decrease, many areas are left for the benefit of woodlands to the detriment of landscape diversity. This decline is particularly marked in Valais and Ticino. Forests Forests cover less than a third of the territory, but the area is increasing year by year. The reforestation is essentially natural, mainly in the Alps where the forest areas reoccupy those abandoned by farmers. Afforestation contributes 13% to reforestation, and is conducted for compensation following a clearance or to provide protection against natural hazards in the mountainous areas (avalanches, landslides). Forests are more predominant in the Jura and in the southern Alps, occupying respectively 47.7% and 47.2% of the soil in these regions. On the northern slopes of the Alps, Alpine forest occupy 33.2% and on the Plateau 24.6%. It is in the Central Alps that forest areas occupy less floor with about 22% coverage. Switzerland is home to mixed maple-ash forests of fertile and deep earth that collects at the base of slopes. They replace the moist oak-hornbeam forests in areas with higher rainfall. This type of forest has been called "one of the most productive in Switzerland" and the tree growth has been described as "aggressive". It takes one third of the time for trees to reach the same height as it would in a mull-beech forest and within 100 years trees in maple-ash forests can reach a height of 35m, though the quality of wood will not be as high. The rich undergrowth of these forests is dominated by the allium ursinum (wild garlic) common throughout Western Europe. Unproductive areas The unproductive areas correspond to all areas occupied by rocks, boulders, ice, snow fields and unproductive vegetation beyond the limits of forests. Lakes, rivers and wetlands are also unproductive areas. Occupying 25.5% of Swiss soil, these surfaces are in very slight decline (-0.1% over 10 years). They are predominant in the Central Alps (half of the soil), on the contrary they only cover 10% of the surface of the plateau and 1% of the Swiss Jura. The uncultivated mountain areas are exploited by the tourism and the production of hydroelectricity. Climatic conditions strongly affect the landscape of these areas: water seepage, landslides, avalanches, torrents in spate. Man intervenes on 0.2% of this surface area to create infrastructure protecting against floods or avalanches. The channels of communication, with many works of art occupy a portion of these surfaces. In the plains,