High levels of precipitation cause the glaciers to descend to permafrost levels in some areas whereas in other, more arid regions, glaciers remain above about the 3,500 m (11,483 ft) level. The 1,817 square kilometres (702 sq mi) of the Alps covered by glaciers in 1876 had shrunk <answer>to 1,342 km2 (518 sq mi)</answer> by 1973, resulting in decreased river run-off levels. Forty percent of the glaciation in Austria has disappeared since 1850, and 30% of that in Switzerland.
From 1876 to 1973, how much did the glaciers that covered the Alps shrink?
to 1,342 km2 (518 sq mi)