When Ice Turns to Water

Glacial melting poses potentially costly problems for Peru and Bolivia

FOR centuries, the run-off from the glaciers atop the spectacular snow-capped mountains of the Carabaya range has watered the pastures where alpacas graze around the small town of Macusani. More recently, the mountains have provided the town with drinking water and hydroelectricity, as well as hopes of attracting tourists to one of Peru's poorest areas. But in Carabaya, as across the Andes, the glaciers are melting fast. Their impending disappearance has large, and possibly catastrophic, implications for the country's economy and for human life.

Peru is home to the world's biggest expanse of tropical glaciers. Of the 2,500 square kilometres (965 square miles) of glaciers in the four countries of the tropical Andes—Bolivia, Colombia, Ecuador and Peru—70% are in Peru and 20% in Bolivia. The last comprehensive satellite survey by Peru's National Environmental Council, carried out in 1997, found that the area covered by glaciers had shrunk by 22% since the early 1960s. In the Carabaya range, they had receded by 32%.

Partial surveys by geologists suggest that the rate at which the glaciers are melting has speeded up over the past decade. The glacier at Pastoruri, in the Cordillera Blanca range north of Lima, shrank by more than 40% between 1995 and 2006, with the loss of ice caves popular with tourists, according to Marco Zapata, a glaciologist at the government's Natural Resources Institute. He reckons it will be gone by 2015. That is the fate that has already overtaken many smaller glaciers in Bolivia, and that of Cotacachi in Ecuador. Chacaltaya, above Bolivia's capital, La Paz, has almost disappeared; it is the site of the country's only ski resort, whose future is now uncertain.

“We are already experiencing the effects of global warming,” says Nancy Rossel, the mayor of Macusani. To those who doubt its existence, she offers to show them pictures taken ten years ago of Allinccapac, the mountain above the town, and “they can see how far the glaciers have receded.” A report by a team from the World Bank published last month in the bulletin of the American Geophysical Union (AGU), a scientific association based in Washington, DC, confirms most of the mayor's fears. It predicts that many of the lower glaciers in the Andes will be gone in the next decade or so, and that glacial runoff may dry up altogether within 20 years. It also paints a troubling picture of the future impact on water and power supplies.

One danger is that as the ice melts, newly formed lakes may send water cascading down mountainsides, triggering mudslides that are potentially lethal for the villages below. Another is that if there are no glaciers to regulate water flow, flood will alternate with drought.

That is a particular worry for Peru. After decades of migration from the Andes, two out of three Peruvians now live on its desert coast. Lima, with 8m people, is the world's second largest city located in a desert, after Cairo. Big irrigation projects have made the desert bloom and enabled an agro-export boom. Yet most of Peru's fresh water lies east of the Andes. Water for both irrigation and human consumption from the short, coastal rivers will become more irregular.

The government says it needs to spend about $4.5 billion to bring domestic potable-water coverage up from its current level of 78% to the regional norm of over 90%. Billions more will be needed to divert water along tunnels beneath the Andes if glacial melting accelerates.

Another problem is that more than 70% of Peru's electricity comes from hydroelectric dams sited on the glacier-fed rivers. If their flow becomes more irregular, so will power supply. Once the glaciers disappear, Peru will have to invest $1.5 billion a year in thermal generation, according to the AGU article.

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