Human Impact

1. Stage 1 Biology
Ecology: Human Impact

2. Human Impact on Ecosystems
• There is no doubt that Humans as a species have
more of an impact on their natural environment than
any other species on Earth.
• The increase in the human population to current
levels of more than 6 billion is having an impact on
the biosphere like never before seen in history.
• The severity of human impact on ecosystems is a
result of three major activities:
– Clearing of natural habitat for
agriculture
– Industrialisation
– Urbanisation

3. Introduced Species
• In Australia, the introduction of new species disrupts
the natural ecosystem and sets limits to population
increase.
• Sometimes organisms are introduced to control
pests, for hunting or leisure purposes or ornamental
reasons.
• More often than not, these species do
more harm than good.
• Examples include:
– Cane toads, rabbits,
millipedes, prickly
pear

4. Land Degradation
• Misuse and overuse of the land results in land
degradation – by soil erosion, salting and the effects
of weeds, pests and pesticides.
• Land degradation is the decline in the condition of
the land as a result of this misuse of overuse.
• Australia has one of the worst problems of land
degradation in the world.
• It is estimated that more than half of
the land used for grazing or
growing crops in Australia is
in need of treatment for
degradation.

5. Degradation occurs in a number of ways:
• Clearing too much of the native vegetation,
planting crops in unsuitable areas and grazing of
too many sheep and cattle.
• With this clearing and irrigation, water tables rise,
along with dissolved salts causing increased
salinity in land and water areas.
• Introduced pests contribute.
• Pesticides cause “soil poisoning”.

6. Salinity
• Salinity is a major problem in some areas
of Australia and a form of land
degradation.
• It can be in the form of dryland salinity or salinity of
water systems.
• Dryland salinity affects a large area of land in
Southern Australia and is a direct result of clearing the
land of native vegetation.
• Australia’s soil naturally contains large amounts of
salt, which originally came from the oceans.
• Salt is blown over land, washed onto the shore and
builds up over time in water tables after moving
through the soil.

7. Areas shaded red are already
affected by dryland salinity
An area in Western
Australia affected

8. • Plants take up water from the soil & lose it from their
leaves through the process of transpiration.
• Salt is left behind but is normally harmless to plants as
it remains in the ground water well below the level their
roots can reach.
• However, when over-clearing of native plants such as
eucalypts occurs, the removal of water is decreased
and the level of the groundwater rises.
• As the water rises, it brings the salts to the surface as
well and the water then evaporates leaving the salt
behind.
• Plants struggle to survive in these salty
conditions & the decrease in plants
causes erosion of soil.

9. Pollution
• Pollution is defined as the act of
spoiling and poisoning any part of the
physical, chemical or biological
characteristics of the environment.
• This pollution may result from things
such as oil, chemical waste, nuclear waste, car
exhaust fumes and pesticides.
• Pollution is caused by humans and can harm the
health, survival or activities of living organisms.
• Both water pollution and air pollution are problems
for the Australian environment.

10. Water Pollution
• Water pollution includes releasing
pollutants into streams, rivers,
creeks, lakes and coastal waters.
• Water pollution causes problems such as the
death of organisms living in it and the health of
humans who drink it or swim in it.
• The most common forms of water pollution are:
• bacteria, protozoans and other micro-organisms
• suspended sediments from soil erosion
• toxins from chemicals used in industry and agriculture
• excess nutrients from run-off from farms and other
disturbed areas

11. Air Pollution
• In the past 200 years, human
activities such as industrialisation
and the development of technology have had an
increasing effect on the atmosphere.
• Air pollution is a result of increased land clearing
and industrialisation, burning of fossil fuels, and
aerosol propellants.
• Air pollutants include smoke, toxic chemicals,
photochemical smog.
• These pollutants produce acid rain and holes in the
ozone layer of the upper atmosphere.

12. Air Pollution

13. Greenhouse Gases & The Greenhouse
Effect
• The main greenhouse gas, carbon dioxide, absorbs
infra-red radiation.
• Atmospheric carbon dioxide acts like a thermal
blanket to keep the Earth warm.
• This is a natural process – without it, the Earth’s
surface temperature would be about ̶ 18°C.
• With industrialisation and the growth of the human
population, the release of carbon dioxide,
methane & other gases has increased.
• This may lead to major changes in
the biosphere.
• This is called the greenhouse effect
because of the way it works.

