World population to reach 7 billion

Western Europe and the US

Spain used to give parents 2,500 euros (more than $3,000) for every newborn child to encourage families to reverse the country's low birth rate. But the checks stopped coming with Spain's austerity measures, raising the question of who will pay the bills to support the elderly in the years ahead.

It's a question bedeviling many European countries which have grappled for years over how to cope with shrinking birth rates and aging populations - and are now faced with a financial crisis that has forced some to cut back on family-friendly government incentives.

Spain and Italy, both forced to enact painful austerity measures in a bid to narrow budget deficits, are battling common problems: Women have chosen to have their first child at a later age, and the difficulties of finding jobs and affordable housing are discouraging some couples from having any children at all.

In 2010, for the fourth consecutive year, more Italians died than were born, according to the national statistics agency.Italy's population nonetheless grew slightly to 60.6 million due to immigration, which is a highly charged issue acrossEurope.

Italy's youth minister Giorgia Meloni said earlier this year that measures to reverse the birth rate require "millions in investment" but that the resources aren't available.

Unlike many countries in Europe,France's population is growing slightly but steadily every year. It has one of the highest birth rates in the European Union with around 2 children per woman.

One reason is immigration to France by Africans with large-family traditions, but it's also due to family-friendly legislation. The government offers public preschools, subsidies to all families that have more than one child, generous maternity leave, and tax exemptions for employers of nannies.

Like France, the United States has one of the highest population growth rates among industrialized nations. Its fertility rate is just below the replacement rate of 2.1 children per woman, but its population has been increasing by almost 1 percent annually due to immigration. With 312 million people, the US is the third most populous country after China and India.

Africa

Lagos, Nigeria, is expected to over take Cairo soon as Africa's largest city. Private water vendors there do a brisk business in the many neighborhoods that otherwise lack access to potable water.

The drone of generators is omnipresent, at offices and markets, in neighborhoods rich and poor, because the power grid doesn't produce enough power. Periodic blackouts extend for hours, days, sometimes weeks.

Such is daily life in Nigeria's commercial capital, where the population is estimated at 15 million and growing at 6 percent or more each year. Problems with traffic congestion, sanitation and water supplies are staggering; a recent article in UN-Habitat said two-thirds of the residents live in poverty.

The rest of Nigeriaisn't growing as fast - estimates of its growth rate range from 2 percent to 3.2 percent. But it's already Africa's most populous country with more than 160 million people.

Ndyanabangi Bannet, the UN Population Fund's deputy representative in Nigeria, notes that 60 percent of the population is under 30 and needs to be accommodated with education, training and health care.

"It is a plus if it is taken advantage of," he said of Nigeria's youth. "But if it is not harnessed, it can be a challenge, because imagine what hordes of unemployed young people can do."

Another of the fastest-growing countries is Burundi. With roughly 8.6 million people, it's the second most densely populated African country after neighboring Rwanda.

Omer Ndayishimiye, head of Burundi's Population Department, said continued high growth coincides with dwindling natural resources. Land suitable for farming will decline, and poverty will be rampant, he said, noting that 90 percent of the population live in rural areas and rely on farming to survive.

The government has been trying to raise awareness about the demographic challenges among the clergy, civic leaders and the general public.

"We are suggesting couples to go to health clinics to get taught different birth control methods," Ndayishimiye said. "But we are facing some barriers ... Many Burundians still see children as source of wealth."

At her modest house in Gishubi, Godelive Ndageramiwe ponders the changes that have made her regret her large family.

"Children were a good labor force in the past when there was enough space to cultivate," she said. "Today I can't even feed my family properly. My kids just spend days doing nothing."

After her fourth child, she began to worry how her family could be cared for.

"But my husband was against birth control and wanted as many children as possible," she said. "It was delicate because he could marry another wife.

"My friends advised me to go to a nearby clinic, but I was told I must come with my husband. Now I have laid the issue in the hands of God."