[H-TT15] Geographic Information Systems and Cartography

[HTT15-05] Assessment of the effects of mining activities on forest resources using remote sensing and GIS: A case study of the Atewa Forest Reserve in Ghana

★Invited Papers

*Lukman Boakye Adams¹, Yuichi S. Hayakawa² (1.Graduate School of Environmental Science, Hokkaido University, 2.Faculty of Environmental Earth Science, Hokkaido University)

Keywords:Forest Reserve, GEOBIA, Alluvial , Mine, Land use, Land cover

The geological setting of the Atewa Forest Reserve in southern Ghana has led to the establishment of some registered mining companies around the forest with a good number of illegal miners reported to be operating within the forest as well. The study aimed to use automated methods to map the annual dynamics of mining activities within the Atewa landscape and the Atewa forest reserve. High-resolution Planetscope satellite images for the periods 2018, 2020, 2021, 2022, and 2023 were used to assess the annual dynamics of land use land cover (LULC) within and around the forest reserve with emphasis on alluvial mines through Geographic Object-based Image Analysis (OBIA). With overall accuracies of above 86%, change detection analysis from GEOBIA indicated that Shrub and Herb was the class mostly converted to Alluvial Mine in the landscape constituting 61% of the annual average of all classes converted into Alluvial Mine. Alluvial mines were mostly converted into Shrub and Herb annually, representing 53% of the annual average of all classes that Alluvial mine was converted into in the landscape. Within the forest reserve, Forest was mostly converted into Alluvial Mine, while Alluvial Mine was mostly converted into Shrubs and Herb, representing 36 and 49% of the annual averages of all classes converted into and from Alluvial Mine respectively. Annually, an average of 38% of the total area transformed into Alluvial Mine was backfilled while 69% of vegetation transformed into Alluvial Mine was recovered in the landscape. Annual backfilling within the forest reserve was 27% of the total area transformed into alluvial mines while vegetation recovery rate was 54%. Alluvial mines that exist within the forest reserve have shorter life spans compared to those outside as 3% of mines that existed in the forest reserve in 2018 persisted in 2023. Twenty-one percent of mines that existed in 2018 outside the forest reserve remained in 2023. Average Nearest Neighbour statistics indicated statistically significant clustering in alluvial mines annually while Ripley’s K-function showed that clustering was significant at all distances for all periods except in 2018 and 2022 where dispersion became statistically significant from distances 11 km and 11.5 km respectively. This supports the finding from this study that reveals that contrary to the 100 m riparian buffer zone policy for managing freshwater bodies in Ghana, an annual average of 63.8% of alluvial mines in the study area were concentrated within 300 m off the water mark.
The results from this research show an alarming rate of mining activities within and around the Atewa Forest Reserve and require that swift conservation measures be implemented to protect the forest reserve.