Deforestation and industrial plantations development in Borneo

In Borneo, ‘Forest’ are areas that area mainly composed of closed-canopy (>90% cover) evergreen Dipterocarps. In some highland regions, ‘Forest’ may also include Kerangas and in coastal areas, mangroves. ‘Intact Forest‘ include pristine old-growth forests, i.e. forests that have never been disturbed by humans, or for which disturbances were too localized to be detected by satellites. ‘Logged Forest‘ are areas of old-growth forest that have been impacted by industrial-scale mechanized selective logging at some point since 1973. They have lost their original structure, but have remained in good condition and regenerate quickly. ‘Regrowth Forest’ are areas of forest that were likely young regrowth in 1973 and resemble old-growth forest in 2015. In 1973, before extractive industries began, forests were mainly Intact (old-growth). ‘Forest’ excludes young forest regrowth, scrublands, tree plantations, agricultural land, and non-vegetated areas. The latter are clumped into ‘Non-Forest’. Method: To map 1973 forest area we analyzed 61 LANDSAT MSS satellite images acquired during the 1970s and spanning the whole Borneo.

In Borneo, ‘Forest’ are areas that area mainly composed of closed-canopy (>90% cover) evergreen Dipterocarps. In some highland regions, ‘Forest’ may also include Kerangas and in coastal areas, mangroves. ‘Intact Forest‘ include pristine old-growth forests, i.e. forests that have never been disturbed by humans, or for which disturbances were too localized to be detected by satellites. ‘Logged Forest‘ are areas of old-growth forest that have been impacted by industrial-scale mechanized selective logging at some point since 1973. They have lost their original structure, but have remained in good condition and regenerate quickly. ‘Regrowth Forest’ are areas of forest that were likely young regrowth in 1973 and resemble old-growth forest in 2015. In 1973, before extractive industries began, forests were mainly Intact (old-growth). ‘Forest’ excludes young forest regrowth, scrublands, tree plantations, agricultural land, and non-vegetated areas. The latter are clumped into ‘Non-Forest’. Method: ‘Forest’ was classified using in the near-infrared, mid-infrared, and red bands of LANDSAT satellite imagery. Various existing datasets have been used. We further divided ‘Forest’ into ‘Intact’ and ‘Logged’ using our published dataset of logging roads and a buffer distance method (see information describing how logging roads have been mapped). Briefly, we consider that a forest area has never been logged if our database of satellite images never detected the presence of large (> 10m wide) logging roads in the forest. Degradation by logging usually becomes undetectable within a few years, due to fast forest re-growth. From a satellite perspective, the spectral colors of forests degraded by logging resemble those of intact forests, which explains why satellite-based deforestation analyses categorize logged forests as forest.

Hydroelectric power dam (Bakun and Murun).

Track the history of the type of vegetation present before plantations became established in concessions of oil palm and pulpwood. For each industrial plantation, we determined in which previous periods Forest was present and then Cleared/Deforested, by intersecting them with the Borneo-wide Deforestation map. For the two target years (1990, 1995), for which no island-wide Deforestation map existed, we delineated the Forest boundary inside each Planted polygon by visual interpretation of satellite imagery. We declared an area Forest when we identified spectral colors characteristic of old-growth or selectively logged closed-canopy evergreen forests in Near-Infrared, Mid-Infrared, and Red bands. We declared an area Cleared when the presence of forest was no longer evident following conversion to small-scale agriculture, mining, permanent flooding, drought and fire.

We digitized the extent of primary logging roads by visually analyzing our 268 LANDSAT images acquired over 1972–2010. Wide logging roads were readily detectable in the LANDSAT imagery. We were capable to detect logging roads under most areas of persistent haze, by zooming in closely and applying a local contrast enhancement, and by digitizing logging roads underneath haze by mouse-click. The expansion of the road network overtime was observed for c.1973, 1990, 2000, and 2010. Imagery acquired a year or two before and after these nominal years served to reduce cloud contamination. We also inspected imagery from ca. 1995 and 2005 to better detect disused logging roads less visible due to rapid forest regrowth. Similarly to our approach for mapping industrial plantations LANDSAT 5&7 (TM and ETM+) images were viewed as band 4-5-3 (or 5-4-3) false color composites enhanced to optimize road detection. Likewise, LANDSAT MSS images were viewed as band 4-3-2 (or 3-4-2). We used ancillary public-road maps from the Indonesian Ministry of Public Works and the Sabah-based NGO HUTAN for Sarawak and Sabah to help distinguish unpaved public roads from logging roads. We further divided ‘Forest’ into ‘Intact’ and ‘Logged’ using our published dataset of logging roads and a buffer distance method (see information describing how logging roads have been mapped). Briefly, we consider that the forest has never been logged if our database of images never detected the presence of large (> 10m wide) logging roads in the forest. Degradation by logging usually becomes undetectable within a few years, due to fast forest re-growth. From a satellite perspective, the spectral colors of logged forests resemble those of intact forests, which explains why recently published state-of-the-art deforestation analyses categorized logged forests as forest.

