As a consequence Niger has the fastest growing population in the world. In the wild, a species will naturally expand in population if environmental conditions are right, i.e. there are sufficient supplies of food, space and water, and a low threat from predators or disease. For example, if foxes are introduced to an island with many rabbits, foxes rapidly reproduce and take advantage of the food supply. As foxes multiply, their total demand for rabbits rises. Meanwhile the total number of rabbits is falling from the growing predator numbers.
Finally the foxes have eaten so many rabbits that the rabbit population is in decline, and the foxes run out of food. A famine follows, the surplus fox population dies off, pressure on rabbits declines, rabbits multiply again and the cycle starts once more.
Humans are prone to these cycles too, but agriculture and technology stave off famine in modern societies. This would cause exponential human population growth, except modern contraceptives and family planning keep population growth low. Developed countries have low mortality and low fertility. Completely undeveloped tribal cultures have high mortality and high fertility. Both keep population sizes roughly constant.
Developing countries, where modern medicine and improved agriculture have begun to reduce mortality but culture still values large families, have high fertility and low mortality, causing rapid growth.
This is what Niger is experiencing. Niger is the fox, growing like crazy and eating all the rabbits. And like the fox, it is beginning to run out of food:
Reports from northern Nigeria say a growing number of people from Niger are crossing the border into Nigeria because of the food crisis at home. A BBC correspondent in the northern Nigerian state of Katsina says many women and children from Niger are seeking shelter with local families. Aid agencies say about seven million people in Niger - about half the population - are short of food.
Niger's government has started distributing food, so their response is to keep mortality low. At first this may seem dangerous, since this is simply allowing continued exponential growth. Thankfully humans tend to respond to falling infant mortality rates by reducing their family size, so as mortality declines, population growth tends to eventually stabilise.