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1. Background information
2. State of rainfall induced erosion in the Mediterranean coastal areas
3. Links among mapping/measurement of erosion processes and integrated management of coastal areas
4. Prerequisites and institutional aspects
The Regional Activity Centre of the Priority Actions Programme (PAP/RAC), operating within the Mediterranean Action Plan (MAP) UNEP, has been implementing since 1984 the priority action entitled "Promotion of Soil Protection as the Essential Component of the Environmental Protection in Mediterranean Coastal Areas". The action has enjoyed the participation of almost all Mediterranean countries, FAO and the Arab Centre for the Studies of Arid Zones and Desert Lands (ACSAD), Damascus.
After an initial, fact-finding phase, a proposal of a cooperative project on erosion mapping and measurement in Mediterranean coastal areas was prepared jointly by PAP, FAO and ACSAD, and proposed for implementation at the 5th Ordinary Meeting of the Contracting Parties to the Barcelona Convention (Athens, 1987). The proposal was accepted and Spain offered to host the project. The Spanish authorities nominated their National Institute for the Conservation of the Nature - ICONA (now General Directorate for the Conservation of the Nature - DGCONA), Madrid, to act as the host institution of the project, while FAO agreed to contribute providing scientific and professional support.
Accordingly, the project was defined and divided in two parts, namely:
• a pilot project on erosion mapping and measurement, to be implemented, from 1991 to 1995, in three representative areas selected in Spain, Tunisia and Turkey; and
• a larger project in erosion mapping and measurement to be implemented later on, at a broader scale, with the participation of other interested Mediterranean countries, possibly as a UNDP project.
The proposal of the pilot project was discussed at an expert meeting held in Malaga in December 1989, and after the approval of the Contracting parties to the Barcelona Convention, the project was launched in 1991, being divided into a component on mapping and a component on measurement of erosion processes.
The Mapping Component, implemented by PAP, DGCONA and FAO, in collaboration with Spain, Tunisia and Turkey, was concluded towards the end of 1992 (the Vallcebre area in 1995-96). The results of the activity, as well as a common mapping methodology developed within it, were presented and discussed in a seminar held in Malaga in December 1992, attended by the participants of 10 Mediterranean countries and the EC. The seminar judged the developed methodology favorably and recommended that guidelines be prepared for its application. The terms of reference for the preparation of the mapping part of the Guidelines were formulated during two expert meetings (Rome, April 1993, and Almeria, June 1993). The authors prepared the draft version of their contribution by the end of 1993. The first revision of the draft version was made in Rome in March 1994, and the second one in January 1996.
The Measurement Component, implemented by PAP, DGCONA, and FAO was launched in 1993 and completed in early 1996. The results of the activity were analyzed and discussed in the expert meeting held in Barcelona in July 1996. The terms of reference for the preparation of Part II of the Guidelines were formulated during the expert meeting held in Madrid in November 1993. The first draft of the measurement part of the Guidelines was revised in the expert meeting organized in Barcelona in July 1996.
The final draft of both mapping and measurement components was presented, discussed and amended at a workshop organized in Barcelona on 13-16 October 1996. The amendments and proposals recommended by the workshop were taken into account as appropriate when editing the final text of Guidelines.
A special chapter on the role and place of erosion processes within the process of the Integrated Coastal Area Management (ICAM) in the region is contained as Annex I in the Guidelines.
Due to the complementarity of the mapping and measurement procedures, their joint use and application is recommended whenever possible and/or appropriate.
2. State of rainfall induced erosion in the Mediterranean coastal areas
Mediterranean landscape is the result of long and intense interactions between human activities and natural environment. The soil is the essential component interfacing these relationships, and consequently has become deeply affected.
Soil erosion is severe in the Mediterranean basin and particularly intense in long sectors of its coastal areas. The extent of the phenomena is difficult to assess, nevertheless this point has been subject to attention, mainly at the national level, and some estimations are available.
In the Mediterranean countries of the European Union, 202,000 km2 present high erosion risk (Giordano et al, 1992). Other data compiled by the United Nations indicate that as much as 200,000 km2 of the Mediterranean region may be subject to desertification.
