If consumption patterns continue, the extra bodies will put a profound stress on limited land, food and energy supplies - particularly in developing countries. The most important resource at risk, though, is clean water, not only for drinking, but also for food production and control of hygiene-related disease. Already supplies are strained in some areas, as a result of pollution degradation or overuse in wasteful farming and industrial practices. India is thought to be draining aquifers twice as fast as they are replenished, which points to water shortages. Water tables are falling in China too, particularly in the northern plain, the country's main agricultural area.
Conservation is the only realistic way to prevent catastrophe.
But a bigger goal is curbing population growth in overcrowded areas. True, over the past two decades China has cut its birthrate faster than any other country in history. It is now projecting zero growth by 2050. But stringent mandates like Beijing's exact human and social costs. The more beneficial approach is to empower women with education, better access to family planning, and improved economic opportunities.