Impact assessment of co-management strategies on forest ecosystem in protected areas of Bangladesh using remote sensing and GIS based analysis

Co-management of Protected Areas (PAs) has emerged as a strategy to make forest restoration and biodiversity conservation more effective by encouraging the active participation of local people. This study analyzed the co-management effects in two protected areas i.e. Dharmapur Shal Forest and Nawabganj National Park in Dinajpur District, Bangladesh. Land use and land cover change were monitored between 1990 and 2022 using Landsat images. The study considered four main categories: forests, encroached areas, barren lands and water bodies. The findings indicated that forest cover diminished in both forests between 1990 and 2003, but experienced a significant recovery by 2022. The expanse of Dharmapur Shal forest diminished from 552.05 hectares in 1990 to 469.95 hectares in 2003, then rising to 550.41 hectares in 2022. While the forest cover in Nawabganj National Park declined from 454.18 hectares to 393.72 hectares, it recovered to 432.36 hectares in 2022, suggesting a positive association between co-management implementation and forest recovery. However, 2023 ground-truth data indicates that while native Shorea robusta remains dominant (60–65% in Dharmapur; 75–80% in Nawabganj), the forest recovery includes a significant component of exotic plantations ( Acacia and Eucalyptus ) established in previously degraded areas. This suggests a shift in forest composition alongside overall increase in canopy cover. Classification accuracy for 2022 was assessed using a confusion matrix against 120 ground-truth points, achieving an overall accuracy of 86.67% (Kappa = 0.82). Producer's and user's accuracies ranged from 78.57 to 93.33%, with the primary confusion observed between Barren Land and Encroached Area classes. Barren land initially increased and decreased in both areas, while water bodies remained relatively stable. Ecosystem service values (ESVs) related to carbon sequestration, biodiversity and water regulation also improved, based on global valuation coefficients rather than site-specific estimates. Stakeholder perception analysis, including forest officials and local communities, revealed strong support for co-management, citing enhanced forest cover, increased native species and reduced illegal extraction. However, challenges remain in achieving historical biodiversity levels. This study highlights the potential of co-management in forest restoration and sustainable land governance in developing countries and provides evidence-based insights to inform future policy and planning.