According to ICONA erosion maps, 57% (104,000 km2) of the Mediterranean basins of Spain, are affected by erosion rates higher than 12 t/ha/yr, and 25,700 km2 of them affected by very intense erosion rates of more than 50 t/ha/yr.
Research conducted in the Bleone watershed between Digne and Draix, Alpes Maritimes, France (CEMAGREF, 1988) have proved that two small catchments, one entirely covered by artificial plantations and other presenting bare land have a soil erosion rate of 0.01 t/ha/yr and 30 t/ha/yr respectively.
Turkey presents 22.3% of land severely eroded (Topraksu Koyisler, 1981).
In Tunisia the inter-annual and inter-seasonal irregularity of rainfall combined with the mountainous relief are the main physical factors leading to erosion. According to the erosion map of the northern part of the country, covering 120,000 km2 of the 164,000 km2 total area of Tunisia, 70,000 km2 are directly threaten by erosion. (Abdesslam, 1994).
Gazzolo and Bassi (1966) indicated for Italy a mean specific erosion of 0.15 mm/yr, the highest being that of the Marecchia and Savio basins (both in Emilia-Romagna) with an annual soil loss of 1.4 mm (approx. 23 t/ha/yr. The explanation to this situation can be found in the particularly erodible soil and in the extremely intensive cultivation.
The Albanian Drin river has one of the highest suspended sedimentary load in the Mediterranean basin: 1,082 t/km2/yr.
In Syria, Lebanon and Israel rainfall and wind induced erosion have a cumulative effect. Rainfall induced soil erosion rarely exceeds 50 t/ha/year (FAO/UNEP/UNESCO, 1980).
In Egypt there is no or negligible rain-induced soil erosion, but in several desert areas (erg) and in a narrow strip bordering the Nile delta and the western Egyptian coast wind-induced soil erosion may mobilize more than 200 t/ha/yr.. Libya has moderate rain-induced soil erosion on the mountain range bordering the sea (Jebel Akdhar and Jebel Nefhusa), while in other parts there is extensive wind erosion.
From siltation surveys completed in six reservoirs located in several watersheds in Morocco arose that soil erosion ranges from 2 to 59 t/ha/yr..
The main physical factors influencing soil erosion processes in the Mediterranean region are:
• very high climatic variability characterized by frequent periods of drought and periods of heavy rainfall;
• presence of high erodible soils due to their weak structure, shallowness and lack of organic matter
• uneven relief with steep slopes and very diversified landscapes.
The main socio-economic factors influencing soil erosion in the Mediterranean region are:
• crisis conditions in traditional agriculture with associated land abandonment and deterioration of soil and water conservation structures;
• extensive forest and natural vegetation losses due to frequent wildfires;
• overgrazing of rangeland which has particularly strong environmental impact in semi-arid conditions;
• over-exploitation of agricultural land inducing soil erosion.
The effects of soil erosion are of environmental and economic importance.
On-site damages are loss of soil productivity and reduced agricultural yields.
Off-site effects are far reaching: increasing rates of siltation in streams and reservoirs affecting water quality and the drainage capacity of rivers.
Both on-site and off-site effects have a negative relevant influence on the water cycle, diminishing the natural capacity of the land for river regulation, in a region where water is a critical factor, which limits socio-economic development.
When addressing causes and consequences of soil erosion it is important to stress the great degree of integration and inter-relationship between the physical phenomena and the socioeconomic context.
Most of erosion control plans have focused more on the symptoms than on the real causes of the phenomena. They have tried to tackle overcultivation, overgrazing, deforestation, etc. directly, without addressing the underlying social and economic pressures that have produced them. (Lean, 1995).
It is essential to understand the causes which trigger the human behavior in respect to soil erosion. The United Nations Convention to Combat Desertification, adopted in 1994, focuses on this integrated approach pointing out that affected countries have to "address the underlying causes of desertification, and pay special attention to the socio-economic factors contributing to desertification processes". Soil erosion is the leading direct mechanism of desertification worldwide.
The socio-economic context of soil erosion presents some differences between northern and the southern Mediterranean.
