If a species can no longer be found
in the environment, through detailed
observation over many years it is said
to be extinct.
8 species an hour are estimated to be made
extinct around the globe.
Australian examples – Tasmanian tiger, desert
rat kangaroo, pig footed bandicoot, dwarf emu,
In Australia, European settlement has led to the
demise of several species, in the main due to:
1. the species required large land area
2. the species were restricted to a small
3. Special habitat requirements
4. Habitats were rare
Activities that impact on
• Climate change
• Introduced species
• Habitat clearance – agriculture or Urban
Due to changes in human lifestyle the biosphere has
increased pollutants which have an impact on the biodiversity
of the Earth.
Pesticides, fertilisers & detergents
In a lake, for example, pollution can cause havoc on the
ecological balance by stimulating plant growth and causing
the death of fish due to suffocation resulting from lack of
oxygen. The oxygen cycle will stop, and the polluted water will
also affect the animals dependant on the lake water.(WWF)
An introduced species is one that humans have
displaced and this impacts on the new habitat as it
competes with indigenous species for food and
Species introduced to Australia include:
Cats, rabbits, donkeys, camels, cane toads, salmon,
Weeping willow, blackberry, boxthorn, hops
The camel for example has been named as being
responsible for the introduction of 38 new plant
species to the desert.
Wild hops (see right)
were used as saddle bag
stuffing and is now rife
in south and central A.
The consequences of an introduced species are not
limited to the competition for food. They also include
Destruction of native vegetation
Removal of herbivores (prey)
Displacement of animals from shelters leading to lower
Restricting water flow
Excess nutrient removal from ecosystem
Removing of ecosystems such as rainforest can have
wide ranging impacts.
This is the practice of breeding and removing
organisms from an ecosystem eg over-fishing
Find out more about….
• Mercury in tuna
• Exxon valdez
• Ozone hole
The best way to preserve a species is to preserve its
The clearing of vegetation has led to increased
clearance and urban sprawl …the economic and
social policies of governments allow this to happen
with environmental consequences.
So what are the reasons to keep our native
• Species diversity
• Reduce weeds
• Sustain water table
• Maintain rainfalls
• Protect the soil (erosion/salinity)
• Reduce greenhouse gases
• Produce oxygen
• Reduce feral animals
Human population growth
Humans are estimated to have been around for a
million years and in that time the population has
grown to more than 6 billion.
The Earth is stressed by our need for resources and
energy. A person in a developing country uses less
than 8% of the energy consumption of a person in
the developed world.
• Fossil fuels -coal, oil and gas account for most of
our energy use.
• Land – already cultivate most of the land that can
be…>20% of worlds topsoil has been degraded in
• Water – Australians use 5 times the world average
water consumption per day.
Humans are not following the growth pattern of
other organisms. We have expanded our carrying
capacity through technology.
Rate of growth has slowed since 1960.