District-wise forest area variation in Sri Lanka from 1992 to 2001 for supporting the National Physical Planning Policy

摘要

Sri Lanka does not have a prior experience in preparing a National Physical Planning for its integrated development. The National Physical Planning Department has not only setup a GIS Laboratory to cater to National Physical Planning of Sri Lanka, but it also ventured into acquiring a full Landsat 7 ETM+ coverage of the Island for 1999-2001 in the purpose of updating the island-wide Land Use Mapping. Being a humid tropical country, the large extent of close canopy forest, being mainly primary forest, is the second most important natural resource asset (after water) to be considered for the future development of the Island. Closed Canopy forest mapping was undertaken by the staff of the GIS laboratory on the purpose of deriving district-wise information of forest cover changes over the last 20 years. The method used for classification of the forest land cover was a semi-automated update of previously available map, by means of region growing tools available in GIS/RS typical software. A set of 3 Districts of fast decreasing forest cover and of 5 Districts of substantial increase of forest cover have been identified out of 25 districts of Sri Lanka in the period of 1992-2001. District changes highlight planning policies options of critical importance for the implementation of the National Policy at District level.