Resource Assessments and Land Degradation Monitoring with Earth Observation Satellites

Abstract

Land degradation processes which imply a reduction of the potential productivity of the land (e.g., soil degradation and accelerated erosion, reduction of the quantity and diversity of natural vegetation) are widely spread in the Mediterranean basin. As a continuation of the long history of human pressure upon land resources, the main environmental impact originates from interactions between climatic characteristics and ecologically unbalanced human interventions. which, in the sense of recent definitions of the United Nations Environmental Programme¹, are often summarised as desertification processes (e.g., Thomas and Middleton, 1994). An overview of the ecological, physical, social, economic and cultural issues which are collectively contributing to the increasing risk of further degradation of Mediterranean lands has been presented by Perez-Trejo (1994). The same author concludes that a reconceptualisation of desertification - one more appropriate for the European situation - is needed in which the role of urban-industrial expansion, tourism and agriculture in relation to the allocation of water resources are seen as significant contributors to the problem. Inadequate land use practises (e.g., excessive grazing, fuelwood collection, uncontrolled fires) further contribute to the acceleration of degradation processes which result primarily from complex interactions of plant growth and erosion processes. It is now widely agreed that accelerated water erosion is one of the most important sources of soil degradation; an average yearly soil loss of more than 15 tons/ha was reported by Grenon and Batisse (1989) to occur in more than one third of the Mediterranean basin. This excessive loss of soil, nutrients and seeds from the ecosystem hampers also the regeneration capacity of the vegetation by disrupting plant-water relations, and thus drives a mechanism of sometimes irreversible environmental damage. If erosion is not spectral mixing paradigm or invertible physically-based analytical models, can be used to derive quantitative estimates and improved indicators for land resources and degradation processes.

Article FootNote

¹UNEP (1991) has redefined desertification in the sense of considering it as “the land degradation in arid, semiarid and dry-semihumid areas resulting mainly from adverse human impact” where the term ‘land’ includes land and local water resources, the land surface and its natural vegetation.