DHAKA, Bangladesh — Like most poor countries, Bangladesh needs a lot of energy to develop its economy, the cheaper the better. About 80 percent of its electricity now comes from natural gas. But with gas resources waning and an entrenched, inefficient subsidy system, the government has decided to promote coal instead. This shift comes with great risks: Coal power pollutes, and Bangladesh is at once the most densely populated country on earth and one of the most exposed to the effects of climate change.

Under its 2010 master plan for developing the energy sector, the government hopes that by 2030, 50 percent of Bangladesh’s power will be generated by coal, up from about 2 percent now. (Bangladesh currently has one small plant, which runs on local coal.) It expects to accomplish this by building a dozen new coal-run electricity-generating plants, including a controversial one at Rampal, in the southwest of the country. That facility alone is expected to have a capacity of 1,320 megawatts, or about one-fifth of the country’s total current production of electricity.

But the Rampal plant, which is scheduled to be completed by 2016, will be located less than 10 miles north of the Unesco-listed Sundarbans, the largest mangrove forest in the world and the home to the largest population of Bengal tigers and to the endangered Irrawaddy River dolphin. The forest also acts as a buffer against the deadly cyclones that periodically funnel up the Bay of Bengal. With every storm, estimates Anu Mohammad, an economist at Jahangirnagar University, the mangroves save hundreds of thousands of lives.

Despite the Sudarbans’ designation as a World Heritage Site in 1997, waterways will be dredged through the forest to allow convoys of coal-bearing ships to reach the Rampal station. Half a million tons of toxic sludge will be emitted by the plant annually, according to a report by the nearby Khulna University, and it will flow downstream into the forest’s network of rivulets. Another problem, according to Mr. Anu, is that the Rampal project opens the way for opportunistic land grabs and the development of other polluting industrial activities in the area, including so-called ship breaking, the tearing apart of unwanted ships.