Climate change has shrunk Andean glaciers between 30 and 50 percent since the 1970s and could melt many of them away altogether in coming years, according to a study published on Tuesday in the journal Cryosphere.

Andean glaciers, a vital source of fresh water for tens of millions of South Americans, are retreating at their fastest rates in more than 300 years, according to the most comprehensive review of Andean ice loss so far.

The study included data on about half of all Andean glaciers in South America, and blamed the ice loss on an average temperature spike of 0.7 degree Celsius (1.26 degrees Fahrenheit) over the past 70 years.

"Glacier retreat in the tropical Andes over the last three decades is unprecedented," said Antoine Rabatel, the lead author of the study and a scientist with the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France.

The researchers also warned that future warming could totally wipe out the smaller glaciers found at lower altitudes that store and release fresh water for downstream communities.

"This is a serious concern because a large proportion of the population lives in arid regions to the west of the Andes," said Rabatel.

The Chacaltaya glacier in the Bolivian Andes, once a ski resort, has already disappeared completely, according to some scientists.