OPTIMAL MANAGEMENT OF GIANT-CLAM FARMING IN SOLOMON ISLANDS

Giant-clam farming is undertaken by coastal villagers in Solomon Islands as part of a research and development project of the International Center for Living Aquatic Resources Management (ICLARM). The production technology is simple and does not require a large capital investment. The main inputs are clam seed, labour and time. Labour is used for activities such as seeding, cleaning, thinning and harvesting. In this paper, a bioeconomic model is used to explore optimal farm management. The theoretical basis for this analysis is found in the economic theory of optimal forestry exploitation. The management variables considered are husbandry applied to cleaning and the frequency with which thinning is undertaken. The optimal cycle-length is determined for both a single clam harvest and multiple harvests. The labour requirements of various management scenarios are identified for the multiple-cycle case.bioeconomics, giant clams, subsistence mariculture, Farm Management,

Temporary carbon storage and discount rates

Several approaches have been proposed for accounting for temporary carbon sequestration in land-use change and forestry projects that are implemented to offset permanent emissions of carbon dioxide from the energy sector. In a previous paper, we evaluated the incentives provided by some of these approaches. In this paper, we investigate further what we call the “ideal” accounting system, where the forest owner would be paid for carbon sequestration as the service is provided and redeem payments when the forest is harvested and carbon is released back into the atmosphere. We demonstrate how discounting affects the net present value of the forest when carbon sequestration is taken into account under this ideal system. Not all carbon is released back into the atmosphere at harvest, however, since a large proportion may remain fixed in forest products for many years. Here, we compare the profitability of the forest under full redemption of credits at harvest, with partial redemption of credits at harvest followed by annual redemption post-harvest as the carbon decays in a durable forest product. The analysis is based on simulation of farm-forestry systems in south-eastern Australia.carbon accounting, reforestation, discounting, bioeconomics, Environmental Economics and Policy, Land Economics/Use,

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.Resource /Energy Economics and Policy,

Downstream benefits vs upstream costs of land use change for water-yield and salt-load targets in the Macquarie Catchment, NSW

The net present value (NPV) of downstream economic benefits of changes in water-yield (W) and salt-load (S) of mean annual river flow received by a lower catchment from an upper catchment are described as a 3-dimensional (NPV,W, S) surface, where dNPV/dW > 0 and dNPV/d(S/W) < 0. Upstream changes in land use (i.e. forest clearing or forest establishment, which result in higher or lower water-yields, respectively) are driven by economic consequences for land owners. This paper defines conditions under which costs of strategic upstream land use changes could be exceeded by compensations afforded by downstream benefits from altered water-yields and/or lower salt loads. The paper presents methods, and preliminary calculations for an example river, quantifying the scope for such combinations, and raising the question of institutional designs to achieve mutually beneficial upstream and downstream outcomes. Examples refer to the Macquarie River downstream of Dubbo, NSW, and Little River, an upstream tributary.policy, markets, upstream, downstream, water, salinity, Land Economics/Use,

Minimising costs of environmental service provision: water-yield, salt-load and biodiversity targets with new tree planting in Simmons Creek Catchment, NSW, a dryland farming/grazing area.

Although dryland farming and grazing have been practiced for over 130 years in the 17,000 ha Simmons Creek catchment without surface salinity problems, the area has been identified as a significant source of salt seepage to Billabong Creek in the NSW Murray catchment. Groundwater movement and salinity levels are spatially heterogenous at Simmons Creek. Groundwater of the upper catchment is relatively fresh and seemingly unconnected with the highly saline groundwater of the lower catchment. However, fresh surface water does flow from the upper to the lower catchment. This spatial diversity provokes the question of where high-water-use forest habitats might be placed to achieve different combinations of environmental services (greater water yield, lower stream salinity and greater biodiversity) at least cost. Agro-forestry and or carbon sequestration benefits are not considered here. This paper presents methods and preliminary calculations of land use changes for least-cost delivery of these environmental service targets.Optimisation, opportunity costs, forest-habitat, environmental services, Environmental Economics and Policy,

