Sustainable cities, urban sustainability, or eco-city is a city designed with consideration for social, economic, environmental impact, and resilient habitat for existing populations, without compromising the ability of future generations to experience the same. The UN Sustainable Development Goal 11 defines sustainable cities as those that are dedicated to achieving green sustainability, social sustainability and economic sustainability. They are committed to doing so by enabling opportunities for all through a design focused on inclusivity as well as maintaining a sustainable economic growth. The focus also includes minimizing required inputs of energy, water, and food, and drastically reducing waste, output of heat, air pollution – CO2, methane, and water pollution. Richard Register first coined the term "ecocity" in his 1987 book Ecocity Berkeley: Building Cities for a Healthy Future, where he offers innovative city planning solutions that would work anywhere. Other leading figures who envisioned sustainable cities are architect Paul F Downton, who later founded the company Ecopolis Pty Ltd, as well as authors Timothy Beatley and Steffen Lehmann, who have written extensively on the subject. The field of industrial ecology is sometimes used in planning these cities.
