Assessing Forest Fragmentation and its Impact on Ecosystem Service Value in Relation to Land Cover Change, Nan Province, Thailand

Abstract

The increasing pressure from land use change and agricultural expansion in Nan Province, northern Thai-land, accelerated forest fragmentation and reduced the ecosystem service value (ESV) of the landscape. This study aims to assess land use and forestland fragmentation changes in Nan Province between 2014 and 2022 and evaluate the impact of land use change on ESV. Landsat 8 OLI satellite imagery from 2014 and 2022 was used to classify land cover into five types: forestland, agriculture, developed-up areas, water bodies, and bare land. Forest fragmentation was evaluated using landscape metrics such as the number of patches, mean patch size, edge length, and core area. The ESV was calculated using the benefit transfer method based on standardized coefficients for each land use class. The results indicate a net loss of forest area of approximately 62,000 ha, primarily due to the expansion of agriculture over 8 years. The forest patches became increasingly fragmented, with a 13.23% increase in the number of patches and a 17.81% decrease in the mean patch size. The total forest edge area increased by 4.6%, while the core forest area decreased by more than 75,000 ha. These changes correspond to a 4.85% decline in total ESV, which is equivalent to a reduction of USD 0.14 million per year. Forest ecosystems remained the greatest contributor to the ESV, but their loss significantly reduced the provision of regulating and supporting services. Future land use planning in Nan Province should prioritize forest restoration and the protection of remaining core areas to maintain eco-system functions and enhance landscape resilience.