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An approach to derive relationships for defining land degradation and desertification risk and developing appropriate tools for assessing the effectiveness of the various land management practices using indicators is presented in the present paper. In order to investigate which indicators are most effective in assessing the level of desertification risk, a total of 70 candidate indicators was selected providing information for the biophysical environment, socio-economic conditions, and land management characteristics. The indicators were defined in 1,672 field sites located in 17 study areas in the Mediterranean region, Eastern Europe, Latin America, Africa, and Asia. Based on an existing geo-referenced database, classes were designated for each indicator and a sensitivity score to desertification was assigned to each class based on existing research. The obtained data were analyzed for the various processes of land degradation at farm level. The derived methodology was assessed using independent indicators, such as the measured soil erosion rate, and the organic matter content of the soil. Based on regression analyses, the collected indicator set can be reduced to a number of effective indicators ranging from 8 to 17 in the various processes of land degradation. Among the most important indicators identified as affecting land degradation and desertification risk were rain seasonality, slope gradient, plant cover, rate of land abandonment, land-use intensity, and the level of policy implementation.

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Desertification is the consequence of a series of important processes in the Mediterranean environments, especially in semi-arid and arid regions, where water is the main limiting factor of land use performance on ecosystems. Among the most important processes of desertification are soil erosion and salinization particularly affecting hilly areas and lowlands, respectively. Various methodologies have been developed in identifying and mapping environmentally sensitive areas (ESAs) to desertification. Studies have shown that the various types of ESAs have different behavior on crop production, plant growth, grazing capacity, and soil erosion rates. For example, olive oil and cereal production decreased as the type of ESA changes from non-threatened to critical areas. Soil erosion measures have shown that soil erosion rates increased as the sensitivity of land to desertification increased. Loss in land productivity greatly affects farmer's income and measures applied for protecting the land from further degradation and desertification.The necessity of elaborating indicators is one of the priorities identified by the United Nations Convention to Combat Desertification (UNCCD). The use of indicators can generally simplify complex processes and provide appropriate tools for combating desertification. Indicators can be classified to those related a) to the physical environment (soil, vegetation, climate), b) to the land management (tillage operations, irrigation practices, animal density grazing the land, forest fire protection, erosion measures, etc), and c) to the socio-economic characteristics (farmer age, family size, farm size, subsidies, farmer income, etc). Indicators can be better used for defining land desertification risk if they are classified according to the land use type. For example important indicators for defining desertification risk for vineyards are related to land management as well as to land characteristics such as tillage operations, tillage direction, slope gradient, parent material, plant cover, etc. Studies, conducted in areas in which the main process of desertification was salinization, showed that important indicators for defining desertification risk were ground water depth, drainage, water quality, frequency of flooding, distance from the seashore, type of land use, rainfall, etc.

The need for reliable estimates of soil loss under different land management practices (LMPs) is becoming imperative in the Mediterranean basin to inform decisions on more effective strategies for land management. The effect of LMPs on soil erosion and land degradation has been investigated using experiments from November 2008 to November 2011 in an olive grove in central Crete (Greece). The study area was on sloping land with soils formed on marl deposits which are vulnerable to desertification because of surface runoff and tillage. The experimental design included three treatments with two replicates (3 × 5 m experimental plots) corresponding to the following LMPs: (i) no tillage–no herbicide application, (ii) no tillage–herbicide application and (iii) ploughing to 20 cm perpendicular to the contours. The following variables were monitored: surface water runoff, sediment loss, soil temperature at 10 cm, soil moisture content at depths of 20 and 50 cm, as well as selected climatic variables. The results show that the no tillage–no herbicide management practice gave the lowest sediment loss (1.44–4.78 g/m2/yr), the lowest water runoff (1.8–11.5 mm/yr), the greatest amount of water stored in the soil, the lowest soil temperature and the lowest desertification risk compared with the other treatments. Tillage resulted in the greatest sediment loss (13.6–39.2 g/m2/yr) and surface runoff (16.5–65.0 mm/yr), and an intermediate amount of water stored in the soil. In addition, this treatment led to the loss of soil thickness of 3.7 mm/yr because of ploughing. The results demonstrate the high risk of desertification in the investigated region and the methodology can be used in other Mediterranean areas as an assessment framework for evaluating land degradation and the impact of land management on soil erosion.