Tiny Termites Hold Back Entire Deserts from Spreading to Savannas and Grasslands

Termites may be able to hold back entire deserts. Scientists have taken a closer look at these insects and have found that their large dirt mounds are crucial when it comes to stopping the spread of deserts into semi-arid ecosystems and agricultural lands.

In the parched grasslands and savannas of Africa, South America and Asia, massive termite mounds rise up against the landscape. These mounds store nutrients and moisture. In addition, their internal tunnels allow water to better penetrate the soil. Because of this, vegetation often flourishes near termite mounds.

"The vegetation on and around termite mounds persists longer and declines slower," said Corina Tarnita, one of the researchers, in a news release. "Even when you get to such harsh conditions where vegetation disappears from the mounds, re-vegetation is still easier. As long as the mounds are there the ecosystem has a better chance to recover."

For grasslands and deserts, five stages mark the transition to desert. In this case, the scientists used satellite images to determine which stage a savanna was in and which stage it was headed toward. In the end, they found that a pattern of termite mounds, covered by dense vegetation, could actually be preventing desertification.

That said, the termite-mound pattern looked deceptively similar to the last and most critical of the five stages that mark the transition of drylands to desert. Two different mechanisms are responsible for this pattern; one stems from vegetation self-organizing in response to limited rainfall, and the other results from bustling termite mounds improving the lives of nearby plants.

"That made me wonder if more than one mechanism is responsible for vegetation dynamics in dryland ecosystems, as is often the case in nature," said Tarnita. "We created a mathematical model that revealed that these mechanisms can co-exist, but likely at different scales. It pointed to where we should look in nature to find the nested patterns that eventually led us to empirically confirm that both mechanisms are indeed at play."

In the end, the researchers found that the coexistence of multiple patterns at these scales makes ecosystems less prone to collapse. The study also shows that climate models for every ecosystem need to better account for organisms such as termites and mussels that engineer their own environment. It also reveals how termites can drastically impact their surroundings and, in this case, prevent desert encroachment.

The findings are published in the journal Science.

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