Great social change occurs in several ways. A technological breakthrough – the steam engine, computers, the Internet – may play a leading role. Visionaries, such as Mahatma Gandhi, Martin Luther King Jr., and Nelson Mandela, may inspire a demand for justice. Political leaders may lead a broad reform movement, as with Franklin Roosevelt and the New Deal.Our own generation urgently needs to spur another era of great social change. This time, we must act to save the planet from a human-induced environmental catastrophe.Each of us senses this challenge almost daily. Heat waves, droughts, floods, forest fires, retreating glaciers, polluted rivers, and extreme storms buffet the planet at a dramatically rising rate, owing to human activities. Our $70-trillion-per-year global economy is putting unprecedented pressures on the natural environment. We will need new technologies, behaviors, and ethics, supported by solid evidence, to reconcile further economic development with environmental sustainability.United Nations Secretary-General Ban Ki-moon is taking on this unprecedented challenge from his unique position at the crossroads of global politics and society. At the political level, the UN is the meeting place for 193 member states to negotiate and create international law, as in the important treaty on climate change adopted at the Rio Earth Summit in 1992. At the level of global society, the UN represents the world’s citizenry, "we the peoples,” as it says in the UN Charter.  At the societal level, the UN is about the rights and responsibilities of all of us, including future generations.In the past two decades, governments have come up short on solutions to environmental threats. Politicians have failed to implement properly the treaties adopted at the 1992 Earth Summit. Ban knows that strong government action remains vital, but he also recognizes that civil society must also play a larger role, especially because too many governments and politicians are beholden to vested interests, and too few politicians think in time horizons that extend past the next election.To empower global society to act, Ban has launched a bold new global initiative, for which I am grateful to volunteer. The UN Sustainable Development Solutions Network is a powerful effort to mobilize global knowledge to save the planet. The idea is to use global networks of knowledge and action to identify and demonstrate new, cutting-edge approaches to sustainable development around the world. The network will work alongside and support governments, UN agencies, civil-society organizations, and the private sector.Humanity needs to learn new ways to produce and use low-carbon energy, grow food sustainably, build livable cities, and manage the global commons of oceans, biodiversity, and the atmosphere. But time is running very short.Today’s mega-cities, for example, already have to confront dangerous heat waves, rising sea levels, more extreme storms, dire congestion, and air and water pollution. Agricultural regions already need to become more resilient in the face of increased climate volatility. And as one region in one part of the world designs a better way to manage its transport, energy needs, water supplies, or food supplies, those successes should quickly become part of the global knowledge base, enabling other regions to benefit rapidly as well.Universities have a special role to play in the new UN knowledge network. Exactly 150 years ago, in 1862, Abraham Lincoln created America’s "land-grant” universities to help local communities to improve farming and the quality of life through science. Today, we need universities in all parts of the world to help their societies face the challenges of poverty reduction, clean energy, sustainable food supplies, and the rest. By linking together, and putting their curricula online, the world’s universities can become even more effective in discovering and promoting science-based solutions to complex problems.The world’s corporate sector also has a significant role to play in sustainable development. Now the corporate sector has two faces. It is the repository of cutting-edge sustainable technologies, pioneering research and development, world-class management, and leadership in environmental sustainability. Yet at the same time, the corporate sector lobbies aggressively to gut environmental regulations, slash corporate-tax rates, and avoid their own responsibility for ecological destruction. Sometimes the same company operates on both sides of the divide.We urgently need far-sighted companies to join the Sustainable Development Solutions Network. These companies are uniquely placed to move new ideas and technologies into early-stage demonstration projects, thereby accelerating global learning cycles. Equally important, we need a critical mass of respected corporate leaders to press their peers to cease the anti-environmental lobbying and campaign-finance practices that account for the inaction of governments.  Sustainable development is a generational challenge, not a short-term task. The reinvention of energy, food, transport, and other systems will take decades, not years. But the long-term nature of this challenge must not lull us into inaction. We must start reinventing our productive systems now, precisely because the path of change will be so long and the environmental dangers are already so pressing.  At the Rio+20 Summit this past June, the world’s governments agreed to adopt a new set of goals on sustainable development for the period after 2015, to build upon the Millennium Development Goals’ success in reducing poverty, hunger, and disease. In the post-2015 era, the fight against poverty and the fight to protect the environment will go hand in hand, reinforcing each other. Secretary-General Ban Ki-moon has already initiated several global processes to help establish the new post-2015 goals in an open, participatory, and knowledge-based way.  The Secretary General’s launch of the Sustainable Development Solutions Network is therefore especially timely. Not only will the world adopt a new set of goals to achieve sustainable development, but it will also have a new global network of expertise to help achieve those vital objectives.  Jeffrey D. Sachs is a professor at Columbia University, Director of its Earth Institute, and a special adviser to United Nations Secretary-General Ban Ki-Moon.Copyright Project-Syndicate.org