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Conclusions

A series of 72 indicators related to physical environment, social, economic and institutional characteristics were described in 15 study sites located in Mediterranean and Eastern Europe, Latin America, Africa and Asia. The selected indicators are directly or indirectly related to land degradation and desertification. Questionnaires were prepared and a number of indicators corresponding to specific land degradation process were described in 1641 field sites. The most important process of land degradation identified in the described field sites was soil erosion followed by soil salinization, water stress, forest fires, overgrazing, and urbanization. The number field sites in which each indicator was described varied since each process of land degradation included a group of indicators varied from 30 to 49, and data for some indicators were not available in the various study sites. The defined, indicators were described separately for all study sites using distinct classes. All data have been included on a harmonized data basis on excel form. The collected data from a variety of environmental, social and economic conditions presenting valuable information for areas affected from desertification for deriving tools for assessing the effectiveness of various land management practices and techniques for combating land desertification. After classified the various indicators in categories, a description was carried out separately including all study sites. The main characteristics are summarized as follows.

  • The climatic conditions of the study sites are mainly characterized as semi-arid with rainfall ranging from 280-650 mm in 72.3% of the study field sites, with high aridity index (BGI>125) in 61.1% of the cases. The seasonality of rainfall is mainly characterized as rather seasonal to mark seasonal in 79.2% of the sites with very low to low erosivity in 82.4% of the study field sites.
  • The water resources includes mainly water of good quality with low to moderate electrical conductivity in 55.9% of the field sites, while 44.1% of the sites have low water quality for irrigation. The water quantity is characterized as adequate to moderate in 70.4% of the cases. Ground water exploitation has been assessed as without facing problems in 62% of the sites, and the ratio water consumption/water demands was mainly low to moderate in 67.5% of the study filed sites.
  • The soils are mainly characterized as well to imperfectly drain in 50.9% of the study field sites, formed mainly on sedimentary and unconsolidated parent materials in 83.6% of the cases, free of rock fragments to moderately stony in 84.2% of the sites. relatively deep to very deep in 51.5% of the sites, moderately fine to fine textured in 56.4% of the sites. Slope gradient greater than 12% has been defined in 57.5% of the cases, with northern slope exposure as dominant class defined in 62.2% of the cases. Soil water storage capacity has been characterized as moderate to high in 51.3% of the cases. Rock outcrops were not present or few in 86% of the study field sites. Soil organic matter content in the soil surface has been identified as low to very low in 77.1% of the sites. Soils were moderately to severely erode in 71.9% of the sites. Finally field sites in which soil salinization was the most important process of land degradation had low to moderate electrical conductivity in 73.2% of the study sites.
  • The existing vegetation was mainly agricultural crops in 51.4% of the sites while pastures cover 25% of the cases. Vegetation cover types were: cereals (33.2%), olives (18.2%), vines (18.5%), cotton (10.5%), generating vegetation cover less than 50% in 50.9% of the cases. The rate of deforestation was characterized as low in 91.2% of the study field sites.
  • Water runoff systems has been characterized by fine to very fine drainage density in 57.2% of the study field sites, while flooding frequency in the lowland is rare to no flooding in 60.3% of the cases. The presence of impervious surfaces covered with inert materials was low to moderate in 73.8% of the study areas.
  • Forest fires have been occurred mainly with low frequency (ecosystem burned every 50-100 years) in 85.5% of the study field sites, even though the fire risk has been characterized as high to very high in 91.4% of the cases. The rate of burned area in the last decade has been defined as low (<10 ha/10 km2).
  • The agricultural structure has been characterized as owner-farmed in 64% of the study field sites with variable farm size ranging form 2 to more than 100 ha. Land has been subjected to high fragmentation with more than 7 parcels in 58.5% of the cases. Farmer's income has been assessed as moderate in 70.6% of the study field sites, while farmers are mainly working in the agriculture sector in 60% of the cases.
  • Cultivation of the land by plowing has been defined in 36.5% of the study field siteswhile no tillage operations were identified in 35.7% of the cases. The main tillage frequency defined was twice per year in 33.7% of the field sites. Dominant depths of cultivation were less than 20cm and 20-30 cm in 23. % and 26.6% of the cases, respectively. Tillage direction for the fields cultivated was mainly down slope in 37.6% and parallel to the contour lines in 41.6% of the cases. Mechanization index has been characterized as low in 63.5% and moderate in 33% of the study field sites.
  • Husbandry has been mainly characterized with no grazing control in 50.9% of the field sites, while sustainable grazing has been recorded in 43% of the cases. Grazing intensity has been defined as low in 56.8%, while high has been characterized in 36.2% of the study field sites.
  • Land management with respect to fire protection has been characterized as low in 62.5% of the study field sites. No sustainable farming has been identified in 53.4%, while no-tillage or minimum tillage has been defined in 33.9% of the cases. No reclamation of affected areas by salts has been identified in 95.3% of the corresponding field sites. No actions for reclamation of miming areas have been defined. No soil erosion control measures have been identified in 73.1% of the cases; while low to moderate measures have been defined in 19.6% of the field sites. No soil water conservation measures have been recorded in 56.3% of the study field sites, while measures such as weed control, mulching have been found in 43.7% of the cases. The study field sites were mainly no terraced in 84. % of the cases.
  • Land use in relation to the rate of land abandonment has been defined as low (less than 10 ha/10 years/km2) in 52.8% of the study fields sites, while moderate to high rate of land abandonment (10-50 ha/year/10km2) has been identified in 45.4% of the cases. Land use intensity in agricultural areas has been characterized as high in 38.5% of the cases, while moderate and low in 29.7% and 31.7% of the field sites, respectively. The period of existing land use was mainly long (more than 25 years) in 70.4% of the study field sites. Urban area and rate of urban area change has been defined low in few of the study sites measured. The field sites studied for soil salinization were located in distance less than 5 km from the seashore in 49.2% of the cases, while the 45% of the fields were in distance greater than 15 km.
  • The water use for irrigation was mainly limited in less than 5% of the land irrigated in 53% of the fields, while more than 50% of the land irrigated has been defined in 25.4% of the sites. Runoff water storage actions were not defined in 64% of the fields. Water consumption based on the limited number of fields was mainly allocated for agriculture in 61.4% and the rest for other uses. Water scarcity was characterized as high in 42% of the sites while low to moderate in 48.8% of the cases.
  • Tourism data were available for few study sites in which tourism intensity and tourism change have been characterized as low.
  • Human characteristics such as poverty index were low in 42.9% of the field sites, while moderate in 47.5% of the cases. Old age index have been characterized mainly as high in 63.9% of the field sites. Population density was basically low in 66% of the cases (less than 50 people/km2). Population growth rate has been characterized as low (0.2-0.4% per year) in 72.6% of the sites.
  • Institutional indicators such as subsidies have been mainly allocated for production in 64% of the field sites, while for environmental protection only in 8% of the cases. Protected areas and particularly protected landscapes have been defined only in 14.9% of the study field sites. Finally, policy enforcement of exiting regulations was characterized as low to no enforcement in 72.5% of the study field sites.

