By using high tech scanners, researchers have mapped the location of thousands of termite mounds in Africa. Their newly-released map of these insect civilizations gives us clues about the future of weather on the savannas.
Researchers from the Carnegie Institution's Department of Global Ecology flew over 192 square miles of Kruger National Park in South Africa, and used a scanning method called LIDAR to map 40,000 termite mounds and the surrounding vegetation in three dimensions, and the chemistry of the soil beneath.
It turns out the insects only construct their houses under very specific soil conditions. Like Goldilocks, they want soil that's not too dry, and not too wet. Basically they seek out regions where the soil is well drained, at elevations above what's known as a seepline (the yellow line in the image below).
Seeplines occur where water flows below ground through sandy soil, then backs up at areas high in clay. Above the line, you get trees and termites; below it, grassland. However, seasonal fluctuations in foliage make the division tricky to spot, so static termite mounds are a great indicator of where the seepline is, and of the overall soil conditions. Lead author Shaun Levick said:
"We found that precipitation, along with elevation, hydrological, and soil conditions determine whether the area will be dominated by grasses or woody vegetation and the size and density of termite mounds."
By understanding the links between soil, the termite mounds, rainfall, and vegetation, it becomes possible to project how climate change will affect the savanna. Co-author Greg Asner says:
"The predictions are that many regions of the savanna will become drier, which suggests more woody species will encroach on today's grasslands. These changes will depend on complex but predictable hydrological processes along hill slopes, which will correspond to pattern changes in the telltale termite mounds we see today from the air."
So the movement of termite mounds is a distant early warning system of the encroaching dryness of the savannas.
Research published in Nature Communications