Combining indicators to calculate desertification risk due to salinisation and erosion under different land uses
DIS4ME editor: Jane Brandt <desertlinks@medalus.demon.co.uk>

The landscape of Mediterranean Europe is very varied, from the open, rolling montado of southern Portugal, to steeply sloping terraced olive groves of Greece. But there a number of land uses such as pasture and pine forest which are common to many areas. Different land uses place different demands on the natural resources and have different management regimes. Consequently they also have different desertification risks. (Photo by C. Kosmas.)

These pages give examples of how field data has been obtained for a wide range of indicators in the DIS4ME database. It also describes a methodology for combining the indicator values to calculate desertification risk due to salinisation and erosion, and applies the methodology to the risk of erosion under the following land uses.

• Pine forest
• Cereals
• Olives
• Pasture
• Vines
• Oaks

The concept of desertification risk summarises the vulnerability or sensitivity of the land to further degradation and desertification according to existing land, socio-economic, and management characteristics. The assessment of risk is a pre-requisite of any early warning system. In DIS4ME measures of sensitivity to desertification incorporating soil, vegetation, climate and management indicators can be calculated in terms of Environmentally Sensitive Areas (ESAs) and at a point, the Environmental Sensitivity Index (ESI).

The tools presented in this section of DIS4ME calculate salinisation risk and erosion risk for a given location, from a range of statistically significant factors (or indicators). A demonstration is provided using data from the Greek island of Lesvos. As well as summarising the risk according to the current situation, the tools can be used to predict changes in risk resulting from changes in any of the contributory factors.

As an example, consider a hilly landscape where the soil may be vulnerable to erosion. If the land is ploughed soil erosion risk may be increased, particularly if there is a storm event. However, if agricultural management ensures that a cover of vegetation or agricultural crops is maintained, the risk of soil erosion can be greatly reduced. It is the combination of the different factors that contributes to an overall risk of desertification.