We mapped the Borneo-wide decline in forest area over four consecutive periods (1973–2000, 2001–2005, 2006–2010, 2011–2015) by combining four published LANDSAT-based datasets (1,2,3,4). First, we combined two comparable Forest maps (1,2), each showing the extent of natural forests for year 1973 and year 2000 to determine the decline in forest area for the period 1973–2000. Forest in 1973 and Non-Forest in 2000, were recoded as Deforestation for the period 1973–2000. Areas classiﬁed as Non-Forest in 1973 and Forest in 2000, were recoded as Forest Regrowth from 2000 and onwards.
Second, we determined the decline in forest area for recent periods (2000–2005, 2005–2010, and 2010–2015) by combining the 2000 Forest map with a Tree Loss map, derived using an automatic computer code, and revealing annual losses of trees from January 2001 to December 2015 (3,4). We highlight that this Tree Loss map does not distinguish between removal of natural and planted trees. To reduce any error resulting from this ambiguity, we excluded Tree Loss signals that were outside of the area occupied by natural forests according to the 2000 Forest map, to only determine losses in natural forest area rather than losses in planted trees. In doing so, we generated three Deforestation maps for 2000–2005, 2006–2010, and 2011–2015 and three additional Forest maps for years 2005, 2010 and 2015. The ﬁnal Borneo-wide map is a map showing losses in natural forest area over four consecutive periods between 1973 and 2015.
(1) Gaveau, D. L. A. et al. Four decades of forest persistence, clearance and logging on Borneo. PloS One 9, e101654 (2014).
(2) Margono, B. A., Potapov, P. V., Turubanova, S., Stolle, F. & Hansen, M. C. Primary forest cover loss in Indonesia over 2000–2012. Nature Climate Change (2014).
(3) Hansen, M. et al. High-resolution global maps of 21st-century forest cover change. science 342, 850–853 (2013).
(4) Hansen, M. C. et al. Humid tropical forest disturbance alerts using Landsat data. Environmental Research Letters 11, 034008 (2016).