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Biodiversity
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Biodiversity is the number and variety of plant and animal species that exist in a particular area, or in the world. It is the variety of life forms, the different plants, animals and microorganisms, the genes they contain, and the ecological systems they form. It includes diversity within species, between species, and among
ecosystems.
Plant and animal diversity depends on climate, soils, altitude, and the presence of other
species.
Biodiversity is constantly changing, and is increased by new genetic variations, or reduced by habitat degradation and extinctions.
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Biodiversity is the key requirement for healthy and functioning
ecosystems.
An ecosystems consists of all plants, animals and micro-organisms in an area functioning together, with all of the non-living physical factors of the
environment. A healthy ecosystem includes large numbers of highly-developed symbiotic, or complementary relationships between
and among species, often formed over many thousands, or hundreds and thousands of years.
Our natural environment, consists of many ecosystems, creating the life support systems of our planet. Our natural environment provide us with food, clothes, medicine, fuel, timber, crop pollination, water purification, soil regeneration, nutrient recycling, and waste re-circulation.
Plants create oxygen for the atmosphere, and can regulate local
climatic conditions, as well as regulate hydrological movement
within the soil and along river courses.
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One of the many symbiotic relationships between plants and animals in Sydney, is between the ants and acacia (wattle) trees. The fruit of the Acacia
trees (including Acacia decurrens, Acacia falcata, Acacia longifolia,
Acacia parramattensis, Acacia pubescens, and Acacia stricta) is a straight legume
or seed pod. Multiple hard-coated seeds are contained within its fruits. On the outside of the seed, there is a protein-rich, white-orange appendage, called an aril. These arils attract Sugar ants (Camponotus species), who take the seeds back to their
nests. The ants feed the arils to their young.
The tree benefits from this relationship, because the ants bury the acacia seed beneath the soil in their ants nest. When a bushfire comes, the acacia seed is not destroyed, but is buried just deep enough for its hard coating to be opened by the heat of the bushfire. After the fires have passed, and new rains come, acacia seedlings can often be seen germinating from old ants' nests. The new trees will then provide future food for the ant colonies.
This symbiotic relationship highlights the importance of maintaining the integrity of ecological systems, and how the ant and the tree provide for each other, and aid each other's continued existence.
An Acacia falcata seed pod, showing the
protein-rich, white-orange aril around the seed.
The acacia tree also enjoys a symbiotic relationship with Rhizobium bacteria.
The bacteria form nodules on the roots of the acacia tree, and fixes nitrogen to the soil.
As another example, we say that ants and birds in an ecosystem, have a "complementary" rather than symbiotic relationship. The birds prey on the ants as a food source. If the ant population increases, then the bird population will also increase. If the ant population decreases, then the bird population will also decrease.
If we plant many acacia trees, then we can expect to increase both
the ant population and the bird population. Farmers who have planted many acacia trees,
also report that echidnas will come to the area looking to feed off
the ants.
Although we might find some thousands of plant species at our local nursery, we would not call a nursery a highly
biodiverse area. The plants in a nursery have no highly-developed symbiotic or complementary relationships.
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Land clearing, loss of habitat, loss of food sources, pollution, foreign
species plants and animals all contribute to the degradation of biodiversity.
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No. Introducing foreign plants or weeds increases the number of plants in
an area, but degrades the ecological system, and biodiversity. This is because there are no highly-developed symbiotic, or complementary relationships between the foreign species, and local species. The introduction of
foreign species plants simply introduces a new competitor to the environment, and
commonly removes habitat or food sources for local
(animal) species. Often the foreign plant has no natural predator to
limit its expansion.
For example, the planting of the Northern Hemisphere willow tree (Salix species) along Duck River has in past years fouled the river course. The willow tree's roots form a thick reddish matting which clogs the side of the river bed, destroying the habitat for yabbies and native fish.
It also strangles the growth of juncus sedges at the river edge,
resulting in loss of habitat for frogs. The foreign willow tree has no symbiotic relationships with the
local insects. Its presence displaces local trees, and it adversely affects all native creatures further up the food chain, such as
birds, possums, bats and other marsupials.
The only significant benefits the willow tree provides, is to
reduce erosion on the river banks, as well as providing considerable
shade and cooling with its deciduous leaves in summer.
However, an indigenous tree could provide these benefits too, if it
had been selected at the time of planting.
Jet-setting humans are now dispersing plant and animal genes to all parts of the world. This rapid mixing of plants and animals in the past 60 years, is causing major extinctions and degradations of many ecological systems. In the longer term, this new mixing of world gene stock will
create vast new varieties of plants and animals in the next million years or
so, just like the Cretaceous geological period of 70 million years
ago, when the flower petals of angiosperms co-evolved with insects.
Symbiotic,
complementary and co-evolutionary relationships will eventually establish themselves and a
whole new ecological balance will form. Who knows what amazing new and varied
life forms will evolve after the huge intermixing of biological and
botanical species that is occurring with modern aircraft ?! Unfortunately, we will not be around to see this, and nor will our children, and nor our grandchildren !
