Describing mountains
To date, mountain complexity has made it impossible to provide a thorough definition of mountains with universal application and acceptance. The following characteristics help describe mountains and highlands (adapted from Messerli, B. & Ives, J.D. 1997. Mountains of the world: a global priority).
Elevation zones: Forty-eight percent of the world's total terrestrial surface lies above 500 m; 27 percent above 1 000 m; 11 percent above 2 000 m; 5 percent above 3 000 m; and 2 percent above 4 000 m. These statistics provide an approximation for describing mountain areas.
Morphology and climate: Steep slopes (characterized by geomorphologically high-energy environments with frequent mass transfers downslope) and altitude (characterized by low temperatures and, in certain cases, aridity) are aspects of mountain or highland landscapes which individually or as a system lead to marginality for human utilization and adaptation.
Latitude: Because of the climatic effects, significant areas in higher latitudes have mountainous characteristics despite only moderate altitudes.
Biodiversity and food security: Mountains contain high biological diversity, often of global relevance. Consequently, mountains are also important centres of crop diversity, a key factor in agriculture worldwide.
Land-use opportunities and constraints: From the humid subtropical and temperate zones polewards, all land-use activities in mountain areas are disadvantaged compared with the lower, neighbouring, and more densely populated lowlands. But from the subtropical arid zones to the tropical humid zones, some higher altitudinal belts are more beneficial for human land use than lower altitudes because of better moisture and temperature conditions.
Conflicts and cooperation: Mountains often constitute geopolitical borders and can be sites of potential/current tensions or even conflicts owing to their rich natural resources and strategic relevance. Within countries too, mountain areas can be places of tension and conflict: because of their inaccessibility and remoteness, mountain regions sometimes harbour opposition groups. However, mountains also offer opportunities for transborder cooperation and promoting peace.