Integration of Conservation Strategies of Plant Genetic ... - Genres
Integration of Conservation Strategies of Plant Genetic ... - Genres Integration of Conservation Strategies of Plant Genetic ... - Genres
Threats to conservation of plant genetic resources Biological diversity is under threat, with large-scale extinctions and severe genetic depletion forecast for the coming decades. Some of the major threats to the maintenance of plant diversity arise from: ♦ land-use change, ecosystem change (eg. caused by intensive application of agrochemicals) and genetic change (eg. through the spread of monocultures and, potentially, through the spread of genes from bio-engineered organisms into natural ecosystems); ♦ over-harvesting of natural resources or other forms of over-use (eg. overgrazing); ♦ the generation of pollution and wastes. Threats to conservation of plant genetic resources - Habitat conversion Loss of habitat is one of the biggest threats to plant diversity. An example is the conversion of more natural habitats into those highly simplified and chemically augmented ecosystems used for the production of large quantities of food, timber and other products for human consumption using modern agricultural and forestry techniques. The genetic diversity of these replacement ecosystems is extremely low, but the cultivars used require continual replacement or enrichment with new genetic material, for instance to overcome, at least temporarily, the deprivations of evolving pests. Thus, modern agriculture and plantation forestry depends fairly immediately on the existence of other ecosystems as sources of new genetic material, including natural ecosystems containing wild crop relatives (Hoyt 1992). The spread of more intensive systems of agriculture and forestry causes loss of genetic diversity, not only in natural habitats, but also through the loss of more traditional farming systems, with their large numbers of cultivated plant species and many local land races. The FAO and many agricultural specialists recognise that the conservation of crop and livestock genetic resources is inseparable from the ways they are used by farmers, especially traditional farmers practising low-input agriculture. In situ conservation of land races, to be successful, must include measures to support low-input, sustainable agriculture, based on traditional farming systems. The spread of invasive species is another threat to the conservation of plant diversity. The best documented cases come from oceanic islands, southern Africa and Australia, but invasive species are not confined to such places and the threat is growing as the rate of movement of germplasm around the world increases. The continuing spread of built-up areas is also a threat to plant diversity. For example, urban developments, mainly associated with tourism, have contributed to the disappearance of three quarters of European sand dunes along the coast between Gibraltar and Sicily and, as a result of this, over 500 Mediterranean plant species are threatened with extinction. Threats to conservation of plant genetic resources - Overuse Unsustainable harvesting of "wild" plants, especially for commercial purposes, is a major threat to biodiversity. Harvesting for local subsistence use is not generally a major issue, at least in less degraded more mesic environments [for instance, Cunningham (1993 a,b) reports that over-exploitation of medicinal plants in Africa is overwhelmingly associated with trade not subsistence gathering, the trade
eing mainly to local and regional urban centres, but also for external markets]. Similarly, the great majority of the more than 600 species of medicinal plants imported into the European Community are collected from the "wild" by a process of scavenging, with no regard for the sustainability of supply from particular localities (Lewington 1993). Likewise, much logging in tropical forest is carried out with little or no regard to regeneration of the timber stock, the conservation of genetic diversity of valuable timber trees or indeed conservation of forest biological diversity as a whole. It also often disregards the value of existing economic uses of forest resources by local communities, and the value of 'ecosystems services', such as stabilisation of soils, the maintenance of soil fertility and catchment protection. Market forces are such that, both with timber and medicinal plants, traders simply switch to new sources of supply as shortages occur, leaving behind successive areas of degraded habitats and associated environmentally impoverished rural communities, one after another. Threats to conservation of plant genetic resources - Generation of pollution and wastes Growing levels of pollution and wastes threaten biodiversity. The magnitude of threats from these sources is rising, as the absolute levels of consumption increase in industrialised nations and as human population mounts. Injection of greenhouse gases into the atmosphere, through the burning of fossil fuels and from other man-made sources, will have major impacts on ecosystems during the coming century, placing the survival of many species and local populations of plants in jeopardy. Ozone depletion in the upper atmosphere, resulting from CFC emissions, has led to increased levels of ultraviolet radiation at the Earth's surface, which, in turn, are thought to be damaging to phytoplankton and which may also have adverse effects on terrestrial plant species. Acid rainfall is causing damage to large areas of forest in Europe and elsewhere. In Europe alone, the costs of forest damage from pollution has been estimated at $30 billion each year during the 1980's. Waste dumping also damages biodiversity. The pollution problems associated with waste disposal are well-known and