Geoscience Reference
In-Depth Information
conditions develop. Plants are adapted for
growing in standing water or saturated soils,
which include shoreline, emergent, l oating and
submerged types of vegetation. Wetlands inter-
vene between dry, upland and deep-water habi-
tats. Distinct zones are evident in vegetation and
soils based mainly on water depth and salinity.
Wetland classii cation is a hierarchical scheme
of systems, subsystems, and classes. At the
highest level are the i ve wetland systems:
marine, estuarine, riverine, lacustrine, and palus-
trine. Within each system, classes are based pri-
marily on substrate conditions or dominant
vegetation cover. The primary emphasis of this
topic is the palustrine system of wetland envi-
ronments, as well as other water bodies not
more than 6 m deep.
Peatland is one of the most widespread
groups of palustrine wetlands around the world.
Peat consists of partly decayed plant remains
that accumulate in bogs, fens and swamps to
thickness of one foot (30 cm) or more. Peat
contains in its macro- and microfossils a record
of past environmental conditions, and this
record is crucially important for understanding
climates and environments of the past several
millennia. The nature of water supply and nutri-
ents are key criteria for classifying peatlands.
Ombrotrophic peatlands include raised and
blanket bogs that are characterized by acidic
water and scarce nutrients, whereas fens and
swamps fall into the minerotrophic category in
which water is more alkaline and nutrients more
abundant.
The anthropogenic dimension of wetland
ecosystems accounts for the important role wet-
lands play in providing services and resources
to humans, while also recognizing the important
inl uence of human systems in managing these
habitats and allocating resources obtained from
them. Even though the importance of wetland
conservation and protection is widely acknowl-
edged, countries face daunting challenges as
demands for land and resources continue to
increase and the vagaries of climate change
heighten vulnerabilities and complicate man-
agement strategies.
