A bio-economic model for optimal harvest of timber and moose

We present a dynamic optimization model for harvesting timber and moose when the moose inflicts costs by browsing young trees. To illustrate its behaviour, the model was run numerically for Norwegian market conditions. Optimal management in our model kept moose at an approximately 70% lower density than if managed without concern for timber production. Further, the harvest of moose was slightly reduced around the time of timbering to take advantage of increased forage production in coming years. Thereby a fluctuating pattern in moose harvest was generated over time. The amplitude of these fluctuations depended on the productivity of the site, while the period of the fluctuations depended on the fixed costs of harvesting timber. On a particular land, the optimal harvesting strategy for timber was determined by (i) the relationship between timber prices and fixed costs of harvesting, (ii) the relationship between prices of timber and moose, and (iii) the length of the planning period in relation to initial standing biomass of trees. Within a wide range of the present market regime, combined production of both timber and moose was the most profitable strategy. Still, for all our planning scenarios more than 90% of the income came from timber. To give this and similar models accurate applied value, more field data are needed to adequately quantify the interactions between moose and forest vegetation.