Natural and anthropogenic drivers of wetland change

The hydrology of wetlands is dynamic owing to daily, seasonal, and inter-annual changes in water levels caused by tides, river flooding, and/or precipitation events. The resulting water regimes are primary determinants of many wetland ecosystem attributes including soil properties, water chemistry and biotic composition. Human-caused changes to wetlands that result in anomalous water regimes usually trigger a cascade of ecological effects, including species losses and invasions and altered biogeochemical cycles. These, in turn, often cause a loss in ecosystem services. Compared to other ecosystems, rates of wetland degradation and loss have been greater, primarily due to six drivers: 1) infrastructure development, 2) land conversion, 3) water withdrawal, 4) eutrophication and pollution, 5) overharvesting and overexploitation, and 6) introduction of invasive species. Wetland degradation is often caused by multiple drivers, some of which are site based, while others are regional or global in scope. This makes wetland degradation difficult to reverse, even where social and institutional support is strong. However, in the past twenty years, the complexity and scale of wetland restoration has advanced, resulting in successful attempts in many different contexts around the world. In many cases, though, it is not possible to fully restore the water regime of a wetland modified by human use, so partial fixes must be accompanied by ongoing water level management to achieve desired conditions. An important future challenge is to develop and implement strategies that ensure the sustainability of wetland ecosystem services under increasing stress from climate change, increasing human population and the drivers that have historically threatened wetlands.