9We live in unprecedented times - the Anthropocene - defined by far-reaching human impacts on the natural systems that underpin civilisation. Planetary Health explores the many environmental changes that threaten to undermine progress in human health, and explains how these changes affect health outcomes, from pandemics to infectious diseases to mental health, from chronic diseases to injuries. It shows how people can adapt to those changes that are now unavoidable, through actions that both improve health and safeguard the environment. But humanity must do more than just adapt: we need transformative changes across many sectors - energy, housing, transport, food, and health care. The book discusses specific policies, technologies, and interventions to achieve the change required, and explains how these can be implemented. It presents the evidence, builds hope in our common future, and aims to motivate action by everyone, from the general public to policymakers to health practitioners.