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Trees: The Anti-Desert
Geoff Manaugh, 15 Oct 06

In this year of deserts and desertification, there is finally "good news from Africa," New Scientist reports. "Farmers are reclaiming the desert, turning the barren wastelands of the Sahel region on the Sahara's southern edge into green, productive farmland."

And they're doing it with trees:

Tree planting has led to the re-greening of as much as 3 million hectares of land in Niger, enabling some 250,000 hectares to be farmed again. The land became barren in the 1970s and early 1980s through poor management and felling of trees for firewood, but since the mid-1980s farmers in parts of Niger have been protecting them instead of chopping them down.

According to one researcher quoted by New Scientist: "The results have been staggering."

This success stems from what the magazine calls a "virtuous circle of benefits" between trees and their surrounding landscapes. "Leaves and fruits provide food, fodder and organic matter to fortify the soil," for instance. "More livestock means more manure, which further enriches the soil enabling crops to be grown, and spreads tree seeds so new trees grow. The trees also provide shelter for crops and help prevent soil erosion. In times of drought, firewood can be sold and food purchased to tide families over."

Further, pro-tree land use policies – including better rainwater management practices – "are helping communities in Niger re-establish control over their fate, simultaneously halting the march of the desert and helping to prevent famines like the one that hit Niger in July 2005."

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Great post Geoff - thanks. The article notes that the trees are a type of acacia. Acacia's are leguminous: they coexist with bacteria and fungi, living in nodules on their roots, that are able to fix atmospheric nitrogen into the soil. Another important benefit.

Posted by: David Foley on 16 Oct 06

This has been done in Israel since its creation. They're starting on the Negev now, I understand.

Posted by: Jickup on 16 Oct 06

Thanks Geoff for this post!I would like to add just a small comment..this is just one of the hundred examples where trees played the key role in very difficult environmental situation. One of the reason why tree are the "anti-desert" is that they can contribute to change microclimate. With their activity (transpiration and photosynthesis) they give life! We should take care of them more seriously!

Posted by: Rossella on 16 Oct 06

A similar worldchanging practice is being researched and demonstrated in Central Texas.

Despite the 66 cm/year rainfall, and a large aquifer and system of lakes and rivers, much of Central Texas has become considered "arid" land - but according to some that is a recent, man-made condition. Waves of English, German, and Czech immigrants in the mid-1800's converted the native Texas savannah into farm and ranch land. Displacement of native species has, over a century later, resulted in an ecological and agricultural disaster.

Following the pattern of transitioning from high-tech to cleantech, Richard and Sally Taylor left their Silicon Valley success behind for drought-stricken rural Texas, to pursue R&D efforts in reviving the pre-European savannah and microclimate. In 2001, they purchased Blue Mountain Peak Ranch and have turned it into a multi-use research facility:

On a visit this summer during 40C weather, the microclimate effects of their work was startling: ranches on one side of the highway seemed parched, fiercely hot, choked by non-native species, with little or no topsoil remaining. However, on the BMPR side of the highway, the air was noticeably cooler, the soil looked rich, native species flourish, and our jaws dropped to see running water above ground. While the neighboring Bush-zealot ranchers seem to have no clue how or why BMPR has realized such success (and resist any efforts to learn) researchers from far and wide have come to study the facility.

Posted by: Hugo JUNOT on 16 Oct 06

A very similiar type of tree was used in the Columbian Llanos. They planted Carribian pines in the savannah and a similiar symbiotic effect happenend with the fungal organisms they seeded into the root system.

Posted by: Chris on 16 Oct 06

That Blue Mountain Peak is an interesting site. Reading through the front page, it appears that they're a case of doing the opposite -- getting rid of trees that are sucking up all the water. I'm going to have to go visit them.

Posted by: ERic on 16 Oct 06

Nice post.

This kind of thing may be happening all over the Sahel.

But there is still a bit of debate over whether is "recovery" of the Sahel is due to human actions, or a natural shift back from the droughts of the 1970s and 1980s. (There is still a lot of debate about what triggered the droughts and desertification in the first place -- was it human-induced, natural or both?)

Anyway, a very good summary of this debate can be found at:

Jon Foley
Univ. Wisconsin

Posted by: Jon Foley on 16 Oct 06

On the basis (perhaps wrong) that agroforestry is essentially population driven, should we asume that the population density in Niger has reached some critical point where agroforestry can take off?

