Eurowet - Diversity of wetlands

There is a wide diversity of wetland types, exemplified by the challenge of providing a satisfactory, universal definition of wetland. To date there are many definitions of wetland in use, reflecting different national traditions and characteristics of the environment in which they occur. Wetlands vary greatly in size, position in the landscape, ecology and water dynamics. The fundamental characteristic of all wetlands is that in some way or other water is a key feature either temporarily or permanently. Therefore it is logical that when describing or classifying wetlands the fundamental
criteria that should be considered is their hydrology. However, this in itself is not as straightforward as it may at first appear, as wetland hydrology is controlled by many other characteristics such as geology, climate, morphology and position in the landscape. Wetland hydrology affects the biogeochemical processes that occur and together, these exert a large influence on the ecology of a wetland. Many classification systems are based on ecological factors, but generally ecology is controlled by more fundamental factors, namely hydrology and biogeochemistry. Together all these factors combine to result in the performance of wetland functions, which also can vary widely in type and extent to which they are performed.  By considering wetlands in terms of their hydrological connections, functioning and ecology, a more comprehensive view of the potential role of wetlands in the WFD can be gained. Therefore, in this section wetlands are described in terms of their water transfer mechanisms, functioning, position in the landscape, ecology and societal value. (see Chapter 2: Diversity of wetlands - pg. 23)