At three trillion strong, Earth’s trees are estimated to outnumber the stars in the Milky Way. These woody wonders sponge carbon dioxide out of the skies, brace soil against erosion, cycle water through ecosystems and support countless forms of life. And we largely have their sophisticated root systems to thank.
Sprouting from the base of tree trunks, roots are the arboreal equivalent of a digestive tract, exchanging water and nutrients with surrounding soils. Roots literally anchor a plant, and the more extensive they are, the bigger and stronger the stuff above ground can grow. In their modern forms, they helped trees dominate their habitats—and spread across the globe.
“Roots maximize [a tree’s] physiological capacity,” says Christopher Berry, a paleobotanist at Cardiff University in the United Kingdom. “An efficient rooting system is key to being a successful tree.”
But roots didn’t always look as they do today, and researchers have long puzzled over how and when trees evolved their expansive underground plumbing.