Wetlands Ecosystems those planned for future alteration, will provide the greatest diversity of plant and animal organisms Numerous woody and herbaceous plant species can arise from transplanted soil, via whole plants, seeds, roots, rhizomes, and stolons Including leaf litter, detritus, and, for forested wetlands, large amounts of coarse woody debris are beneficial Herbivores cause many wetland restoration projects to fail, directly (by feeding) and indirectly (by burrowing, by dam building) Invasive species, such as Lythrum salicaria, Phragmites australis, and Tamarix spp., also must be controlled if plant and animal diversity are desired Understanding the ecological factors that control the diversity of animals in wetlands is key to altering these factors to restore, enhance, or create wetlands for the benefit of wetland fauna Because hydrology underpins so much of wetland ecology, manipulation of wetland hydrology through waterlevel regulation is the most common and cost-effective way to manage wetland habitats for wetland fauna More specifically, water-control structures can be used to flood or drain wetlands and thereby alter plant communities and the habitats available for wildlife By drawing down water levels, a germination phase can be produced, which can be followed by gradual reflooding once plant communities become established Timing, duration, and degree of drawdown (for example, shallow, growing season drawdowns versus complete overwinter drawdowns) influence subsequent plant species composition and the types of wildlife later attracted Several years of stable water levels of moderate depth following drawdown are often required to establish the submerged plant communities that are important to many wetland animals (invertebrates, ducks, fish) Manipulation of wetlands to produce early stages of plant succession can create a diversity of habitat niches for wetland animals, particularly if practiced within a wetland complex in which management of different units is staggered for different successional stages This practice permits the wetland fauna, elements of which can be quite mobile, to track habitat conditions over time and persist over the long-term within the same local area Manipulation of wetland hydrology also has been used to manipulate salinity in coastal areas by blocking natural drainages, thereby permitting the fresh water that accumulates to leach out salt The resultant shift in plant communities to more salt-intolerant species also changes wildlife communities In addition to water-level manipulation, a number of artificial procedures can be used to modify wetlands to enhance wildlife habitats These include creation of openings in dense emergent vegetation through cutting, application of herbicides or, more permanently, by blasting Planting of select forage species is sometimes attempted but is usually expensive and rarely successful Provision of artificial nest sites for select species, especially ducks, has been one of the most common and visible forms of wetland management to benefit wildlife Artificial nesting and loafing sites can be constructed for birds Large, whole tree boles, including partially hollowed-out trees, can be placed within or adjacent to the restoration site While perhaps aesthetically pleasing, the overall contribution of such efforts to boost local populations is at best modest given the small fraction of regional populations that can be supported by such structures These artificial procedures, in general, are expensive and time-consuming and 401 should be considered a minor complement to a larger strategy of natural management that uses hydrological manipulation to produce habitat changes over large areas in a cost-effective manner The tradeoffs between community types must be articulated and considered in management and planning For example, flooding bogs and meadows to produce marshes, a not uncommon occurrence in North America, entails losses of certain species, many rare or unusual, and gains of others, many common and sought after by recreational users In general, maintaining wetlands in a productive and natural state that meets the needs of the entire wetland fauna is more likely to meet diverse public needs than is species-specific management (e.g., for waterfowl only) Conclusions Despite lack of systematic comparisons, the existing scientific literature on wetland ecosystems is unambiguous in conveying the high level of diversity supported by wetlands The source of this high diversity lies in the exceptionally large number of different types of wetlands that occur worldwide Because wetlands occur on every continent except Antarctica, in every climatic region, in most biogeographic regions of the globe, and in a wide array of geological and topographic settings, the number of different types of wetlands created by the myriad combinations of these factors is very large and has yet to be catalogued The extraordinary richness of plant and animal species that depend on wetlands arises from this diversity of types Relative to the area they occupy, wetlands support a disproportionately large fraction of the world’s rare, endangered, and threatened plant and animal species Maintaining the high diversity of wetland species means maintaining a high diversity of wetland types See also: Estuarine Ecosystems Lake and Pond Ecosystems River Ecosystems Wetland Creation and Restoration References Chapman VJ (1960) Salt Marshes and Salt Deserts of the World New York: Interscience Chapman VJ (1976) Coastal Vegetation, 2nd edn Oxford: Pergamon Press Chapman VJ (1977) Wet Coastal Ecosystems Amsterdam: Elsevier Cowardin LM, Carter V, Golet FC, and LaRoe ET (1979) Classification of Wetland and Deepwater Habitats of the United States U.S Fish and Wildlife Service Publication FWS/OBS-79/31 Washington, DC: U.S Fish and Wildlife Service Crow GE (1993) Species diversity in aquatic angiosperms: Latitudinal patterns Aquatic Botany 44: 229–258 Crum H (1988) A Focus on Peatlands and Peat Mosses Ann Arbor: The University of Michigan Press Curtis JT (1959) The Vegetation of Wisconsin Madison, WI: University of Wisconsin Press Ellison AM (2004) Wetlands of Central America In: Whigham DF, Dykyjova D, and Hejny S (eds.) Wetlands of the World, vol Dordrecht, The Netherlands: Kluwer Finlayson M and Moser M (eds.) (1991) Wetlands New York: Facts on File Good RE, Whigham DF, and Simpson RL (eds.) (1978) Freshwater Wetlands: Ecological Processes and Management Potential New York: Academic Press