Of the two largest Southasian deltas, one flourishes as the other faces the threat of being overrun by the sea.
At a time when melting glaciers, shrinking coastal lands, depleting freshwater sources and vanishing forests are hot issues across the world, the tidal mangrove forests of the Sundarban constitute an encouraging example of effective conservation. Spread over 10,000 sq km in India and Bangladesh, with some 60 percent falling in the latter, the Sundarban, part of the Ganges delta, the world's largest, takes in the endpoints of the mighty Ganga, Meghna and Brahmaputra rivers. A fusion zone of fresh- and saltwater, constituting a complex network of tidal waterways, vast scattered mudflats and hundreds of small islands filled with salt-tolerant mangroves, and home to a dizzying array of plants and animals, the Sundarban was recognised as a World Heritage Site in 1987.
Standing in stark contrast, on the other side of Southasia, is the Indus delta, an area that in Sindhi is referred to as Daryah jo Chhor, or End of the River. According to the 1929 gazette of the Indian government, a detailed survey of the delta by the Indian Botanical Society had found it to be equal to the Sundarban in terms of area, variety of trees, diverse presence of fauna and flora and general ecosystem. Although still stretching 350 km from the Rann of Kutch to Karachi and comprising close to 6000 sq km, the Indus delta has lost some 1000 sq km since just the 1960s.
Much of this shrinking is due to the construction of dams in Punjab province, which began in the 1960s. Already constricted by 23 major barrages and the 45 major irrigation canals built by the British, the Pakistani government has since Partition added three major dams to the Indus – the Mangla, Tarbela and Warsak – as well as 80 smaller ones. Furthermore, since the 1980s (first under General Zia ul-Haq), Pakistan Army officials have been allocated about a million acres of land in Punjab, with most subsequently siphoning off Indus waters for irrigation. On the other side of the frontier, India's construction of the Kishanganga and the Baglihar hydropower projects (on the Jhelum and the Chenab rivers, respectively, both tributaries of the Indus) has further impacted downstream flows.