ADDIS ABABA – What does the future hold for the global economy? Will living standards rise worldwide, as today’s poor countries leapfrog technologies to catch up with richer countries? Or will prosperity slip through our fingers as greed and corruption lead us to deplete vital resources and degrade the natural environment on which human well-being depends? Humanity faces no greater challenge than to ensure a world of prosperity rather than a world that lies in ruins.Like a novel with two possible endings, ours is a story yet to be written in this new century. There is nothing inevitable about the spread – or the collapse – of prosperity. More than we know (or perhaps care to admit), the future is a matter of human choice, not mere prediction.Despite the ongoing economic crisis in Europe and the United States, the developing world has sustained rapid economic growth. While the International Monetary Fund forecasts that the advanced economies will grow by just 1.5% in 2013, developing-country growth is projected to reach 5.6%. Asia’s developing economies, now the world’s pacesetters, are expected to grow by 7.2%, with output in Sub-Saharan Africa set to rise by a healthy 5.7%.What is happening is both powerful and clear. Technologies that were once found only in rich countries now belong to the entire world. Mobile phone coverage in Sub-Saharan Africa, for example, has gone from nearly zero subscribers 20 years ago to around 700 million today. And those phones are helping to bring banking, health care, education, business, government services, and entertainment to the poor. Within a few years, the vast majority of the world will have access to wireless broadband.Yet there is another truth as well. Last year was the hottest ever recorded in the US. Droughts afflicted around 60% of US counties, including the breadbasket states of the Midwest and the Great Plains. In October, an extraordinary "superstorm” smashed into the Atlantic coastline around New Jersey, causing losses of around $60 billion. Climate problems – floods, droughts, heat waves, extreme storms, massive forest fires, and more – also ravaged many other parts of the world in 2012, including China, Australia, Southeast Asia, the Caribbean, and Africa’s Sahel region.These environmental disasters are occurring with rising frequency, as they are partly caused by human actions, such as deforestation, coastal erosion, massive pollution, and, of course, the greenhouse-gas emissions that are changing the world’s climate and acidifying the oceans. What is new is that scourges like climate change – until recently described as a future threat – are now clear and present dangers. Scientists have even given a name to our era, the Anthropocene, in which humanity ("anthropos” in Greek) is having a large-scale impact on the planet’s ecosystems.Herein lies our great challenge – the one that will determine whether we follow the path of prosperity or ruin. The rapidly growing developing countries cannot simply follow the economic-growth path that today’s rich countries traveled. If they try, the world economy will push the planet beyond safe operating conditions. Temperatures will rise, storms will intensify, the oceans will become more acidic, and species will go extinct in vast numbers as their habitats are destroyed.The simple fact is that humanity faces a stark choice. If the world economy’s current growth patterns continue, we face ecological disaster. If the world economy embraces a new growth pattern – one that harnesses advanced technologies like smart phones, broadband, precision agriculture, and solar power – we can spread prosperity while saving the planet.I call today’s growth pattern the business-as-usual option; the smart-technology growth pattern, by contrast, represents the sustainable-development option. Business as usual can work for a while, but it will end in tears, while the sustainable-development path can lead to long-term prosperity.So, what will it take to write the happy ending? First, we must recognize that we, as a global society, have a choice to make. Business as usual is comfortable. We think we understand it. Yet it is not good enough: on our current trajectory, short-term prosperity is coming at the cost of too many future crises.Second, we must recognize the powerful new tools and technologies that we have at hand. Using advanced information technologies – computers, satellite mapping, image processing, expert systems, and more – we now have the means to grow more food with less environmental damage; improve public health for rich and poor alike; distribute more electricity with lower greenhouse-gas emissions; and make our cities more livable and healthier, even as urbanization raises their populations by billions in the coming decades.Third, we should set bold goals for the years ahead – to spread prosperity and improve public health while saving the planet. Fifty years ago, US President John F. Kennedy said that we should to go to the moon not because it was easy, but because it was hard – it tested the best in us. In our generation, sustainable development will be our test, encouraging us to use our creativity and human values to establish a path of sustainable well-being on our crowded and endangered planet.I am proud and honored that United Nations Secretary-General Ban Ki-moon has asked me to help mobilize the world’s expertise as we seek to achieve that goal. The greatest talents in our societies – in universities, businesses, NGOs, and especially among the world’s young people – are ready to take on our greatest challenges, and are joining the UN’s new Sustainable Development Solutions Network. In the months and years ahead, these leaders will share their visions of a prosperous and sustainable global society.Jeffrey D. Sachs is Professor of Sustainable Development, Health Policy and Management, and Director of the Earth Institute at Columbia University. Copyright: Project Syndicate