result of termites’ burrowing activity, which draws more moisture up from depth and creates above-ground structures known as “sheeting” that help lock in water. More termites meant much more rapid leaf litter decomposition and more variability in soil nutrient content. And both the changes in moisture and nutrients, Griffiths said, could have contributed to the fact that seedlings were way more likely to survive the drought on termite-filled versus termite-impoverished plots.

“Whilst there has been some work exploring how severe drought affects plants in tropical rainforests, our study shows for the first time that having termites helps protect forest from the effects of drought,” study co-author Kate Parr, an ecologist at the University of Liverpool, said in a statement.

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The study only looked at a single drought in a single forest, and more research is needed to see how widely applicable the results are. It also isn’t yet clear what termites mean for tropical drought resistance over longer timescales, or how they might alter a rainforest’s response to long-term drying associated with climate change. Still, Adriane Esquivel Muelbert, a tropical ecologist at the University of Leeds who wasn’t involved with the work, called the results “very interesting,” noting that we know very little about how different groups of organisms contribute to tropical forests’ response to environmental stress. “[T]his is an important step for the field,” Muelbert told Earther in an email.

The findings point to the need to ensure rainforests maintain their biodiversity to give them the best chance of surviving climate change. Other human-caused disturbances, like rampant logging, have been shown to depress termite abundance and diversity, per the study. And termites are just one group of insects among countless others.

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“Had we not encountered this drought, we might not have known how important termites were,” Griffiths said. “That raises alarm bells because there are plenty of other species [for which] we don’t know about their impacts.”

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Maddie Stone

Maddie Stone is a freelancer based in Philadelphia.