Jukka Miettinen

Remotely sensed evidence of tropical peatland conversion to oil palm

Rising global demands for food and biofuels are driving forest clearance in the tropics. Oil-palm expansion contributes to biodiversity declines and carbon emissions in Southeast Asia. However, the magnitudes of these impacts remain largely unquantified until now. We produce a 250-m spatial resolution map of closed canopy oil-palm plantations in the lowlands of Peninsular Malaysia (2 million ha), Borneo (2.4 million ha), and Sumatra (3.9 million ha). We demonstrate that 6% (or ≈880,000 ha) of tropical peatlands in the region had been converted to oil-palm plantations by the early 2000s. Conversion of peatswamp forests to oil palm led to biodiversity declines of 1% in Borneo (equivalent to four species of forest-dwelling birds), 3.4% in Sumatra (16 species), and 12.1% in Peninsular Malaysia (46 species). This land-use change also contributed to the loss of ≈140 million Mg of aboveground biomass carbon, and annual emissions of ≈4.6 million Mg of belowground carbon from peat oxidation. Additionally, the loss of peatswamp forests implies the loss of carbon sequestration service through peat accumulation, which amounts to ≈660,000 Mg of carbon annually. By 2010, 2.3 million ha of peatswamp forests were clear-felled, and currently occur as degraded lands. Reforestation of these clearings could enhance biodiversity by up to ≈20%, whereas oil-palm establishment would exacerbate species losses by up to ≈12%. To safeguard the regions biodiversity and carbon stocks, conservation and reforestation efforts should target Central Kalimantan, Riau, and West Kalimantan, which retain three-quarters (3.9 million ha) of the remaining peatswamp forests in Southeast Asia.

2010 land cover map of insular Southeast Asia in 250-m spatial resolution

In this letter, we present the methodology and accuracy assessment of a new regional 250-m spatial resolution land cover map of insular Southeast Asia. Nearly 500 daily Moderate Resolution Imaging Spectroradiometer images (acquired 2 January–3 July 2010) were used in the production of the map. Additionally, peatland maps, elevation information and Daichi-Advanced Land Observing Satellite mosaic data were utilized in the mapping process. The map covers the Malaysian Peninsula and the major islands of Sumatra, Java, Borneo, Sulawesi and Mindanao, in addition to the western part of New Guinea and numerous smaller islands. The classification scheme of 13 classes reflects the special characteristics of land cover of insular Southeast Asia, including, for example, peatswamp forests and large-scale palm plantations. The map was assessed to have 85% overall accuracy using high-resolution (10–30 m) satellite data as reference material. It can therefore be considered to provide reliable information on the current status of land cover in this region experiencing rapid land cover changes.

Extent of industrial plantations on Southeast Asian peatlands in 2010 with analysis of historical expansion and future projections

Tropical peatlands cover over 25 Mha in Southeast Asia and are estimated to contain around 70 Gt of carbon. Peat swamp forest ecosystems are an important part of the regions natural resources supporting unique flora and fauna endemic to Southeast Asia. Over recent years, industrial plantation development on peatland, especially for oil palm cultivation, has created intense debate due to its potentially adverse social and environmental effects. The lack of objective up‐to‐date information on the extent of industrial plantations has complicated quantification of their regional and global environmental consequences, both in terms of loss of forest and biodiversity as well as increases in carbon emissions. Based on visual interpretation of high‐resolution (30 m) satellite images, we find that industrial plantations covered over 3.1 Mha (20%) of the peatlands of Peninsular Malaysia, Sumatra and Borneo in 2010, surpassing the area of Belgium and causing an annual carbon emission from peat decomposition of 230–310 Mt CO2e. The majority (62%) of the plantations were located on the island of Sumatra, and over two‐thirds (69%) of all industrial plantations were developed for oil palm cultivation, with the remainder mostly being Acacia plantations for paper pulp production. Historical analysis shows strong acceleration of plantation development in recent years: 70% of all industrial plantations have been established since 2000 and only 4% of the current plantation area existed in 1990. ‘Business‐as‐usual’ projections of future conversion rates, based on historical rates over the past two decades, indicate that 6–9 Mha of peatland in insular Southeast Asia may be converted to plantations by the year 2020, unless land use planning policies or markets for products change. This would increase the annual carbon emission to somewhere between 380 and 920 Mt CO2e by 2020 depending on water management practices and the extent of plantations.

Two decades of destruction in Southeast Asia's peat swamp forests

We used land-cover maps and active fire detection based on satellite imagery to evaluate the rates and spatial distribution of peatland deforestation in Southeast Asia from 1990 to 2010. Over this time period, the proportion of forest cover in the peatlands of Peninsular Malaysia, Sumatra, and Borneo fell from 77% to 36%. After two decades of extensive deforestation (31 000 km2; 4.9% yr−1) strongly associated with fire activity, Sumatra has been left with just 28% of its historical forested peatlands. If peatland deforestation is allowed to continue at current rates, the Southeast Asian peat swamp forests will disappear by around 2030. This will have serious consequences for the local communities that rely on the environmental services provided by peat swamp forests, will lead to the extinction of peat swamp forest species endemic to this region, and will contribute to global carbon emissions.

