Economic analysis of insect damage in forests in terms of sustainable forestry (Bartın example)

One of the factors that have a negative impact on the development, continuity, production amount, diversity and operating income of forest ecosystems and thus on sustainable forestry is insects that cause damage in forests. For this reason, it is necessary to determine the value of the economic losses caused by harmful insects in the forest tree stock, wood production amount and business income and to include the results in the decision-making processes in insect control efforts. This study was carried out to analyze the economic losses caused by insects that damage forests in the Bartın province on tree stock and wood production with a multi-dimensional approach and to reveal how the obtained results can be included in decision-making processes in sustainable forest management. For this purpose, in this study carried out between 2021-2024; a total of 648 increment pencils were taken from 19 temporary trial areas, nine from black pine stands affected by the pine processionary moth (Thaumetopoea wilkinsoni Tams.) and five from same-aged and different-aged fir stands affected by the fir engraver beetle (Pityokteines curvidens Germ.), and data on increment and growth were obtained. In addition, rainfall and temperature data, production costs and product sales prices, culture and general management costs, amount of damaged products, product variety conversion rate and pest control costs were obtained from different data sources. As a result of the evaluation of the obtained data; in the damage period (2015-2017), 26.72% volume increase loss in the medium damage group and 35.09% in the very damage group in the black pine stands were detected, while the damaged tree volume percentage in the fir stands varied between 23-25%. The determination of land yield and tree stock values of healthy and damaged stands was made via the Forest Valuation Methods, the foundations of which were developed by Faustmann (1849). In black pine, economic value losses (AFK = ADK + FDK) were calculated by taking the differences between the values of healthy and damaged stands within a total of seven scenarios. By adding the pest control expense (MEK) to these losses, the total economic loss (KTEK) was found as KTEK=225,180 TL/ha for 100-year-old good site in the medium-damaged group and 175,681 TL/ha for bad site; and KTEK=251,257 TL/ha for 100-year-old good site in the very-damaged group and 187,395 TL/ha for bad site. Since there is no damage caused by increment losses in fir, economic losses (GTEK) were found as GTEK=2,343.80 TL/ha for same-aged stands and GTEK=6,016.70 TL/ha for different-aged stands in the first period by adding the value losses caused by the transformation of product varieties (UDK) and the actual cost increase (FDK) and the pest control cost (MEK). According to the findings, by comparing the costs of pest control with the economic value losses caused by the insect in tree stock and wood raw material production, it was revealed how the decision of whether or not to combat insects will be carried out in terms of sustainable forestry will be reflected in the decision-making processes. Accordingly, it was determined that it is economically viable to control the insect in good sites and only in young stands in black pine, but it is not economically viable to control it in good sites after 100 years of age and in bad sites after 80 years of age. In fir, it was determined that it is economically viable to combat the fir engraver beetle at all ages, regardless of the type of operation and site. According to these results, some suggestions were developed to form a basis for strategies that evaluate economic and ecological criteria together to reduce the negative effects of harmful insects in forests and to increase the effectiveness in sustainable forest management.