Introduction

We are living in the Anthropocene (Crutzen and Stoermer, 2000), an epoch in which human activities have started to have a significant global impact on the Earth’s geology and ecosystems. Humankind has, in this epoch, moved from being primarily rural to urban. Soon the large majority of us will live in cities and towns of different sizes; already by 2030 this will be 60 per cent of all humans (United Nations, 2015). Urban areas make up only 3 per cent of the Earth’s land surface, but they account for no less than 60–80 per cent of energy consumption and 75 per cent of carbon emissions. Urbanization is especially dramatic in the developing world, where 95 per cent of future urban expansion will take place (United Nations, 2015). Continuing urbanization and urban sprawl places tremendous pressures on, for example, fresh water supplies, public health, and on biodiversity.