The Natural Environment of Mountain RegionsMountains comprise a specific type of natural environment found in both terrestrial (continents) and submarine (seas and oceans) areas. According to Barry (2008), terrestrial areas with altitudes greater than 1,000 m above sea level account for 8% of the land surface. If terrestrial areas with altitudes of 500 to 1,000 m are also considered, this percentage increases greatly. For example, Meybeck et al. (2001) estimated that approximately 25% of the land surface is occupied by mountains (at altitudes of 500 m or more) that are home to 26% of the world's population. Basic information about mountains and the mountain environment is provided below. Due to the well-known nature of the information cited, references and other sources are provided only where specific or debatable issues are discussed.The definition of mountainous areas is unavoidably arbitrary (Messerli & Ives, 1997). In general, no qualitative or quantitative distinction is made between mountains and hills (Barry, 2008). In simple terms, a mountain is a landform that rises prominently above its surroundings and generally exhibits steep slopes, a relatively confined summit area and considerable local relief. As part of the earth's surface, mountains tower over their surroundings and tend to be highly or heavily fragmented. It is commonly understood in North America that a relief of 600 m or higher distinguishes mountains from hills (Thompson, 1964). Such an altitudinal range is sufficient to cause vertical differentiation of climatic elements and vegetation cover. Finch and Trewartha (1949) proposed that a relief of 1,800 m could serve as the criterion for mountains of a 'Sierran type'. A relief in this range also implies the presence of steep slopes. To provide a rational basis for definition, Troll (1973) delimited high mountains by referencing landscape features. Based on Troll's criteria, the lower limit of the high-mountain belt occurs at elevations of a few hundred metres above sea level