Termites cause about $5 billion in damage in the United States each year, which makes them a fairly formidable pest. Even so, it turns out that their presence can be very beneficial to ecosystems in semi-arid regions. A new study published in Science describes how large termite mounds can actually stop deserts from spreading by storing moisture, creating an oasis of plant life in vulnerable areas. Corina Tarnita from Princeton University was senior author on the paper.
Some species of termites can create nests called mounds that reach a staggering nine meters (29.5 ft) tall. In order to make these huge structures, the termites effectively need to displace over 500 pounds of soil. In arid or semi-arid areas, tilling the soil in this manner and creating tunnels allows the mound to retain water and nutrients better than the surrounding soil, providing an ideal place for plants to grow.
"The vegetation on and around termite mounds persists longer and declines slower," Tarnita said in a press 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.”
The study focuses on termites within the genus Odontotermes and their ability to prevent the spread of desertification, which can take hold when precipitation is low and is hard to overcome once the rain returns. The termite mounds retain water better than the soil, allowing it to ration out the water over time and provide sufficient resources for these plants even when precipitation is infrequent. This phenomenon could give important information regarding other types of ecosystems as well.
The pattern of termite mounds analyzed by the researchers bore a striking resemblance to the patterns of dwindling vegetation as drylands fade into deserts. Previous research has not been clear if it was because dense patches of vegetation grow better when clumped together in arid conditions, or if nesting by termites improved the soil and made more hospitable conditions. The researchers believe it may have been a bit of both, and used computer analysis to investigate the possibility.
Indeed, the modeling showed that both groupings of plants and improved soil conditions caused by the termite mounds led to the preservation of these ecosystems during trying, arid periods of time. Not only does this study help explain how the vegetation was able to hang on in semi-arid conditions, but could also be applied more widely. While negative human interactions with the environment are often accounted for in climate modeling, beneficial interactions such as these termite mounds might be worth considering in the future.
"This is an eye-opening study that says we really need to investigate these ecosystems in more detail and incorporate all these other mechanisms before we can say what will lead to a catastrophic collapse in ecosystem function," commented Jef Huisman of the University of Amsterdam, who was not involved in the study. "We should always be humble in our model predictions because nature can always be more complex than we initially anticipate.”