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Proposed regional environmental weed management strategy (more detail)
These articles are extracts that are totally verbatim in many places, and are all derived from text by Carr, Yugovic and Robinson, 1992.
The full text forms another more detailed part of our full weed strategy but text is not included here.
Very extensive research was carried out for the State of Victoria to produce their publication. We are unaware of any similar information for North Queensland, but the principles are almost certainly very similar.
- Agricultural & environmental weeds, weed origin, hybridisation
- How were weed species introduced
- "Experts" deliberately recommend seriously weedy species
- what areas are free from environmental weeds, are they secure
- monitoring, local Government, botanical consultants
- conservation groups,and public pressure
Introduction:back to weeds main page
Environmental weeds are plants that invade native vegetation, usually adversely affecting regeneration and survival of the indigenous flora and fauna.
Weed invasions pose one of the most serious nature conservation problems. They contribute to the global conservation crisis of natural vegetation loss and degradation caused by increasing human activity. Vast areas of Australia are threatened by weed invasions, this is especially evident in Northern Australia.
Without appropriate management, gross alteration of vegetation will occur in many, if not all areas. A spectacular demonstration of this occurs on a National Park mountain range near Geelong, Victoria, where indigenous vegetation has been substantially eliminated by invasions of the tall shrub Boneseed Chrysanthemoides monilifera and Bridal Veil Creeper Myrsiphyllum asparagoides and numerous exotic grasses, over a period of 25 years. (..35 years ago I frequently rockclimbed here, and am keenly disappointed. This area is similar in size and height to Townsville's Mt. Stuart) However preventative action can be taken to avert such losses.
Adverse effects of environmental weeds on animal and animal communities have only recently received attention, but similar conservation impacts are apparent as for indigenous vegetation. Animals may be affected directly and indirectly, and complex interactions with native and exotic plant and animal species can be involved. Negative and positive (at least in the short term) effects of environmental weeds on native animals in Australia have been documented. Changes in ecosystem function or structure may adversely affect some species and favour others, but in the long term massive ecosystem disruption and animal extinction seem inevitable.
Agricultural and environmental weeds are discussed, weed origin, hybridisation:
Many exotic plant species are considered weeds of undesirable species depending on perceptions and the context under consideration. Three categories are particularly recognised:
- weeds of agricultural land
- ruderal weeds of waste places
- environmental weeds that invade natural vegetation
These categories are not mutually exclusive, and many species may be placed in more than one category. Agricultural and weeds of waste places (urban/mining revegetation... Ed)are the major preoccupation of weed scientists and weed management endeavours. These largely include the proclaimed noxious weeds of agriculture. Of the 120 proclaimed species for Victoria, 64 are also classified as environmental weeds.
While agricultural weeds have received considerable research attention over the years, environmental weeds have largely been overlooked (with a couple of exceptions).
Environmental weeds are defined for this series of articles as exotic plants that invade native vegetation, usually adversely affecting the survival of the indigenous flora. Distinguishing these by origin:
- Species introduced from overseas
- Native species from other states of Australia
- Species native to the state but where outside their pre European distribution.
(note, all these are considered "exotic" in this series of articles)
Another category of problem plant is ecologically out of balance species that behave as weeds in vegetation in which they are a natural component. Such species, although sometimes highly problematic, are generally not included in this discussion.
An additional, but potentially important invasion problem is caused by invading genes, rather than species. This is brought about by the hybridisation between in situ indigenous plant species and an exotic member of the genus which has been deliberately introduced. Serious genetic swamping problems have arisen for populations of some plant species, especially for regionally rare plants. Genera for which hybridism of this kind has been reported include: Acacia, Correa, Grevillea, Leptospermum and Pittosporum.
Environmental weeds in Victoria comprise 48 % of the states exotic flora, and 28 % of Victorian flora.
How were environmental weed species introduced. What potential for more.
Accidental introduction of species can be accomplished in various ways e.g. with livestock, as contaminants of grain and other products, and in ballast and soils.
Deliberate introduction is of the most concern for environmental weed management, as well as for the prediction of the future or potential weed concern. In Victoria 65-70 % of naturalised exotic species have been introduced deliberately for ornament (most species) or utility.
The nursery industry and the rural advice industry (producing literature relating to land management) have played a concerning role as introducers and promoters of environmental weeds, especially regarding the establishment and spread of new weeds. Of the 548 environmental weeds listed for Victoria, 43% are known to be commercially available. While some of these have economic importance, E.G. Pinus radiata Monterey Pine, the majority are horticultural ornamentals for which non-invasive alternatives are readily available.
Many agricultural scientists in the public and private sectors are currently involved in plant introductions for agricultural purposes, with unknown, but potentially serious consequences. Examples include the importation of 450 herbaceous species for trial on land affected by secondary salinisation in WA (1971) and the importation of 331 species of grasses into WA potentially for use as fodder (1979). Such species will ideally behave as weeds, as intended by their importers. Unfortunately they are often successful.
