Biodiversity, defined by the World Wide Fund for Nature (WWF) as the different kinds of life found in an area, is in a state of crisis all across the world, with declines in the numbers of organisms and many species declared as at risk of extinction. All types are affected, from plants and fungi to large mammals, and there is a clear link to human activity being the cause. Although farming methods and climate change due to greenhouse gases play a major role, cities and buildings can play a small but important role in countering this decline.
