with booming animal and plant populations, if we know where to look. In today's urbanised planet, natural forces - be they floods, storms, droughts or pandemics - look set to determine the future of our cities. In a time of climate crisis, cities that once built walls and towers to defend against attack; now they have to become greener to protect themselves from external threats. Our future - and that of the planet - will be made in the city. Only by looking deep in to the past, examining the present and casting an eye to the future can we really begin to understand the bountiful potential and wonder of our extraordinary urban ecosystems.