Land degradation affects today, according to the evaluations United Nations, two billion people in the world. It concerns a third of the planet's surface and affects a hundred countries on all continents, but more particularly Africa (north and south of the Sahara), Central Asia, the Middle East and part of the American continent.
Par land degradation means a process leading to a permanent loss of the biological and economic productivity of ecosystems; this is due to the erosion of wind and water, to the loss of the capacity of soils to store water, to the drop in their fertility, to the absence of any vegetation. The desertification represents its ultimate stage.
In the countries concerned, three quarters of the pastures and half of the cultivated areas are thus threatened, inevitably causing the deterioration of the living conditions of the populations and the increase in poverty.
We now know that the degradation of climatic conditions increases the risks of land degradation, in particular with an increased phenomenon of desertification: prolonged droughts, unsuitable modes of exploitation of natural resources lead to their overexploitation, exacerbate their fragility and cause irreversibility situations. The soil becomes uncultivable, there is no more vegetation, we can no longer live in these conditions.
The last two IPCC reports thus predict an increase in droughts and floods, a decrease in the flow of large rivers and an increase in desertification.
A vicious circle
Affected countries, particularly in the Sahel, generally derive their income from the exploitation of renewable natural resources. If these come to decrease, they will see their GDP fall, the poverty of their population will increase and will enter “poverty traps”: without other sources of income, farmers and herders will increase the cultivated areas.
If they do not change their practices, this will lead to further land degradation and desertification, resulting in an accentuation of the fall in income, the weakening of social ties, and forced migration.
Added to this is the issue of demographic pressure: a third of the world's population already live in dry regions of the world and will therefore find themselves exposed to climate change and land degradation. In Africa, for example, we will have to feed twice more inhabitants in the next 20 years.
If agricultural productivity cannot be increased enough to feed these future populations, migration within countries (rural and urban migration), regional migration and South-North migration will intensify.
Fight against degradation
In the affected countries, farmers have put in place ad hoc control methods that allow successful adaptations to drought situations; and sometimes, with the support of scientists, more integrated methods such as stone bunds, water infiltration aids, tree plantations,agro-ecology...
But it is also essential to compensate for soil nutrient deficiencies (phosphorus and nitrogen). Global statistics show that the average consumption annual fertilizer per hectare is, in Africa, around 10 kg while in Asia it is around 60 kg and over 200 kg in Europe. We can consider that it is too much in Europe, but too low in Africa… but nutrient deficiencies must be remedied if we want to double or even triple yields with agroecological practices.
Physical and biological restoration works are yielding positive results in West Africa, India and China. Analyzes have shown that the investments necessary for the rehabilitation of the environments, with a minimum contribution of fertilizers, amount to approximately 300 to 400 dollars per hectare and per year for three or four years and that they allow a doubling of the yields and economic rate of return up to 20% to 30%. On the occasion of its twentieth anniversary, the French Scientific Committee on Desertification (CFSD) devoted a seminar to these questions and proposes on his website many resources on this subject.
Insufficient agricultural investments
Studies to assess the overall cost of soil degradation give estimates of between 1 to 9% of agricultural GDP for each country concerned. A global assessment, carried out in 1992 and partially reassessed, indicates annual losses of $ 42 billion per year; adjusted today, this gives an amount of over 80 billion.
But for more than thirty years, agricultural investments from official development assistance (ODA) have been declining. In Africa they amounted in 1981 to 1,9 billion dollars, or 22% of ODA; in 2001, to 0,99 billion dollars, or only 6% of ODA.
A study from December 2006 shows that the financial contribution to reducing degradation would thus be lower than the costs of degradation; she suggests that ODA increase its contribution to sustainable land management by 10-15% for 10 years, freeing up $ 10-12 billion per year, which would be enough to reverse the process of land degradation and provide income to the poorest.
Tracks to explore
Farmers and pastoralists in affected countries are among the poorest and they cannot invest.
It seems essential to consider other sources, such as money from the return of migrants for example, which could serve as collateral for private loans. Good conditions must also be guaranteed so that these investments are economically, socially and environmentally profitable: stable public policies, guaranteeing access to resources (land, water), stability of agricultural prices (inputs, harvests), training of farmers and breeders, existence of professional groups and a civil society capable of dialoguing with the State.
Another imperative concerns the modalities of the aid which must be ensured that it reaches farmers. Finally, it is important to establish investment priorities: restoration and rehabilitation of degraded environments, improvement of soil fertility; adoption of sustainable cropping systems meeting the dual objective of production and protection; investment in human capital and societal capital; promotion of export sectors; promotion of activities other than agricultural activities.
As long as governments and official development assistance do not increase their financial efforts, farmers will become poorer and desertification will worsen.
Marc Bied-Charreton, Emeritus professor, agro-economist and geographer, member of the French Scientific Committee on Desertification (CFSD), University of Versailles Saint-Quentin en Yvelines - Paris-Saclay University et Robin Duponnois, Director of research, microbiologist, president of the French Scientific Committee on Desertification (CFSD), Research Institute for Development (IRD)
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