The book starts with a summary of ecological principles, including the simplest models of population growth, food webs, and species interactions, drawing on examples from agriculture, disease, fisheries, and human population growth. It moves on to summarize the human demographic transition and increase in wealth. The centre piece describes six critical threats to biodiversity: Climate Change, Over-harvesting, Pollution, Habitat conversion, Invasive species and Disease (“COPHID”). Each threat is concisely covered in sections on history, current status, and economic and environmental impacts. That leads naturally to an assessment of the status of the “sixth mass extinction”, followed by a discussion of principles of conservation biology in addressing these threats. The book concludes with a critical review of the importance of species to humans, including economic benefits, improvements in human health (e.g. by reducing disease outbreaks), and general quality of life.