Every year in the world an estimated 20 million hectares of
arable land are rendered infertile simply owing to water-induced
erosion. It is therefore crucial to understand how these
processes arise in order better to protect the layer of a few
tens of metres of fertile soil essential for plant growth and
therefore for sustaining agriculture. In the North of Mexico,
about ten years ago IRD teams studied the erosion phenomenon
which affects this region where pastoral activities and tree
felling aggravate the process. As part of field studies
conducted from 1993 to 2000 on the mountain crests of the
western Sierra Madre and in the more arid regions in the south
of the Chihuahua Desert, the scientific team established a soil
classification according to climatic and topographic
characteristics. They used a rainfall index type hydrological
model which gives real-time simulation of the humidity state of
soil on the basis of a range of parameters including soil
humidity, runoff rate, water storage capacity. This meas