Since the turn of the present century, the use of city waste in fisheries and agriculture in the wetlands to the east of Calcutta has begun to provide an alternative resource system for the rural communities on the outskirts of the city. By the middle of this century these reuse practices in the vast wetlands had become the largest ensemble of integrated resource recovery systems in the world. In the 3000 ha waterbodies that could still be retained in the area the entire city sewage of 150 Mgd can be treated, at least 5 tonnes of fish can be grown in them per hectare annually. 377 tonnes of vegetables are produced daily from the garbage farms. Surprisingly, the environmental significance of this unique ecosystem was not understood even a decade back. It was necessary to redefine the Calcutta wetlands and bring them from obscurity to preeminence as an outstanding example of multiple use of wetlands on the outskirts of the city. A number of problems have reduced the profitably of the reuse practices. Together with this, the phenomenal increase in the price of land on the edge of the city and a determined lobby of developers and speculators are posing the most serious threat to the future existence of the wetlands. The conservation efforts in such an uncertain milieu were twofold: to conserve the wise use of these wetlands and to derive a technology option for municipal sanitation from the Calcutta experience. As regards the first, a number of effective development controls have been enforced by the government. The entire region is now being planned as a waste recycling region and is under the appropriate Act of the State. Public awareness is also increasing in favour of conserving these wetlands. Secondly, with respect to the task of developing the technology option, it has been possible for a number of municipalities in West Bengal under the national Ganga Action Programme to replace the proposal of setting up conventional sewage treatment plants by the wetland option derived from Calcutta experience. A model ecosystem for 25 Mid of city sewage has already been developed by a fishery co-operative as a demonstration site for similar projects to suit the needs of the poorer countries with ample sunshine.