Geography Reference
In-Depth Information
40
GIS, remote sensing and the problem of
environmental change
Roy Haines-Young
environmental problems that confront modern
societies. Figure 40.1, for example, shows the recent
deforestation history of Madagascar. It is important
to understand these types of change, because the
world's tropical forests are resources in their own
right and because of the wide-ranging effect that
such changes might have on global climates through
the release into the atmosphere of the carbon stored
in such ecosystems. Figure 40.2 shows data from a
very different type of environment, namely that of
central Asia. This map comes from a study that
attempted to monitor land cover at a time when
there had been a change in land holding and
grazing patterns in some areas. These case studies
are but two examples of scientists using map data to
understand the nature of environmental change. In
this chapter, we will consider some of the technical
and scientific issues that lie behind such work.
It would clearly be a difficult and time-
consuming task if data such as those shown in
Figures 40.1 and 40.2 had to be collected by
ground survey and drawn up by hand. Fortunately,
we now have access to computer-based tools that
can help to speed up the process. On the one hand,
we have access to satellite and airborne remote-
sensing systems that can automate the collection
of data about the Earth's surface. On the other, we
have available computer-based systems, in the
form of GIS, that can store, analyse and display
such data, and link them with other sources of
information. Figure 40.3 sets out the relationships
between the processes of
data
capture
and
data
INTRODUCTION
People cannot help but change their environment.
It is a characteristic we share will all other species.
Change comes about because we need to acquire
energy and materials to live, and these activities
have an inevitable consequence for the
environment. What sets us apart from all other
organisms, however, is the scale and speed of the
changes that we have initiated. There are few
places on the Earth today that do not bear some
trace of human activity. The impacts of modern
lifestyles can now be seen by environmental
changes going on at local, national and global
scales.
Concern about the impacts of people on the
environment has stimulated a good deal of scientific
work directed at understanding the nature of
environmental change, its consequences and what
needs to be done to avoid its worst effects. In this
chapter, we will look at some important computer-
based technologies that have been used in such
work. Our goal will be to consider how the
technology has been used to monitor
environmental change and help us to develop
appropriate management strategies for the future.
The technologies that we will consider are those
of geographical information systems (GIS) and
remote sensing (RS). We need to understand these
technologies because they have become important
tools that can be used by geographers and other
scientists to apply their knowledge to many of the
