Wetlands are ecosystems typically found on the transition between terrestrial and aquatic systems. In order to be classified as a wetland, an area typically has at least one of the following three characteristics:
- a water table at or near the ground's surface during the growing season (including when the land is covered by shallow water)
- poorly drained or hydric soils
- be home to a unique diversity of wildlife and vegetation specifically adapted to thrive in wet environments.
Water tables
To be classified as a wetland, an area of land must have water on the ground's surface or in the root zone for at least a portion of the growing season. This seasonal fluctuation of the water period (known as a hydroperiod), is continually affected by the weather, the season, water feeding into and draining from nearby streams, the surrounding watershed and other nearby bodies of water. However, an area can still be a wetland, even if it doesn't appear to be wet. Because of the changing hydroperiods, water is the most transient part of a wetland ecosystem. Often, when ecologists suspect an area is a wetland, they focus on the last 2 characteristics, because these are less likely to fluctuate seasonally.
Hydric soils
Soils found in wetlands are called hydric soils. Hydric soils exist when an area is saturated, flooded, or ponded for so long during the growing season that the upper soil level is without oxygen. There are two types of hydric soils: those with decomposed organic material, and those without. Each has unique characteristics.
Wildlife and Vegetation
Wetlands support a wide diversity of life. Many organisms depend on wetlands completely for their survival, but even those who live in primarily aquatic or terrestrial habitats may rely on the ecotone border for a portion of the year, or for a portion of their life cycle. Fluctuating water levels and variable salt concentrations create a harsh environment for wetland plants and animals. In order to survive these harsh conditions, vegetation and wildlife develop special adaptations.