Wetlands.

After commencing with a summary of the current status, importance and productivity of natural wetlands, the chapter reviews the contribution of wetland ecological functions to sustaining vital ecosystem services. Wetlands are vulnerable to a range of anthropogenic pressures, notably land use change, disruption to regional hydrological regimes as a result of abstraction and impoundment, pollution and excessive nutrient loading, the introduction of invasive species and overexploitation of biomass, plants and animals. Natural wetlands have often been modified to accommodate agricultural and aquaculture production, or wetlands may be created in the process of establishing farming systems. Prospects for established practices, such as culturing fish in rice fields, culture-based fisheries and integrating aquaculture with livestock production or into water storage and irrigation schemes are critically reviewed. Apparent conflicts between agricultural development and intensification and wetland conservation are discussed, and opportunities to reconcile competing demands are considered. Wetlands, whether classified as natural or as agroecosystems, sustain a wide range of ecosystem services that contribute to water and food security, but the appropriation of these services should be maintained with adequate provision for sustaining environmental stocks and flows and conserving and protecting aquatic biodiversity.