Economic evaluation of the management of bitou bush ('chrysanthemoides monilifera' subsp. 'rotundata'(DC.) T.Norl.) to conserve native plant communitites in New South Wales
The bitou bush ('Chrysanthemoides monilifera' subsp. 'rotundata' (DC.) T.Norl.) Threat Abatement Plan (TAP) aims to reduce the impacts of bitou bush on biodiversity in New South Wales. This is the first weed TAP in Australia and so its effectiveness in conserving threatened biodiversity, as well as its cost of implementation, must be examined to determine if this new approach should be adopted as a template for managing the biodiversity impacts of other major weed species. We therefore consider the question 'is the TAP a good investment in relation to protecting biodiversity'? We combine the costs of implementing the TAP with conservative, published estimates of the benefits of protecting biodiversity, to calculate the benefit-cost ratios of the investment. The ratios indicate that the benefits of the TAP exceed the costs under a wide range of economic conditions. While this result supports the approach, the cost of implementation should be analysed over the five years relative to the biodiversity outcomes in order to determine the ex post benefit of the TAP.
Economic evaluation of the NSW Bitou Bush Threat Abatement Plan
The NSW Bitou Bush Threat Abatement Plan (TAP) aims to reduce the impacts of bitou bush on biodiversity in New South Wales. This is the first weed TAP in Australia and so its effectiveness in conserving threatened biodiversity, as well as its cost of implementation, must be examined to determine if this new approach should be adopted as the template for managing the biodiversity impacts of other major weed species. We therefore consider the question "is the TAP a good investment in relation to protecting biodiversity?".
Valuation of the cost of a weed incursion in a natural environment: a simulation approach
The damage that weeds inflict on natural ecosystems over time reduces the flow of services from these areas, thus reducing the flow of benefits to society. A simulation model of a natural ecosystem is a useful tool to analyse the effects of an alien plant invasion over time. Such an approach is developed here to apply the theory of production economics to value the damage through a dynamic bioeconomic model. The approach integrates the principles of benefit-cost analysis to value the costs of the incursion and the benefits of control.
The Economic Impact of Weeds in Australia
Weeds have a wide variety of impacts on society, the environment and the economy. The economic impacts are usually losses and these can be measured as costs of control, decreases in yields, and reductions in economic surplus. In this paper, we attempt to estimate these economic effects of weeds in Australia. The impacts of weeds on agriculture were calculated through all three measures. But due to lack of data, the impacts of weeds on natural environments, other public land, and Indigenous land, could only be measured as the costs of control. Weeds reduce agricultural output, and so decrease farm income and increase the cost of food to consumers. The combined annual loss to farmers and consumers in 2001-02 was estimated to lie between $3442 m and $4420 m, and to average $3927 m. About 80 per cent of this annual loss falls on farmers and 20 per cent on consumers. The annual loss of $3927 m is one half of one percent of gross domestic product and 14 per cent of the value added by agriculture to the economy. These impacts in agriculture were calculated as the change in farm income and the cost of food between the current with-weeds situation and a without-weeds scenario. The difference is the maximum benefit that could be achieved by reducing the weed population, so it represents the size and national significance of the current problem. This kind of impact estimate, and information on how the loss is distributed across sectors of the economy and across industries, is a benchmark for policy and a starting point for the decision-making process. Weeds attract at least $116.4 m of government expenditure on control, surveillance and other management activities. Of this total, $19.6 m is the expenditure on natural environments by National Parks and Wildlife Services and the National Heritage Trust. Expenditure by four of the state and territory services has increased over the last four years. Of the total, $80.8 m is expenditure by other government agencies on control, inspection, research, and extension. Data on the distribution of weeds in natural environments were not available, so the value of the decrease in outputs in natural environments due to weeds could not be estimated.
The Economic Impact of Weeds in Australia: Report to the CRC for Australian Weed Management
1. - Weeds have a wide variety of impacts on society, theenvironment and the economy. Some of the economicimpacts are benefits but most are costs.2. - The costs of particular weeds in given areas have beenestimated by many writers in a rich literature on theassessment of the impacts in agriculture. Only Combellack(1987) has attempted to estimate the nationwide impactof weeds in general.3. - In his innovative study, Combellack valued the economiccosts of weeds in 1981–82 to be $2,096m. New methodsof weed control and techniques of farm managementhave since been developed, and new weed species nowoccur. Therefore the current costs of impacts cannot bereadily compared with those of 1981–82.4. - The nationwide impact of weeds needs to bere-estimated to provide a more recent benchmark thatreflects current costs, prices and technologies, and thecurrent distribution of impacts within the community.A current estimate provides useful information fordecisions on the allocation of resources, cost sharing,and management of specific weed problems.5. - In this report, we attempt to estimate the economiccosts of weeds across Australia. In addition, we offer aneconomic framework to help consider the problems thatweeds create, and the generation and use of informationto resolve those problems.
