Biodiversity and Conservation
by Dr Barbara Corker
What is Biodiversity?
Biodiversity is a modern term
which simply means " the variety of life on earth". This variety can be measured
on several different levels.
Genetic - variation
between individuals of the same species. This includes genetic variation between
individuals in a single population , as well as variations between different populations
of the same species. Genetic differences can now be measured using increasingly
sophisticated techniques. These differences are the raw material of evolution.
Species - species
diversity is the variety of species in a given region or area. This can either be
determined by counting the number of different species present, or by determining
taxonomic diversity. Taxonomic diversity is more precise and considers the relationship of
species to each other. It can be measured by counting the number of different taxa (the
main categories of classification) present. For example, a pond containing three species
of snails and two fish, is more diverse than a pond containing five species of snails,
even though they both contain the same number of species. High species biodiversity is not
always necessarily a good thing. For example, a habitat may have high species biodiversity
because many common and widespread species are invading it at the expense of species
restricted to that habitat.
Ecosystem - Communities of plants and animals, together with the physical
characteristics of their environment (e.g. geology, soil and climate) interlink together
as an ecological system, or 'ecosystem'. Ecosystem diversity is more difficult to measure
because there are rarely clear boundaries between different ecosystems and they grade into
one another. However, if consistent criteria are chosen to define the limits of an
ecosystem, then their number and distribution can also be measured.
How many species are there?
|Estimates of global species diversity vary enormously because it is
so difficult to guess how many species there may be in less well explored habitats such as
untouched rain forest. Rain forest areas which have been sampled have shown such amazing
biodiversity (nineteen trees sampled in Panama were found to contain 1,200 different
beetle species alone!) that the mind boggles over how many species there might remain to
be discovered in unexplored rain forest areas and microhabitats.
Global species estimates range from 2 million to 100 million
species. Ten million is probably nearer the mark. Only 1.4 million species have been
named. Of these, approximately 250,000 are plants and 750,000 are insects. New species are
continually being discovered every year. The number of species present in little-known
ecosystems such as the soil beneath our feet and the deep sea can only be guessed at. It
has been estimated that the deep sea floor may contain as many as a million undescribed
new species. To put it simply, we really have absolutely no idea how many species there
Losses of Biodiversity
||Extinction is a fact of life. Species have
been evolving and dying out ever since the origin of life. One only has to look at the
fossil record to appreciate this. (It has been estimated that surviving species constitute
about 1% of the species that have ever lived.)
However, species are now becoming extinct at an alarming rate, almost entirely as
a direct result of human activities. Previous mass extinctions evident in the geological
record are thought to have been brought about mainly by massive climatic or environmental
shifts. Mass extinctions as a direct consequence of the activities of a single species are
unprecedented in geological history.
The loss of species in tropical ecosystems such as the rain
forests, is extremely well-publicised and of great concern. However, equally worrying is
the loss of habitat and species closer to home
in Britain. This is arguably on a comparable scale, given the much smaller area involved.
Predictions and estimates of future species losses abound. One such
estimate calculates that a quarter of all species on earth are likely to be extinct, or on
the way to extinction within 30 years. Another predicts that within 100 years, three
quarters of all species will either be extinct, or in populations so small that they can
be described as "the living dead".
It must be emphasised that these are only
predictions. Most predictions are based on computer models and as such, need to be taken
with a very generous pinch of salt. For a start, we really have no idea how many species
there are on which to base our initial premise. There are also so many variables involved
that it is almost impossible to predict what will happen with any degree of accuracy. Some
species actually benefit from human activities, while many others are adversely affected.
Nevertheless, it is indisputable that if the human population continues to soar, then the
ever increasing competition with wildlife for space and resources will ensure that
habitats and their constituent species will lose out.
It is difficult to appreciate the scale of human population
increases over the last two centuries. Despite the horrendous combined mortality rates of
two World Wars, Hitler, Stalin, major flu pandemics and Aids, there has been no dampening
effect on rising population levels. In 1950, the world population was 2.4 billion. Just
over 50 years later, the world population has almost tripled, reaching 6.5 billion.
In the UK alone, the population increases by the equivalent
of a new city every year. Corresponding demands for a higher standard of living for all,
further exacerbates the problem. It has been estimated that if everyone in the world lived
at the UK standard of living (and why should people elsewhere be denied this right) then
we would either need another three worlds to supply the necessary resources or
alternatively, would need to reduce the world population to 2 billion.
The only possible conclusion is that unless human populations are
substantially reduced, it is inevitable that biodiversity will suffer further major
Some species are more vulnerable to extinction than others.
- Species at the top of food chains, such as large
Large carnivores usually require fairly extensive territories in order to provide them
with sufficient prey. As human populations increasingly encroach on wild areas and as
habitats shrink in extent, the number of carnivores which can be accommodated in the area
These animals may also pose a threat to people, as populations expand into wilder areas
inhabited by large carnivores. Protective measures, including elimination of offending
animals in the area, further reduces numbers.
- Endemic local species (species found only in one
geographical area) with a very limited distribution.
These are very vulnerable to local habitat disturbance or human development.
- Species with chronically small populations.
If populations become too small, then simply finding a mate, or interbreeding,
can become serious problems.
- Migratory species
Species which need suitable habitats to feed and rest in widely spaced locations (which
are often traditional and 'wired' into behaviour patterns) are very vulnerable to loss of
these 'way stations'.
