A tool to assess the risk of desertification

Using a general model of desertification, researchers from the Escuela Técnica Superior de Ingenieros Agrónomos of the Universidad Politécnica de Madrid managed by Javier Ibáñez have developed indicators that predict the future state of an area and hence the sustainability of the current situation. This general desertification model is used as a virtual laboratory where it is possible to reproduce the different syndromes of desertification, such as overgrazing and overdrafting of aquifers.

Desertification has been described as the biggest environmental and socioeconomic problem faced by many countries all over the world. In arid regions, the cause of the problem is mainly the way the land is used. The definition that is most extended and that was approved by the United Nations in 1994 is that desertification is the degradation of land in arid, semi-arid, sub-humid and dry areas resulting from different factors such as climatic variations and human activities.

There are two ways to fight desertification. One of them consists in cancelling out the effects it causes, which is very expensive considering all the investments required to restore lost fertility to the ground. The other is to anticipate the problem, since during its initial stages it can still be managed and turned around. In this sense, the diverse existing methods seek to detect the early symptoms of degradation.

The traditional indicators, based on physical measurements such as plant density and erosion rates, are precise but have two serious inconveniences. Firstly, since they measure characteristics of desertification, they give information about an on going process without providing information about the long term result of such processes. The second drawback is that they often focus on very particular characteristics of the landscape, such as certain plant species, making these techniques hard to export to other territories.

The proposed tool aims to complete the information offered by the conventional indicators with simulations that would virtually reproduce the threatened environments, allowing for the development of specific indicators that would sound an alarm when critical thresholds representing long term desertification effects are reached.

In particular, the study carried out by the researchers from the Universidad Politécnica de Madrid consists of the development of a set of generic equations that represent different desertification syndromes. The model, constructed by means of systems dynamics, links physical and socioeconomic processes. This implies that phenomenons like aquifer salinisation or soil degradation can be studied along with the benefits for the farmers and their opportunity costs.

The procedure is born with the goal of estimating the risk of desertification in any part of the world, including regions where field data is non existent and it is for this purpose that it has been designed. Up to now, it has been applied to the field of Dalías (Almería) and its system of coastal aquifers, the grazing grounds of Lagadas (Greece) or the oases at Morocco and Tunisia.

Currently this method is being used to study the erosion of the olive plantations in Andalusia and their impact of livestock in grazing lands in Senegal.

(*) ECOLOGICAL MODELLING 213 (2): 180-190 MAY 10 2008: “Assessing desertification risk using system stability condition analysis”

Ibáñez, Javier; Martínez Valderrama, Jaime; Puigdefabregas, Juan