In the Southern Mediterranean, the erosion phenomena are mainly linked to the demographic increase. Since 1950 population has triplicate, while in the Northern Mediterranean has grown barely by 30%. As the irrigated area remains unchanged, an extraordinary increase of the agricultural pressure over the marginal lands have been necessary to keep the population. The overcultivation and overgrazing of uncertain yield appears and the soil erosion spreads. The forest area retreats about 1 to 2% yearly and the steppe and natural pasture are destroyed at a pace of 1% every year.
In the Northern Mediterranean the technical, economical and social changes of the rural life since 1950, led to the litoralization of the economy, characterised among others by the demographic vacuum in the less productive inner zones and an extreme concentration of the population in the littoral areas. The fast expansion of the abandoned marginal areas, prone to forest and wild fires, led to the deterioration and subsequent erosion processes. (Puigdefábregas, 1994).
All these processes show once more the critical relationship of the coastal areas with the watersheds that dominate them. The success of the coastal areas management requires the integral view of the whole watershed, which is the spatial scope where the water, ecological and geological cycles take place. Any disbalance in the upper part of the watershed could be felt in the lower coastal area.
In this inter-dependence the erosion phenomena can be taken as an example. The existence of sustainable ecosystems and agriculture in the upper parts, free of erosion phenomena, is critical for the regulation and quality of the vital water supply and the protection against the floods, which would put at risk most of the coastal areas. Furthermore, the socio-economical imbalance in the upper parts affect the equilibrium of the coastal areas and vice versa. The mentioned litoralization of the economy can be taken as an example.
It is remarkable that in all these processes erosion phenomena are present as a mechanism but also as an indicator of the sustainability and sound socio-economic integration of the coastal and upper areas of the Mediterranean watersheds.
The direct measures to mitigate and prevent erosion are well known. Some of them have been extensively applied in the Mediterranean basin.
The planning and design of erosion mitigation actions relies in the concept of Watershed Restoration and Management Project (WRM), which represents an integrated analysis of the land resources of the watershed and its degree of degradation, as a basis to formulate a proposal of sustainable land-use in terms of soil and water resources protection. (Rojo Serrano, 1996).
The land-use proposal must satisfy the socioeconomic demands of the inhabitants, inside and outside the basin. The implementation of the WRM implies a series of activities to restore the eroded land and to prevent further development of soil erosion. The main actions considered are: Reforestation with Mediterranean species; Silvicultural treatments to improve and promote natural vegetation cover; forest management to consolidate and improve the ecological quality of existing forest stands; grazing management to achieve sustainability of pasture exploitation; agricultural soils conservation practices specifically designed to prevent soil erosion; and torrential watercourses stabilization structures, mainly check-dams to stabilize the deepening of gullies and scouring of "rambles" which may lead to generalized channel erosion.
The WRM is not only a planning instrument of technical measures but also a tool to integrate the erosion control measures in the socioeconomic context. The public information of the project and the official promotion of the prescript measures are among the mechanisms to reach such integration.
Experiences in erosion mapping and measurement provide the critical basic knowledge to assess the phenomena and formulate the mitigation actions required. The complex nature of the erosion phenomena with multiple physical factors implied, as well as the complexity of its off-site projection, calls for a sound scientific basis, which can be only established with an adequate field experimental programme.
The adequate address of the soil erosion problems as well as the correct formulation of mitigation and prevention plans requires the understanding of the complexity of the phenomena and their implications. It is essential to avoid simplifications which could lead to fictitious solutions, sometimes with undesirable collateral effects. In such a context the field measurement presents its real value as a tool to guide the management actions.
3. Links among mapping/measurement of erosion processes and integrated management of coastal areas
Erosion is an essential factor to be considered in any territorial planning. This assert relies in the fact that the degree of erosion is a primary indicator of the sustainability of the land use scheme of a territory.
Erosion mapping is the essential tool for the knowledge of the distribution and geographic extent of the phenomena as well as for its qualitative characterization. The Common Consolidated Methodology of Mapping of Rainfall Erosion in the Mediterranean Coastal Areas, established as the first component of this cooperative project provides both predictive and descriptive mapping of the erosion phenomena.
Through erosion mapping, it is possible to incorporate the erosion phenomena as a factor in the process of land-use planning and management, and particularly in the process of Integrated Coastal Areas Management (ICAM).
