China and India, the emerging economic giants of the world, will play a significant, perhaps a dominant, role in shaping the environmental outcomes for our planet in the 21st century. Both countries are expected to maintain an 8 to 9% rate of economic growth over the next several years (1). Even when much of the world is experiencing a recession, China and India in 2009 are projected to achieve high Gross Domestic Product growth (China, 8.4%; India, 6.2%; world, -2.2%) (1). Development in China and India is fueled not only by the natural capital within the countries, but also increasingly by imports of raw materials, particularly from southeast Asia. Both nations import ~9 million tons of crude palm oil annually—almost one-quarter of global production—mostly from Malaysia and Indonesia (2). The degree to which China and India consume natural resources within their boundaries, and beyond, will largely determine future environmental, social, and economic outcomes. The two countries have been engaged in a border dispute that included a bitter, but brief, war in 1962. We propose that much more earnest cooperation between the world's two most populous countries will be vital for mitigating biodiversity loss, global warming, and deforestation.