Landscape fragmentation analysis using geospatial tools in Periyar Tiger Reserve, Kerala

Abstract

Periyar Tiger Reserve (PTR) is one of the largest conservation units in Western Ghats and many conservational efforts are formulated and applied in this area. It is also important to monitor the outcome of these efforts to strategize further management techniques. Geoinformatics approach widely used to monitor land use change as well as forest fragmentation, as the satellite data are easily accessible and they are more consistent in assessing global forest change (Hansen et al., 2013, Carranza et al., 2014, Srinivasan et al., 2022). This study compared the fragmentation status of forest habitats of PTR in 1987, 2000 and 2020 by analysing the landscape level and class level conservation measures by employing remote sensing-based datasets on forest cover and fragmentation. The FRAGSTATS software analysis along with the LULC (Land Use Land Cover) classification and NDVI (Normalised difference vegetation Index) analysis of the forest/nonforest classifications for each of the three distinct years revealed the pattern of forest cover change over time. Image frames were compared for each year for PTR and a one km buffer around PTR boundary showed a considerable variation in the forest patch pattern. The results revealed that dense forest patches within PTR had a favourable increase in the area combined with a decrease in fragmentation. The increase in the largest patch index of the dense forest in 2020 showed the positive effect of the declarations, policies and other conservation measures implemented in this area. Comparative increment in NDVI values over the years, 2000 and 2020 indicated a steady increase of healthy vegetation. The prevalence of agriculture and habitation haven't increased noticeably in this study area, despite the fact that open forest, grassland, and rocky and barren terrain exhibit fragmentation during this particular study period. The meagre construction works inside the administrative buffer of PTR and the expansion of dense forest can vote for the decrease of barren land and grassland counted in this study. A slight increase of open patches and an increase of semi-evergreen and moist deciduous patches near the forest adjacent to the buffers showed minor negative effects of buffer on adjacent forest. At the same time a similar trend was observed while comparing PTR with buffer. In fragmentation analysis, buffer also showed decreased fragmentation in the dense vegetation patch after 2000 but here a proportional increase of agriculture and settlement was observed. The findings indicated that this tiger reserve area is very dynamic. After the declaration, efficient conservation measures and eco-friendly regulations showed positive results and has been successful in preventing forest fragmentation. The improvement of protected areas like PTR depends on conservation strategies for its ecological development. The baseline data from this study can be used to prioritise conservation efforts of Periyar Tiger Reserve in Western Ghats. The study also recommends PTR model of conservation to be further extended to other protected areas with local adaptations and modifications.