June 30, 2009 – First of all, my apologies for the dark print in my last post. I realize this is very difficult to read. I’m not sure what caused this! Perhaps enlarging the font will make it easier to read. Again, I’m sorry that happened.
I referred, in my last post, to the Sahara and Gobi Deserts. When I said they were advancing I meant, of course, that they were expanding. The expansion, in both cases, is caused by irrigation and animal grazing, activities associated with farming. Different types of land can support different amounts of irrigation and grazing. Clay soils, sandy soils, cannot support as much as top soil containing humus. Dry soils which are over-irrigated become salty, then parched. Over-grazed land gradually loses the vegetation that holds soil in place. An over-abundance of these activities occurs when too many people are trying to eke a living out of soil meant to support fewer people. The result is desertification.
This is what has taken place in both Africa and China. In each case, the decision has been made to fight back by planting trees. I don’t believe that the long-term results are yet known. The thinking, of course, is that the roots of the trees will stabilize the soil, thus preventing it from blowing away. Furthermore, the roots will form a vegetative mass below the ground over time. The roots and the trees they support will also hold water. Ultimately, the hope is that other plants will take root, allowing the stabilization process to progress. When this occurs, desertification has been reversed. The long-term solution to this problem must also include a decrease in the number of people farming marginal lands.