emission of methane from polluted wetlands exceeds that from non-polluted wetlands by as much as two or three times. According to a study conducted by scientists of the Centre for Water Resources and Ocean Management, Anna University, and the National Physical Laboratory, New Delhi, waste from urban areas and industrial units has polluted the wetland ecosystem near Chennai, leading to an increase in emission of the greenhouse gas methane. Such areas needs to be monitored and human-induced changes controlled, say the scientists (Ambio, Vol 26, No 6).

The study, conducted between July 1993 and June 1994 along the Adyar river right up to its confluence with the Bay of Bengal, observed that methane (