The major characteristics of natural peatlands are permanent water logging, the formation and storage of peat, and the continuous upward growth of the surface. These characteristics determine the specific goods, services, and functions associated with peatlands.

Peatlands are wetland ecosystems that are characterised by the accumulation of organic matter called "peat" which derives from dead and decaying plant material under high water saturation conditions.

In peatlands, water, peat and specific vegetation are strongly interconnected. If any one of these components is removed, the nature of the peatland is fundamentally changed.

Peat accumulates in layers year by year, forming a deposit which can amount up to 20 m thick. Peat deposits have developed during different geological times. Recent deposits remain as peat while earlier deposits have been transformed over millions of years into lignite and coal.

Peat comprises more than 90% water and so peatlands have a unique ability to store large amounts of water. Although trees can grow and people can walk on peatlands - it is better to think of peatlands as water bodies with a high organic content. This explains the major impact that drainage has on peat.

Of global importance is the long-term storage of carbon and water within peatlands. Worldwide, peatlands contain 550 Gtonnes of carbon and 10% of the global fresh water in their peat (cf. Ball 2000). Carbon storage is made possible by the permanent water-logging of the peat body. Water-logging and the continuous upward growth of the surface further determine the special and extreme site conditions to which peatland organisms are exposed. These conditions typically include:

• A scarcity of oxygen and the presence of toxic ions such as Fe²⁺, Mn²⁺, S^2- in the root layer (Hook and Crawford 1978, Sikora and Keeney 1983)
• Continuously rising water levels that can suffocate perennial plants (Van Breemen 1995, Grosse-Brauckmann 1990, Malmer et al. 1994)
• Spongy soil that makes trees fall over easily or drown under their own weight (Joosten and Clarke 2002)
• A scarcity of nutrients. This is the result of peat accumulation (by which nutrients are fixed in the peat), a limited nutrient supply (as in rainwater-fed mires) and chemical precipitation (as in groundwater-fed peatlands, where phosphates are bound by calcium and iron (Boyer and Wheeler 1989). The scarcity of ions in the water further complicates osmoregulation (an organism’s control of the balance between water and ions) in submersed organs and organisms (Burmeister 1990)
• A generally cooler and rougher climate than the surrounding mineral soils, with stronger temperature fluctuations (Joosten and Clarke 2002)
• Acidity caused by organic acids and cation exchange (Ross 1995, Van Breemen 1995)
• The presence of toxic organic substances produced during decomposition (Verhoeven and Liefveld 1997, Salampak et al. 2000)
• The humus rich water, which can complicate orientation and recognition in aquatic animals.

As a result of these extreme conditions, natural peatlands are generally species-poor compared with mineral soils in the same biographic region. However, many peatland species are strongly specialised and not found in other habitats, highlighting the biodiversity value of peatland areas