Arid and savanna lands (for example, those where annual rainfall is under 800 mm) are most in need of reforestation. These are regions where aerial seeding in principle has exceptional potential. They include vast tracts of unused or poorly used land that has sparse tree cover and that is not confined to private land holdings, so it is generally accessible to aircraft. The native trees (such as species of Acacia, and other genera) in these areas are generally well adapted for survival under difficult field conditions. These are not species for timber as much as for firewood, forage, fruit, gum, erosion control, and other such uses.