No abstract

Agriculture and municipal wastewater are the principal sources of eutrophying nutrients in many water ecosystems. We develop a model which considers the characteristics of agricultural and municipal nutrient abatement. The model explicitly accounts for the investment needed to set up wastewater treatment facilities, and makes it possible to determine the optimal timing of investment as well as the optimal agricultural and municipal abatement levels. We apply the model to the Finnish coastal waters of the Gulf of Finland. Our results indicate that substantial savings in abatement costs and the damage associated with eutrophication could be obtained by constructing the facilities needed to process all the wastewaters entering the coastal ecosystem. The optimal timing of investment is shown to hinge on both the economic and ecological characteristics of the ecosystem.

The paper puts forward a model of the Atlantic salmon fishery in the Baltic Sea that integrates the salient biological and economic characteristics of migratory fish stocks. Designed to be compatible with the framework used for actual stock assessments, the model accounts for agestructured population dynamics, the seasonal harvest and competing harvesting by commercial and recreational fishermen. It is calibrated using data and parameter estimates for the Simojoki River stock. The socially optimal policy for maximizing discounted net benefits from the fishery within an uncertain environment is determined using a dynamic programming approach and numerical solution method. Our results indicate that substantial economic benefits could be realized under optimal management without compromising stock sustainability.

\W_e examine cooperative harvesting in a sequential fishery with stochastic shocks in recruitment. Two fleets harvest in a stochastic interception fishery. We analyze cooperative management as a non-cooperat ive game, where deviations from cooperative harvesting are deterred by the threat of harvesting at non-coopera tive levels for a fixed number of periods whenever the initial stock falls below a trigger level. We illustrate the sequential harvesting game with an application to the Northern Baltic salmon fishery. Cooperative harvesting yields participants substantial gains in terms of expected payoffs. The greatest gains accrue to the fleet harvesting the spawning stock, the actions of which are not observed by the competitor. An explanation for the prevalence of fish wars is provided in that even if a cooperative agreement is reached, shocks in recruitment trigger phases of non-cooperativ e harvesting. Further, the cooperative solution can only be maintained when stock uncertainty is not too prevalent.

No abstract

No abstract

Designing efficient agri-environmental policies for agricultural nutrient load reductions calls for information on the costs of emission reduction measures. This study develops an empirical framework for estimating abatement costs for nutrient loading from agricultural land. Nitrogen abatement costs and the phosphorus load reductions associated with nitrogen abatement are derived for crop farming in south-western Finland. The model is used to evaluate the effect of the Common Agricultural Policy reform currently underway on nutrient abatement costs. Results indicate that an efficiently designed policy aimed at a 50% reduction in agricultural nitrogen load would cost € 48 to € 35 million, or € 3756 to € 2752 per farm.Key-words: water pollution, agriculture, abatement, nitrogen, phosphorus, nutrient load IntroductionExcessive concentrations of nutrients that regulate phytoplankton growth cause eutrophication of marine and freshwater ecosystems. The most heavily loaded marine areas in Europe show symptoms of severe eutrophication (see for example AErtebjerg et al. 2001). The Baltic Sea ecosystem has proved particularly vulnerable to nutrient pollution. Blooms of toxic blue-green algae occur during the warm summer months, and filamentous algae cover the seabed in coastal areas. Eutrophication results in significant damages through reduced value of fisheries and recreational activities (e.g. Gren et al. 1997, Söderqvist and Scharin 2000, Sandström et al. 2000, Kosenius 2004. Nutrient loading from land-based sources and the atmosphere builds up nutrient concentrations. The state of eutrophied water ecosystems can be improved by reducing nutrient loads from inland sources, which include agriculture, municipalities and industry. Agriculture has been identified as the major source of eutrophying nutrients in developed countries (see e. g. Shortle and Abler 2001). For example in the Nordic countries, municipal and industrial nutrient A G R I C U L T U R A L A N D F O O D S C I E N C E Helin, J. et al. Abatement costs for agricultural nutrient load in SW Finlandloads have been reduced significantly during the last few decades, while agricultural nutrient loads remain substantial (HELCOM 2005).Linking nutrient load reductions with the costs of those reductions is essential for informed decision making. Abatement costs are relatively easy to assess in the case of municipal and industrial point-source pollution, whereas quantifying abatement costs for agricultural non-point pollution poses a challenge (see e.g. Russel and Shogren 1993). Nutrient removal at municipal and industrial sources requires setting up wastewater treatment facilities, after which chemical or biological nutrient removal occurs at an approximately constant cost. Agricultural abatement instead takes place through changes in agricultural practices and through adopting abatement measures that filter runoff, such as buffer strips and wetlands. Nutrient loading is affected both by agricultural management practices, such as crop choice, fertilizer use, and til...

This paper puts forward a model for managing eutrophication that integrates the salient ecological and economic characteristics of a coastal area suffering from severe nutrient enrichment. The model links the development of phosphorus concentration over time to nutrient emissions from agriculture and habitation. It accounts for differences in agricultural and municipal abatement options and their costs, as well as the need to undertake irreversible investments to set up wastewater treatment facilities. Furthermore, it considers sediment release of phosphorus as a function of annual nutrient loads. The model is parameterized for a 30-km-wide area off the Finnish coast of the Gulf of Finland. The socially optimal policy, which minimizes the sum of monetary damage caused by eutrophication and the costs of nutrient abatement over time, is determined using a dynamic programming approach. The results suggest that considerable investments are warranted to bring wastewater treatment facilities up to date. Continued efforts to reduce agricultural nutrient loading are nevertheless also called for. The analysis provided is a first step toward an integrated analysis of eutrophication that accounts for complexities inherent in the problem, such as sediment release of phosphorus and irreversible investments in abatement technology. The results are sensitive in particular to ecological assumptions and parameterization, and further research is needed in these areas.