We are squandering our planet's natural capital-its biodiversity, water and soil, and energy sources-at a blistering pace. Major changes must be made to steer our planet and people away from our current, doomed course. Though technology has been one of the drivers of the current trend of unsustainable development, it is also one of the essential tools for remedying it. Earth at Risk maps out the necessary transition to sustainability, detailing the innovations in technology, along with law, science, institutional design, and economics, that can and must be put to use to avert environmental catastrophe. Claude Henry and Laurence Tubiana begin with a measure of the costs of ecological damage-the erosion of biodiversity; air, water, and soil pollution; and the wide-reaching effects of climate change-and then consider the solutions that are either now available or close on the horizon that may lead to a more sustainable global trajectory. What market-based tools can be used to promote clean growth? How can renewable energy help us decrease our use of fossil fuels? Is international agreement on climate goals possible? Henry and Tubiana tackle a range of urgent questions, emphasizing possibilities for-and obstacles to-implementation and action. Building on the experience of the most significant climate negotiation of the decade, they show what a world organized along the principles of sustainability could look like.