As a result of human activities, many organisms on Earth face serious and worsening threats to their continued existence. This is usually regarded as a matter of concern because maintaining a healthy non-human environment affects the well-being of humans. This book adopts a very different approach, defending in detail the claim that all organisms, sentient and non-sentient, have a claim in justice to a fair share of the planet's environmental resources. It makes a thoroughly developed, ground-breaking case for ecological justice.