Swamps, marshes, floodplains and mangrove forests, all known as wetlands, are a precious resource. In their natural state they provide a range of eco-system services. They regulate water flows, store eroded materials and nutrients and provide water, food and raw materials. Wetlands are defined as areas that are subject to seasonal or permanent flooding up to a depth of 6m. Throughout history, the general trend has been to convert wetlands from their natural state to allow other more intensive uses. In some parts of the world this has involved the creation of rice paddies, sugar estates or even fish farms. In Europe, North America, Australia and New Zealand more than 50% of wetlands were converted to other uses during the 20th century by controlled flooding and drainage. Mostly they were used for intensive farming and urban development.
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