[LUM#15] Research major soils

[LUM Magazine] - Published on November 10, 2021 in Science-Society

In Africa, 45% of land is considered "degraded." A process of desertification, resulting of human pressure and exacerbated by climate change, which is undermining the future of the continent and threatens the food security of its populations.

"Desertification is not at all the advance of the desert," insists Jean-Luc Chotte, soil specialist at the Eco&Sols* laboratory. "It is a generic process of soil degradation that will lead to a loss of soil productivity as well as a loss of biodiversity and services rendered. " Although degraded land can be found everywhere, we only talk about desertification when this phenomenon affects arid, semi-arid or dry sub-humid areas. It is estimated that 25% of the planet's land is degraded. This figure rises to 45% in Africa.

From soil to climate

How can we explain why Africa is so severely affected? "Generally, it is the result of overexploitation or misuse of the soil," explains the researcher, who is also president of the French Scientific Committee on Desertification. Over-exploitation is not measured in quintals of production but in the ratio between production and the natural potential of the soil. When land is cultivated, some of its chemical constituents (nitrogen, potassium, etc.) are extracted from the soil by plants, leading to a decline in fertility that is all the more pronounced in fragile soils. Another harmful effect of this misuse of soil is the release of carbon stored in the soil "into the atmosphere, contributing to global warming," emphasizes Jean-Luc Chotte.

150 million people affected in the Sahel

In the Sahel alone, 150 million people are affected by desertification, "and we know that the population will grow, and with it food needs." This immense challenge prompted the United Nations to launch the United Nations Convention to Combat Desertification (UNCCD) in 1994. Seven years later, in 2001, the Great Green Wall project was launched with the ambition of restoring more than 100 million hectares of degraded land between Dakar and Djibouti by 2030 (watch the Global Days conference). "This wall should be seen as a vast mosaic of landscapes in which practices are adapted to the different environmental, climatic, and socioeconomic situations in Burkina Faso, Niger, and Chad."

For an integrated approach

In northern Senegal, significant work has been done to combine annual crops with tree plantations adapted to local drought conditions. Pastoralism is also encouraged there for its beneficial effects on the soil. "The idea is to find trees that, by producing gum arabic for example, will provide additional income for farmers while helping to restore degraded land, " continues Jean-Luc Chotte. Documenting best agroecological practices and mapping the health of ecosystems in order to prioritize areas "where intervention will have the greatest impact on populations and biodiversity, because we cannot act on all degraded land." Given the immensity of the task, this is a way of keeping our feet... on the ground.

*Eco & soils (IRD – CIRAD – INRAE – Institut Agro)

Keywords: Agriculture, Environment, LUM#15, LUM Magazine, Research, Company