Minimum annual rain fall for afforestation/desalination/greening sahara desert

Hi again Zach-

I had one other question for you. Any thoughts on the minimum annual rainfall in an area to create a forest ecosystem? What sort of projects has Sepp done in bone dry deserts? Odemira where Tamera is located apparently gets about 390 mm annually, or about 15 inches of rain. For a region with more like 5 inches of annual rain fall would there need to be some dryer, more scrubby areas, with smaller patches of oases where the majority of water is directed?

Also, I read in Desert or Paradise (pg 28) about a plan to use plastic/glass and wind power to desalinate sea water, then send it via wind power to retention basins for extreme desert locations... I'm curious if anyone is planning to try this on a small scale, or if it already exists in some places.

This is the main paper I've come across that discusses the potential to re-green the Sahara- the plan is based on a monoculture of eucalyptus, but it is a starting point at least. If we're going to have to do some sort of geo-engineering to combat climate change, I believe that something along these lines is the most appealing rout. http://link.springer.com/article/10.1007%2Fs10584-009-9626-y

If anyone reading this is familiar with Geoff Lawton's work, I'm curious about annual rainfall at the site in Jordan, and how much irrigation they do with outside water.

Cheers!

Hi again Luke,

These types of techniques are applicable anywhere in the world, all be it the return can take much longer in drier climates. To my knowledge the project in the Extremadura is the driest climate Sepp has worked in, despite this it not has quite an extensive water retention landscape. Understanding where the property lies within the bigger landscape becomes even more important the drier the climate. You are never going to be able to build a pond on top of a mountain in a climate with 5 inches annual precipitation. But building a retention landscape in the erosion gullies becomes even more important in these dry climates. In the worst climates I feel as though you need to work in from the outsides of the desert. The water retention and forestry systems will gradually increase the precipitation that a landscape receives.

I think the best strategy for reversing desertification in the harshest climates is to start at the edges of the desert, and get the boundaries moving in the other direction; shrinking deserts by making oases on their edges, regenerating the climate as you go. Reversing the inertia is what I believe to be the biggest change that can happen within a given lifetime.