Contents

• What are Environmental Weeds?
• The Disaster of Prickly Pear
• The Victorian Catchment & Land Protection (CaLP) Act
• Noxious Weed Lists For Other States
• Other Environmental Weeds
• A Litany Of Horticultural Disasters
• The Cost of Environmental Weeds
• Sleeper Weeds
• Is there a place for exotic plants in our gardens?
• Alarming Report From Weeds CRC

What are Environmental Weeds?

            Indigenous plants are an integral part of the local ecosystem and there is a complex web of interactions between them, other indigenous plants, disease micro-organisms, mammals, birds and insects. As a result of the combined effects of these checks and balances long term take over bids by any one individual species is prevented.

            When you plant an exotic plant, or even an Australian native plant of distant origin, in that same ecosystem equivalent checks and balances on the species are very unlikely to be present. As a result it is possible for that species to mount a successful and prolonged take over bid of the ecosystem. 

            Environmental weeds behave in a very similar manor to human cancer cells so it is also appropriate to describe them as environmental cancer.

            As the environmental weed infiltrates the surrounding indigenous vegetation and spreads throughout it indigenous plant species are progressively lost until little else remains but the weed. Indigenous mammals, birds and insects soon become locally extinct as their food sources and preferred nesting sites etc disappear. They are often replaced by feral animals such as rabbits, foxes and rats.

            It is important to note here that the process of invasion by environmental weeds is aided by:

1. Land clearing

2. Soil disturbance, e.g. excavations

3. Dispersal of propagates (seeds, bulbs, rhizomes, stems, leaves) through:

   1. Mowing and slashing

   2. Earth moving

   3. Livestock & pets

   4. Wild animals

   5. Wind

   6. Water

   7. People - shoes & clothing

             This huge loss of biodiversity results in a greatly 'downsized' and simplified ecosystem that does not provide any where near the same level of 'ecosystem services'. Such an ecosystem has no where near the resilience of the original one. It is much more susceptible to continued degradation such as further weed invasion, salinity, erosion and loss of productivity.

              Once an ecosystem is degraded to this extent it requires huge amounts of effort and expense to halt the decline. It is rarely possible to restore the ecosystem to the same level of biodiversity, resilience and productivity.

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The Disaster of Prickly Pear

            Prickly pear (Opuntia) is in our history books as one of the most invasive weeds ever imported into Australia. It  had a devastating impact on life in rural eastern Australia during the early part of the 20th century. Special acts of Parliament were passed to enforce control measures in an attempt to halt its spread through Queensland and New South Wales. The story started over two hundred years ago.

Click here to read the full story on the North West Weeds website.

PPDC Inspector Jack Bailes standing in amongst a major common pear area - Scone 1938 (photo Norris J Small)

PPDC Inspector Alf Britton and large patch of rope pear - Cobar area 1938 (Photo NJ Small). Rope pear was a popular garden plant in dry areas...

The Victorian Catchment & Land Protection (CaLP) Act

            A subset of environmental weeds pose a major threat to agriculture, as well as the environment and biodiversity. Consequently the  CaLP Act declares these species as 'noxious weeds'.

          Landowners, whether private or public, have a statutory duty to control or eradicate noxious weeds from their property and/or road sides adjoining their properties.

            Here is the current list of declared noxious weeds for Victoria. For full details of these plants and the CaLP Act click here.

Noxious Weed Lists For Other States

• Northern Territory
• Tasmania
• New South Wales
• Western Australia
• South Australia (including feral animals)
• Queensland

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Other Environmental Weeds

             Environmental weed are only added to state noxious weed lists many years after their introduction when they are causing major problems for agriculture. Unfortunately by this time they have spread beyond any hope of eradication and the environmental damage is done.

             Worst still, some environmental weeds don't grow in major agricultural areas, and are unlikely to ever be added to the noxious weeds lists despite the devastating damage they do to our environment and our native flora and fauna.

             You may have heard the term 'sleeper weed'. This refers to exotic plants that are recognized as being potential environmental weeds within the conservation sector. Such plants may simply require sufficient time (perhaps decades) to be spread through retail distribution and garden escapes etc. Eventually these escaped populations reach a critical mass where reproduction and spread occurs rapidly.

