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Title Exploring the disturbance of East African rainforests using three spatially explicit indices

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Short title Spatially explicit rainforest disturbance indices

Author(s) Mitchell, N.; Schaab, G.

Presenting author Mitchell, N.

Institution(s) Faculty of Geomatics, Karlsruhe University of Applied Sciences

Keywords Rainforest; disturbance; forest cover change; logging; historical

Abstract Anthropogenic disturbance of rainforest in highly populated regions is often cited as the main threat to biodiversity and its effect on forest ecology is a major feature of BIOTA-East research. Three spatially explicit indices on local disturbance, commercial disturbance, and forest cover change are presented here aiming to assess and quantify the varied disturbance regimes at play across both time and space. Satellite imagery, aerial photography, maps, oral histories and forestry records all contribute to the indices which are scaled from 1-10. The spatially explicit nature of most of this input data allows for its combination within a GIS. The local disturbance index is derived from values awarded for proximity to forest edge, roads and settlements, and according to documented reports of illegal activities. Detailed forestry records with supporting evidence from local interviews enable the creation of the commercial disturbance index. The forest cover change index is calculated from the overlay of a visual interpretation of forest cover classes from aerial photography of 1948/(52), (the gaps being filled by old maps), with a Landsat satellite classification of 2003. As such this index reflects the change in forest classes since the start of main commercial extraction from the forest. Comparison with the other indices provides insight into the extent to which forest disturbance in Kakamega should be attributed to locally driven factors and to what extent to commercial factors. A clear correlation is seen between forest cover change and the historical pattern of legal logging which has drastically fragmented the forest. The effects of local people utilizing the forest are less pronounced but are also visible in some areas of higher population with easy road access. The indices show the localised nature of forest disturbance and demonstrate that forest disturbance should be traced by detailed research into both spatially and temporally explicit data sources.

Congress Topic Land use, impact and value

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