Geoscience Reference
In-Depth Information
Mountains pack a wide range of environmental
conditions into relatively restricted geographic areas,
leading to hazards and conflicts of interest in terms of
their human occupation and use. High altitude, steep
slopes and more extreme weather conspire to make them
one of the least inhabited and productive areas on Earth,
yet they draw us in disproportionate numbers as tourists.
Indigenous and inward-migrant populations grow as
crowded lowland regions exceed human resource
demands. Industrial regions exploit mountain water,
hydro-electric potential, forest and mineral resources at a
distance. Tourism exploits dramatic mountain scenery
and alpine snowfields, bringing welcome income to
poorer indigenous communities. Yet it conflicts with their
traditional life style and is driven by short-term economic
interests inimical to the sensitivity and stability of their
physical environment. Sustainable management of global
mountains requires us to understand first the character
and operation of their physical systems.
KEY POINTS
1
Polar climate is characterized by low inputs of radiant energy on an annual basis. There is negative net
radiation, so that temperatures are low. Precipitation is generally small, as atmospheric moisture content
is low and conditions in the atmosphere are rarely favourable for air to rise and form deep rain clouds.
There is a marked contrast between the Arctic, with its frozen (but shrinking) sea ice cover surrounded by
continents, and Antarctica, with its high ice plateau surrounded by a cold southern ocean.
2
Mountain areas of high absolute elevation or relative relief develop their own distinctive climate, weather
and ecosystems. Mountains penetrating the mid-troposphere generate major weather disturbances,
especially in Earth's jet streams and monsoon circulation systems. Locally, the presence of topographic
surfaces in the mid-troposphere alters energy and moisture balances compared with the free atmosphere
and channels topographic winds.
3
Altitudinal zonation extends climate and other environmental attributes and processes of polar latitudes
into lower-latitude mountains. Hostile alpine landsystems and environmental sensitivity limit human
population levels yet, paradoxically, stimulate a substantial tourist industry in landscapes of spectacular
scenery. Surviving alpine glaciers and many other facets of mountain environments and their human
occupation and use are threatened by climate change.
4
Alpine landsystems represent the integration of glacier, cryonival and slope processes above the timberline,
which buffers them from lower-lying fluvial landsystems. High potential energy, continuing uplift in many
orogens and Quaternary glaciation ensure that the modern glacier-cryonival-slope landsystem is a high-
energy, unstable-slope and high-sediment transfer system.
5
Polar ecosystems have low productivities and ecological diversities. Animal species have to hibernate or
out-migrate during the harsh winters, and all biological activity is concentrated in a brief summer period.
Soil processes and ecological mechanisms act at a low intensity. Geomorphology and soils are dominated
by the presence of permafrost in the subsoil, sensitive to any change in the surface vegetation and easily
disturbed by human activity. Any interference with the insulating properties of soil and vegetation and
addition of heat to the surface (through global warming, industry and buildings) will inevitably cause
permafrost melting and ground subsidence.
6
Polar ecosystems have low resistance to outside impacts, and their low resilience means that recovery is
a long-term process. Polar ecosystems are also very variable in time and space. Soil and vegetation
conditions change quite rapidly over short distances, due to the effects of rock type, topography and depth-
to-permafrost. Temporal variability causes big contrasts in weather and biological activities from one year
to the next. It is another factor which makes polar environments so fragile and so unpredictable.
