Glaciers in South America's Andes have been retreating at an increasing rate, which could affect the region's water supply in the near future, scientists say. Writing in the journal The Cryosphere of the European Geosciences Union, researchers blame the melting rate, which has been increasing since the 1970s, on rising temperatures as the region has warmed about 1.2 degrees Fahrenheit over the past 50 years. Glaciers in the Southern Hemisphere mountain range have shrunk by an average of 30 to 50 percent since the 1970s, said Antoine Rabatel, a researcher at the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France, and lead author of the study. The melting is most pronounced for small glaciers at altitudes below 17,000 feet, he said, which have lost an average of 4.4 feet of ice thickness per year. "Because the maximum thickness of these small, low-altitude glaciers rarely exceeds 40 meters [131 feet,] with such an annual loss they will probably completely disappear within the coming decades," Rabatel said. The tropical Andes host 99 percent of all tropical glaciers in the world, most of them in Peru. "The ongoing recession of Andean glaciers will become increasingly problematic for regions depending on water resources supplied by glaciered mountain catchments, particularly in Peru," the researchers wrote.