Chad. Ennedi rock art. Real forests grow on the dry bed of the Toli wadi. Their deep roots pump the water under the sands. After the storms; we see the acacias reverdir and bloom. Some would even wake up feeling the first wet winds. They are transformed; wrote botanist Hubert Gillet; into "huge white or yellow bouquets that embalm tens of metres away". These forests bear witness to the time when the Sahara was not a desert.