Tiny termites can hold back the advance of deserts moving into agricultural lands or semi-arid ecosystems by creating oases of plant life in their mound homes, researchers say.
Towering termite mounds can store both moisture and nutrients that provide a refuge for vegetation and their internal tunnels can also improve the ability of water to penetrate the surrounding soil, scientists at Princeton University say.
The result is flourishing plant life in ecosystems in Africa, South America and Asia that otherwise are vulnerable to potential collapse into deserts, a process dubbed "desertification," they report in the journal Science.
Those parched grasslands and savannas, or drylands, where termite mounds exist can be maintained with significantly less amounts of rain than regions where there are no termite mounds, they explain.
"The rain is the same everywhere, but because termites allow water to penetrate the soil better, the plants grow on or near the mounds as if there were more rain," says study researcher Corina Tarnita, a professor of ecology and evolutionary biology.
Termite mounds also help preserve seeds during dry periods, which allows surrounding areas to rebound faster once rainfall resumes, she says.
"The vegetation on and around termite mounds persists longer and declines slower," she explains. "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."
That function of termites in grasslands and savannas suggests that other mound-building species, including gophers, prairie dogs and ants, could also be serving important roles in maintaining the health of such ecosystem, says study co-author Robert Pringle, like Tarnita a professor of evolutionary biology and ecology.
"This phenomenon and these patterned landscape features are common. It's not always termites causing them, but they may very well have similar effects on the ecosystem," he says. "However, exactly what each type of animal does to the vegetation is hard to know in advance. You'd have to get into a system and determine what is building the mounds and what are the properties of the mounds."
Grasslands and savannas undergo five stages in the transition to desert, each having a distinct pattern of plant coverage and growth.
The termite-mound pattern looks deceptively similar to the last and most critical of the five stages that mark the transition to desert, the researchers note, which could lead to projections of climate change that don't accurately match what is really going on in an ecosystem, the researchers say.
Vegetation patterns that might be interpreted as the onset of desertification could in fact represent the total opposite, they say, showing instead that plants are persevering thanks to termite mounds.
"I like to think of termites as lynchpins of the ecosystem in more than one way," Pringle says. "They increase the productivity of the system, but they also make it more stable, more resilient."
