Dongtan Eco-city, just outside of Shanghai, is set to be the world’s first fully sustainable cosmopolis when it’s completed in 2040. The goal is to develop a city with an ecological footprint that completely balances nature’s supply and human demand. This is done through a new tool called the Resources and Energy Analysis Program (REAP) that measures the amount of resources consumed in an area and defines how much productive land and sea is needed to provide the energy, food and materials for daily consumption and how much land, air and water is needed to absorb the waste and disperse the emissions. From this information an ideal ecological footprint emerges to guide the master plan – that ultimately 500,000 people will reside here. You might think that this is a drop in the bucket for a country of 1.3 billion people and plenty of people have already criticised this project for being just a showcase with no real impact. But we applaud them for this ambitious carbon-neutral experiment which could potentially be a future model for the development of cities worldwide. London-based Arup is working on the integrated master-planning together with the Shanghai Industrial Investment Corporation. Recently the University of East Anglias’ carbon reduction group and Alsop Architects have joined the team.