THE AUSTRALIAN SITUATION
Ed Lonnon’s Endangered Species Homepage
http://home.swiftdsl.com.au/~endangered/discuss.htm
More than thirty percent of all recorded mammal extinctions in Australia
occurred between about 1800 and the present. It is generally accepted that 20
species are extinct and many more greatly reduced in numbers and range,
sometimes with only tiny surviving populations.
Mammals have been chosen for the purposes of illustration in this note because
of the severity of the situation with these taxa. It must be pointed out, however,
that there are similar problems with some species of all other vertebrate taxa of
Australian fauna. There are, of course similar issues of preservation and
conservation of invertebrate fauna, and this fauna is a most important
component of the total biodiversity of Australia because of the huge number of
species involved, relative to vertebrates.
The precise causes of the extinction of most Australian mammal species is open
to some debate. Europeans brought many changes to the country including new
species which were competitive with or predatory upon the native wildlife.
In recent years, through the use of modern radio-tracking equipment on captive
bred animals of threatened species released into the wild, it has become clear that
introduced predators, and particularly foxes, are capable of wiping out a small
group of a susceptible species in a matter of a few weeks.
Effective methods of predator control over most of the continent are imperative if
endangered species are to survive in the wild. This is proving to be a difficult
problem.
The Australian wildlife conservation agencies, the IUCN and the statutory zoos
have been working in collaboration to develop "action plans" for the preservation
/ conservation of rare and endangered native fauna. These plans involve
relocating selected species to facilities in which they can be kept in open range
but captive conditions, free of exotic predators, introduced diseases and
competitors, where they can increase in numbers under careful management and
be the subjects of sound studies, the results of which can assist in their long term
future.
The decline in biodiversity in Australia is serious. Because the country was first
occupied by Europeans in only 1788, and the biota was subject to relatively
intense scientific study during the past two centuries, the decline is well
documented.
The most severely depleted taxa are mammals in the weight range of 35-5500
grams. Many of these species have lost more than 80% of their original ranges
and most are extinct in the semi-arid and arid parts of the mainland. Habitat loss
and introduced predators and competitors have been the major threats to these
animals. About 14.4 percent of Australia's known 15,638 vascular plants are
listed as threatened by IUCN.
LOSS OF WILDLIFE HABITAT
On a global basis, habitat destruction is the cause of most extinctions. Loss of
terrestrial wildlife habitat is massive and is increasing. Tropical moist forests in
particular have been, or are being, greatly impacted. These forests support an
extraordinarily diverse biota and are being cleared at a very rapid rate. Citing
several IUCN and United Nations sources, McNeely et al (1990) acknowledged
the lack of precision in the estimates of contemporary rates of clearing of such
forests, but conclude that this rate is likely to be at or above 0.6% per year. They
further concluded that about 65% of wildlife habitats in Sub-Saharan Africa and
Tropical Asia had been lost by 1990.
These levels are clearly not sustainable. Their impacts are not only on
biodiversity, but also on global climate, rates of soil loss, fresh-water and marine
pollution and ultimately on the capacity of the planet to produce food, fibre and
fuel for humans.
THE IMPACT OF THE HUMAN POPULATION
The increase in recent extinction rates is related to human population size and
the exploitation of natural resources. The rate of human population growth has
been extraordinary. It has been estimated that, in 1 AD, the global human
population was about 150 million, concentrated on the coastal fringes ofEast
Asia, India and the Mediterranean. The population did not double to 300 million
until 1350, but by 1950 there were 2.4 billion and in 1985 there were 5 billion
(Tanton 1994).
This population and its activities has had dramatic impacts on biodiversity and
natural ecosystems. Diamond (1992), indicated some of the more dramatic
ecological impacts of a large and increasing population size:
"At present, humans are commandeering 40 percent of all the biological energy fixed
from sunlight on the planet, either by eating, clearing the land, or grazing their animals
on it. The human population is doubling every 40 years, so in 40 years from now - 2032
-we will be commandeering nearly 80 percent of all the energy from sunlight that is fixed
by biological systems. By 2050 we will be using 100 percent, and we will be fighting
each other in dead earnest. "
The assumptions implicit in the statement above are rather broad and open to
challenge, specifically in relation to timeframe. In reality, this does not matter
much - we humans are consuming the resources on which we depend at rates
which are unsustainable in the medium term and those rates are increasing as
the global population grows and strives for a better material quality of life.
Recent trends in wildlife extinctions are valuable examples of what could happen
to humans and which could happen rapidly and soon. Species at the highest
trophic levels in an ecosystem are those most severely affected by breakdown of
the ecological processes that drive the system.
Humans are right at the top of a very complex suite of ecosystems, many of
which have been greatly changed. One of the few physical type principles in
ecology is that a stable ecosystem displaced from stability will oscillate violently
until it finds a new stability. Because of the complexity of ecosystems and their
driving processes, the nature of new equilibria are very difficult to predict, as are
the losses sustained along the way from the old to the new stabilities.
I would not like to see humankind go into a dramatic decline, with all the strife
and suffering that will attend such a decline, because of failure to heed the
obvious lessons of the past and the physical, sociological and ecological
knowledge now available. We are, however, heading inexorably in that
direction.