Alpine pastures are mainly located above the tree line and are only used during the summer months. Without this Alpine farming, it would have been hardly possible for there to have been any significant Alpine settlement from Neolithic times up until the economic upheavals of the 19th century. Alpine farming takes the pressure off the meadows in the valleys and enables the vital stockpiling of resources for the winter. Even today, Alpine farmland accounts for around 35 percent of agriculturally usable land in Switzerland. In summer, about 20% of the total number of livestock grazes on these 7,500 Alpine farms for 100 days. They are supported by 12,000 Alpine herdsmen and women.