- Species with exceptionally complex life
If completion of a particular lifecycle requires several different elements to be in place
at very specific times, then the species is vulnerable if there is disruption of any
single element in the cycle.
- Specialist species with very narrow
requirements such as a single specific food source, e.g. a particular plant species.
Loss of an individual species can have various different
effects on the remaining species in an ecosystem. These effects depend upon the how
important the species is in the ecosystem. Some species can be removed without apparent
effect, while removal of others may have enormous effects on the remaining species.
Species such as these are termed "keystone" species.
Why Conserve Biodiversity?
|Ecological ReasonsIndividual species and ecosystems have
evolved over millions of years into a complex interdependence. This can be viewed as being
akin to a vast jigsaw puzzle of inter-locking pieces. If you remove enough of the key
pieces on which the framework is based then the whole picture may be in danger of
collapsing. We have no idea how many key 'pieces' we can afford to lose before this might
happen, nor even in many cases, which are the key pieces. The ecological arguments for
conserving biodiversity are therefore based on the premise that we need to preserve
biodiversity in order to maintain our own life support systems.
||Two linked issues which are currently of great
ecological concern include world-wide deforestation and global climate change.
Forests not only harbour untold numbers of
different species, but also play a critical role in regulating climate. The destruction of
forest, particularly by burning, results in great increases in the amount of carbon in the
atmosphere. This happens for two reasons. Firstly, there is a great reduction in the
amount of carbon dioxide taken in by plants for photosynthesis and secondly, burning releases huge quantities of carbon dioxide
into the atmosphere. (The 1997 fires in Indonesias rain forests are said to have
added as much carbon to the atmosphere as all the coal, oil and gasoline burned that year
in western Europe.) This is significant because carbon dioxide is one of the main
greenhouse gases implicated in the current global warming trend.
|Average global temperatures have been showing a steadily increasing trend.
Snow and ice cover have decreased, deep ocean temperatures have increased and global sea
levels have risen by 100 - 200 mm over the last century. If current trends continue,
scientists predict that the earth could be on average 1oC
warmer by 2025 and 3oC warmer by 2100. These changes, while small, could have
drastic effects. As an example, average temperatures in the last Ice Age were only 5oC
colder than current temperatures. Rising sea levels which could drown many of our major cities,
extreme weather conditions resulting in drought, flooding and hurricanes, together with
changes in the distribution of disease-bearing organisms are all predicted effects of
Forests also affect rainfall patterns through
transpiration losses and protect the watershed of vast areas. Deforestation therefore
results in local changes in the amount and distribution of rainfall. It often also results
in erosion and loss of soil and often to flooding. Devastating flooding in many regions of
China over the past few years has been largely attributed to deforestation.
These are only some of the ecological effects of
deforestation. The effects described translate directly into economic effects on human
Environmental disasters such as floods, forest fires
and hurricanes indirectly or directly caused by human activities, all have dire economic
consequences for the regions afflicted. Clean-up bills can run into the billions, not to
mention the toll of human misery involved. Susceptible regions are often also in the
less-developed and poorer nations to begin with. Erosion and desertification, often as a
result of deforestation, reduce the ability of people to grow crops and to feed
themselves. This leads to economic dependence on other nations.
Non-sustainable extraction of resources (e.g.
hardwood timber) will eventually lead to the collapse of the industry involved, with all
the attendant economic losses. It should be noted that even if 'sustainable' methods are
used, for example when harvested forest areas are replanted, these areas are in no way an
ecological substitute for the established habitats which they have replaced.
Large-scale habitat and
biodiversity losses mean that species with potentially great economic importance may
become extinct before they are even discovered. The vast, largely untapped resource of
medicines and useful chemicals contained in wild species may disappear forever. The wealth
of species contained in tropical rain forests may harbour untold numbers of chemically or
medically useful species. Many marine species defend themselves chemically and this also
represents a rich potential source of new economically important medicines. Additionally,
the wild relatives of our cultivated crop plants provide an invaluable reservoir of
genetic material to aid in the production of new varieties of crops. If all these are
lost, then our crop plants also become more vulnerable to extinction.
There is an ecological caveat here of course.
Whenever a wild species is proved to be economically or socially useful, this
automatically translates into further loss of natural habitat. This arises either through
large-scale cultivation of the species concerned or its industrial production/ harvesting.
Both require space, inevitably provided at the expense of natural habitats.
Perhaps the rain forests and the seas should be allowed to keep
Do we have the right to decide which species
should survive and which should die out?
Do we have the right to cause a mass extinction?
Most people would instinctively answer 'No!'. However, we have to
realise that most biodiversity losses are now arising as a result of natural competition
between humans and all other species for limited space and resources.
If we want the luxury of ethics, we need to reduce our populations.
Most people would agree that areas of vegetation,
with all their attendant life forms, are inherently more attractive than burnt, scarred
landscapes, or acres of concrete and buildings. Who wouldn't prefer to see butterflies
dancing above coloured flowers, rather than an industrial complex belching smoke?
Human well-being is inextricably linked to the natural
world. In the western world, huge numbers of people confined to large urban areas derive
great pleasure from visiting the countryside. The ability to do so is regarded not so much
as a need, but as a right. National governments must therefore juggle the conflicting
requirements for more housing, industry and higher standards of living with demands for
countryside for recreational purposes.
Copyright 2003 Dr Barbara