Conversion of wetlands for commercial development, drainage schemes, extraction of minerals and peat, overfishing, tourism, siltation, pesticide discharges from intensive agriculture, toxic pollutants from industrial waste, and the construction of dams and dikes, often in an attempt at flood protection, are major threats to wetlands everywhere.
A major threat is the draining of wetlands for commercial development, including tourism facilities, or agricultural land. In addition, unwise use of freshwater to feed these developments poses a further threat. In all too many places, the amount of water being taken from nature's underground aquifer is far outstripping its ability to replenish itself. The result is that as the water level drops, millions of trees and plants are dying because they are deprived of their life-sustaining supplies.
Hundreds of thousands of hectares of wetlands have been drained for agriculture
. Globally, agriculture accounts for 65% of the total water withdrawal on Earth. Agriculture and other industries such as paper making are often very wasteful and inefficient with water.
Alien invasive species
have had severe impacts on local aquatic flora and fauna, and can upset the natural balance of an ecosytem. For example, the introduction of Nile perch to Lake Victoria
has pushed many of the lake's native cichlid species to extinction.
Pollution in wetlands is a growing concern, affecting drinking water sources and biological diversity. Drainage and run-off from fertilized crops and pesticides used in industry introduce nitrogen and phosphorous nutrients and other toxins like mercury to water sources. These chemicals can affect the health and reproduction of species, posing a serious threat to biological diversity.
is also taking its toll. Increases in temperature are causing polar ice to melt and sea levels to rise. This in turn is leading to shallow wetlands being swamped and some species of mangrove trees being submerged and drowned.
Yet at the same time, other wetlands - estuaries, floodplains, and marshes - are being destroyed through drought.
Dams alter the natural flow of water and impact on existing ecosystems. Whilst there is much debate about the need for dams to be built, WWF argues that development should be as sustainable as possible to ensure minimum negative impact on biodiversity.