Separability of insular Southeast Asian woody plantation species in the 50 m resolution ALOS PALSAR mosaic product

Four types of woody plantations dominate in insular Southeast Asia: oil palm (Elaeis guineensis), rubber (Hevea brasiliensis), wattles (Acacia spp.) and coconut (Cocos nucifera). Because of the economic importance and socio-environmental controversies related particularly to oil palm cultivation, capability to perform large-scale plantation monitoring is urgently needed in this region. In this letter we report initial findings on the potential of Daichi-Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data for regional level woody plantation monitoring. We found very high separability between rubber, wattles and palms (oil palm and coconut combined) in known closed canopy plantation areas using the annually created 50 m resolution orthorectified mosaic products. Further investigation is needed to find the best ways to implement this ability in practice. Nevertheless, the findings may enable regional plantation monitoring in insular Southeast Asia at an unprecedented level of accuracy and detail.

Burnt area estimation for the year 2005 in Borneo using multi-resolution satellite imagery

Humid tropical South-East Asia suffers significant yearly biomass burning. This paper evaluates and compares the results of medium-resolution (MODIS) burnt area mapping and hotspot-based assessment of fire affected areas in Borneo in 2005, using field observations and high resolution Landsat ETM+ data as reference. Based on burnt area mapping, over 600 000 ha burnt in large-scale vegetation fires. Approximately 90% of this burning took place in degraded ecosystems and was related to agricultural land clearing activities or logged over forests. The estimation based on active fire detection (hotspots) resulted in a total burnt area of more than 1.1 million hectares. The reason for this significant difference was that small scale shifting cultivation fires could not be detected in MODIS images. These results indicate that a combination of both methods is required to reliably assess burnt areas in Borneo using medium-resolution MODIS satellite imagery.

Burn-scar patterns and their effect on regional burnt-area mapping in insular South-East Asia

This study aimed to deepen understanding on the limits imposed by burn-scar patterns and size distribution on regional burnt-area mapping with medium to coarse resolution (250–1000 m) satellite imagery in insular South-East Asia. Burnt-area maps based on 16 high-resolution SPOT 4 HRVIR and 5 HRG images were analysed in combination with land-cover and soil maps. Although the number of small burn scars (<25ha) was high throughout the region, the proportion of total burnt-area found in small scars varied remarkably (from 3 to 97%) between study sites. Unlike land cover, soil type was found to be a good indicator for usability of medium to coarse-resolution burnt-area mapping owing to the high occurrence of large burn scars on peatland and other wetland areas. A medium-resolution burnt-area mapping simulation (where 500 × 500-m grid cells containing ≥50% burnt area were considered detectable) resulted in 86% detected burnt area in wetlands (peat and alluvial soils) as opposed to only 33% in non-wetland areas. We thereby conclude that burn scar patterns and size distribution permit reliable regional burnt-area mapping with medium to coarse-resolution satellite imagery in the wetlands of insular South-East Asia, whereas alternative methods may need to be used in non-wetland areas.

Global extinctions of freshwater fishes follow peatland conversion in Sundaland

The peat swamp forests (PSFs) of Sundaland, in Southeast Asia, support many endemic freshwater fish species. However, the future of these species is in doubt, owing to ongoing PSF deforestation. Here, we show that, if current rates of PSF conversion to a predominantly agricultural mosaic landscape continue through 2050, 16 fish species may become globally extinct. In the worst-case scenario, where the rate of conversion across the region matches that of the most rapidly deforested river basin, 77% (79 of 102 species) of the narrowly adapted (stenotopic) fish species are likely to become extinct, a figure that would more than double known extinctions of the worlds freshwater fishes. As indicated by our analysis, the PSFs of Indonesias Central Kalimantan region would be most severely impacted.

New 500 m spatial resolution land cover map of the western insular Southeast Asia region

This letter presents the methodology and accuracy assessment of a new 500 m spatial resolution land cover map of the western part of insular Southeast Asia. The map was produced using 250 Moderate Resolution Imaging Spectroradiometer (MODIS) images (acquired 1 January–2 July 2007), elevation information and peatland maps. The map covers the Malaysian Peninsula and the major islands of Sumatra, Java and Borneo, in addition to numerous smaller islands. The classification scheme of 12 classes reflects the special characteristics of land cover of insular Southeast Asia. With an overall accuracy of 82%, the map provides reliable new information on the current land cover distribution in this region, which is experiencing rapid land cover changes.

Detection of vegetation fires and burnt areas by remote sensing in insular Southeast Asian conditions: current status of knowledge and future challenges

The humid tropical insular Southeast Asian region is one of the most biologically diverse areas in the world. It contains around 70 Gt of carbon stored in peat deposits susceptible to burning when drained and it has significantly higher population density than any other humid tropical region. This region experiences yearly fire activity of anthropogenic origin with widely varying extent and severity. At the same time, there are several geographic, climatic, and social aspects that complicate fire monitoring in the region. In this review article, we analyse the current knowledge and limitations of active fire detection and burnt area mapping in insular Southeast Asia, highlighting the special characteristics of the region that affect all types of remote-sensing-based regional-level fire monitoring. We conclude that the monitoring methods currently employed have serious limitations that directly affect the reliability of results for fire and burnt area monitoring in this region. With the materials and methods presently available, the regional and global effects of fire activity taking place in insular Southeast Asia are in danger of being underestimated. New approaches utilizing higher spatial and temporal resolution remote-sensing data are needed for more detailed quantification of fire activity and subsequently improved estimation of the effects of fires in this region.