Characteristics of Australia
Lyneham, Australia
Australia is an isolated, island continent slightly smaller than the continental US. It is sparsely populated and highly urbanized with 60% of the people living in five cities. Seventy-percent of the continental area is arid and the vegetation is characteristically low, open woodlands or shrublands. High rainfall areas are very small; tropical rainforest covers less than 1% of the continental area. A relatively narrow coastal and sub-coastal band in the east and southwest has adequate rainfall to support some tall forest, intensive agriculture and permanent human settlements. Soils are characteristically infertile, shallow, stony and/or salt-prone.
The bulk of the continental area is grazed by sheep and/or cattle. Feral grazers, particularly rabbits whose range has now spread to more than half of the continental area, are a major management problem.
The complement of native plants and animals is unique; Australia has:
Since European settlement:
The natural environment over much of the continental area is degraded to various extents through different processes including over-stocking, grazing of marginal country, over clearing, spread of non-indigenous species, and intensive irrigation. The poor record of past management, together with an increasing sense of the uniqueness of Australia's plants, animals and ecology has led to marked changes in the land ethic in the 1990s.
Non-indigenous plants as an environmental threat
Among the greatest threats to Australia's natural communities, apart from land clearing, is the spread of non-indigenous plant species. Almost every major ecosystem has been extensively altered and degradation continues as these species infill and expand their range. Of the 17,000 plant species occurring in Australia, 11% are introduced and about half of these become weeds. A smaller percentage becomes weedy in the natural environment but it only takes one aggressive species to totally destroy an ecosystem.
Most of the major weeds are intentional introductions. Of the 220 species proclaimed noxious, over 50% were brought in deliberately. The majority of these were for ornamental purposes. This is compelling evidence for changing the current screening systems for plant imports, a process now in train. (See Appendix 2, Draft Model Law)
Broad-scale, single species invasions tend to dominate in the extensive grazing country of northern Australia. Grazing, together with a very different fire management regime, induces drastic direct or indirect changes to the natural ecosystems. Exotic trees and shrubs are now displacing native vegetation over thousands of square kilometers of the semi-arid and monsoonal tropics. Among the more aggressive tree/shrubs are prickly acacia (Acacia nilotica), rubber vine (Cryptostegia grandiflora) parkinsonia (Parkinsonia aculeata), mesquite (Prosopis spp.), giant sensitive plant (Mimosa pigra). The vast distances, the low human population density, and the low economic value of the land, results in an almost impossible management scenario under current land-use (i.e. grazing) regimes which maintain disturbance.
In the eastern and southwestern parts of the continent, multi-species invasions are the dominant pattern. In these more populated parts of Australia, the vegetation is highly fragmented and thus also vulnerable to invasion, mainly by ornamental species grown locally, and the ubiquitous grasses. The native fragments are often repositories of rare species, being the last vestiges of once more widespread communities. Rainforest communities are typically highly resilient to invasion unless fragmented. Edges become infested with large numbers of sun-loving exotic vines (e.g. Thunbergia grandiflora, Cardiospermum grandiflorum,), creepers (e.g. Tradescantia albiflora), shrubs ( e.g. Lantana camara, Ligustrum lucidum) and grasses ( e.g. Melinis minutiflora).
Some of the more invasion resistant ecosystems appear to be the intact areas of rain and temperate forests, mangroves, the alpine vegetation and red sand deserts.
Grasses are particularly insidious weeds. They are pervasive, are next to impossible to control, and their ecological effect is often indirect through changed fire behavior, or it is subtle, such as through the choking out of regenerating native species. Grasses have been introduced to most parts of Australia and there is now a current and unresolved debate as to how to manage the inherent conflict between producers who want to introduce more species, and the conservationists who wish to protect natural systems from further invasion by new species.
A review of environmental impacts of non-indigenous plants in Australia can be found in Humphries et al. (1991, 1995).
