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Publication
Degradação de solos, aridez e desertificação no sul de Portugal : caracterização e alguns factores físicos intervenientes
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| 11.9 MB | Adobe PDF | |||
| 6.13 MB | Adobe PDF |
Abstract(s)
Três conceitos estiveram na origem do presente estudo. O conceito de degradação do solo, formulado no quadro da Convenção das Nações Unidas para o Combate à Desertificação, o de alterações e mudança climática, desenvolvido pelo IPCC, e o de susceptibilidade ecológica.
Um diagrama representando os impactes do aumento do efeito acrescentado de estufa no ciclo hidrológico, adaptado nas ópticas da degradação do solo e da susceptibilidade ecológica, foi também uma referência de trabalho importante. O quadro conceptual estabelecido foi aplicado, enquanto case study, ao Sul de Portugal, durante um período que se iniciou em Outubro de 1931 e se estendeu até Setembro de 1990 ou, em algumas componentes, até Março de 1997.
A avaliação incidiu particularmente sobre quatro indicadores físicos: a precipitação, a disponibilidade de água no solo, o defictt hídrico anual e a erosão hídrica potencial do solo.
O estudo proporcionou a apresentação de uma Cartada Susceptibilidade Ecológica do Sul de Portugal. A interpretação da Carta conduziu a três resultados fundamentais:
identificaram-se variações no regime da precipitação e na disponibilidade de água no solo;
constatou-se que a erosão hídrica potencial do solo é o indicador físico mais importante, tanto para a caracterização do território, como para integrar em estudos mais vastos de avaliação ambiental, económica e social da região, como ainda para fundamentar medidas de ordenamento e gestão do espaço físico;
por outro lado, a disponibilidade de água no solo, particularmente nos meses da Primavera, é também um factor a ter presente nas situações de risco moderado, quer na óptica da caracterização do espaço físico, quer na da concepção e adopção de medidas de gestão e ordenamento do território.
Three hey concepts were considerd in the beginning ofthis study. Soil degriidation, according to the definition presented hy the 1994 United Nations Convention to Comhat Desert.ificatz'on, climate change, as the 1995 IPCC Report wrote it, and landscape sensitivity. A schematic representation ofthe impacts of increasing greenhouse gas concentrations on the natural hydrological systems, adapted to soil degradation and landscape sensitivity points of view, was another important reference. This conceptualframeworle was applied to the South ofPortugal, as a case study. The time span under research started on Octoher1931 andfinished on Septemher 1990. Some data analysis was enlarged until March 1997. The study wasfocused on four physical parameters: precipitation, soil moisture content, annual hydrological deficit and rainfall erosz'vity. A South ofPortugal Landscape Sensitivity Map was drawn. Three major results camefrom the map interpretation, as well as, from all the worh carried out to prepare thefinal delineation ofthe South ofPortugal landscape sensitivity.- ' changes in precipitation pattern and changes in soil moisture content were identified; ' potential water erosion is the most important indicator, it must he con.siÍdm~i-ri on landscape description, on environmental, economical and social evaluation, as well as to support planning and management decisions and measures,- on the other hand, soil moisture content mainly in Spring time, is an indicator that must he considered when the ecological sensitivity is moderated, hoth to local and regional description, and to support additional planning and management decisions and measures.
Three hey concepts were considerd in the beginning ofthis study. Soil degriidation, according to the definition presented hy the 1994 United Nations Convention to Comhat Desert.ificatz'on, climate change, as the 1995 IPCC Report wrote it, and landscape sensitivity. A schematic representation ofthe impacts of increasing greenhouse gas concentrations on the natural hydrological systems, adapted to soil degradation and landscape sensitivity points of view, was another important reference. This conceptualframeworle was applied to the South ofPortugal, as a case study. The time span under research started on Octoher1931 andfinished on Septemher 1990. Some data analysis was enlarged until March 1997. The study wasfocused on four physical parameters: precipitation, soil moisture content, annual hydrological deficit and rainfall erosz'vity. A South ofPortugal Landscape Sensitivity Map was drawn. Three major results camefrom the map interpretation, as well as, from all the worh carried out to prepare thefinal delineation ofthe South ofPortugal landscape sensitivity.- ' changes in precipitation pattern and changes in soil moisture content were identified; ' potential water erosion is the most important indicator, it must he con.siÍdm~i-ri on landscape description, on environmental, economical and social evaluation, as well as to support planning and management decisions and measures,- on the other hand, soil moisture content mainly in Spring time, is an indicator that must he considered when the ecological sensitivity is moderated, hoth to local and regional description, and to support additional planning and management decisions and measures.