Wetlands

n. area of land that has wet soil (such as a marsh or bog)

In physical geography, a wetland is an environment "at the interface between truly terrestrial ecosystems and  aquatic systems making them inherently different from each other yet highly dependent on both" (Mitsch & Gosselink, 1986). In essence, wetlands are ecotones. Wetlands often host considerable biodiversity and endemism. In many locations such as the United Kingdom and USA they are the subject of conservation efforts and Biodiversity Action Plans.
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Noun
1. a low area where the land is saturated with water
(hypernym) land, ground, soil
(hyponym) bog, peat bog

An area that is saturated by surface or ground water with vegetation adapted for life under those soil conditions, as swamps, bogs, fens, marshes, and estuaries.

Areas regularly saturated by surface or groundwater and subsequently characterized by a prevalence of vegetation adapted for life in saturated-soil conditions.