include contamination of both land and water, including ground water. Wastes, apart from their sheer volume, present enormous problems of environmental persistence and toxicity. Many synthetic chemicals have been developed specifically to be inert and unreactive to other materials and, once they enter the environment, they tend to be resistance to decay. PCBs, some pesticides and heavy metals are all examples of such materials. The accumulation of these substances in either the physical or biological components of ecosystems can cause great damage, even at extremely low concentrations. Toxic chemicals inhibit growth of more sensitive species, leaving opportunities for invasion by less sensitive species and consequent ecosystem simplification. The importance of land planning The great and increasing human pressure on the Earth makes it essential that land is used efficiently to produce required quantities of products and services. This means that the use of land must be planned, a process which cannot be left entirely to individual people, with their sometimes short-term or personal mercenary interests, but which must involve higher authorities, such as national governments, acting to achieve objectives of long-term benefit for communities as a whole. Conservation of biodiversity should be a consideration in all land management plans, from the level of the homestead or farm upwards. Local land use plans should always consider the wider environmental context. For example, the presence of a very rare plant on a farm property places a special obligation
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Threats to conservation <strong>of</strong> plant genetic resources<br />
Biological diversity is under threat, with large-scale extinctions and severe genetic depletion forecast for<br />
the coming decades. Some <strong>of</strong> the major threats to the maintenance <strong>of</strong> plant diversity arise from:<br />
♦ land-use change, ecosystem change (eg. caused by intensive application <strong>of</strong><br />
agrochemicals) and genetic change (eg. through the spread <strong>of</strong> monocultures and,<br />
potentially, through the spread <strong>of</strong> genes from bio-engineered organisms into natural<br />
ecosystems);<br />
♦ over-harvesting <strong>of</strong> natural resources or other forms <strong>of</strong> over-use (eg. overgrazing);<br />
♦ the generation <strong>of</strong> pollution and wastes.<br />
Threats to conservation <strong>of</strong> plant genetic resources - Habitat conversion<br />
Loss <strong>of</strong> habitat is one <strong>of</strong> the biggest threats to plant diversity. An example is the conversion <strong>of</strong> more<br />
natural habitats into those highly simplified and chemically augmented ecosystems used for the<br />
production <strong>of</strong> large quantities <strong>of</strong> food, timber and other products for human consumption using modern<br />
agricultural and forestry techniques. The genetic diversity <strong>of</strong> these replacement ecosystems is extremely<br />
low, but the cultivars used require continual replacement or enrichment with new genetic material, for<br />
instance to overcome, at least temporarily, the deprivations <strong>of</strong> evolving pests. Thus, modern agriculture<br />
and plantation forestry depends fairly immediately on the existence <strong>of</strong> other ecosystems as sources <strong>of</strong><br />
new genetic material, including natural ecosystems containing wild crop relatives (Hoyt 1992).<br />
The spread <strong>of</strong> more intensive systems <strong>of</strong> agriculture and forestry causes loss <strong>of</strong> genetic diversity, not only<br />
in natural habitats, but also through the loss <strong>of</strong> more traditional farming systems, with their large<br />
numbers <strong>of</strong> cultivated plant species and many local land races. The FAO and many agricultural<br />
specialists recognise that the conservation <strong>of</strong> crop and livestock genetic resources is inseparable from<br />
the ways they are used by farmers, especially traditional farmers practising low-input agriculture. In situ<br />
conservation <strong>of</strong> land races, to be successful, must include measures to support low-input, sustainable<br />
agriculture, based on traditional farming systems.<br />
The spread <strong>of</strong> invasive species is another threat to the conservation <strong>of</strong> plant diversity. The best<br />
documented cases come from oceanic islands, southern Africa and Australia, but invasive species are<br />
not confined to such places and the threat is growing as the rate <strong>of</strong> movement <strong>of</strong> germplasm around the<br />
world increases.<br />
The continuing spread <strong>of</strong> built-up areas is also a threat to plant diversity. For example, urban<br />
developments, mainly associated with tourism, have contributed to the disappearance <strong>of</strong> three quarters<br />
<strong>of</strong> European sand dunes along the coast between Gibraltar and Sicily and, as a result <strong>of</strong> this, over 500<br />
Mediterranean plant species are threatened with extinction.<br />
Threats to conservation <strong>of</strong> plant genetic resources - Overuse<br />
Unsustainable harvesting <strong>of</strong> "wild" plants, especially for commercial purposes, is a major threat to<br />
biodiversity. Harvesting for local subsistence use is not generally a major issue, at least in less degraded<br />
more mesic environments [for instance, Cunningham (1993 a,b) reports that over-exploitation <strong>of</strong><br />
medicinal plants in Africa is overwhelmingly associated with trade not subsistence gathering, the trade