The full capacity to integrate both methodologies, erosion mapping and ICAM, into geographical information systems (GIS), facilitates the joint use of both elements as a improved tool to guide decision making in the land-use planning and management of the Mediterranean coastal areas.
The erosion map provides a synthetic, systematic information about the nature, intensity and distribution of the relevant phenomena. On this basis is possible to identify the most severely affected areas and the dominant types of erosion. On a more detailed basis, the measurement of the erosion phenomena in selected environments provides accurate qualitative and quantitative data necessary as detailed inputs to ICAM, as well as the reliable basis for the planning and design of the prescribed erosion control activities.
The measurement area should be previously surveyed and mapped at both landscape and more specific, land unit levels, where identified erosion processes can be considered as representative.
Measurement operations and experiments are meant to complement or compensate for the lack of quantitative assessment within the systematic mapping procedure.
Erosion mapping identifies and describes dynamic processes in a qualitative way, including extreme situations such as overall irreversible degradation on one hand, and stable, non-affected areas on the other. Experimental measurement data would be of particular need and relevance to all intermediate and typical cases where land degradation, and specifically soil erosion, need to be quantified and assessed in terms of priority after having been identified and located by means of systematic mapping.
Measurement plots and experimental plots not related to any systematic mapping surveying have been considered of very reduced utility, especially if they have to be integrated in a management plan. The exercises related to experimental plots and watersheds mapping should be integrated in the general policy of erosion control. The results of the measurements should be used in the determination of the priorities of action and the design of technical solutions of a management plan. To this objective contributes essentially the formulation of a link between the different mapping units identified and the data from the corresponding experimental plots or watersheds. Therefore, a close association and interaction between erosion measurement and mapping have been recognized as one of key prerequisites of sound soil management and land-use planning.
Additionally, erosion measurement can be used for the systematic characterization of erosion landscapes extensively represented in the Mediterranean. This exercise includes the detailed description of the erosion-specific mechanisms and the quantitative data ranges associated to them. It has the potential to build a kind of systematic landscape inventory to be used as a primary reference for ICAM and general land planning purposes.
In summary, a close association and interaction between erosion measurement, erosion mapping and ICAM has been recognized as one of the key prerequisites of sound soil management in coastal areas.
4. Prerequisites and institutional aspects
The application of a common, standardised mapping and measurement procedure by various countries offers great advantages related to the possibility of exchange of information, assistance, transfer of knowledge, implementation of comparative studies, joint research and/or technical programmes/projects. On the other hand, the application of the recommended procedures requires a certain number of prerequisites to be met. The most important of them are:
• Political will: The responsible political and executive authorities must develop and express a positive will to define and implement harmonized activities and adequate institutional instruments relative to soil protection and erosion control problems as an essential component of the national development/environment policy;
• Institutional capacity: The authorities, institutions and professionals involved (Government and administration at national and local levels; university departments and research institutions; institutes; soil management authorities) are supposed to possess an average level of appropriate organizational, scientific and/or professional capacity, and a certain previous experience in soil erosion related activities;
• Capacity of integration: Due to the fact that erosion phenomena are of a multidisciplinary and multisectorial nature, the will and ability to establish horizontal and vertical integration / coordination / cooperation, including the integration within a larger ICAM framework, is highly necessary;
• Knowledge of erosion related problems: a certain level of information and scientific knowledge of relevant and representative erosion phenomena; understanding of impacts of erosion processes on the national economy and environment; understanding of the benefits of application of a common consolidated methodology; finally, understanding of priorities.
• Existence of a National Erosion Control Programme, as part of the National Development Policy and Strategy;
• Existence of a specific, area-related Erosion Control Programme, as part of the National Programme.
• Public awareness, to be achieved through education, information, demonstration and sensitizing of the farmers at household and rural community levels.
The experience gained by PAP/RAC in the implementation of the programme indicates that the above prerequisites can be reasonably met in almost all of the Mediterranean countries. However, even if some of these prerequisites do not exist, or are not fully met, it is strongly recommended that training courses be organized in order to achieve the necessary level of capacity and experience. Furthermore, preparatory training, and on-the-job training in particular, are recommended when starting the application of the presented procedures.