The cumulative environmental challenge of sustainable development in the twenty-first century is larger than anything humanity has ever had to deal with in the past. The good news is that solid progress is being reached in the understanding of issues in scientific terms and understanding what needs to be done. The bad news is twofold. First, although many of the environmental problems of earlier centuries are now being confronted, a new generation of difficulties is eclipsing what were the older difficulties. Secondly, much of the progress is being achieved by the wealthier parts of the planet, rather than the developing world. From population growth to climate change to unprecedented habitat and species loss, whether environmental sustainability can be achieved in the twenty-first century is an open question.
