In 2011, a team of undergraduate students from Imperial College London devised a fresh way of halting the spread of deserts: Make bacteria that will persuade plants to grow more roots.

Drylands—areas that get little rain—cover around 40 percent of the Earth’s surface. They are already fragile places and a combination of drought, climate change, overgrazing, and unsustainable farming can finish off any plants precariously clinging to life there. Without roots to hold the soil together, wind and water erode the top layers, leaving only the infertile lower ones. In this way, more and more land transforms into barren desert with each passing year.

There are many possible ways of countering or preventing desertification but the Imperial team