AN OPTIMAL MANAGEMENT MODEL FOR INTENSIVE AQUACULTURE - AN APPLICATION IN ATLANTIC SALMON

In this paper the optimal management strategy for intensive aquaculture is viewed in terms of a combined strategy of releasing the optimal number of recruits and harvesting those recruits at the optimal harvesting time. A model which can be used to determine the optimal management strategy is developed. In the model the optimal harvesting model documented by Bjorndahl (1988, 1990) in which harvesting and feed costs are considered, is extended by including release costs and how they influence the optimal number of recruits. The model forms the basis for an empirical analysis in which the optimal management strategy for a yearclass of Atlantic salmon farmed in Australia during 1989-91 is considered

AN OPTIMAL MANAGEMENT MODEL FOR INTENSIVE AQUACULTURE - AN APPLICATION IN ATLANTIC SALMON

In this paper the optimal management strategy for intensive aquaculture is viewed in terms of a combined strategy of releasing the optimal number of recruits and harvesting those recruits at the optimal harvesting time. A model which can be used to determine the optimal management strategy is developed. In the model the optimal harvesting model documented by Bjorndahl (1988, 1990) in which harvesting and feed costs are considered, is extended by including release costs and how they influence the optimal number of recruits. The model forms the basis for an empirical analysis in which the optimal management strategy for a yearclass of Atlantic salmon farmed in Australia during 1989-91 is considered.Environmental Economics and Policy, Research Methods/ Statistical Methods,

OPTIMAL MANAGEMENT OF GIANT-CLAM FARMING IN SOLOMON ISLANDS

Giant-clam farming is undertaken by coastal villagers in Solomon Islands as part of a research and development project of the International Center for Living Aquatic Resources Management (ICLARM). The production technology is simple and does not require a large capital investment. The main inputs are clam seed, labour and time. Labour is used for activities such as seeding, cleaning, thinning and harvesting. In this paper, a bioeconomic model is used to explore optimal farm management. The theoretical basis for this analysis is found in the economic theory of optimal forestry exploitation. The management variables considered are husbandry applied to cleaning and the frequency with which thinning is undertaken. The optimal cycle-length is determined for both a single clam harvest and multiple harvests. The labour requirements of various management scenarios are identified for the multiple-cycle case

Mariculture of giant clams, 'Tridacna crocea' and 'T. derasa': management for maximum profit by smallholders in Solomon Islands

The International Center for Living Aquatic Resources Management (ICLARM) has demonstrated that coastal village communities in Solomon Islands can successfully farm giant clams. The production technology is simple and does not require a large capital investment. The main inputs are clam seed, labour and time. Labour is used for activities such as planting, cleaning, thinning and harvesting. In this paper, a bioeconomic model is used to explore optimal farm management for two species of giant clam fanned for the aquarium and seafood markets. The theoretical basis for this analysis is found in the economic theory of optimal forestry exploitation. Optimal management involves finding the combination of the decision variables and the cycle-length that maximises a stream of discounted profits. The decision variables considered here are husbandry which relates to cleaning, and the frequency with which thinning is undertaken. The optimal cycle-length is determined for both a single clam harvest and multiple harvests for various management scenarios. The labour requirements for these management scenarios are identified for the multiple-harvest case and input substitution between optimal combinations of labour and cycle-length is investigated. Results indicate that profits are maximised for both species when husbandry is excellent and labour usage is most intensive. Thinning is only necessary for seafood clams for which the optimal cycle-length is longer. Village farmers may not be profit maximisers however, and labour spent on giant-clam farming takes them away from other activities. Rather than investing more labour and harvesting the clams earlier, a village farmer with other objectives may devote less labour and harvest the clams later, and spend more time on other activities. In general, these results are consistent with extension advice provided to village farmers by ICLARM. Optimal solutions were found to be very stable when incorporated into global optimisation routines and sensitivity analysis of a wide range of parameter values