Wetlands are a major feature of the landscape in many parts of the world. They are among the most important ecosystems on earth and are sometimes described as the kidney of the landscape. Up to the mid-nineteenth century wetlands were considered storage tanks of diseases and were often given a sinister image. As a consequence of this view and the need for more agriculture land, wetlands have disappeared at alarming rates. They were drained and turned into agricultural land, which has resulted, particularly in industrialized countries, in a massive pollution threat of pesticides and nutrients discharge by agriculture—a pollution that the wetlands and other natural ecosystems (ditches, trees, wind shelterbelts, ponds, forests, and so on) otherwise would eliminate. The lack today of many different small or large ecosystems in the landscape has been a disaster for the abatement of the non-point pollution from agriculture. The various natural ecosystems are crucial for the health of the landscape.