            Awareness of environmental weeds is slowly growing within the general public and the nursery and landscaping sector, however change will not be fast enough to stop many hundreds or even thousands of new environmental weeds entering Australia. By the time we finally get serious about biosecurity we may have lost most of our native flora.

            Here is a list of environmental weeds in the Melbourne region as widely recognized by conservation workers and the environment departments of local councils. These are not yet declared as noxious weeds under the CaLP Act. Note the presence of popular garden plants in this list.

Weeds Australia and CRC Weed Management both provide control and ID information on a large range of environmental weeds across Australia. 

This list is of invasive or potentially invasive exotic and out of place Australian native plants that are a threat to Australian ecosystems and their biodiversity. Conservation groups strongly recommend that these species be immediately  withdrawn from sale and existing infestations eradicated. It is derived from a federal Department of Environment & Water study.

A Litany Of Horticultural Disasters

            Many of our current noxious weeds are former exotic ornamental plants from the 1800's and early 1900's. Examples include Cape Broom, Soursob, Paterson's Curse, Briar Rose, Hawthorn and European Gorse. Incredibly Cape Broom (from the Canary Islands) was named 'Plant of the Year' by the nursery industry in 1988. 

            In fact  the retail nursery and garden industry is responsible for the introduction of around 65% of environmental and noxious weeds to Australia. It continues to introduce large numbers of new exotic ornamental plants every year, many of which will become major environmental or noxious weeds at some point in the future. In so doing it is continuing to selfishly threaten the Australian environment, the agricultural sector and the economy.

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The Financial Cost of Environmental Weeds

            Local councils, Melbourne Water and Parks Victoria (among others) take environmental issues quite seriously in the current era of growing environmental awareness. All are continually undertaking erosion mitigation works and revegetation along water courses and in remnant indigenous flora reserves with the aims of restoring lost indigenous flora, preserving remaining indigenous flora, providing habitat corridors for indigenous fauna, improving water quality and fulfilling their statutory duties in regards to the CaLP act.

            Control and eradication of environmental weeds, including many not listed as noxious weeds in the CaLP act, is a major part of these environmental works. They cost the Australian economy around $500 million annually. 

            They also invade agricultural land reducing  productivity, increasing overheads when it becomes necessary to eradicate them and therefore increasing produce prices. It is estimated that they cost the wool, beef and wheat industries around $4 billion annually in lost production.

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Is there a place in our gardens for exotic plants?

            Of course there is a place in our gardens for exotic and alien Australian native plants. No one expects that everyone will have a 100% indigenous garden. But we do need to exercise a great deal more caution when selecting non-indigenous plants for our gardens.

            You can obtain excellent advice on which plants to use and which to avoid from the environment department of your local council. Many will also supply you with helpful brochures and leaflets. 

            Enviroweeds, Greening Australia, Landcare Groups, Department of Sustainability & Environment and 'Friends of' groups are other excellent sources of advice and information.

            There is little point in seeking advice from employees or proprietors of retail nurseries. Employees are more than likely unaware/uninterested in the issue of environmental weeds. Proprietors have an obvious vested interest in selling you their plants and are unlikely to give you advice that is might dissuade you from doing so.

            If there is any doubt in your mind about the plants weed potential then give it a miss and choose an indigenous plant instead. If you absolutely must have a risky exotic or Australian native plant then be responsible for it and take all necessary measures to prevent it from spreading outside your garden. Again, if that is beyond your capabilities to contain the plant then give it a miss and select an appropriate indigenous plant instead.

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Alarming Report From Weeds CRC

GARDEN PLANTS THREAT TO NATIVE SPECIES

More than 400 of Australia's threatened species of plants and animals are at risk of extinction from weeds.

The recently released 2006 State of the Environment (SoE) Report has highlighted the major threat posed by introduced plants to Australian fauna and flora, and lists a range of native species directly threatened by invasive plants.

It follows hot on the heels of Australia's first-ever report quantifying the impact of alien plants on Australian biodiversity, produced by the CRC for Australian Weed Management. That report found invasive plants are the biggest threat to the survival of native species after land clearing.

