Jonathan Levin, La Paz
WHEN the Chacaltaya glacier vanished six years sooner than scientists predicted, a victim of global warming, so, too, did the world's highest ski run. The loss of the 18,000-year-old glacier this year that loomed above Bolivia's Altiplano threatens to diminish water supplies to 2 million people clustered around La Paz, according to the World Bank.
''Chacaltaya was my bride in white; now, she's dressed for a funeral,'' Alfredo Martinez, 74, said of the 5280-metre glacier where he and Club Andino Boliviano members skied its sole run north of La Paz, Bolivia's capital.
Chacaltaya, bridge of ice in the Aymara indian language, has been a barren slope devoid of permanent snow for about six months. That's when the glacier succumbed to warming weather during the southern hemisphere's summer, its final two glacial tongues melting away even faster than the year 2015 that scientists had forecast for its disappearance.
Like shrinking ice sheets in Antarctica, climate change blamed on greenhouse-gas emissions has raised sea levels, led to the extinction of less-adaptable species and cost the world another glacier. From the Andes to the Alps, glaciers have retreated for 18 years, twice as fast as a decade ago, says the University of Zurich's World Glacier Monitoring Service.
Worrisome to city planners is that as Bolivia's glaciers recede the landlocked Andean nation's water supplies grow more at risk - a trend that may spread throughout South America and elsewhere as glacial melting is accelerating at a quicker pace than a United Nations forecast of just two years ago.
Global warming, dams and the diversion of water for agriculture and industry are already drying up stream flows in 45 of the world's largest rivers, including India's Ganges, the Yellow River in China, and the Congo and Colorado rivers. Tens of millions of people are affected.
South American residents, including those in La Paz and its sister city El Alto, may be similarly affected. La Paz's main water supplies come from rainwater and melt-off from tropical glaciers in the Cordillera Real range, which includes Chacaltaya and the Tuni-Condoriri glacial system set in the mountains above the region's largest reservoir.
Glacial run-off feeds into 10 hydroelectric plants that provide about 80 per cent of the region's power, said Edson Ramirez, head hydrologist at San Andres University in La Paz.
''Sooner or later, all the tropical glaciers without exception are going to disappear,'' Juan Carlos Alurralde, an engineer studying water solutions, said in an interview at his office in La Paz.
On a cold morning, about 20 tourists climbed from the Club Andino ski lodge to Chacaltaya's summit for a broader view of the Cordillera Real mountains. Just below the summit, a tennis court-sized slab of ice was all that remained where there once was a glacial field navigable for 10-minute runs by skiers.
While Chacaltaya was Bolivia's sole ski area, first developed in 1939, Club Andino sold its last ski ticket for its only tow line in 2003 after a tower anchored in the glacier fell to the ground as the melting worsened. The glacier has lost 80 per cent of its volume over the past 20 years, according to scientists.
A lodge just below the peak remains open for hikers, while views from Chacaltaya's summit on a clear day include snowcapped peaks and Lake Titicaca, the world's highest commercially navigable lake.
Climate change has also led to extended dry seasons and condensed periods of heavy rain in the region. Every month this year, precipitation in La Paz has been below historic averages, recorded from 1961 to 1990, except for February, when downpours set off mudslides that left 60 families homeless.
In addition to the costs to cities, poor rural populations may migrate en masse as water supplies drop.
Meanwhile, the World Bank is financing projects in Peru, Bolivia and Ecuador to help those countries find and implement solutions related to water issues.