1. 1. Dependent mostly on a combination of the above conditions, the "traditional terminology" distinguishes between two major wetland types – mineral and organic (Encyclopædia Britannica; FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices), such as marsh, swamp, fen and bog:

1. Mineral Soil Wetlands:

• Marsh – a type of wetland ecosystem characterized by poorly drained mineral soils and by plant life dominated by grasses (see. Fig. 2, Fig. 3 and Fig. 4). Marshes are common at the mouths of rivers, especially where extensive deltas have been built. The marsh plants slow down the flow of water and allow for the nutrient enriched sediments to be deposited, thus providing conditions for the further development of the marsh.

Figure 2 – Marsh (source – FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices).

Figure 3 – Tidal marsh along the Edisto River, South Carolina (source – the US Environmental Protection Agency website).

Figure 5 – Swamp (source – FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices).

The dominant vegetation, therefore, distinguishes the two major types of mineral soil wetlands: grasses dominate marshes, while trees dominate swamps. Both marshes and swamps may be freshwater or saltwater.

1. Organic Soil Wetlands:

Generally these wetlands are referred to as "peatlands" in recognition of their common ability to form peat (organic soil produced by the accumulation of plant material). There are two major types of peatlands – bogs and fens, both of which occur in similar climatic and geographic regions.

• Bog – a type of wetland ecosystem characterized by wet, spongy, poorly drained peaty soil, dominated by the growth of bog mosses, Sphagnum, and heaths, particularly Chamaedaphne (see Fig. 6 and Fig. 7). Bogs are usually acid areas, frequently surrounding a body of open water. Bogs receive water exclusively from rainfall.

Figure 6 – Bog (source – FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices).

Figure 7 – Bog (source – FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices).

Figure 8 – Fen (source – the US Environmental Protection Agency website).

The two major types of organic soil wetlands are, therefore, distinguished by their hydrological regime (see Fig. 9): bogs receive water mainly from precipitation, while fens are supplied with water mostly from surface and groundwater sources:

Figure 9 – Main differences between a bog and a fen (source – FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices).

Bogs and fens often occur side by side (FORESTED WETLANDS: Functions, Benefits and the Use of Best Management Practices). Often there is no strict borderline between the two wetland types but a smooth transition from one type to the other, as is the case of the Augstumal mire/peatland complex in Lithuania (see Figure 10):

Figure 10 – Augstumal mire/peatland complex in Lithuania (source – the International Mire Conservation Group website).

Unfortunately, the "traditional terminology" has the significant disadvantage of being based on the traditional concept of a wetland (see part on what wetlands are). As such, it takes into account comparatively few wetlands, mostly of inland freshwater character and of a relatively narrow climatic zone. Another great disadvantage of these traditional names is that many of them are highly localized – for example, Johnson outlines that a "heath" in New Hampshire or Maine might be referred to as a "spong" in New Jersey (Johnson, 1985, in Johannesen and Gurganus), and Aber (2003) notes that the term "mire" is used mainly in Europe to denote any peat–forming wetland (either bog or fen). To avoid these disadvantages, attempts have been made to develop a classification system that would take into consideration the various wetland types all over the world.

1. 2. Two main scientifically-based and in a way comprehensive wetlands classification systems, developed for the purpose of wetlands inventory and management, have gained broad acknowledgement nowadays: the first of them has been developed by Cowardin and co-workers for the needs of the US government, and the second has been adopted by the Convention on Wetlands:

• The system developed by Cowardin and co-workers is organized in a hierarchical structure. In tribute to the "traditional terminology", in their system they distinguish between "wetlands" and "deepwater habitats", because "traditionally the term wetland has not included deep permanent water" (Cowardin et al, 1979). Nevertheless, the scientists recognize the importance of the holistic approach to classification of wetlands, therefore in their classification they have included both types. Figure 11 shows the classification system developed by the team which defines five main Systems (Marine, Estuarine, Riverine, Lacustrine, and Palustrine), which are further divided into smaller Subsystems, Classes, Subclasses, and Dominance Types:

Figure 11 – Classification hierarchy of wetlands and deepwater habitats, showing Systems, Subsystems and Classes. The Palustrine system does not include deepwater habitats (source – Cowardin et al, 1979).

As initially developed, the classification system set up by Cowardin and co-workers (1979) did not include many wetland types that have resulted from human activities.

• To avoid the weak point of Cowardin et all’s classification system, the Convention on Wetlands developed a new and more comprehensive wetland classification system (adopted in 1990 and modified in 1996) – the Ramsar Classification System for Wetland Type:

Note : "floodplain" is a broad term used to refer to one or more wetland types, which may include examples from the R, Ss, Ts, W, Xf, Xp, or other wetland types. Some examples of floodplain wetlands are seasonally inundated grassland (including natural wet meadows), shrublands, woodlands and forests. Floodplain wetlands are not listed as a specific wetland type herein.