Biodiversity and Conservation
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 intergrade
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 are in virtually unexplored habitats such as
the deep sea and untouched rain forest areas. (Nineteen trees sampled in Panama were found
to contain 1,200 different beetle species alone!) 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 soil 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. However, species are now becoming extinct at a greater rate than at any previous
time in geological history, almost entirely as a direct result of human activities. In
former geological times, species which became extinct would have been replaced by new ones
evolving to fit the gaps left behind. In current times, this is in many cases impossible
because whole habitats have been lost.
of future species losses calculate that a quarter of all species on earth are likely to be
extinct, or on the way to extinction within 30 years. It has been predicted 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". In practice, these
figures are probably immaterial, as the ecosystems and processes sustaining life would
more than likely have collapsed long before such drastic losses were sustained. However,
it must be emphasized that these are only predictions, often based on computer models and
as such, also need to be taken with a pinch of salt.
Some species are more vulnerable to extinction than
others. These include:
- Species at the top of food chains, such as large
carnivores (e.g tigers).
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?
Individual 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 pieces, the whole
framework collapses. The more habitats and species that are lost, the greater the danger
of this total collapse becomes. The loss of
species in tropical ecosystems such as the rain forests, is extremely well-publicised and
worrying. 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. Escalating, unsustainable use of biological
resources worldwide, is leading to the total degeneration of the
planets life-support systems.
Nearly 80% of the worlds large areas of ancient forest have
been removed, much of it in the last three decades. Forests 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
||Forest destruction at present rates increases world
carbon emission by nearly 20%. This is significant because carbon dioxide is one of the
main greenhouse gases implicated in the current global warming trend. (Climate
|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, causing drought, flooding and hurricanes, and changes in the
distribution of disease-bearing organisms are all predicted effects.
Forests also affect rainfall patterns through transpiration losses
and protect the watershed of vast areas. Deforestation therefore results in decreases in
rainfall and changes in the pattern of its distribution. 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,
which may be 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, also 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 from forests
(e.g. hardwood timber) will also eventually lead to the collapse of the industry involved.
If sustainable methods are used, even when harvested areas are replanted, the resulting
areas are in no way a substitute for the forests which have been removed. These may have
taken thousands of years to develop into intricate systems containing myriad's of closely interdependent
species. Where trees are planted purely for harvesting, the ground layer and understory
layers of the original forest are discouraged by management. The new young trees will
support only a fraction of the original species which may have been there before. Rain
forest hardwoods take many years to grow to a commercially useful size and cannot be
quickly replaced. Nor can the extremely complex communities which they once supported.
General loss of biodiversity also means that species
which potentially have great economic and social importance may be lost 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.
When forests and other habitats are removed or
degraded, so are the local traditions and livelihoods based on those habitats. The
lifestyles, and in extreme cases, lives of people, may be severely threatened as a result.
The fisheries industry in Britain and other parts of the world is a good example.
Unsustainable international fishing practices, along with ill-advised legislation and
control have resulted in decimation of fish stocks. As a result, many traditional local
fishing industries are going out of business. In other regions such as the tropics,
forest-dwelling peoples with age-old traditions which allowed them to subsist off the
land, are being displaced by activities such as cattle ranching, logging, hydroelectric
power schemes, large scale farms and mining schemes. The question is, is it acceptable to
destroy lifestyles and traditions or to cause mass extinction's, in the pursuit of short
term economic gain?
The fate of the entire planet is now dependent upon a
single species. This is unprecedented in the Earths history.
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. 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