Water stands at or near the surface long enough to shape the soil and the plants. A wetland is an area that is saturated or inundated for significant periods and supports vegetation adapted to wet conditions. Marshes, swamps, bogs, and fens are major types.

Wetlands filter water, store floodwaters, and provide critical habitat for fish, birds, and other wildlife. They rank among the most productive ecosystems and also among the most threatened by drainage and filling for agriculture and development.

Recognition of wetland values has led to legal protection and restoration programs in many countries. Delineating wetland boundaries remains a technical and sometimes contentious task because water levels fluctuate. The distinctive vegetation and soils of wetlands make them recognizable even to casual observers.

• Area saturated with water for extended periods
• Supports specialized wet-adapted plants
• Provides water filtration and flood storage
• Highly productive yet widely threatened