Global birthrates are falling. But with many in their fertile years and political and cultural forces against contraception, the population explosion is far from over.
In fast-growing countries, many young men are unable to find employment or pay dowries. Frustrated ambitions can be an explosive force — and a reason for joining the Taliban.
Nearly 1 billion people are malnourished, and a child dies of hunger every 11 seconds. By 2050, farmers would have to double crop production to meet the demand.
China's 'one-child' policy has slowed population growth and brought prosperity — but it couldn't avert massive damage to the environment.
In the Philippines, access to contraceptives is limited for the most part to those with the means to pay. The Catholic Church has fought a "reproductive health bill" in the legislature that would change that.
India's Punjab is running out of water. High-intensity agriculture has also exhausted or contaminated soils, depleted streams and aquifers, and led to resistant pests.
Around Uganda's Bwindi park, home to rare mountain gorillas, the human population is booming, spreading disease to the gorillas and putting pressure on habitat.
The birthrate plunged, helping to usher in social changes, particularly concerning the role of women.
Fish stocks are being depleted, and some desperate Filipinos are using cyanide and dynamite on the fish. A nonprofit is trying to protect nature and ease poverty by limiting family size.