It is common knowledge that the Sahara Desert is one of the least hospitable and driest places on Earth, though it hasn't always been that way. And if conditions change, it could become hospitable again. Five years ago, an experiment was conducted in which 500 African spurred tortoises (one of the world's largest land tortoises) were released into a particularly hard-hit part of the desert, and since then they have succeeded where machines, chemicals, and other methods have failed, namely, in making the area green again.
This is reported by the Indian Defence Review, which notes that the difference has become so significant that it is visible from space. The secret is that the spur-thighed tortoises burrow underground to escape the heat, and they dig deep, 10-15 metres. This has created porous cavities underground that have helped make the soil moister, allowing plants to grow there.
The plants, in turn, attract insects, which eventually leads to birds and other animals moving into what was, until very recently, a parched desert. The researchers call the spur-thighed tortoises "ecosystem engineers," but emphasize that they cannot do this alone; rather, humans must contribute by not destroying their habitat and hunting them (it is an endangered species).