What is Desertification?

Transcription

1 Maria José Roxo Pedro Cortesão Casimiro Tiago Miguel Sousa What is? DesertLinks Project Framework 5 European Union Geografia e Planeamento Regional Faculdade de Ciências Sociais e Humanas Universidade Nova de Lisboa

2 What is desertification? degradation of the soil, landscape and bio-productive terrestrial system, in arid, semi-arid and sub-humid areas, resulting from several factors, including climatic change and human activities. United Nations definition (1994) The phenomenon has been wrongly confused with Depopulation, which affects a large portion of the inner part of the country. However, these two phenomena can in fact be related. The loss of soil fertility ends up leading to a decline in agriculture, to land abandonment and ultimately to emigration. Therefore it is essential to distinguish between the two phenomena, to allow for correct and appropriate measures that combat and its advance. is a progressive loss of soil fertility, through the destruction of the structure and composition of the soil, which doesn t permit good agricultural productions, or the existence of a vegetation with varied natural species. Formation Rock Young Soils Mature Soil Erosion

3 The destruction of the soil has other aggravants, as when the soil becomes shallower, it allows only the infiltration of small amounts of rainfall water. This wise, the amount of underground water decreases. Recent studies have revealed that about 36 % of the country presents a serious risk to, and that 28 % of this area is already severely affected by this phenomenon. Several areas of Inner Portugal (Alentejo, Algarve, Beira Interior, Trás-os- Montes), present already vast areas high a high degree of soil and vegetation degradation. In the particular case of the Mértola municipality, 47% of its surface is already affected by a high degree of degradation, which can be easily observed by the enormous extensions with little vegetation and with many rock and stones on the surface. Environmental Sensitive Areas Mértola Municipality 2001 Critical Areas Fragile Areas Non Affected Areas

4 Causes There are several factors that contribute to. Some are natural causes (intense rainfall events, droughts), others are directly related to human activities (agriculture, industry, among others). In reality, the conjunction of these factors has had a very big negative impact on the natural resources (soil, water and vegetation). Agricultural activities, because they are based on the use of soil, contribute decisively to. Therefore, a series of practices and actions, which are bad and degrade the soils and the environment, can be identified. Pastures Overgrazing Excessive use of the same pastures; Excessive density of animals per area; Use of pastures not adapted to the soils and climate conditions; Compaction of the soil surface by cattle; Appearance of a trail net, which favours the action of runoff water.

5 Arable Lands Removal of the vegetation cover (cut, stubble burn);; Incorrect agricultural practices, like ploughing too deeply, successively and along the slopes, among others; Loss of organic matter in the soil, through soil wash by rainfall water; Destruction of the soil structure, with incorrect works (ploughing and other); Compaction use of heavy machinery; Stored nutrient removal (fallow) monocultures (e.g. wheat, vineyards, among others), species inadequate to the soil and climate conditions (e.g. sunflower); Pollution contamination by toxic residues and chemical products (fertilisers, herbicides, pesticides). Irrigated Areas Incorrect agricultural practices, like excessive use of water and consequent erosion; Salinization formation of salt layers on the surface of the soil, due to the use for irrigation of groundwater with high contents of salt; Worrying decrease on the quantity of available underground water; Loss of soil fertility by continuous use depletion.

6 Forest Deforestation; Use of fast growing exotic species, like the eucalyptus; Fires. Other activities Surface sealing infrastructure and urbanization; Excessive water consumption in tourist areas (e.g. Algarve). All these activities lead and intensify the soil erosion processes by action of the rainfall water. When rain drops hit the unprotected and disaggregated soil, they fragment the soil aggregates into particles, which are afterwards easily transported by surface run off water. For that reason, it is common to see the rivers with a clayish colour, mainly during Autumn (time of ploughing and seeding), or in other times of the year, when the occurrence of severe rainfall events coincides with agricultural labour on the soil (like during Spring when fields are ploughed).

7 Consequences The consequences of are very grave, despite being a phenomenon that doesn t occur like a sudden catastrophe, but progresses steadily in time. The main consequence is land abandonment, following the loss of soil fertility. There is loss on the quality of life of the populations, which makes them emigrate. As a consequence of these migratory movements, a chaotic growth of town receiving these migrants can occur, which means increasing unemployment and marginal behaviours, as well as pollution and other environmental problems. Several aspects result from the loss of soil fertility : Breakdown of agricultural production and productivity; Decrease of yield and purchase power of the populations; Oscillation of product prices, at regional and national markets; Social, economical and political instability; Increase in wealth disparity between regions;; Increase of environmental problems due to the bad use of natural resources; Poverty and unemployment.

8 In terms of natural resources, several issues are observable: Loss of biodiversity (less variety of plants and animals); Soil loss by erosion, which implies less capacity for rainfall water to infiltrate and feed groundwater tables and springs; Decrease of sweet water availability, as rivers carry much sediment and dams fill up with this load; Degradation of Montado ; Progressive increase of the pressure upon the resources, in order to maintain some income. As it can be concluded, we stand before a very GRAVE phenomenon, to which governments and populations haven t paid the necessary attention. For this reason it is fundamental to realise that exists and is in course, which makes it extremely urgent to take measures preventing its further advance. Despite there being a National Action Plan to Combat, elaborated because Portugal signed the United Nations Convention to Combat and Drought, it is in the hands of EVERYONE to contribute for the conservation of vital resources for the human being, like SOIL and WATER, as the FUTURE of all of us depends upon the actions and attitudes of the Present. Being informed is a decisive step to participate combating. Photos taken by the authors, Mértola Municipality 2003/2004 PANCD - Plano de Acção Nacional para Combate à Desertificação Aprovado pela Resolução de Conselho de Ministros nº 69/99 de 17 de Junho Direcção Geral dos Recursos Florestais sede do Ponto Focal da UNCCD

9 DesertLinks /desertlinks/index.htm Faculdade de Ciências Sociais e Humanas Framework 5 Maria José Roxo mj.roxo@iol.pt Pedro Cortesão Casimiro pjcc.casimiro@sapo.pt Tiago Sousa sousatiago@netcabo.pt