humans and ecosystems

1. Human Impact
Way of the dodo?

2. Extinction
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,
paradise parrot.

3. Why?
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
geographical location
3. Special habitat requirements
4. Habitats were rare

4. Activities that impact on
communities
• Mining
• Forestry
• Climate change
• Pollution
• Introduced species
• Habitat clearance – agriculture or Urban
development

5. Pollution
Due to changes in human lifestyle the biosphere has
increased pollutants which have an impact on the biodiversity
of the Earth.
Sewage
Pesticides, fertilisers & detergents
Acid rain
CFCs
Heavy metals
Radioactive waste
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)

6. Introduced Species
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
shelter.
Species introduced to Australia include:
Cats, rabbits, donkeys, camels, cane toads, salmon,
Weeping willow, blackberry, boxthorn, hops

7. Consequences…
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.

8. 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
reproductive rates
Restricting water flow
Excess nutrient removal from ecosystem

9. Habitat clearance
Removing of ecosystems such as rainforest can have
wide ranging impacts.
Harvesting
This is the practice of breeding and removing
organisms from an ecosystem eg over-fishing
or dredging.

10. Find out more about….
• DDT
• Mercury in tuna
• Exxon valdez
• Ozone hole
• Eutrophication
• Fracking

11. Preservation
The best way to preserve a species is to preserve its
habitat.
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
vegetation?

12. Reasons include:
• Species diversity
• Reduce weeds
• Sustain water table
• Maintain rainfalls
• Protect the soil (erosion/salinity)
• Reduce greenhouse gases
• Produce oxygen
• Reduce feral animals

13. 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.

14. Some impacts:
• 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
last 70years.
• Water – Australians use 5 times the world average
water consumption per day.
• biodiversity

15. Exponential growth
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.

17. Typical bacterial growth profile