From 2001 to 2005, FAO Forestry Department staff participated in drafting Chapter 24: Mountain Systems of the Current States and Trend Assessment as part of the Millennium Ecosystem Assessment, a major research exercise on the current situation and future trends of planet ecosystems. The entire report was issued in 2006, summarizes the current understanding of the situation of the planet and of the actions needed to manage major risks and threats. The following information is summarized from Chapter 24.
Based on the definition by the United Nations Environment Programme World Conservation Monitoring Centre (which uses elevation and slope as the main criteria) approximately 23% of the global land surface can be considered mountain areas. According to altitude, three belts can be distinguished for mountain regions where latitude and precipitation regimes affect vegetation growth:
- The montane belt which extends from the lower mountain limit to the upper limit of forest;
- The alpine belt which is the treeless region between the natural climatic forest limit and the snow line; and
- The nival belt which is the area above the snowline.
Altitude and degree of slope influence many of the biophysical processes in mountain environments. However, latitude and distance from oceans affects local climate making some mountains almost permanently wet, others dry, and some highly seasonal. Geological substratum adds a further dimension of geo-diversity and influences soil type, erosion processes, and vegetation cover.
In many parts of the world’s mountains, physical processes such as erosion, landslides, mud flows, avalanches, and rock falls influence environmental conditions on varying spatial and temporal scales. These processes become enhanced when volcanic or seismic activity is a factor, which is particularly the case in geologically young and steep mountain regions (i.e. the Alps and the Himalayas).
Vegetation on lower mountain slopes may be broadly similar to that of surrounding lowlands. However, within an elevation range of 1,000 meters, altitude-related temperature change is enough to cause a full bioclimatic vegetation belt to be replaced by another (i.e. montane forest by alpine).
Because of the compression of climatic zones along an elevation gradient, biodiversity in mountains commonly exceeds that in the lowlands. Thirty-two percent of all protected areas in the world are located in mountainous regions, providing habitats for rare, relict, and endangered plants and animals.
Twenty percent of the world’s population - about 1.2 billion people - live in mountains. Most of them inhabit lower elevations. Most of the 90 millions people living above 2,500 meters live in poverty and are considered highly vulnerable to food insecurity. There are many historical examples of flourishing mountain economies and societies. However, special efforts and techniques are required to sustain agricultural production at altitudes close to the upper tree line level. Subsequently, lowland economies and societies have generally dominated mountain ones. Although there are some exceptions, very seldom does the exploitation of mountain resources (land, rangeland, timber, minerals, leisure sites, etc.) benefit local communities.