Reuters: On the eastern tip of Chongming, the world’s largest alluvial island in the mouth of the Yangtze River, birdwatchers wait patiently to glimpse an occasional crane or plover rising from the wetlands’ reeds. A few kilometers to the southwest, in an area of fishponds, marshes and farmland, developers are plotting out a city for up to 400,000 people that they hope will be a model of ecological harmony, powered entirely by renewable energy. Shanghai’s Dongtan Eco-city has a lofty …