Questions arise over Earth's ability to sustain mankind, Shan Juan, Cui Jia and Jiang Xueqing report in Beijing.

The world's population is expected to reach 7 billion on Monday, four years later than once predicted largely thanks to China's family planning policy, according to the country's top population experts.

Population growth has rocketed. It took just 13 years for 1 billion more people to live on the planet, yet only at the dawn of the 19th century did a billion people first inhabit the Earth, according to a report by the United Nations Population Fund.

Baby No 7 Billion will probably be born in the Asia-Pacific region, where the population growth rate is the highest in the world.

China's family planning policy, which limits most mainland couples to one child, has prevented 400 million births since 1979, according to the National Population and Family Planning Commission.

The rising population presents challenges to humanity, Safiye Cagar, director of information and external relations for the fund, said on Tuesday.

"If we do not voluntarily stabilize population, we risk a much less humane end to growth as the ongoing destruction of the earth's natural systems catches up with us," the UN report said.

"How do we ensure that each of us has a decent standard of living while sustaining Earth's resources?" Cagar said.

Such a huge population will put a lot of pressure on Earth, said Yuan Xin, a professor at Tianjin-based Nankai University's population and development institute. For example, the population increase plus the pursuit of a better quality of life will require more resources and therefore put the environment in danger.

"The prevented births of China are also significant for natural resource and environment preservation across the world," Yuan said Tuesday. "But that merit might be offset if the Chinese consume relentlessly like the Westerners did, given China's sheer population size."

Official data released by China and the United States show that per capita consumption in China is 20 percent of that in the US. If the Chinese were to use as much energy per capita as Americans, its total power use would be more than four times that of the US.

"Today, the individual Chinese is among the top energy consumers in the developing world, which would definitely impact the world's resources and environment," Lu Jiehua, a sociology professor at Peking University, said on Tuesday.

Another healthy baby enters the world at Ruijin Hospital in Shanghai on Monday. [Carlos Barria/Reuters]