What are weeds ? Weeds are plants that are growing in the wrong
place. To environmentalists, plants that are not indigenous to an
area, are weeds. Some people say that weeds (1) could be an extremely valuable ally to
humans in the fight against against global warming. They grow very
quickly, and can contribute to oxygen production. Some people suggest (2)
that if weeds are allowed to grow, and are then slashed, the weed
mulch can quickly add considerable fertility to the ground, through
their decomposition, perhaps more so than slower growing indigenous
plants. Some say (3) the presence of weed vegetation
can also help provide a cooling air-conditioning effect to land,
that will reduce evaporation of moisture from the soil. Retaining
moisture in the soil helps retain soil microbial activities, which
generally work symbiotically with plant roots. Some say that (4)
weeds might grow better in any area, because the soil might be too
salty, or too degraded, or too dry, or too polluted for native
plants. Weeds, and especially Northern Hemisphere plants, can grow very
quickly in Australia, when water is present. A sensible appraisal needs to
be made when selecting any plants.
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The survival of plants and animals are linked together through symbiotic or
complementary relationships cultivated over many hundreds of
thousands of years. Many plants require
specific insects or animals to pollinate them, and many animals rely on
particular plants for their diet. The best way to conserve biodiversity, is to retain and
maintain the environment
and habitat, which sustains the original variability of living
organisms. Keeping the indigenous or endemic plants of your botanical
provenance, is the best way for us to sustain the habitat and
environment for our indigenous animals.
However, if
soils have been poisoned through toxic pollution, or if land cleared of
trees has already resulted in rising salinity, or if changes in the
weather pattern occur, indigenous plants may no longer survive in the
area, and foreign or non-indigenous plants may need to be selected. The survival of indigenous
animals without indigenous plants in such areas, is less likely.
While we encourage local students and people to look after the plants of the Duck River botanical provenance, we hope students of all other botanical provenances round the world will look after their own heritage. This means that the students of Penrith, or Hornsby, or indeed New Zealand, Indonesia, or any other area, each have a small, but different part of the world's species to look after.
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When European settlers arrived to Australia, they knew nothing about the indigenous Australian plants. There was little dialogue with the aborigines. So they brought and grew the plants that they knew about from overseas, both for food, for flowers, and for other agricultural products.
These foreign plants have been essential for our survival, and have
been of great economic value to Australia.
However, if you walk around Auburn, Granville, Berala or Regents
Park today, you will find that most people do not even have one
indigenous plant species in their garden. Most people will say they do
not know, nor care about where their plants come from. Many will say
that our modern gardens with totally foreign plants look very
pretty. Some claim that Australian plants do not produce big enough
flowers. Most people tend to follow their parent's choice of plants,
or the plants they grew up with, when they were young.
So the plants brought and cultivated here from overseas, by all cultures of migrants, have now substantially displaced local plants, and reduced the food supplies for many native animals. This is how some 30% of Australian mammal species have become extinct, and why only 5% of Australia's indigenous vegetation remains intact, after just 230 years…
In past times, Duck River was a source of drinking water and food
for local aborigines, but has since been extensively modified.
Sydney Water considers that Duck River exists purely to function as
our storm-water drain during rain periods. Local Council planning is
for the watercourse also to exist as a wildlife corridor, or passive
recreation corridor. Many community groups have barbecues at the
Auburn Botanic Gardens area, and do enjoy the ambience.
There are five reasons why we would choose to retain Auburn's
indigenous plant species at Duck River (and even around our own
homes!);
1. If we retain and use indigenous vegetation, we will be able to maintain the food sources and
habitat for indigenous animals, and thereby retain biodiversity, and the symbiotic animal and plant relationships developed over the past hundreds of thousands of years. We will be able to retain and enhance our bird-life and marine life along the river.
Duck River is one of the few areas left in the whole community,
where this is allowed to happen.
2. Indigenous vegetation is adapted to the local soils and climate,
(except where the soil has been degraded or polluted) and therefore requires minimum extra maintenance after establishment. It does not require modification
of the soil profile, extra manure, or extra fertilizers, and is
therefore the cheapest cost to the local Council and community.
3. There are huge scientific and common knowledge gaps about Australian plants. Australian plants have many unusual adaptions, both to salinity, and drought conditions, which may yet be of significance to humans globally. Wouldn't it be more prudent to retain and investigate our heritage, rather than simply destroying and replacing it all with foreign or non-indigenous plants?
4. Australia is a unique continent of almost a million species of plants and animals that are found no where else in the world. While
many Australians have no knowledge, connection, or interest in
the unique botanical and biological Duck River heritage, it is quite possible that future generations will not feel the same
indifference. For these reasons, we should try to preserve the indigenous biodiversity of the area for future generations, and be proud of our national
heritage.
5. Australian plants are beautiful !
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