Indicators in the terrestrial ecosystem are either of state or of influxes. State indicators are the values of characteristics, which describe the state of its components. In the case of land degradation and desertification, they should be applied to land characteristics describing its principal functions. It is important to know how far or how close are these components to or from describing the state of desertification. State indicators are parameters of soil, vegetation, water and geology. The first three vary with time, where as, the last is rather constant. Influx indicators are parameters of climate, fires, and natural catastrophies and of human interventions, all varying with time. To assess the danger or vulnerability of land to degradation and or to its extreme stage: the desertification, is necessary to accurately define its present state and if possible its past states. Furthermore, land is subjected to influxes that either improve or deteriorate it. The rate of change depends on the intensity of influx indicators, as well as, on the state of land at the particular moment. Therefore, the sensitivity of land to degrading or improving influxes is not a constant but rather an ever changing parameter, requiring a continuous monitoring.

The proposed number of indicators, even though are directly or indirectly related to land degradation, it is too large to be practically applicable. Some of them, easily evaluated, could substitute a number of others. For example vegetation area burned per unit of time, could be used instead of inflammability, management, prevention practices and fire sufficiency extinction methods and facilities. Soil storage capacity could be estimated from soil depth, texture and rockiness. The ratio: of wader demand / available water is powerful indicator of the water regime of an area. Some of the indicators could be estimated from others, and to be easier evaluated, by making use of pedotransfer functions. When crucial indicators, such as soil depth, water scarcity, and destructive human activity reach or surpass critical thresholds, land is heading to desertification, regardless of other favorable state and influx indicators. In some of such cases, human influxes may reverse the course of land decline. However, the respective benefit/cost ratio should be considered.

The effects of the influxes on the state parameters are usually complex and interdependent. They may also have opposite effects depending on the state indicators (e.g. land abandonment, terracing). This makes the accurate scaling and the weighing of the indicators difficult. Scaling the indicators on experience, observations and educated guessing could be useful tool for some practical applications and for comparative evaluations. They should, however, be checked against real situations in the field. The above are some points, which must be considered in evaluating the sensitivity of land to degradation and desertification.

Finally, the above list of indicators will be further analyzed to identify the most appropriate and effective indicators suited to a range of local physical and socio-economic conditions for assessing the effectiveness of the various land management practices in land uses and landscapes prone to desertification.