The state government is set to prepare an action plan to help preserve the ecological balance in the east Calcutta wetlands. The wetlands, which inlcude sewage-fed fisheries, cover an area of 12,500 hectares. They are the only one of their kind in the country. This is the first time a conservation action plan has been mooted for an urban wetland anywhere in the world. A field base survey, on which the management action plan will be based was submitted to the state government last week.