The other problem is… how easy would it be to remove these mountains later on?

A question of Stephen Klaber… how invasive are those plant species? If the climate were wetter, would they be supplanted by more native/healthy species, or would they continue to spread?

A Desert is:
1) Hot (daytime, cool at night… but the heat is the bigger problem, though fluctuation is contributive)
2) DRY [the main consideration]
3) Shifty (windy, usually anyways)
4) Sandy (as opposed to healthy soil)
5) Barren (lifeless of plants and animals on the whole) [organisms are typically +80% water]

The war against the desert must be won in the wetlands. The enemy still has the initiative. He has completely overrun the entire Eastern portion of the Lake Chad basin, most of the lake itself and is well established in the western tributaries, meeting sporadic resistance in Nigeria. I’ve read reports of a start of organized resistance in Mauritania. Typha Australis (southern cattail) is the shock army of the desert. It, and its cousins (Typha spp.) are quickly overrunning the African continent, Asia, and Australia. It has allies: Phragmites, hyacinth, water lettuce… In the area relevant to the Sahara’s expansion, we are talking upwards of 5 million hectares. There is a lot of weeding to be done.

Typha is a dessication machine and a siltation machine. Its presence (cover) more than quadruples the evapotranspiration losses in a body of water. The silt it produces raises the stream or lake bed until it is no longer viable. Every change we make to a body of water creates some place where the water level has changed to favor weed growth. Dams and irrigation accelerated the natural process called hydrosere beyond what could be naturally recovered from during a drought.

We must clear these weeds! They are killing off whole continents. Their resilience makes clearing them a never ending process. The biofuels market provides a way to finance the job. From charcoal to ethanol, Typha is good feedstock. This is the one biofuel source which improves your water supply.

Picture the Sahara, stopped and shrunk. Picture the Sahel greener, healthier. Picture Lake Chad restored. IT CAN BE! What’s in the way is some weeds: 5-10 million hectares of them.

@ Brian: Well put. Martians had this same debate a couple of years ago, and look what happened to that place.

I think this scientist ought to focus on ecology to restore these areas, as desertification happens most rapidly when there are no root systems laid down by species that can tolerate dry conditions. These root systems prevent topsoil erosion and the plants of course create habitat for a range of other species – plants, animals, fungi, etc.

That’s a pretty negative viewpoint, don’t you think? I agree that some interventions by mankind in nature have had problems, and others have been outright disasters. However EVERY change by man is bad? Really? You want a second chance to consider that statement?

Larsson is proposing a couple of ideas to limit the desert, and desertification as a process. You’d have a point if the desert were a disappearing biome, but it isn’t. The Sahara is the world’s largest desert and it’s been growing for centuries. In fact there are numerous archeological sites documenting times of growth and plenty, in areas that are in the deep desert now. Some of these sites are thousands of years old.

In general water means life. The desert lacks water and is thus severely limited in how much life it can support. The lack of water and continuous desertification causes hardship and starvation in the Sahel region surrounding the Sahara. That’s for all animals and plants, not just the humans living there.

One more point. Way back, decades ago, the Chinese government sponsored an effort to plant millions of trees around Beijing. This area is subject to dust storms and hot, dry winds coming off the Gobi desert. The Chinese were successful and planted so many trees that they altered the local climate. The result was a more livable capital city, but that’s not all. The climate cannot be limited and thus the entire region benefits, including all animals and plants in the area.

Larsson deserves a little better than “mankind is bad. Bad!!”.