The results of a new research reveal how the savanna terrain of Africa has evolved and show how termite mounds can be used to predict ecological shifts from climate change. The research is published online in Nature Communications .
Using sophisticated airborne imaging and structural analysis, scientists at the Carnegie Institution's Department of Global Ecology mapped more than 40,000 termite mounds over 192 square miles in the African savanna. They found that their size and distribution is linked to vegetation and landscape patterns associated with annual rainfall.
Mound-building termites in the study area of Kruger National Park in South Africa tend to build their nests in areas that are not too wet, nor too dry, but are well drained, and on slopes of savanna hills above boundaries called seeplines.
Seeplines form where water has flowed below ground through sandy, porous soil and backs up at areas rich in clay. Typically woody trees prefer the well-drained upslope side where the mounds tend to locate, while grasses dominate the wetter areas down slope, according to a Carnegie Institution press release.
“These relationships make the termite mounds excellent indicators of the geology, hydrology, and soil conditions,” commented lead author Shaun Levick at Carnegie. “We looked at the mound density, size, and location on the hills with respect to the vegetation patterns.”
Research into the ecology of these savannas has focused on the patterns of woody trees and shorter vegetation over larger, regional scales.
The research was conducted by the Carnegie Airborne Observatory (CAO) which can penetrate the canopy all the way to the soil level and probe about 40,000 acres per day.
Explained Levick: “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.”
The advantage of monitoring termite mounds in addition to vegetation is that mounds are so tightly coupled with soil and hydrological conditions that they make it easier to map the hill slope seeplines. Furthermore, vegetation cover varies a lot between wet and dry season, while the mounds are not subject to these fluctuations.
“By understanding the patterns of the vegetation and termite mounds over different moisture zones, we can project how the landscape might change with climate change,” explained co-author Greg Asner at Carnegie.
