Wetlands are amongst the most productive ecosystems on the Earth and provide many important services to human society. However they are also ecologically sensitive and adaptive systems. Wetlands exhibit enormous diversity according t their genesis, geographical locations, water regime and chemistry, dominant species and soil and sediment characteristics. Globally the areal extent o wetland ecosystems ranges from 917 million hectares to more than 1275 m ha with an estimated economic value of about US$15 trillion a year.