The world's richest nation dare not forget the world's poorest people. Obama's top priority should be adopting a strategy of what I call sustainable development -- a strategy that combines economic development with environmental sustainability, for the United States and for the world. Such an approach merges science and policy, thinks in terms of decades rather than years, and recognizes that solutions must be cooperative and global rather than unilateral and national.

Currently, we lurch from crisis to crisis, from food to energy to natural disaster to finance, without recognizing that these cascading shocks are interconnected. Darfur, Somalia and Afghanistan are at least as much about water scarcity, climate and population as they are about politics; even the global financial crisis was triggered in part by the contemporaneous energy crisis. As president, Obama will need to lead the U.S. government in addressing these problems holistically. As thankless as government reorganization can be, he should create a new Department of International Sustainable Development to work together with the rest of the world on the Millennium Development Goals and the interconnected long-term challenges of poverty, disease, energy, climate, water and population -- all of which are key to sustainable growth, prosperity and security.

-- Jeffrey Sachs, director of Columbia University's