A related problem is the genetic 'improvement' of existing environmental weed species to increase their ecological amplitude (such as drought hardiness) or palatability (such as the seriously weedy Toowoomba Canary-grass Phalaris aquatica, and African Love-grass, Eragrostis curvula.)
Thousands of Australian plant species are cultivated in Victoria and many of these are likely to become naturalised in the future. The ease with which Australian species become naturalised is well illustrated at Anglesea, where 36 of a total of 45 planted species from 2 plantations were present as escapes in adjacent heathland and heathy woodland. These species threaten nationally significant vegetation in the area. Another case of spectacularly successful naturalisation of Australian species at Mt. Martha Park on the Mornington Penninsula. Here 40 (35 %) from a total of 113 planted species have become naturalised. Many threaten the indigenous vegetation of the reserve.
"Experts" recommending seriously weedy species, exotic "native plant" environmental weeds; what areas are free from environmental weeds, are they secure?
The use or advocacy of exotic species to stabilise soils is a problem where species become invasive rather than simply persistent. Species recommendations (1980) listed 153 plants for erosion protection in Victoria, of which 50 are environmental weeds. Another 10 species (1985) that were advocated for coastal situations are mostly seriously or very seriously weedy.
Of 584 environmental weed species listed for the state of Victoria, 50 (9 %) are native to Australia. And 22 (4 %) are native to Victoria. These have been spread beyond their natural range by human agency. One of the most damaging that originated from within Victoria is Sweet Pittosporum Pittosporum undulatum (... Note by an editor... Gray haired little old ladies from community revegetation projects actually go out and serepticiously poison Pittosporum street trees to reduce their seedling removal work. I have personally noticed that this plant has self sown and is grown to at least large shrub size in at least 25% of Melbourne gardens in several areas... well conservatively say 10% ..., people don't think it looks like a weed. Indeed virtually all will argue that it should be left growing in their garden, councils do not remove their Pittosporum street trees. Of course it is rampant in Melbourne's native bushland remnants)
The bulk of environmental weeds have not fully occupied the available habitat and are enlarging their range. Some extensive and remote areas of Victoria remain free of environmental weeds. However even in such remote localities, disturbed roadsides and streamlines provide a network of source areas in which many weeds are abundant. Another study of heath and heath woodland on low nutrient soils close to highly populated areas at Anglesea found a very low overall percentage of exotic species, and many sites were free of exotics. Many small patches of native vegetation close to developed areas currently remains in moderate to good condition, depending on site characteristics and management history. Such remnants are not necessarily stable , and almost always experience weed invasion along boundaries.
Monitoring, the role of local Government, conservation groups, botanical consultants, and public pressure in the control of environmental weeds.
Monitoring is an essential part of vegetation management, and is particularly relevant to weed control. Early action forms the basis of effective weed management. (e.g.Balloon Cotton Bush on Mt. Stuart summit). Large populations build up at a variable rate, and become intractable problems. Perhaps the invading species is only perceived to be a problem when the population reaches a critical size. Management agencies often only tackle the problem after the population explosion.
Unfortunately little of the literature produced mainly by botanical consultants dealing with environmental weed invasions and their management in Victoria has been disseminated. They should be encouraged to publish work on environmental weeds. For this to occur financial incentives will probably be necessary. This has hindered both the recognition of, and the management of environmental weed problems.
A small number of councils, mostly in the Melbourne area of Victoria, have developed local conservation strategies to provide broad directions in managing local resources. All too often local government awareness of environmental weeds, vegetation management skills, and resource allocations are limited. Particularly when early eradication or control of a developing infestation is critical, the urgency for action is often unappreciated.
Funding of reserve management by local government is very small relative to overall expenditure on the maintenance of parks, gardens and street plantings. The low priority given to indigenous vegetation management is at odds with the large and growing public interest in local conservation.
The community currently plays a major role in managing environmental weeds, not only in a practical sense, but also through influencing management agencies in terms of priority setting and resource allocation. There are currently more than 100 Friends of parks and friends of flora and fauna groups in Victoria. There are also several hundred local conservation groups in Victoria.
Governments are responsive to community attitudes and pressures. State, national and to a lesser extent local conservation organisations, are not sufficiently aware of environmental weeds and their conservation implications. So fail to lobby effectively for environmental weed management. Such organisations often treat the conservation implications of environmental weeds as local issues, which do not demand their attention. This attitude overlooks the fact that the environmental weed problem is likely to affect all vegetation formations in Australia, and is one of the most serious threats to vegetation and fauna survival. Management agencies can and will continue to justify the low priority often given to weed control, where there is an apparent lack of interest from within the environment movement.
The impact of weeds on native vegetation has been catastrophic, and the process continues today at an accelerating pace.
These articles are extracts that are totally verbatim in many places, and are all derived from text by Carr, Yugovic and Robinson, 1992. Very extensive research was carried out for the State of Victoria to produce their publication. Similar information is not available yet for North Queensland, but the principles are almost certainly very similar.
Extracts from "Environmental Weed Invasions in Victoria, Conservation and Management Implications"; Carr G.W; Yugovic J. V; Robinson, K. E; Dept. of Conservation and Environment; 1992
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