Glaciers are increasingly threatened by climate change. The French Alps are home to more than 4,000 of these fascinating natural monuments, of which 80 to 90 percent are set to disappear by 2100 due to global warming. Among the most emblematic glaciers is the Mer de Glace, or Sea of Ice, which retreats a little more each year, under the watchful eye of tourists. Meanwhile, the Bossons glacier reveals aircraft debris that was thought to be lost forever. FRANCE 24 went to meet some of the guardians of the glaciers.