Assessing Forest Fragmentation and Edge Expansion in Nan Province, Thailand, Using Landsat Data (2014–2022)

Abstract

The increasing pressure from land-use change and agricultural expansion in Nan Province, northern Thailand, has accelerated forest fragmentation and reduced the ecosystem service value (ESV) of the landscape. This study aims to: assess land use and forest fragmentation change 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: forest, agriculture, settlements, exposed soil, and others. Forest fragmentation was evaluated using landscape metrics such as patch number, mean patch size, edge length, and core area. 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 65,000 hectares, primarily due to the expansion of agriculture and exposed soil over 8 years. Forest patches became increasingly fragmented, with a 16.4% increase in patch number and a 26.6% decline in mean patch size. The total forest edge area increased by 7.9%, while core forest area decreased by more than 82,000 hectares. These changes correspond to a 5.95% decline in total ESV, equivalent to a reduction of USD 252 million per year. Forest ecosystems remained the highest contributor to 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 protection of remaining core areas to maintain ecosystem functions and enhance landscape resilience.