We have funds to set up an Agroforestry Centre here on our farm in Northern Edo State, Nigeria.

I quote from my recent report:
"The most obvious natural resource of Weppa Farm is the trees, fascinating and varied because the farm is right on the transition between high forest and savanna. Contemporary climax conditions might be described as either Southern (Moist) Guinea Savanna where drainage is good, or peat swamp where it is impeded. A third zone is very obvious where conditions are sufficiently wet to preclude the dry savanna species but dry enough for the small tree, Mytragyna intermis, to be unique over large areas of boggy ground. A fourth zone as a distinct ecosystem, is remnant gallery forest along the banks of the rivers that are tributaries or sub-tributaries to the Niger. Here are even found high forest trees such as Nauclea (Nauclea diderrichii) and the Silk Cotton Tree, Ceiba pentandra . The lower galleries, very obviously dominated by Pterocarpus santalinoides, are flooded during June-October."
"However, THE Weppa tree is the typical Guinea Savanna Daniellia oliveri, pure stands of which are the pioneer species of abandoned dry farmland. The woodland in the south of the farm IS Daniellia oliveri woodland. Throughout this woodland can be found the Locust Bean tree, Parkia biglobosa, Lophira lanceolota and Vitex doniana. In certain areas, for reasons not yet understood, Pterocarpus erinaceous is found mixed with D. oliveri in equal numbers or even outnumbering it to create a P. erinaceous woodland. Other savanna tree species include Etada africana, typical of dry open areas (Field 20), Pilostigma thonningii of degraded areas, and the Borassus Palm (Borassus aethiopium) as a good indicator of seasonal wetlands. Also, Kigelia africana, with its conspicuous hanging fruit."
"Additional useful species continue to be recognised. For instance, the Spondia (Spondias mombin), well known for its sweet orange coloured fruit, high in vitamin C, has been discovered in Fields 3, 18 and 20."

The aim of the mixed farm is to be commercially viable upon the basis of sustainable farming. There are about 2000 hectares of good land, which has been farmed before and which is in various grades of revocable degradation.
There are some 1000s of hectares of woodland and wetland.

Agroforestry process are quite well understood but local farmers, foremost, have to survive from one year to the next. As was explained to me years ago in Cameroon: "we cannot lie down and die, tomorrow will have to look after itself". It is the immediate economic environment that drives agricultural practices. As much cassava as possible and yams where the soil is suitable.

If agroforestry is population driven and since the population density here is relatively low it is difficult to get farmers interested in trees let alone trees with cassva. The prime interest is in Oil Palm (sub-ecological but not-sub economic here) and Irvingia wombulu - Diku Nut). We have found that cassava provides a wonderful nurse crop for both these species in addition to Cashew, I. wombulu, I. gabonensis (Bush Mango, Ogbono), OP and Parkia biglobosa (Locust Bean).

Advice concerning the aim and objectives of the Agroforestry Centre would be most welcome, especially in turns of the economic viability and short-term competiveness of agroforestry activities.

Thank you,

Nick Ashton-Jones, Derby and Leventis Foundation, Nigeria

Posted by: Nick Ashton-Jones on 17 Oct 06

The Blue Mountain Peak Ranch hints at an important distinction that should be made when talking about forestation. I'm not an expert, but it seems clear that forestation is helpful in some cases and harmful in others. What are the goals? More crops or more aquifer water? How does soil content impact what would "naturally" be growing -- would there be trees, and what kind, if humans had historically only had a minimal impact on the local ecosystem? What is the role of fire?

When one drives around Austin and the Hill Country, it is abundantly clear that the forests are all new. Some were clear cut as timber in the 19th century, including many ashe juniper. That had a devastating effect on wildlife in the area, including a number of now endangered birds and amphibians. Nevertheless, it does stand to reason that those junipers "should" (due to fire) have been growing not as a blanket over the hills but down in the ravines, which by the way is where you get the mix of junipers and hardwoods loved by species such as the golden cheeked warbler. Out on the east side of Austin -- that is, east of the Hill County -- it is common to see new forest that obviously should have burned every few years.

Keeping it short, it thus seems clear that in Central Texas there are quite a few dynamics that influence what the "right" answer should be -- deforestation or reforestation? Thus we need to keep training ecologists and conservation biologists to get out in the field, try to understand the dynamics, and come up with the best plans for regulating future sustainability in a given ecosystem.

Posted by: Stephen A. Fuqua on 18 Oct 06



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