ECONOMIC IMPACTS OF NOXIOUS WEEDS, OTHER WEEDS, AND TREE GROWTH, ON AGRICULTURAL PRODUCTION IN THE NEW ENGLAND TABLELANDS, NEW SOUTH WALES

The economic impact of weeds on farms in the New England Region of New South Wales is estimated from data from a cross -sectional survey. Weeds can be classed as noxious or declared plants, plants that the farmers perceived as weeds, and trees -- which many farmers also perceived as weeds. Variables were defined for several levels of intensity of infestation for each of these three classes of weeds. The impact of each these variables, on property income and stocking, was estimated through Cobb-Douglas production functions. The presence of very-heavy infestations of non-noxious weeds, and heavy infestations of non-noxious weeds, were found to be associated with reductions in income. In total, the income of the representative property would be increased by 15 per cent, ceteris paribus, if these infestations were removed.Weeds, trees, income, stocking, Farm Management,

Inverted and mirror repeats in model nucleotide sequences

We analytically and numerically study the probabilistic properties of inverted and mirror repeats in model sequences of nucleic acids. We consider both perfect and non-perfect repeats, i.e. repeats with mismatches and gaps. The considered sequence models are independent identically distributed (i.i.d.) sequences, Markov processes and long range sequences. We show that the number of repeats in correlated sequences is significantly larger than in i.i.d. sequences and that this discrepancy increases exponentially with the repeat length for long range sequences.Comment: 12 pages, 6 figure

Modelling the Dynamics of Weed Management Technologies

An appropriate economic framework for valuing the benefits of weed management technologies is to treat weeds as a renewable resource stock problem. Consequently, the weed seed bank is defined as a renewable resource that changes through time due to management and seasonal conditions. The goal of decision-makers is to manage this (negative) resource so as to maximise returns over some pre-specified period of time. A modelling framework is presented for evaluating the biological and economic effects of weed management. The framework includes population dynamics, water balance, crop growth, pasture growth and crop/pasture rotation models for measuring the physical interactions between weeds and the environment. These models link in with numerical optimal control, dynamic programming and stochastic dynamic programming models for determination of optimal decision rules and measuring economic impact over time of policy scenarios.weeds, modelling, dynamic analysis., Land Economics/Use,

Spatial chaos of an extensible conducting rod in a uniform magnetic field

The equilibrium equations for the isotropic Kirchhoff rod are known to form an integrable system. It is also known that the effects of extensibility and shearability of the rod do not break the integrable structure. Nor, as we have shown in a previous paper does the effect of a magnetic field on a conducting rod. Here we show, by means of Mel'nikov analysis, that, remarkably, the combined effects do destroy integrability; that is, the governing equations for an extensible current-carrying rod in a uniform magnetic field are nonintegrable. This result has implications for possible configurations of electrodynamic space tethers and may be relevant for electromechanical devices

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 10,000 hectares of eucalypt woodland at 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. An active program to manage this invasion is being implemented by the National Parks and Wildlife Service. The management issues include whether eradication or containment is economically desirable, and when biological control is economically desirable. Management choices depend on the marginal costs of increments of government intervention, effects of uncertain budgets on the control of broom, choice of control measures and effects of uncertain values of biodiversity. These issues are addressed through the application of a detailed bioeconomic model of broom management.Scotch broom, economic issues, management issues, natural environments, bioeconomic model, Environmental Economics and Policy,

Book reviews

Teaching/Communication/Extension/Profession,

Valuing the biodiversity gains from protecting native plant communities from bitou bush (Chrysanthemoides monilifera subsp rotundata (DC.) T.Norl.) in New South Wales: application of the defensive expenditure method

Valuation of the gains from protection of biodiversity is difficult because the services that provide the benefits do not normally pass through markets where prices can form. But the services sometimes pass through markets where consumers or producers behave in a market-oriented manner, and so the values implicit in this behaviour can be identified and derived. Estimates of the benefits of biodiversity protection are derived from the costs of protecting native plant communities from a major weed in Australia, by following this approach. In 1999, invasion of coastal areas of New South Wales by bitou bush (Chrysanthemoides monilifera subsp. rotundata (DC.) T. Norl.) was listed as a key process threatening native plants under the NSW Threatened Species Conservation Act 1995. In accordance with the Act, the Department of Environment and Climate Change prepared a Threat Abatement Plan (TAP) to reduce the impacts of bitou bush on biodiversity at each threatened site. The costs of protecting sites vary closely with the number of priority native species and communities at each site. Following standard economic assumptions about market transactions, these costs are interpreted to provide values the benefits of protecting extra species, communities, and sites. Key words: Bitou bush, Chrysanthemoides monilifera, threat abatement plan, valuation of biodiversity, benefit-cost analysis, weed control, defensive-expenditure method.Bitou bush, Chrysanthemoides monilifera, threat abatement plan, valuation of biodiversity, benefit-cost analysis, weed control, defensive-expenditure method, Demand and Price Analysis, Environmental Economics and Policy,

Eradication of Exotic Weeds in Australia: Comparing Effort and Expenditure

Weeds have many adverse impacts on agriculture and the environment and therefore are often targets of eradication attempts. Eradication attempts involve large commitments of labour and financial resources over significant periods of time. Using data from 12 Australian weed eradication attempts the authors compare work hours and expenditure on each attempt for various initial-infestation sizes. Analysis of a limited data set shows: (1) that while the eradication effort increases with the initial area of infestation, the effort applied per hectare actually decreases; (2) that application of a greater work effort was not the reason why completed eradications were successful; and (3) that the larger the initial infestation size, the smaller the amount of resources applied per hectare for eradication.weeds, eradication, work effort, expenditure, infestation size, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Space and Time: Wind in an Investment Planning Model

Investment planning models inform investment decisions and government policies. Current models do not capture the intermittent nature of renewable energy sources, restricting the applicability of the models for high penetrations of renewables. We provide a methodology to capture spatial variation in wind output in combination with transmission constraints. The representation of wind distributions with stochastic approaches or an extensive historic data set would exceed computational constraints for real world application. Hence we restrict the amount of input data, and use boot-strapping to illustrate the robustness of the results. For the UK power system we model wind deployment and the value of transmission capacity

Dynamic phase transition in the conversion of B-DNA to Z-DNA

The long time dynamics of the conformational transition from B-DNA to Z-DNA is shown to undergo a dynamic phase transition. We obtained the dynamic phase diagram for the stability of the front separating B and Z. The instability in this front results in two split fronts moving with different velocities. Hence, depending on the system parameters a denatured state may develop dynamically eventhough it is thermodynamically forbidden. This resolves the current controversies on the transition mechanism of the B-DNA to Z-DNA.Comment: 5 pages, 4 figures. New version with correction of typos, new references, minor modifications in Fig 2, 3. To appear in EP