Geoscience Reference
In-Depth Information
INTRODUCTION
So far we have addressed the physical processes
operating within the three main 'spheres' of Earth -
the atmosphere, the geosphere and the biosphere. By
now, it is hoped that the reader will have an under-
standing of these processes that generate particular
features of our physical environment. However we
have tended to deal with each process within the
context of its own sphere. In reality they are set in a
much wider context with interactions between the
various components of physical geography and can
have major impacts onto the human environment
through such features as slope failure, tropical
cyclones, and loss of biodiversity through population
expansion and economic growth. In this final part, we
focus on a variety of environments, partly chosen
through our own research experiences and interests.
We aim to examine each in more detail and explore
the interrelationships between the physical processes
and the consequences they may produce. It also gives
us the opportunity to conclude with a final chapter
concentrating on the theme of environmental change.
Although we have considered the prospects of change
within our process chapters, the aim is to examine
what might happen to our varied environments over
a range of time-scales.
In the opening
chapter (23)
to this part, we exam-
ine how we can reconstruct former environments
using information that is preserved as part of our pre-
sent environment. Using the principle that the present
is the key to the past, we can use our understanding
of present day processes and environments to make
deductions about what has happened in former times.
For example, many of the geomorphological features
of the British mountains can only be explained by
knowing how our environment has changed in the
recent geological past. When considering former
events, it is vital that we know something about the
time periods involved. Fortunately absolute dating
methods now allow us to make more detailed inter-
pretations of what happened at specific periods of time
although there are still a number of limitations that
prevent us being able to pick up a particular piece of
evidence, such as organic material, and tell its age and
the precise environment within which it formed.
Examples are taken from North Wales and North
Yorkshire to demonstrate how this environmental
reconstruction works in practice.
The environments chosen for more detailed
examination are key parts of Earth's surface.
Chapter
24
covers polar and alpine environments, where the
consequences of cold conditions is the main theme.
They are both sensitive environments that can easily
be damaged through careless exploitation. Their
sustainable management requires us to understand the
character and operation of their physical systems. The
explosion of interest in these environments in scientific
circles, the media and the general public results from
concern over their sustainable development in the face
of increasing pressure on their renewable and non-
renewable resources, and their growing geopolitical
importance. Another area experiencing increasing
stress through development and economic expansion
is the Mediterranean environment, which is covered
in
Chapter 25.
As the original birthplace of western
civilization, the core region has been affected by
human activities for a long period of time but even
California, the Cape area of South Africa and southern
Australia now suffer similar problems of development,
such as water shortages, soil salinization and wild fires.
Even drier conditions are discussed in
Chapter 26
and
much space is devoted to the problems of providing
adequate water supplies. Although they can be sim-
plistically viewed as areas of too little rain, many
problems are related to political instability and in
reality the problem of dryness and desertification is a
multi-faceted feature of this environment. The final
environment (
Chapter 27)
is the humid tropics where
we experience the reverse of the dryland areas with
water being abundant in most seasons. Here the main
environmental problems have been deforestation and
loss of biodiversity resulting from overexploitation of
the natural forest. The future task is sustainable
development without damaging their contribution to
the global environment in terms of moisture provision,
carbon exchanges and biodiversity.
This part concludes with arguably one of the most
important chapters where consideration is given of
how Earth's environments are currently experiencing
change and what the future may hold. The predictions
depend upon our ability to understand and model
this complex system. The views here represent those
of the authors but we have tried to provide a dis-
passionate, scientific consensus of the arguments
proposed for Earth's future.
