Arguably the greatest challenges facing humanity are environmental. However, they are routinely under-reported in the media. Pressure groups and governments trying to get information through to the public often blame the media, but the picture is not necessarily this simple. This text presents the state of knowledge about media treatment and public understanding of key environmental issues, above all, climate change and biodiversity loss, which have enormous implications for economic, social and environmental security, yet mean little to the person in the street. The concept of sustainable development, which underpins responses to these problems is also shown to be unknown by most people.