In the dry scrub forests of northeastern Brazil, termites have been hard at work for thousands of years—and the millions of mounds they’ve created in a Michigan-size swath of terrain are grand testaments to those efforts.
The species responsible for the mounds (pictured), which measure 2 meters to 4 meters high and up to 9 meters across, is Syntermes dirus. Those heaps aren’t homes for the insects, as mounds built by other termite species can be. Nor are they part of a ventilation system, because the mounds are sealed off and aren’t open to the air. Instead, researchers suggest, the structures are merely waste material brought to the surface by the termites as they carve out the extensive networks of underground tunnels they live in.
Eleven mounds the researchers sampled range from 690 years to 3820 years in age. Together, the millions of Brazilian termite mounds contain an estimated 10 cubic kilometers of soil, the team reports today in Current Biology. That volume, equal to about 4000 Great Pyramids of Giza, renders the structures the largest known example of ecosystem engineering by a single insect species, the scientists say.