In the upper Midwest, many of the natural wetlands, when drained, made excellent agricultural soils. Because of this, more than half of America's wetlands have been converted to farmland, filled for housing developments or industry, or used as receptacles for household and hazardous waste. Wetlands are mostly semi-aquatic lands that are either inundated or saturated by water for varying periods of time during the growing season. The soils develop characteristic hydric properties. A wide variety of wetlands have formed across the country due to regional and local differences in vegetation, hydrology, water chemistry, soil variation, topography, and climate.
Mottled soil indicates zones of soil wetness.
Mottles and gray soil colors are signs of redoximorphic features which indicate wetness. In their natural condition, wetlands provide many benefits including food and habitat for fish and wildlife, water quality improvement, flood protection, shoreline erosion control, and opportunities for recreation and aesthetic appreciation. Wetlands can also be used to treat sewage from small to large developments when city sewer is not available . Each wetland works in combination with other wetlands as part of a complex, integrated system that delivers these benefits and others to society. An assessment of the value of any specific wetland must take this critical interrelationship into account.