There has been recent interest in determining the upper limits to the feasibility of weed eradication. Although a number of disparate factors determine the success of an eradication program, ultimately eradication feasibility must be viewed in the context of the amount of investment that can be made. The latter should reflect the hazard posed by an invasion, with greater investment justified by greater threats. In simplest terms, the effort (and hence investment) to achieve weed eradication comprises the detection effort required to delimit an invasion plus the search and control effort required to prevent reproduction until extirpation occurs over the entire infested area. The difficulty of estimating the required investment at the commencement of a weed eradication program (as well as during periodic reviews) is a serious problem. Bioeconomics show promise in determining the optimal approach to managing weed invasions, notwithstanding ongoing difficulties in estimating the costs and benefits of eradication and alternative invasion management strategies. A flexible approach to the management of weed invasions is needed, allowing for the adoption of another strategy when it becomes clear that the probability of eradication is low, owing to resourcing or intractable technical issues. Whether the considerable progress that has been achieved towards eradication of the once massive witchweed invasion can be duplicated for other weeds of agricultural systems will depend to a large extent upon investment (> $250 million over 50 yr in this instance). Weeds of natural ecosystems seem destined to remain more difficult eradication targets for a variety of reasons, including higher impedance to eradication, more difficulty in valuing the benefits arising from eradication, and possibly less willingness to pay from society at large.

RIM, or “Ryegrass Integrated Management,” is a user-friendly weed management software that integrates long-term economics. As a model-based decision support system, RIM enables users to easily build 10-year cropping scenarios and evaluate the impacts of management choices on annual rigid ryegrass populations and long-term profitability. Best used in a workshop format to enable learning through interactions, RIM can provide insights for the sustainable management of ryegrass through “what-if” scenarios in regions facing herbicide resistance issues. The upgrade of RIM is presented, with changes justified from an end-user perspective. The implementation of the model in a new, intuitive software format is presented, as well as the revision, update, and documentation of over 40 management options. Enterprises, establishment systems, and control options were redefined to represent current practices, with the notable inclusion of customizable herbicide options and techniques for weed seed control at harvest. Several examples of how RIM can be used with farmers to demonstrate the benefits of adopting recommended practices for managing or delaying the onset of herbicide resistance are presented. Originally designed for the dryland broadacre systems of the Australian southern grainbelt, RIM's underlying modeling was restructured to facilitate future updates and adaptation to other weed species and cropping regions.

Invasive species change ecosystems and the economic services such ecosystems provide. Optimal policy will minimize the expected damages and costs of prevention and control. We seek to explain policy outcomes as a function of biological and economic factors, using the case of Hawaii to illustrate. First, we consider an existing invader, Miconia calvescens, a plant with the potential to reduce biodiversity, soil cover, and water availability. We then examine an imminent threat, the potential arrival of the Brown treesnake (Boiga irregularis). The arrival of the snake in Guam has led to native bird extirpations, power outages, and health costs.

We present a bioeconomic model of three invasive aquatic plants (hydrilla, water hyacinth, and water lettuce) in 13 large Florida lakes, and simulate one-year and steady-state impacts of three control scenarios. We estimate that the steady-state annual net benefit of invasive plant control is $59.95 million. A one-year increase in control yields steady-state gains of $6.55 million per year, and a one-year lapse causes steady-state annual losses of $18.71 million. This model shows that increased control of hydrilla, water hyacinth, and water lettuce is optimal.

Nest predation can threaten marine turtle nesting success, and having to address dissimilar predator species complicates nest protection efforts. On Florida's Keewaydin Island predation by raccoons Procyon lotor and invasive feral swine Sus scrofa are disparate, significant threats to marine turtle nests. Using 6 years of nesting data (mostly for loggerhead marine turtles Caretta caretta) we examined the impacts of swine predation on nests and the benefits of swine eradication, caging nests to protect them from raccoon predation, and the effects of nest caging on swine predation. Nest predation by swine began in mid nesting season 2007, after which swine quickly annihilated all remaining marine turtle nests. During 2005–2010 raccoon predation rates for caged nests (0.7–20.4%) were significantly lower than for uncaged nests (5.6–68.8%) in every year except 2009, when little raccoon predation occurred. The proportions of eggs lost from raccoon-predated nests did not differ between caged and uncaged nests. Caging did not prevent destruction by swine but median survival time for caged nests was 11.5 days longer than for uncaged nests, indicating that caged eggs in nests have a greater chance of hatching before being predated by swine. The financial cost of the eradication of swine greatly outweighed the value of hatchlings lost to swine predation in 2007.

We examined impacts from effective predator management on nesting success of marine turtles in an exceptional nesting year at Hobe Sound National Wildlife Refuge, Florida, USA, a beach with a high density of nesting marine turtles that has a history of severe nest predation. Historically up to 95% of nests were predated, primarily by raccoons Procyon lotor and, more recently, armadillos Dasypus novemcinctus. Predator control was identified as the most important conservation tool for marine turtle reproduction. Predator management by refuge staff as ancillary duties typically only held predation levels to c. 50%. However, when experts in predator control were employed predation was substantially reduced. An extraordinary opportunity to evaluate the biological and economic benefits of this management approach occurred in 2008, a year with exceptionally heavy nesting. Loggerhead turtle Caretta caretta nesting resurged, green Chelonia mydas and leatherback Dermochelys coriacea turtles nested in record numbers, producing twice or more than their median number of nests, and the first Kemp’s ridley Lepidochelys kempii nest was observed. Overall predation was 14.7%, resulting in an estimated > 128,000 additional hatchlings emerging compared to estimates had no predator management been in place and historical predation rates occurred, and > 56,000 hatchlings more than expected had predator management been conducted as ancillary duties rather than by experts. The USD 12,000 investment for expert predator management equated to only USD 0.09 spent for each additional hatchling produced compared to the scenario of no predator control and only USD 0.21 compared to the scenario of predator control as ancillary duties.

Tropical shrimp fisheries are characterized by various interactions with their natural environment and with other fisheries. These latter interactions can be explained by the high quantity of bycatch taken by industrial trawler fleets, which has a significant impact on fish populations associated with shrimps and thus also on finfish fisheries. Bycatch also includes emblematic species, which are subject to strict conservation measures decided by the international community. It seems important to identify and assess the biological and economic consequences of different mitigation measures (increase of mesh size, turtle excluder devices and bycatch reducing devices). This communication is based on case studies undertaken on the Indian white prawn (Fenneropenaeus indicus) and speckled shrimp (Metapenaeus monoceros) fisheries in Madagascar and on the brown shrimp (Farfantepenaeus subtilis) and pink spotted shrimp (Farfantepenaeus brasiliensis) fishery in French Guiana. A review of the impacts of these fisheries on resources and ecosystems is made and some results of experiments on mitigation devices given. Finally, the results of simulations obtained using a multi-species, multi-fleet, age-structured bioeconomic model, including modifications of catchability and costs related to the adoption of these devices, is presented and discussed.