The Weeds CRC study also implicates Australian householders directly in the loss of native species, pointing out that two thirds of the most damaging plants entered the country as ornamentals and escaped from parks and private gardens.

Among the native plants and animals directly threatened by weeds, the 2006 SoE Report lists:

1) The mountain pygmy possum in NSW and Victoria.

2) The tussock skink in Tasmania.

3) Spiked rice flower and hairy quandong in NSW.

4) The spider orchid in SA.

5) The Richmond birdwing butterfly in Queensland and NSW.

6) The wing-fruited lasiopetalum in WA.

7) The button wrinklewort in ACT and NSW.

"We've always strongly suspected weeds were a factor in the decline and loss of native species, but until our research was completed there was no clear confirmation," the CEO of the Weeds CRC, Dr Rachel McFadyen says.  

The CRC study, by Aaron Coutts-Smith and Paul Downey of the NSW Department of Conservation and Environment and commissioned by the Weeds CRC, looked at the threats to 945 threatened species, populations and ecological communities, and concluded invasive plants were a major factor affecting 419 of them. These included 279 native plants and 62 native animals.  

They found that the main threats came from 127 invasive plants, of which the worst were lantana, bitou bush, blackberries, kikuyu and Scotch broom.

Of these 127 invaders, 82 gained their foothold in the Australian environment after escaping from parks, gardens and ornamental collections. Between them, these 'garden escapes' threaten at least 190 native species in NSW alone and maybe as many as 300.

Fifty-six of these 'killer weeds' are still available for sale in garden centres across Australia, despite the fact they have previously been identified as highly invasive.

"This study, more than any yet, highlights the responsibility of the home gardener and the garden centre in helping to protect our native species from extinction due to an alien plant invasion," Dr McFadyen says.

"Many of these plants look beautiful - and harmless - in a small pot. But when they get loose in the landscape they cause havoc, strangling and smothering native vegetation and depriving our native birds and animals of their main sources of food."

Since European settlement an estimated 27,000 plant species have been introduced into Australia - almost twice as many as existed here before.

Three thousand of these have adapted well to the Australian landscape and are now 'naturalised - i.e. they successfully reproduce in the wild.

Dr McFadyen says both reports are a big wake up call to all Australians to take greater responsibility for the survival of our native landscapes, and its fauna and flora.

"This is a problem we can all do something about," she says. "We need to become educated consumers of plants. Before we buy a plant at the garden centre or market we should first check whether it has a record for invasiveness, no matter how pretty it looks.

"Garden centre staff need to become the local experts in invasive plants", says Dr McFadyen. "They have a brilliant opportunity to become part of the solution."

"And we must take the greatest care in disposing of all plants and plant material from our gardens, in case it contains weed seeds or has the ability to regenerate.

"If we truly want our grandchildren to see a genuine Australian landscape in the future, we have to act now to stem this continuing invasion."

Dr McFadyen warns there is a particular threat in the trendy decorative grasses and succulents which are now being planted in low-water-use gardens. They are naturally tough, and many are highly invasive in both agricultural and natural landscapes.

The Weeds CRC, which has been Australia's leading scientific research centre in invasive plants and warned consistently of the importance and scale of the problem, has been told by the federal Government it will close as a CRC in 2008. Dr McFadyen says they are actively seeking other ways to keep this important work going.

More information

Dr Rachel McFadyen, CEO, Weeds CRC, 0409 263 817

Peter Martin, Weeds CRC, 0429 830 366

Full report: www.weeds.crc.org.au/documents/tech_series_11.pdf

Summary: www.weeds.crc.org.au/documents/tech_series_11_summary.pdf

SoE Report:

www.deh.gov.au/soe/2006/publications/drs/indicator/489/index.html

Images

Images of weeds and the threatened species mentioned above are available

at www.weeds.crc.org.au/publications/media.html

--

Kelly Nankivell (nee Scott)

Office Manager

CRC for Australian Weed Management

PMB 1, Waite Campus

Glen Osmond  SA  5064

Ph    : +61 8 8303 6692

Fax   : +61 8 8303 7311

e-mail: Kelly.Scott@adelaide.edu.au

www.weeds.crc.org.au

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