Government responses to the problems of non-indigenous species
Marked attitudinal changes have taken place in Australian society in the 1990s toward greater awareness of ecological imperatives and the need for limits to resource exploitation and more active conservation. This is reflected in new government policy initiatives and in the implicit or explicit adoption of four major principles which underlie them:
Federal actions to address the newly emerging ethics of the 1990s regarding resource use, land management and conservation include restructuring of institutional arrangements, a plethora of strategies, legislative reviews, and funding of new programs.
A number of levels of government are responsible for various aspects of non-indigenous species in Australia: Commonwealth, State, Local, and Sectoral. Constitutionally, non-indigenous species are a state responsibility except when they are involved with import, are on federal land, impact national initiatives or facilitation of change, where market forces do not give the desired outcome, or when community ownership issues are involved. The federal government has instituted agreements to bring state policy in line with its own.
Key federal strategies that are relevant to non-indigenous species management include:
The Decade of Landcare is a program worthy of note because of its extent, its bottom-up approach and its immense and growing success. It is a community-level program coordinated and funded by the federal government. It brings together the range of regional and local interests to address various aspects of land management from soil erosion to tree planting to pest control and catchment management. Funding is provided to local groups through a competitive grant scheme for projects which fall within the guidelines. The small cell social structure that has developed through Landcare across Australia has important spin-offs for integrating new initiatives which further augments the community power base.
The fund (a total of $105 million in 1993-94) is distributed among a number of programs within which aspects of non-indigenous species management could be funded: $14 million for community Landcare activities; $12 million for land management and sustainable agriculture projects; $10 million for catchment management projects; $2.3 million for "Save the Bush" program; $4.3 million for the "One Billion Trees" program.
The Endangered Species Program, funded at $4.3 million in 1992-93, provides for research and surveys, recovery plans, and threat abatement plans relating to protection of endangered species from any threatening processes, including non-indigenous species.
The Feral Pest Program was funded at $2.2 million in 1992-93. The main feral animals are the rabbit, fox, goat, pig, and horse.
Australia's National Weeds Strategy
The development of the Australian National Weeds Strategy began in 1992 in response to an unprecedentedly large ad hoc request to the federal government for the control of a single species - Mimosa pigra. The species had, in just a few years, invaded, to the exclusion of the native community, large areas of flood plain near Darwin, in the Northern Territory. Its rapid growth and its potential to spread to the adjacent river flood plains of the Kakadu World Heritage Area and to the remainder of northern Australia's rivers called for an immediate response. However, the government wanted rationalization of future funding priorities. Weeds such as mimosa fell outside the charter of the usual administrative processes set up primarily for agricultural weeds and outside the funding capabilities of state conservation agencies.
The Strategy was completed in 1994 under the auspices of the Standing Committee on Agriculture and in 1995 is in the process of review by the production, conservation and forestry portfolios. Funding and administrative arrangements within the federal government are still being decided.
The linkages between human activity and invasion by non- indigenous species have been recognized increasingly by land managers and policy makers. The scale of the weed problem dictates that direct control by mechanical and chemical means can be effective only at a local and possibly regional scale. An integrated management approach is the only strategy with some long-term possibility of success. Prevention, judicious and limited application of direct control and an emphasis on appropriate land use and sustainable land management practices are foundation principles for the Strategy.
Some specific features of the Strategy include:
The success of the strategy in conservation terms will depend heavily on the sustained level of Cabinet funding (which is related to public pressure) and on the institutional arrangements for its implementation. The institutional arrangements are a sensitive and important factor because principles and priorities could differ between the conservation and production portfolios. Traditionally weeds, as a problem of agriculture, were dealt with in the production portfolio. The recent awareness of weeds as a major conservation threat requires traditional areas of jurisdiction to shift or the problem "falls between the cracks". The shifting responsibilities are currently under negotiation.
References
Humphries S. E., Groves R. H. and Mitchell D. S. (1991) Plant invasions of Australian ecosystems: a status report and management directions. Kowari 2:1-127. Australian National Parks and Wildlife Service.
Humphries S. E., Groves R. H., and Mitchell D. S. (1993) 149-170. Plant invasions: the implications for conservation. In: Conservation Biology in Australia and Oceania ed. by C. Moritz and J. Kikkawa. Surrey Beatty & Sons.