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9.5 Introduced Species and the Australian Environment: 1. Survey of introduced species
Extract from Earth and Environmental Science Stage 6
Syllabus (Amended October 2002), © Board of Studies, NSW.
[Edit: 6Aug 08]
Prior Learning: Preliminary module 8.3.5 and 6.
Background: Australia has had a varied past when it comes to introduced species. Humans are the most invasive introduced species and have introduced plants and animals at an alarming rate, often to the detriment of native plants and animals.
process and analyse secondary information to define and identify introduced species.
- Perform a search of the Internet for introduced species
to Australia. One site you could begin with when looking for a definition
is listed below. To find Australian examples you should use a search engine
and use words like: introduced species Australia.
Here today, gone tomorrow
, Access Excellence, the National Health Museum, USA.
This site has a simulation for students. You may like to skip the simulation
and go to Student Handout And Procedure: Introduction to find some definitions.
- Process the information you gather by making
a judgement on the validity of the source of information you have gathered
and then compare the reliability of what you have gathered by checking it
with other reliable sources.
- Analyse the information obtained and decide on a list of species introduced to Australia. Rather than list every single species you found you might like to classify them as animals and plants, then group them again into types of animals, such as mammals, amphibians, fish and invertebrates. Keep your list to the best known and most harmful species.
define an introduced species as one that is not indigenous to a particular locality
- An introduced species is one that is not indigenous
to a particular locality.
- Introduced species may be “native” to the country but not to the locality or district. E.g. Acacia saligna (a wattle) is a native of Western Australia so is an introduced species to Sydney.
identify data sources, choose resources, plan and perform a first-hand investigation by visiting a local environment and identifying, classifying and accounting for the presence of non-indigenous flora and fauna
- In planning this investigation keep in mind the need to decide what information
to collect and how you are going to collect the information. Tracks, leaves,
and other traces can all be used as evidence of the presence of introduced
species.
- You will need to collect information on animals (fauna)
and plants (flora).
You could use photographs, videos and classification keys to identify plants, and tables to record statistical information.
- As animals are often elusive in the daytime scats (droppings) and tracks
may be your best evidence. To be able to identify the signs of animals, borrow
the book, Tracks, scats and other traces, a field guide to Australian
mammals by Barbara Triggs, (1996), from the library. Take the book with
you and refer to it when you find scats or tracks.
- Once you have made the plan for the investigation,
you should perform it. In your results you need to:
- identify the introduced species
- classify the species
- account for their presence in the area by giving reasons as to why or how the species may have arrived in this area.
Some information on Invasive
species can be found on Environment Australia’s website. Click on
feral animals or weeds to find more information.
A specific example of introduced species
on Kangaroo Island, South Australia is called Reimbursing
the Future : An evaluation of motivational, voluntary, price-based, property-right,
and regulatory incentives for the conservation of biodiversity PART 2 –
Appendices, Department of Environment and Heritage, Australian Government,
Biodiversity. Go to Edit, then Find on this page, to get the information on
‘weeds and feral animals’.
identify the criteria that can be used to classify introduced species.
Some criteria commonly used are:
- not found in the fossil record of the country
- brought to the country or district by people
- migrated to the district from other districts
- escaped from human control.
discuss examples of introduced aquatic or terrestrial plants or animals to identify:
- food, soil or nutrient requirements
- distribution
- levels of mediation by humans
Choose which plants and/or animals to investigate. You might choose one plant and one animal. Be sure that you include the three points listed above as you investigate the species.
Some examples of introduced species that could be considered are:
Example 1: Prickly Pear, Opuntia spp.
For a photo of prickly pear growing in Western Australia
click here
Flora Base, Western Australian Herbarium.
This plant was introduced in the early days of settlement from USA as an ornamental
plant. By 1925 it had covered 250 000 square km. It does well in low nutrient
soils and competes with other plants by crowding them out. It became so widespread
that farmers had to walk off their land as stock couldn’t graze. The
seeds are wind borne, so can spread quickly. This plant is terrestrial and
was brought here by humans but became widespread by natural seed dispersal. It
has now largely been brought under control by a caterpillar.