14. The “greenhouse” effect:
• The glass in a greenhouse lets light in, but once inside it is
degraded to heat which is trapped by the glass.
• This warms the greenhouse.

15. Climate Change & Global
Warming
• Carbon dioxide in the atmosphere traps heat & this
leads to global warming.
• Global warming is defined as an increase in the near
surface temperature of the Earth.
• Global warming has occurred in the distant past as a
result of natural influences however in recent times this
has become a more pressing problem.
• Increases in greenhouse gases caused by human
activities have caused global temperatures to
rise by approx 0.6°C over the last 100 years.
• Such an increase may result in the melting of
polar icecaps & raise sea levels
around the world.

16. A simple explanation:

17. Hunting and Poaching
• Humans hunters are different from other predators.
• Other predators do not drive their prey to extinction.
• As a prey species becomes rare, predators switch to
hunting an alternative food source or the predator
dwindles in number.
• Humans continue to hunt a species even after its
numbers have declined.
• Often the rarer the animal, the more
the catch is prized.
• Humans kill not only for food but
sport, financial gain and fear.

18. Humans as Hunters
• Skins are used for furs or leather, tusks
used for jewellery, plants & animals are
shipped around the world as house plants &
pets.
• Large animals are most vulnerable because they
require large territories and are not numerous.
• Large animals also compete with humans and can kill
livestock and people.
• Humans & the animals they have introduced
play a significant role in the
endangerment & extinction of animals
such as white rhinos, blue whales &
cheetahs.

19. Conservation – What Can We Do?
• Conservation involves the preservation & protection
of natural resources.
• Without human involvement in conservation
programs, many species of animals and plants are
in danger of becoming endangered or even lost
forever.
• We need to commit both nationally and globally to
limit the effects of hunting, habitat destruction,
industrialisation, pollution and climate change.
• There are many things you can do to help, such as
being energy efficient, donating money and time to
volunteer etc.

20. Why Save Species?
Aesthetic value:
• The simple pleasure of enjoying the living
record of biodiversity.
Ecological value:
• All species interact with one another including us.
• All organisms are linked & the loss of one could
affect many others.
Practical value:
• Plants provide us with food, shelter, fuel, medicines.
• Animals provide us with food, clothing, labour,
companionship etc.

21. Extinction
• When a species disappears forever, we
say that the species is extinct.
• Examples include the Dodo & Tasmanian tiger.
• The fossil record shows that species and groups of
species become extinct naturally.
• Since European settlers arrived in Australia, 21 birds
and 19 mammals have become extinct.
• Rate of extinction of birds &
mammals since 1900 is 1/yr.
• Many extinctions are caused by
the ignorance of people.

22. Endangered Species
• When a species is officially rated as endangered, it
means that the species is threatened with extinction.
• Species that are close to be endangered are rated as
vulnerable or threatened.
• Many species are endangered due to their habitats
being destroyed or due to hunting.
Giant Panda <1000 Cheetah <25,000 Leadbeater’s Possum

23. Captive Breeding Programs
• Some species that would otherwise be extinct by
now have been saved in this way.
• With successful captive breeding programs, animals
are sometimes able to be released back
into their natural habitat.
• Breeding in captivity also provides data
about reproductive behaviour that can be
applied in the conservation of species.
• Both Adelaide and Monarto zoos are
involved in captive breeding programs for
many endangered Australian animal
species.

24. Management
• Reserves & National parks:
– Governments put aside land for the
preservation of animals & plants
– Hunting of animals & collection of plants is banned.
– Domestic animals & plants excluded.
• Zoos
– Educate the public so they will want to help
– Conduct research
– Captive breeding & other programs
• Other programs
– University research (eg. tracking)
– Volunteers (eg. to help clean up areas)

25. International Cooperation
• Conservation is a world-wide problem that requires
global action:
• CITES (Convention on International Trade in
Endangered Species):
– Regulates international trade in wild species
– Lists species for which no permits are to be issued
for international trade
• WWF (World Wide Fund for nature):
– Raises money & teaches about endangered species
• World Heritage List
– Countries list their areas of natural
heritage which ensures their protection
eg. Great Barrier Reef.

26. If you’re interested…
http://www.wwf.org.au/
http://www.adelaidezoo.com.au/
http://whc.unesco.org/en/list
http://www.acfonline.org.au/default.asp