Desert greening

Desert greening is the process of man-made reclamation of deserts for ecological reasons (biodiversity), farming and forestry, but also for reclamation of natural water systems and other Life support systems. It is done by various methods. So far only arid and semi-arid desert are meant when using the expression. Icy deserts are considered unsuitable. Desert greening is an important topic as it can help solve global water, energy, and food crises. It pertains to roughly 32 million square kilometres of land.

Desert greening is more or less a function of water availability. If sufficient water for irrigation is at hand any hot, cold, sandy or rocky desert can be greened. Water can be made available through saving, reuse, rainwater harvesting, desalination, or direct use of seawater for salt-loving plants. These different paths have unique features, i.e.: conserving water is a cheap solution. Reuse of treated water and the closing of cycles is the most efficient because closed cycles stand for unlimited and sustainable supply - rainwater management is a decentralized solution and applicable for inland areas - desalination is very secure as long as the primary energy for the operation of the desalination plant is available - Direct use of seawater for seawater agriculture is the most potent, only limited by the need for pumping up the water from sea-level.

Novel type of desalination is done with the Sahara Forest Project. This project uses solar stills for the generation of the freshwater. Another novel technique is cloud seeding, either by artificial means or through the action of cloud-seeding bacteria that live on vegetation (e.g. Pseudomonas syringae). Another, "atmospheric water generation" or air to water, uses dehumidification and is used by the military for potable water generation. However this technology uses 200 times more energy than desalination, making it unsuitable for large scale desert greening. An exception is the Integrated Biotectural System, which performs air-to-water in a greenhouse - a closed environment with optimized atmospheric conditions.

...
Wikipedia