The 21st century will overturn many of our basic assumptions about economic life. The 20th century saw the end of European dominance of global politics and economics. The 21st century will see the end of American dominance too, as new powers, including China, India and Brazil, continue to grow and make their voices heard on the world stage. Yet the century's changes will be even deeper than a rebalancing of economics and geopolitics. The challenges of sustainable development—protecting the environment, stabilizing the world's population, narrowing the gaps of rich and poor and ending extreme poverty—will render passéthe very idea of competing nation-states that scramble for markets, power and resources.

The defining challenge of the 21st century will be to face the reality that humanity shares a common fate on a crowded planet. We have reached the beginning of the century with 6.6 billion people living in an interconnected global economy producing an astounding $60 trillion of output each year. Human beings fill every ecological niche on the planet, from the icy tundra to the tropical rain forests to the deserts. In some locations, societies have outstripped the carrying capacity of the land, resulting in chronic hunger, environmental degradation and a large-scale exodus of desperate populations.

We also face a momentous choice. Continue on our current course, and the world is likely to experience growing conflicts between haves and have-nots, intensifying environmental catastrophes and downturns in living standards caused by interlocking crises of energy, water, food and violent conflict. Yet for a small annual investment of world income, undertaken cooperatively across the world, our generation can harness new technologies for clean energy, reliable food supplies, disease control and the end of extreme poverty.

21世纪将推翻许多有关经济生活的基本假设。20世纪欧洲在全球政治和经济的主导地位结束。21世纪随着中国、印度和巴西等新兴强国的国际地位进一步加强，美国的主导地位也将结束。然而，本世纪的变化远比经济和地缘政治的重新平衡要深刻。可持续发展的挑战：保护环境、稳定世界人口、缩小贫富差距和消除极端贫穷将使得国家间为争夺市场、权力和资源而相互竞争的想法变得过时。

21世纪明确的挑战将面对这样一个现实：在一个拥挤的星球上，人类分享一个共同的命运。本世纪已开始，66亿人口生活在一个相互联系、每年有惊人的60万亿美元产值的全球经济中。从冻土地带到热带雨林再到沙漠，人类占据着每一处生态壁龛。在有些地方，人类社会的生存已经超越了土地的承载能力，造成持续的饥饿、环境恶化和绝望人口的大规模出走。

我们也面临一个重大的选择，继续我们现行的道路，这个世界将可能经历更多的贫富间的冲突，加剧环境灾难和由能源、水、食品和暴力冲突的连锁危机造成的生活水平的下降。然而，全世界联合行动，每年从世界收入中拿出一小部分来投资，我们这代人就能掌握使用清洁能源，提供可靠的食品和控制疾病的新技术并消除极端贫穷。