The document discusses the economic arguments for maintaining and enhancing the green belt around cities in the UK. It argues that natural capital, like the green belt, provides significant economic and health benefits by being located near populated areas. Maintaining the green belt is important for sustainable economic growth because neglecting natural capital would negatively impact the environment, public health, and biodiversity. While some argue building on the green belt is needed for housing and economic development, the document counters that brownfield sites and increasing density are better alternatives that do not require sacrificing natural areas. The green belt could also be improved by enhancing its environmental quality and public access to provide even greater economic returns to the population.