Applying search theory to determine the feasibility of eradicating an invasive population in natural environments

The detectability of invasive organisms influences the feasibility of eradicating an infestation. Search theory offers a framework for defining and measuring detectability, taking account of searcher ability, biological factors and the search environment. In this paper, search theory concepts are incorporated into a population model, and the costs of search and control are calculated as functions of the amount of search effort (the decision variable). Simulations are performed on a set of weed scenarios in a natural environment, involving different combinations of plant longevity, seed longevity and plant fecundity. Results provide preliminary estimates of the cost and duration of eradication programs to assist in prioritising weeds for control. The analysis shows that the success of an eradication program depends critically on the detectability of the target plant, the effectiveness of the control method, the labour requirements for search and control, and the germination rate of the plant.     

An economic approach to soil fertility management for wheat production in north-eastern Australia

Soil fertility decline and soil management for crop production are important economic issues for grain growers in north-eastern Australia. In that region, there is evidence of soil fertility decline which is attributed to past crop management practices. The questions addressed in this article are first, whether components of soil fertility can be improved by better management and second, by how much soil fertility would change. Soil fertility for crop production is considered in terms of soil organic carbon and nitrogen. A stochastic dynamic economic analysis of soil fertility management for wheat production is presented. A sequential analysis of first deriving the optimal nitrogen stock and application rates is followed by an assessment of tillage, stubble, and fertilizer strategies to obtain an optimal level of soil organic carbon. The recommended management practices are consistent with emerging management trends in the region. The derivation of optimal levels of soil fertility for agricultural purposes has other policy implications, which we discuss.     

The importance of seasonal variability and tactical responses to risk on estimating the economic benefits of integrated weed management

Seasonal variability is an important source of risk faced by farmers and, regardless of an individual's attitude to risk, there are options to tactically adjust production strategies as the outcomes of risk become known. The objective of this article is to measure the economic benefits of alternative approaches to managing weeds, one of the most serious production problems in Australian cropping systems. A bioeconomic model that combines weed biology, crop growth and economics is developed to value the effects of seasonal variability and the role of tactical responses and sequential decision making in determining an optimal integrated weed management strategy. This shows that there are substantial differences in the measured long‐term benefits from deterministic and stochastic simulations. It is concluded that, for research evaluation of technologies that involve complex biological and dynamic systems, ignoring the impacts of seasonal variability, responses to risk and sequential decision making can lead to an incorrect estimate of the economic benefits of a technology. In this case study of optimal weed management strategies in Australia, the size of the error is high.     

An economic analysis of farm forestry as a means of controlling dryland salinity

Large areas of agricultural land under conventional crops and pastures are at risk of dryland salinisation in Australia. The salinisation problem can be controlled by strategic and large-scale planting of trees; however, farm forestry enterprises evaluated with conventional discounting techniques do not generally rank as an attractive alternative to annual crops on productive land. In this article, an optimal control model that explicitly accounts for decline or improvement in land quality over a period of 40 years is presented. The optimal area planted to trees and the optimal groundwater-table trajectory through time are determined under a variety of scenarios. Implications of the results for policy design are discussed.     

A Genetic Algorithm Approach to Farm Investment

A farm portfolio model is specified with two risky enterprises and a risk-free asset which may be held short or long by the farmer. The model is solved numerically using a genetic algorithm. It is shown that the assumption of competitive adaptation leads to a violation of normative efficiency. Those who survive are not the most efficient in a normative sense.     

Carbon-accounting methods and reforestation incentives

The emission of greenhouse gases, particularly carbon dioxide, and the consequent potential for climate change are the focus of increasing international concern. Temporary land-use change and forestry projects (LUCF) can be implemented to offset permanent emissions of carbon dioxide from the energy sector. Several approaches to accounting for carbon sequestration in LUCF projects have been proposed. In the present paper, the economic implications of adopting four of these approaches are evaluated in a normative context. The analysis is based on simulation of Australian farm–forestry systems. Results are interpreted from the standpoint of both investors and landholders. The role of baselines and transaction costs are discussed.     

Testing for pre‐committed quantities of Australian meat demand

Pre‐committed consumption represents the portion of demand that is determined by non‐price and non‐income factors. This study uses quarterly data to estimate a Generalised Almost Ideal Demand System (GAIDS) to test for the existence of pre‐committed meat consumption in Australia. Two specifications are estimated to evaluate the impact of seasonal and time trend factors on pre‐committed demand. Evidence is found for the existence of pre‐committed chicken consumption when jointly estimated with seasonal and time trend factors. Results support improved demand modelling of Australian meat consumption using the GAIDS and provide insights into how Australian meat demand is affected by price, expenditures, pre‐committed consumption, seasonality, and trends.     

Deriving efficient frontiers for effort allocation in the management of invasive species*

Invasive species cause significant losses through their effect on agriculture, human health and the environment. Their importance has increased with time owing to globalisation, as the spread of invasive species is facilitated by the increased movement of people, cargo and genetic material around the world. There is a vast literature on the economics of invasive species and their management. Here, we contribute to this literature by applying a spatio‐temporal model to the allocation of surveillance resources. We focus on three questions regarding resource allocation to control a newly discovered invasion: the budget, which determines the amount of search effort available; the duration of the control program; and the allocation of surveillance and control in time and space. We also explore the complementary role of passive surveillance by members of the public. We derive efficient frontiers for effort allocation that represent the trade‐off between cost and probability of eradication after inefficient strategies have been eliminated. We use the results to illustrate how to evaluate whether introduction of passive surveillance is desirable based on cost and eradication probability. We conclude by discussing the implications of our findings in the design of control programs.