Steven Devijver

Cj Verde wrote:The wiki page on Milankovitch cycles makes no mention of the Sahara at all. And the Sahara page makes no mention of the Milankovitch cycles.

These cycles may or may not cause/exacerbate the desertification process but that doesn't mean the regreening is not possible.

Regreeing has been proven to be possible. However, regreening the entire Sahara seems such a gargantuan task, I just don't see how that's possible. Regardless, the Sahara did not become a desert because people chopped all the trees.

Paul has done a podcast on regreening parts of the Western Sahara. Even in such a relatively minute area there are tough challenges.

Cj Verde wrote:There are examples of desertification caused by deforestation all over the world.

There are examples of undoing the damage by planting trees.

I'm sure you're correct. However, this does not apply to the Sahara. The Sahara has oscillated between desert and lushness for dozen of times since 3 million years ago.

Paul,

The Sahara did not become a desert because people chopped all the trees. In fact, the story of the Sahara is much more fascinating than this. There is a 18,000 year cycle that oscillates the Sahara between lush greeness and desert. Actually, 3,000 years from now the next green period will start. This cycle is driven by the Milankovitch cycles (a slight but influential periodic oscillation in the earth's tilt).

There's a good documentary about this here:

I've watched Geoff Lawton's food forest film and I have a question regarding fruit trees and nitrogen fixing plants. I was under the impression that fruit trees in the rosaceae family don't do well in nitrogen-rich soil. However, Geoff is going wild with nitrogen fixing plants and also planting apple and plum trees.

Is it correct that the rosaceae family does not do well in nitrogen-rich soil? If so, why does Geoff combine them?

Has anybody seen the Urban Permaculture DVD?

http://permaculture.org.au/2011/10/10/urban-permaculture-dvd-you-may-order/

Have you seen this method from the UK (potato section starts at the 4:15 mark)?


http://www.youtube.com/watch?v=6YjnMlSX1us&feature=youtube_gdata_player

It involves car tires and no digging.