Climate change has been described as the biggest market failure of all time, but loss of biodiversity and of nature’s economically important services must surely be running it close, if not equalling it. Year in and year out, the world economy may be losing $2.5 to $4.5 trillion-worth of natural capital as a result of deforestation alone, quite apart from the cost of the losses of other key ecosystems. Decisive action must be taken to reverse these declines, or the bill will continue to climb. And, at the same time, the chance will disappear of fully achieving the poverty-related Millennium Development Goals and of ushering in a sustainable 21st century for six billion people, rising to nine billion by 2050.