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Abstract. The concept of geodiversity appears to have grown out of the discussions around biodiversity, and has evolved over time to become both a tool and a theoretical concept. The paper presents an overview of this conceptual evolution, leading to formulation of the argument that geodiversity is a broader term than geological diversity. Consequently, it is proposed that the concept should take into account all abiotic elements, processes and relations to the natural system and human activity The overview serves as a basis for focussing on the constituent elements of geodiversity that lead to the richness of variety in biotopes, ecosystems or landscapes and that infiuence its use in theoretical, educative and geoconservation terms. The suggestion is made to include four levels in a hierarchy of abiotic diversity (particles, elements, places and landscapes). several approaches to measuring and quantifying geodiversity are discussed, pointing to a need for a geodiversity index which links the different physical elements with processes in the soil, hydrology and geomorphology, as well as with topographical factors (orientation, slope and radiation).

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Land-use changes affecting Mediterranean mountains represent the intensification of use in valley bottoms, accompanied by land-use conflicts, and a generalized abandonment of the hillslopes, which in the past were perfectly integrated in the system of land management. Farmland abandonment, reforestation, diminution of the livestock pressure and substitution of cereal crops by meadows are the most outstanding features of the recent land-use changes. The question is whether the new spatial organisation is in accordance with a longterm policy of sustainable development in mountain areas. The results obtained confirm that farmland abandonment on steep slopesand the resulting colonization of old fields by a dense shrub coverand afforestation contribute to control both soil erosion and surface runoff. As a result some of the most important rivers and alluvial fans have recently stabilized their sedimentary structures.

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