Example 2:Cane Toad, Bufo marinus
Information
on cane toads including photos and research by the CSIRO to try to get
rid of them.
Several were introduced in 1935 to Gordonvale, North Queensland from South America to control two species of cane beetle. They were not successful and the cane beetle was eventually controlled by an insecticide. The cane toad is insectivorous and so competes with local vertebrates for insects. However they will eat anything that moves and will fit into their mouths, including juvenile cane toads. They are poisonous to predators and have caused the death of snakes and other reptiles.
Cane toads lay large numbers of eggs and the eggs hatch more quickly than native amphibian species, giving them an advantage as tadpoles.
They have spread over much of Queensland, Northern Territory, and Northern NSW and entered Kakadu National Park in April, 2001.
The cane toad is terrestrial as adults and aquatic as tadpoles and although they were brought to Australia by humans, have since spread out over new areas naturally and accidentally by humans carrying them in vehicles.
discuss the reasons why different groups of people may have introduced plants and animals into the Australian environment
- Often people introduce species to make the new country
feel more like the country they came from. Sparrows, starlings and blackbirds
were released between 1850 and 1870 for these reasons.
- During the mid 1800s acclimatisation societies were
started to introduce hordes of species from silkworms to elands. Fortunately
most were unsuccessful.
- Many plants species were introduced because people
found them more attractive than native species.
- Some species were introduced to solve a problem (eg cane beetle infestation) but became the problem themselves( eg.cane toad).
discuss the reasons why different groups of people may have different opinions on the presence of an introduced organism as a pest
- Although introduced organisms are usually harmful
to the environment,they may have a benefit to a group of people or to particular
animals. One example is the water buffalo that was introduced to the Northern
Territory.
The Water Buffalo causes damage to wetlands by destroying the banks of streams and billabongs, stirring up the mud and hence reducing the possibility of aquatic plant growth, oxygen availability in the water and reduction in fish numbers and diversity.
Films such as Crocodile Dundee have popularised the Water Buffalo as a species to be seen when visiting the Northern Territory.
Many tourist parks offer the option of seeing Water Buffalo “in the wild” as well as in captivity. This provides jobs for locals and hence the eradication of Water Buffalo would be a difficult political proposition to win.
- Another introduced pest is the family cat. These animals,
when allowed to roam at night produce many kills during a month.
As the city spreads the concentration of these predators is so high that the neighbouring bushland has no hope of sustaining populations of small mammals or birds. This ravaging of the bushland continues despite the fact that the cat is fed by its owners.
Most cat owners say you can’t blame it for doing what is natural. They are blinded by their love for the animal.
Some local governments in Victoria are now proposing, and regulating, cat curfews to stop them being let out at night. It is at night when most of the damage is done.
gather, process and analyse secondary information to determine the reasons, location, time and mode of introduction of named introduced species
- Gather information by looking in encyclopaedias,
books and the Internet. A useful secondary source is the Commonwealth Government’s
Department of Environment and Heritage in Canberra.
One named introduced species could be the Rabbit. Department of Environment and Heritage, Canberra.
- The information gained should be summarised. You should determine the reasons for the introduction, and the events that led to the introduction of the named species (i.e. time, location, and mode of introduction).
A sample is shown below.
Rabbit
- The wild rabbit was released in Australia by Mr Thomas
Austin of Barwon Park, near Geelong, Victoria in 1859. Rabbits were taken
from Barwon Park and bred in other localities nearby.
- It was introduced so it could be hunted for sport.
- Few people foresaw the problems but a Mr Conner speaking
in a Victorian parliamentary debate ten years later said “ the rabbit
nuisance in this colony promises to be as great as that of the locusts in
Egypt”.
- By 1900 the rabbit had effectively covered all parts
of Australia except the tropics. Click here
to see a picture of rabbits at a water hole when they were in plague
proportions in South Australia. The lab, ABC Science
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