Several hundred head of camel, sheep and cattle shoved and bustled in the blistering afternoon heat to get closer to the well. Many of them were crying and braying from thirst. Nearby, also waiting their turn, half a dozen Touareg nomads sat on donkeys carrying empty yellow water containers. Some had traveled a day or more just to get to this well. But the laws that govern water access in this vast and inhospitable stretch of the Niger Sahel dictate that everyone, man and beast alike, wait his turn. "This life has to end," said Mohammed Mousa, a craggy-faced, 60-year-old clan chief who has been feeding his herd from this well for half a century. He knows the desert is advancing, and that the rains are no longer reliable. "Our life is blocked now because of water. We have to find a way to end the thirst." It's difficult to imagine a more fundamental human need than water. Its absence in landlocked Niger, which development studies identify as the world's poorest country, is relentless. It also partly explains why, in Yale and Columbia's Environmental Performance Index, Niger came in last: the world's least green country. Poor scores across the board, from the burden of disease (a measure of illness from environmental causes) to water quality and education rates, confirm Niger as an example of the disaster that can result when environmental weakness, poverty and poor governance collide (Niger scores a pitiable 6 on the 100-point EPI scale). It was also a reminder of how, in those parts of the world that lie on the vulnerable fringes of the development spectrum, environmental degradation and societal collapse often go hand in hand. "If there is anything called extreme vulnerability, it's what I saw in Niger," says Jan Egeland, the United Nations' special adviser on conflict, who is evaluating the impact of environmental damage and climate change on the Sahel region on the Sahara's border. Niger has never been all that green. Most of the countryside is an immense sweep of infertile windswept scrubland. Prolonged periods of drought and flooding have been problems here for as long as anyone cares to remember; almost 90 percent of Nigerois live in rural areas and depend on either agriculture or grazing for survival. Since the 1960s, however, researchers have recorded a 25 percent decrease in rainfall across the Sahel, where desert swallows 120,000 hectares of arable land each year. Nigerois compensate by overusing their shrinking farmland, creating erosion and exacerbating the land loss. This process is why Niger scores low on environmental health in the EPI. "It's extremely difficult for people here to think from year to year or month to month or even day to day," says Jean Bernard Duchemin, director of the Sahel Medical Research Facility. "They are in survival mode, all the time, every single day." Niger's herdsmen and farmers might be able to cope with the erratic rainfall by the time-honored method of diversifying their crops and herds if it weren't for another damaging trend: rising population. In the past 40 years, Niger's population has quadrupled, from 3 million in the 1960s to more than 13 million today. It is still expanding at 3.4 percent a year