There are approximately million named species of living
oganisms. The total number of living species is of course not known and we can
only estimate what the figure might be. Estimates range from about 11 to 30
million or more. What is certain is that human impacts are causing species to
become extinct faster than they can be named. Also of concern is our lack of
knowledge about the named species. Scientists have intensively investigated
only 10 per cent of plant species and a far smaller proportion of animal
species (information from the World Commission in Environment and Develop-ment
198- publication Our common Future, Oxford University Press).
There are many
terms used to refer to different groups of animals, plants and other kinds of
living organism such as fungi, bacteria and viruses. The classification of
biota (living organisms) has been reviewed and changed many times as a result
of new information. In 1969, R. H. Whittaker of Cornell University suggested
five groups of living organisms . More recently, new taxonomic levels
and regrouping of major taxa have been proposed as a result of studies in
molecular biology. Commonly used terms for living organisms include 'wildlife:
and more recently the widely misunderstood term 'biological diversity' (often
ab-breviated to biodiversity). Wildlife is often used only with reference to
mammals and birds. In this book it refers to any kind of wild organism tn
dnmesticated
Biogeography: the nature of the subject geography, taxonomy, geology, climatology and ecology. Many biologists, taxonomists, geologists, climatologists and ecologists have interests in various aspects of biogeography and indeed some have particular views as to the precise nature of biogeography. Those differences in views are based partly on differences of scale, be it in time or spatially. For example, a geologist's view might be particularly biased by an interest in evolutionary processes over very long periods of time (millions of years) perhaps in relation to plate tectonics.
Geographers might take a special interest in researching the distribution of plants and animals over the last few thousand years, perhaps in relation to the post-glacial periods. An ecologist's view of biogeography might be dominated by those factors which determine and maintain the distribution of plants and animals within certain localities and over much shorter periods of time (perhaps in relation to the reduction and fragmentation of habitats in the last few decades). These different views contribute to the rich and varied nature of biogeographical research and its many important, practical applications. The common theme in all approaches to the study of biogeography is the study of the geographical distribution of groups of plants, animals and other organ-isms from a spatial or space perspective (that is, over land, in the soil, in water and in the air) and a temporal or time perspective (that is changes in distribution that occur over time).
Biogeography provides a valuable link between traditional single disciplines (such as ecology, taxonomy and conser-vation biology) and a focus for interdisciplinary studies. That is important because many if not all environmental problems facing us today require an interdisciplinary approach (that is an integration of several disciplines, in-cluding ecology, geology, economics, policy and sociocultural factors). Biogeography is more than about mapping the geographical distribution of organisms (present and past) at different spatial scales or merely dividing the land and sea into regions which are based on groups of characteristic organisms.
Once a predominantly descriptive discipline, biogeography is now a quantitative science. It has applications in conservation, helping to establish a strategy for the location, extent and management of protected areas. It has applications in trying to achieve sustainable use of living resources and in environmental assessment by helping to ensure the least impact on the natural environment.
It has applications in helping to tackle many aspects of environ-mental change, whether it be modelling the effects of changing weather patterns on agriculture or those of introduced and invasive species on native (indigenous) commercial fish species. Before we can look in more detail at biogeography we need to know what we are dealing with and thus a brief introduction to the classification of organisms is helpful.
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