Geoscience Reference
In-Depth Information
2
Mountain environments
Jeff Warburton
2.1
ecological refuge and specialist agricultural
niches. Their significance varies from country
to country and is generally proportional to the
degree of mountain cover, for example in Europe
the proportion of area greater than 1000 m of
altitude varies markedly: 5% in the UK, 44% in
Norway and 100% in Andorra. Mountain areas,
in common with many other environments,
are increasingly endangered by socio-economic
changes, increased recreation and traffic, and
changing land-use, often leading to environ-
mental degradation. These changes often can be
related to direct impacts such as building and
development works, or may be the result of sub-
tle environmental changes such as changing pre-
cipitation patterns, shifts in habitats, changes in
runoff rates, water and soil pollution and changes
in the ground thermal regime. Environmental
degradation of this type is often manifest in
changes in sedimentary processes acting in moun-
tain areas and may result in slope instabilities
and enhanced fluvial erosion and sedimentation.
An understanding of the environmental sedi-
mentology of mountain areas provides a useful
framework for studying the effects of humans
and environmental change on active surface
sedimentary systems. Such an approach is par-
ticularly pertinent to mountain environments
where, due to high relief and steeper slopes, geo-
morphological and sedimentary processes often
operate at greater rates than in lowland environ-
ments and the extreme physical conditions make
mountain environments susceptible to even slight
changes in climate and land-use.
Given the large range in mountain environ-
ments it is impossible in this short chapter to fully
INTRODUCTION AND BACKGROUND
2.1.1 Introduction
Mountain environments account for approx-
imately one-third of the Earth's surface and it
is estimated that about 10% of the world's
population live in mountain and upland regions
(Gerrard 1990). Geomorphologically these are
amongst the most active areas on Earth, often
being characterized by some of the highest
recorded rates of erosion and sedimentation
(Walling & Webb 1983; Jansson 1988). Moun-
tain regions generally have steep slopes and
large relative relief. These are factors that make
mountain environments sensitive to natural and
anthropogenic activity such as extreme clim-
ate events, seismic perturbations, deforestation
and land-use change. The dynamic nature of
mountain environments, however, must not be
overemphasized at the risk of ignoring slow,
continually acting processes, the cumulative effect
of which can be highly significant (Messerli 1983).
Furthermore, sedimentary activity in mountain
environments varies enormously between differ-
ent topographic settings (Milliman & Sivitski
1992) and even within the same general setting;
differences caused by variations in the pressures
posed both by natural and anthropogenic agents
produce differing sedimentary responses (Dedkov
& Moszherin 1992).
An understanding of the environmental
sedimentology of mountain environments is
important because mountains provide essential
resources such as water supply, sustainable energy
(hydroelectric power), recreation and tourism,
