Traffic jam, Karachi, Pakistan photo: Canon/Mauri Rautkari

In 2000, the number of people on Earth passed six billion—more than twice as many as in 1950. And about 88 million more people are added to the planet each year. This annual addition, equivalent to the population of Germany, amounts to almost a quarter of a million births every day.

Most experts think that the human population is likely to stop growing sometime around 2200, when the number of people in the world is expected to reach at least 10 billion.

With a population of around 268 million, the United States is the world’s third most populated country. (China and India are first and second, respectively.) The U.S. Census Bureau projects that the nation’s population will rise to more than 390 million by 2050, which is equivalent to adding a city with the population of Chicago (approximately 2.7 million people) to nearly every state.

There is little doubt that our growing population will result in continuing habitat loss and will put enormous pressure on Earth’s natural resources. While some people argue that new technologies could indefinitely extend the use of nonrenewable resources and allow the use of alternative ones, many others feel that technology can only delay the time when the Earth loses its ability to sustain us.