Forests protect groundwater, an important drinking-water resource, from impurities by retaining pollutants in the soil and allowing the cleaned water to percolate deep into the ground. Drinking water from forest areas is therefore of good quality. Forests provide people with protection against natural hazards, like avalanches, rockfall and debris flows. Their protective effect has improved since 2005 because the forests have grown denser. The increasing lack of regeneration and more browsing of young trees by wild ungulates mean, however, that the forest's long-term protective effect is uncertain.