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Human impact

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humans and ecosystems

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Human impact

  1. 1. Human Impact Way of the dodo?
  2. 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. 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. 4. Activities that impact on communities • Mining • Forestry • Climate change • Pollution • Introduced species • Habitat clearance – agriculture or Urban development
  5. 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. 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. 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. 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. 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. 10. Find out more about…. • DDT • Mercury in tuna • Exxon valdez • Ozone hole • Eutrophication • Fracking
  11. 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. 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. 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. 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. 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.
  16. 16. Typical bacterial growth profile

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