Policies for the management of weeds in natural ecosystems: the case of scotch broom ('Cytisus scoparius', L.) in an Australian national park
Environmental weeds are plants that invade natural ecosystems and present a serious threat to conservation of nature. Environmental weeds have been implicated in the extinction of several indigenous plant species, and they also threaten ecosystem stability and functional complexity. Historically, emphasis in weed control in Australian national parks has been placed on chemicals, manual pulling of small plants, excluding tourists and feral animal control measures. Recently, biological control has been introduced to control weed infestations. These methods typically have been applied as funds have become available, with little opportunity to consider their long-term effectiveness. As the threat from environmental weeds is becoming more fully recognised, an integrated, strategic, ecological and economic approach to weed management is needed. A deterministic dynamic programming model is developed for this purpose in this paper. A case study for scotch broom is presented, to assess the ways in which this approach can address the policy issues that face the community in the management of an environmental weed in a national park. The model takes account of the weed population dynamics, the effectiveness and cost of control measures, and the value of the park outputs (biodiversity, recreation and grazing). The dynamic programming model includes weed density and seed bank as state variables and a budget constraint for the control variables. The model is used to derive optimal control rules for any given state of the weed population. An optimal decision rule provides a package of control measures that can be used to attack the problem each year, depending on the current weed density and seed bank. Optimal trajectories are developed for a planning horizon of 45 years, and the effect of the budget constraint is analysed. The marginal value of an extra dollar for weed control, in terms of discounted future benefits, is estimated. It is shown that a combination of controls that targets both weed density and the seed bank is important. It is also shown (given the assumed parameters) that biological control is worth undertaking, as it appears as part of most of the optimal strategies identified. The paper concludes with policy recommendations for managing weeds in natural ecosystems.
Do the public gains from vegetation protection in North-western New South Wales exceed the landholders loss of land value?
Protection of native vegetation on farms provides many gains for the public as a whole, but may also lead to losses in property value for the landholders. At least 41% of Moree Plains Shire remains in native vegetation, most of which is grazed extensively and all of which must now be protected under recent laws. A benefit-cost analysis was combined with a risk simulation to estimate these gains and losses. The data collection stage of the analysis included a synthesis of the literature on the relationship between protection and land values. The analysis showed that protection of native vegetation leads to substantial public gains and to considerable losses in land value in this region. The public gains and the private losses are of the same magnitude, so there may be an economic case for protection. But the size of the landholders' losses demonstrates the need to better balance the gains and losses through policies to target protection and to redistribute the costs between the landholder and the community.
Cost effectiveness in site selection to protect native plant communities from the weed, bitou bush, in New South Wales, Australia
Government funding to protect native plant communities is usually limited. For cost effectiveness, priority sites for conservation must therefore be identified and funds allocated to protect these sites according to the quantity of communities conserved per dollar of cost. In 1999, invasion of coastal vegetation in New South Wales (NSW) by bitou bush was listed as a key threatening process under the NSW 'Threatened Species Conservation Act' 1995. In accordance with the Act, a Threat Abatement Plan (TAP) was prepared to reduce the impacts of the weed to threatened biodiversity at priority sites. In the present study, data collected for the TAP were analysed by linear programming to determine the feasibility of achieving cost effectiveness in identifying sites and allocating funds, and to explore the impact of associated economic issues on the quantity of native plant communities that are protected. In addition to the total funds and costs per site, the quantity was influenced by alternative funding policies and different site selection strategies. Allocations that recognise these issues can enhance protection outcomes, and promote the cost effectiveness of weed management.
Bioeconomic modeling for control of weeds in natural environments
When a weed invasion is first discovered a decision has to be made on whether to attempt to eradicate it, contain it or do nothing. Ideally, these decisions should be based on a complete benefit-cost analysis, but this is often not possible. A partial analysis, combining knowledge of the rate of spread, seedbank longevity, costs of control and techniques of economic analysis, can assist in making a good decision. This paper presents a decision model to determine when immediate eradication of a weed should be attempted, or more generally whether weed control should be attempted at all. The technique is based on identifying two 'switching points': the invasion size at which it is no longer optimal to attempt eradication but where containment may be an option; and the invasion size at which it becomes optimal to apply no form of control at all. The model is applied to a woody perennial weed in a natural environment. The results show that seedbank longevity is the main constraint on the maximum eradicable area and spread rate is the main constraint on the maximum containment area. Stochastic simulations are undertaken to derive probability distributions of costs which are than used to evaluate the effect of budget constraints on areas that can be eradicated. We find that, in the absence of a budget constraint, it may be desirable to eradicate invasions from areas as large as 8000 ha, but when budget constraints typical of those faced by agencies in Australia are introduced, feasible eradicable areas are less than 1000 ha.
Economic issues in the management of plants invading natural environments: Scotch broom in Barrington Tops National Park
Scotch broom ('Cytisus scoparius, L.'), is an exotic leguminous shrub, native to Europe, which invades pastoral and woodland ecosystems and adjoining river systems in cool, high rainfall regions of southeastern Australia. Broom has invaded 10,000ha of eucalypt woodland in Barrington Tops National Park in New South Wales, and is having a major impact on the natural ecology of the sub-alpine environment. It is extremely competitive with the native flora, retarding their growth and in many areas blanketing the ground and preventing growth of many understorey species in open forest areas. A number of rare and endangered species are believed to be under threat from this invasion. An active program to manage the threat is being implemented by the New South Wales National Parks and Wildlife Service. The management issues relevant to this threat are addressed through the application of a detailed bio-economic model of broom management. The results show that intervention in the management of broom in this natural ecosystem is clearly economically justified, and increases in the existing budgets appear to be justified. A combination of control measures, rather than any single measure, is almost always justified. Attempts to eradicate the broom invasion appear to be undesirable, so containment is the preferable strategy. Further, funding bodies should give assurances of future budget levels. The method of analysis reported here should be applicable to other types of biological invasions.