We mapped the Borneo-wide decline in forest area over four consecutive periods (1973–2000, 2001–2005, 2006–2010, 2011–2015, and for year 2016) 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, and 2016) 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 2016 (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, 2015 and 2016. The final Borneo-wide deforestation maps are: 1) a map showing losses in natural forest area over five consecutive periods between 1973 and 2016; and 2) a map showing annual losses in natural forest area from 2001 until 2016. This dataset is an updated version of similar dataset (Remaining_forest_in_2015_and_deforestation_1973-2015.7z) with an update in year 2016.

Dataset of forest cover in 2016. In Borneo, ‘Forest’ are mainly closed-canopy (>90% cover) and high carbon stock (Above Ground carbon > 150 Mg C/Ha) evergreen Dipterocarps growing on either mineral or peat soils. On peat domes, ‘Forest’ may include low carbon stock pole forests. On highland regions, ‘Forest’ may include Kerangas and in coastal areas, mangroves. ‘Intact Forest‘ are pristine old-growth forests, i.e. forests that have never been disturbed by humans, or for which disturbances were too localized to be detected by satellites. Old-growth forest ecosystems usually include many old (>500 years) closed-canopy emergent trees. ‘Logged Forest’ are intact forests that have been impacted by industrial-scale mechanized selective logging at some point since 1973. They have lost their original structure, but have remained in good condition and regenerate quickly. ‘Regrowth Forest’ are areas of forest that were likely young regrowth in 1973 and resemble intact forest in 2015. In 1973, before extractive industries began, forests were mainly Intact (old-growth). ‘Forest’ excludes young forest regrowth, scrublands, tree plantations, agricultural land, and non-vegetated areas. The latter are clumped into ‘Non-Forest’. This dataset is an updated version from previous version (Forest_area_in_2015.7z) with 2016 deforestation update added to the data.

Track the history of the type of vegetation present before plantations became established in concessions of oil palm and pulpwood. For each industrial plantation, we determined in which previous periods Forest was present and then Cleared/Deforested, by intersecting them with the Borneo-wide Deforestation map. For the two target years (1990, 1995), for which no island-wide Deforestation map existed, we delineated the Forest boundary inside each Planted polygon by visual interpretation of satellite imagery. We declared an area Forest when we identified spectral colors characteristic of old-growth or selectively logged closed-canopy evergreen forests in Near-Infrared, Mid-Infrared, and Red bands. We declared an area Cleared when the presence of forest was no longer evident following conversion to small-scale agriculture, mining, permanent flooding, drought and fire. This dataset is an updated version from previously released dataset (Land_cover_trajectory_before_oil-palm_and_pulpwood establishment.7z) with an update of year 2016.

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).

Burned forests appear distinct from intact and logged forests on LANDSAT imagery. These distinct spectral signals remain visible for several years (Figure 1), which explains why recently published state-of-the-art deforestation analyses detected forests severely degraded by fire as deforested. To estimate the area of burned forest where scrublands have replaced forests before being converted to oil-palm plantations, we reviewed available literature to determine the timing and broad location of fires. Next, we organized our LANDSAT database into imagery acquired before and after seven major fire events noted in our literature search. We then searched for changes in the spectral reflectance of forests that were consistent with changes from high tree cover and species-rich forests to a homogeneous low vegetation cover on the pre- and post-fire imagery. Due to the variety of forest types as well as variable image acquisition conditions in Borneo, and the persistence of cloud cover even during the dry season, we performed this assessment manually by visual interpretation. We note that scrublands mapped in this study may show regeneration potentials in some region, which we do not address in this study