Wetlands make up 6% of the earth's land surface and in the past, people had misconceptions about them. The only policy for management was to drain them, but nowadays, the emphasis is on protection. A wetland has a water level high enough to force vegetation to survive for a significant time in anaerobic conditions. Britain has relied on land drainage to become agriculturally productive and habitable; 61% of its agricultural land has been drained. Wetlands though are amongst the most fertile ecosystems on the planet, providing numerous advantages to humans, such as the ability to cleanse water, remove pollutants, and provide peat, an organic fuel. They also provide fish, food, and stores for floodwater. This report aims to concentrate on the water requirements of two wetlands, lowland wet grasslands and the raised mire. Lowland wet grasslands, such as the Somerset Levels, include wet meadows, a traditional farming system from the 16th century.
Their decline began with the quickening of the pace of conversion to arable land coupled with intensified land management. Britain originally had 1,200,000 hectares of wet grassland, but this is now only 220,000, of which only 20,000 is agriculturally unimproved of a high conservation value. To save this ecosystem, a positive and sympathetic water and land management plan is needed (RSPB). Undisturbed raised mires are ombotrophic peats fed by precipitation and the mire surface is isolated from the regional water table. Western Europe has very few undisturbed mires left; in Britain, 98% have been transformed and utilised leaving only 1170hectares remaining. Positive action is needed to save them.
Water requirements to conserve the wetlands Certain water requirements need to be met to conserve these ecosystems. Most wetlands have been lost through drainage, and one being drained is unhealthy and in decline, and can only be restored by restoring its original water regime. In the case of wet grasslands, drainage, intensified land use, conversion to arable land and river engineering have all led to their decline. Wet meadows are traditional 'flowing' systems with an intentionally high winter water table so they could be used in early spring for grazing. They were then drained before being ‘drowned' again later. Wet grasslands need the water table near the surface for a significant period of the year. The major threat facing them is the dropping water table in surrounding land, making it hard to keep the necessary high water levels in the wet grassland. Raised mires face threats from agricultural reclamation, afforestation, drainage and especially peat extraction. The latter is the most serious, as peat mining can irreversibly damage the underlying substrate below the mire. To conserve a raised mire, a high water level at all times is of paramount importance. In conclusion, a high water level is needed to conserve these ecosystems, but this is exactly what other parties with interests in wetlands don't want.
Water requirements of competing land users Farming is the biggest threat to wetlands in this country, through conversion of land and land intensification. When drained, wetland soils are amongst the most fertile in the country, comparable with fen soils. Those in the Somerset Levels would be Grade One soils if not for the late frost. Farmers who have not drained their land feel they are being deprived of an opportunity that others have already taken advantage of to appease conservationists. Farmers need low water levels so crop roots don't have to endure unnecessary anaerobic conditions, and often to achieve this land has to be protected by levees and pumped dry. Intensive crops need a water level up to 1.5metres below that found in wet grasslands. In the case of raised mires particularly, the extraction of minerals such as phosphorus, along with gravel, coal and peat is the biggest threat. Peat is a very valuable commodity, not only as a fuel but as a raw material for waxes, cellulose and tar, but when this is mined, the wetland is often damaged irreversibly.