Geoscience Reference
In-Depth Information
Environmental hazards in mountain areas
APPLICATIONS
Mountain environments are naturally prone to catastrophic geophysical processes - landslides, debris flows,
earthquakes, volcanic eruptions, glacier lake bursts and flash floods. Quite simply, that is how their landsystems
evolve, and any one may trigger others. There are also biometeorological hazards to high-altitude living. Anoxia,
mountain sickness and pulmonary oedema become apparent above 3 km altitude, owing to the rarefied atmosphere
(see box, p. 602), as do wind chill, frostbite and snowblindness on exposure to cold and snow. Yet all these are
tolerated perennially by 10 per cent of Earth's human population and by a further 20 per cent of us seasonally in
pursuit of recreation.
Mountains themselves are under stress. Indigenous populations are mostly citizens of less developed countries,
often pressed for cultivable land and natural resources and looking increasingly towards more marginal mountain
environments. Sustained growth in the developed world exploits the tourist and hydro-electric potential of mountains
and their water, mineral and timber resources. Demand for open spaces, scenic quality and solitude conflicts with
the impact of atmospheric pollution, expanded economic infrastructure and tourism overdevelopment. Human
pressures are large enough to make it harder to detect those driven by climate change.
Figure 24.14
highlights a
range of threats and sensitivities.
These pressures threaten the fragile mountain geoecosystem, leading to serious landscape degradation and the
diminution or ultimate loss of resources. We are now aware of the harm of irreversible environmental impacts and,
in developing coherent response strategies, we must also avoid mistaking the degree of vulnerability to human, rather
than natural, changes. Apparent linkages between Himalayan deforestation and flooding in Bangladesh, rather than
slope-river destabilization responding to great monsoon intensity, may be one example where thirst for 'issues' can
distort reality. However, as we strive to resolve existing pressures we are aware that global climatic change poses
new threats to the mountains. Their environmental management is experiencing increased conflict due to trying to
balance development with environmental conservation in such sensitive systems. Tourism and other economic
developments can respond even more quickly to economic, rather than climatic, trends. Shrinking snow and ice cover
will affect alpine tourism disproportionately, risking socio-economic disturbance in dependent communities. Land
degradation, once skiing disappears, reduces the potential for agricultural restoration or diversification.
The United Nations Conference on Environment and Development (UNCED) Mountain Agenda 1992 brought a timely
focus of attention. In the same year one of many related national projects was established by the Swiss National
Science Foundation. Climate and Environment in Alpine Regions (CLEAR) was established to explore the possible
multifaceted impacts of climate change on alpine regions. Its second round, concluded in 1999, used climate models
as explanatory rather than forecasting tools to improve our understanding of alpine environmental processes and the
prognosis for successful human and landscape adjustment.
geomorphology, pedology and ecology are more inte-
grated in polar and alpine regions than in many biomes.
Great spatial variability is seen at many scales, from
short-distance gradients to the biome-scale reactions to
climate change. The term
alpine
refers generically in high
mountains to the zone between permanent snowline and
treeline. It is home to an arctic-alpine flora which is
the altitudinal equivalent to arctic ecosystems at high
latitudes. Arctic ecosystems are diversified by local
variations in topography and depth-to-permafrost,
whereas alpine ecosystems owe their diversity to the
they enter lowlands across sharp boundaries from regions
of high orogenic uplift - as with the braided rivers of
eastern South Island, New Zealand.
ALPINE AREAS
The stability and functioning of ecosystems are dependent
on several interacting factors, such as climate, topography,
soils, and biological production (see
Chapter 22).
Climate,
