Mountains and Mountain Forests
Background and Methods
Forests
that grow in mountain areas play an important role in maintaining the
stability of mountain systems and supporting the people who live there.
Mountain forests are vital as sources of water for irrigation and power
generation. They intercept and store water from rainfall, mist and snow,
and release it slowly, thereby reducing soil erosion, avalanches and downstream
flooding impacts. They are important sources of timber and other wood
and non-wood products, and are especially important as sources of fuel
for local populations and for those in nearby foothills and plains.
Mountain forests are very important as repositories of biodiversity and as a result are increasingly important for tourism and recreation as well as hunting and fishing. Because mountain forests are usually isolated from similar ecosystems by steep terrain and intervening lowlands with contrasting climates, they are frequently sites of high species endemism, that is the species occur locally and nowhere else. Local distribution tends to make species more vulnerable to extinction, and this combined with increasing pressures on mountain ecosystems has led to the inclusion of many mountain forest species on the lists of the world's most critically endangered species.
Mountain forests are often highly threatened by the activities of growing human populations around them. Some of the most densely populated areas of the world are mountain zones, where demands for land to grow crops, for fuelwood for cooking and heating, and for construction materials combine to exert high pressure on remaining forests. FAO (1993) has estimated the annual loss of forest from upland regions in the tropics to be 1.1%, 30% higher than elsewhere in the tropics.
Mountain forests are very important as repositories of biodiversity and as a result are increasingly important for tourism and recreation as well as hunting and fishing. Because mountain forests are usually isolated from similar ecosystems by steep terrain and intervening lowlands with contrasting climates, they are frequently sites of high species endemism, that is the species occur locally and nowhere else. Local distribution tends to make species more vulnerable to extinction, and this combined with increasing pressures on mountain ecosystems has led to the inclusion of many mountain forest species on the lists of the world's most critically endangered species.
Mountain forests are often highly threatened by the activities of growing human populations around them. Some of the most densely populated areas of the world are mountain zones, where demands for land to grow crops, for fuelwood for cooking and heating, and for construction materials combine to exert high pressure on remaining forests. FAO (1993) has estimated the annual loss of forest from upland regions in the tropics to be 1.1%, 30% higher than elsewhere in the tropics.
To
provide a global context for a discussion of mountain forests, it is first
necessary to define their locations and types, and this in turn requires
a definition of mountains or mountain areas. Altitude and slope and the
environmental gradients they generate are key components of such a definition,
but their combination is problematic. Simple altitude thresholds both
exclude older and lower mountain systems and include areas of relatively
high elevation that have little topographic relief and few environmental
gradients. Using slope as a criterion on its own or in combination with
altitude can resolve the latter problem but not the former.
The
forest data are from version 3 of the global forest cover data first compiled
by the World Conservation Monitoring Centre in 1997 (Iremonger et al.
1997). In this dataset national and regional data from many sources were
harmonised to display global forest cover in the early 1990s at a resolution
of 1km. The original 26 temperate and tropical forest types (Iremonger
et al. 1997) have been aggregated to present the five forest classes occuring
in mountains shown on these maps.
To
produce the mountains maps, topographical data from the GTOPO30 global
digital elevation model (USGS EROS Data Center 1996) were used to generate
slope and local (5km radius) elevation range on a 30 arc-second grid of
the world. These parameters were combined with elevation to arrive at
the empirically derived definitions of the six mountain classes displayed
on this map. The global mountain area thus defined is 34.5million km2,
or 24% of the earth's surface.
To produce the mountain forests maps the forest cover data set updated from the version compiled by WCMC in 1997 was overlaid on the mountains map.
Sources
Mountains derived from U.S. Geological Survey National Mapping Division, EROS Data Center (EDC) (1996) Global 30 Arc Second Elevation Data (GTOPO30)
Forests derived from WCMC's global forest cover dataset, an update of Iremonger, S., Ravilious, C. and Quinton, T. (Eds.) (1997). A global overview of forest conservation. CD-ROM. UNEP-WCMC and CIFOR, Cambridge, United Kingdom. CD-ROM.
To produce the mountain forests maps the forest cover data set updated from the version compiled by WCMC in 1997 was overlaid on the mountains map.
Sources
Mountains derived from U.S. Geological Survey National Mapping Division, EROS Data Center (EDC) (1996) Global 30 Arc Second Elevation Data (GTOPO30)
Forests derived from WCMC's global forest cover dataset, an update of Iremonger, S., Ravilious, C. and Quinton, T. (Eds.) (1997). A global overview of forest conservation. CD-ROM. UNEP-WCMC and CIFOR, Cambridge, United Kingdom. CD-ROM.
More detailed information on the methods employed can
be found in the following publication:
Kapos, V., Rhind, J., Edwards, M., Ravilious C. and Price, M.F. (In press)
Developing a map of the world's mountain forests. In: Price, M.F., Butt,
N. (Eds) Forests in sustainable mountain development report
for 2000. CAB International, Wallingford, UK.
Disclaimer
The geographical designations in these maps do not imply the expression of any opinion on the part of UNEP-WCMC concerning the legal status of any country, territory or area or concerning the delimitation of its frontiers or boundaries.