Due to the extent of damages and the number of people involved, drought is the number one natural catastrophe. A dry period is marked by less frequent precipitations compared to the annual average of the area. Drought is considered as serious when the average farming production decreases by 10% and catastrophic when it decreases by over 30%.
Dry periods have become more frequent and more intense over the last few decades, involving almost all of the emerged areas.
This tendency to drought has not only affected the dry or half-dry areas of Africa and Asia, that have been the most seriously affected by the different dry spells of the last 30 years, but also the mild and northern countries.
More or less one half of the surface of the emerged lands can be defined as dry or half-dry. Both ecosystems are extremely fragile and vulnerable. If exposed to drought for long periods, they can be affected by desertification, i.e. they can turn into deserts.
According to the UNCCD (UN Convention to Combat Desertification), 25% of the world‘s land area is either highly degraded or undergoing high rates of degradation. It is estimated that two-thirds of African land is already degraded to some degree and that land degradation affects
at least 485 million people – 65% of the entire African population. By the 2050s, 50% of agricultural land in Latin America will be subject to desertification. It is therefore absolutely important to protect these regions.
The history of the biosphere has been marked, during the different geological ages, by natural climatic fluctuations that have altered the width of deserts. Exceptionally dry periods have become more frequent and more intense over the last few decades: from 5 a year in the Seventies to 12 a year in the Eighties. There are many complex causes for such increase: it must however be borne in mind that man’s pressure, through a bad or improper use of the land, can heavily alter the characteristics of the soil, of the vegetal covering and the low atmosphere, thus irretrievably affecting the delicate balance of the hydrological system.
Desertification reduces the ability of an ecosystem to survive when the climate changes, with dramatic consequences, such as:
- loss of productivity of the soil;
- degradation of the vegetal covering, through to its total disappearance;
- dispersion of solid particles in the atmosphere – sand storms, air pollution – with a negative impact on man’s health and productive activities;
- reduction of farming and breeding production: malnutrition and hunger;
- migrations of people and wars.