Environmental Engineering Reference
In-Depth Information
Indonesia, it was decided that Montreal, Canada, would be the home of the UN
Convention on Biological Diversity.
CONCLUSION
The diversity and stability of ecosystems have become an important field of study in
biogeography as human society tries to measure and mitigate its adverse impacts on the
natural world. The assessment of such impacts is made difficult by the lack of many long-
term data sets which would enable conclusions to be drawn. Diversity can be measured
relatively accurately from fieldwork, but stability is a more elusive property to assess.
There are several different aspects of stability, and they can give contrasting indications
of the stability of a particular ecosystem.
Long-term data on bird and animal populations appear to offer the best bet for
assessing stability, but such data are not common. The diversity-stability debate which
has occupied so much attention in the past few decades urgently needs such field data; it
has relied too heavily on the results of laboratory studies and computer modelling for its
predictions.
Future conservation at an international level needs to concentrate on the eighteen 'hot
spots' which contain a high proportion of the world's species and which are particularly
vulnerable. These all occur in tropical and Mediterranean biomes, in areas where the
pressures of economic development increase year by year.
KEY POINTS
1
Diversity is measured by the Shannon index, which takes into account the number of
species and the evenness of distribution of species. Several indices are available to
measure stability, depending on the aims and nature of the investigation.
2
The relation between diversity and stability has come under close scrutiny recently, as
serious doubts have arisen concerning the old adage 'more diversity means more
stability'. Hence it is important to define carefully a priori what particular property of
stability is being studied. Diversity and stability are both relative concepts; they need
to be defined in terms of geographical space, community and time.
3
The upsurge of interest in biodiversity at an international level has been brought about
by the increasing concern for the diversity of species, especially in a number of
tropical locations. What is certain is that many more species on Earth have yet to be
discovered than are at present known. Only by the scientific study of diversity and
stability, according to the principles and methods discussed in this chapter, will it be
possible for effective policies to be formulated at the international and national levels,
and for those policies to be translated into action programmes at a more local level.
