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Description
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This book contains selected papers presented during the Symposium "Sustainability of Dehesas, Montados and other Agrosilvopastoral Systems", held in Caceres, Spain, between September 21 and 24, 2003. Agrosilvopastoral systems are widespread in the Mediterranean but are also found in other areas of the world having similar climatic conditions. In the southern and western part of the Iberian Peninsula these land use systems have existed for many centuries, and are commonly formed by open evergreen oak woodlands, covering approximately 4 million hectares. These are areas referred to as the montados and dehesas of Portugal and Spain, which traditionally are exploited by multiple land use including livestock breeding, forestry and cultivation. The importance of these areas rests on both environmental as well as socio-economic values. They support an outstanding diversity of wildlife, form unique landscapes, are the source of high-quality food derived from animal production, sustain rural population, and constitute an important basis for the growing demand of rural leisure and tourism. However, these areas have undergone rapid changes during the second half of the 20th century, shifting from traditional farming systems with very low external energy inputs to more simplified systems causing decreasing diversity of land use and inadequate management techniques. Land degradation is recognized as a significant problem in many of the dehesas and montados, including the lack of tree regeneration, which threatens the future of the woodlands as well as soil erosion, soil degradation and increased runoff production. A common feature is the coexistence of extensification and intensification, causing different problems of degradation. For example, headage payments led to an unchecked increase in animal numbers, thus increasing the risk of soil and pasture degradation. On the other hand, abandonment of livestock breeding produced vegetation changes, leading to shrub encroachment, and an increased risk of wildfires. The book addresses both academics and practitioners interested in land degradation and conservation of areas with agrosilvopastoral land use in Mediterranean environments or other semi-arid areas with strong seasonal contrasts. The editors hope that the volume will contribute to the sustainable management of such landscapes. The volume is organized in six sections. General aspects of agrosilvopastoral systems in the Mediterranean basin are presented in Section 1. The contribution by Papanastasis describes the variety of land uses found in these systems, subject to recent changes and their effect on vegetation degradation. The role of grazing is analyzed by Enne et al. and Campos-Palacin presents reflections on the sustainable economics of agroforestry systems. Two case studies on land use and land cover changes in dehesas close this section. Section two is dedicated to economic and social aspects of agrosilvopastoral systems. In the third section studies on soil water dynamics and soil degradation are presented, including a modeling approach for analyzing stability in grazing systems. Chapter four examines the linkages between livestock and vegetation, and chapter five presents several studies on tree cover and forest use. The final section is dedicated to the sustainability and management of agrosilvopastoral systems, including studies from the Mediterranean basin as well as from Mediterranean California.
