Peter Westerveld worked in Africa, Mali and other places to promote what he called ‘contour trenching’. This is a way to increase ground water levels, and thus vegetation, by digging trenches that would capture some of the rain that would otherwise wash over the land without benefit. His thinking about prmoting tree growth by this approach even led him to develop a plan to increase rainfall in Spain. Apparently the idea that ground penetration of rain water is good for ground water levens is a novel one, because a study just concluded that Peter (who has died recently) was right.
For some inphatomable reason people held belief in a theory called the ‘Trade-off Theory’ which says that more trees means less groundwater. This may be true, and turns out to be true in regions with a lot of trees. There the humus and trees both absorb and evaporate water instead of letting it sink into the soil. This is no surprise.
In dry and arid regions with barely any trees however trees cause better ground penetration of rainwater, and thus more ground water.
“Without trees, these sensitive tropical soils lose their large pores, which are responsible for leading water down into the ground quickly,”
Again no surprise. Peter showed that even without trees, just increasing the penetration is better for grass, chrubs and of course insect, bird and other wildlife. What we are surprised by is that this ‘Trade-off theory’ was supposed to work in dry and arid regions. Of course there is a difference between deserts, regions with occasional trees and dense forrests. And of course if we have a dense forrests who cares about groundwater?
So it is clear and confirmed : In arid regions ground penetration of rainwater has to be improved, and if it’s possible to plant some trees based on the captured water or otherwise, then do it. The more trees the better.