Mark Halle talks about why sustainable development hasn't worked and what to do about it

The notion of sustainable development was launched two decades ago, and quickly attracted a broad following worldwide. It appeared to offer a means to organize economic development in a way that would address the challenges of poverty and social exclusion while ensuring the health of the planet that sustains us, and a great deal of energy and enthusiasm has been invested in it. Despite that, the enterprise has been a failure. Any sober assessment of trends over the past quarter-century must conclude not only that we have failed but that we have failed spectacularly. We have made a series of assumptions about our societies, our leaders and our international processes that have proved mistaken. And yet sustainable development remains the only acceptable future for humankind. If we are to reach it, or even advance significantly towards it, we will have to change our approach sharply. We will have to take steps to ensure that economic policy - like trade, investment, tax or subsidy policy - offers strong incentives to behave in ways that support sustainability. We will have to change the approach to international consensus-building. And we will have to accept that sustainability will require not an adaptive set of changes but instead that change will have to be transformative. The combination of the economic crisis and a series of looming environmental crises now make it imperative that we not fail in this endeavor.