Lahiru S. Wijedasa

Overcoming Limitations with Landsat Imagery for Mapping of Peat Swamp Forests in Sundaland

Landsat can be used to map tropical forest cover at 15–60 m resolution, which is helpful for detecting small but important perturbations in increasingly fragmented forests. However, among the remaining Landsat satellites, Landsat-5 no longer has global coverage and, since 2003, a mechanical fault in the Scan-Line Corrector (SLC-Off) of the Landsat-7 satellite resulted in a 22–25% data loss in each image. Such issues challenge the use of Landsat for wall-to-wall mapping of tropical forests, and encourage the use of alternative, spatially coarser imagery such as MODIS. Here, we describe and test an alternative method of post-classification compositing of Landsat images for mapping over 20.5 million hectares of peat swamp forest in the biodiversity hotspot of Sundaland. In order to reduce missing data to levels comparable to those prior to the SLC-Off error, we found that, for a combination of Landsat-5 images and SLC-off Landsat-7 images used to create a 2005 composite, 86% of the 58 scenes required one or two images, while 14% required three or more images. For a 2010 composite made using only SLC-Off Landsat-7 images, 64% of the scenes required one or two images and 36% required four or more images. Missing-data levels due to cloud cover and shadows in the pre SLC-Off composites (7.8% and 10.3% for 1990 and 2000 enhanced GeoCover mosaics) are comparable to the post SLC-Off composites (8.2% and 8.3% in the 2005 and 2010 composites). The area-weighted producer’s accuracy for our 2000, 2005 and 2010 composites were 77%, 85% and 86% respectively. Overall, these results show that missing-data levels, classification accuracy, and geographic coverage of Landsat composites are comparable across a 20-year period despite the SLC-Off error since 2003. Correspondingly, Landsat still provides an appreciable utility for monitoring tropical forests, particularly in Sundaland’s rapidly disappearing peat swamp forests.

The need for long‐term remedies for Indonesia's forest fires

In recent months, an environmental disaster with global consequences has been unfolding in Southeast Asia. Unusually extensive and persistent fires in Indonesia have razed thousands of square kilometers of tropical forest and peatland, casting a toxic cloud of smoky haze over the region and dumping billions of tons of CO2 into the atmosphere. Similar fires have occurred annually for decades, but strong El Nino conditions have made this years the worst since 1997. This article is protected by copyright. All rights reserved. Language: en

Time for responsible peatland agriculture.

The 15th International Peat Congress, held in Asia for the first time, brought together industry, policy-makers, and academia to discuss responsible peatland management. In Southeast Asia, peatland management is largely driven by the palm oil industry. After the Congress, misleading reports were

Ant and termite communities in isolated and continuous forest fragments in Singapore

The conservation of tropical rainforest biodiversity is a pressing issue, due to the rapid rate of deforestation. Secondary forests may provide a useful alternative to old growth forests, as they often contain a substantial proportion of the original biodiversity. In this study, we investigate species richness, density and composition of ants and termites in six forest sites in Singapore, each differing in habitat isolation and land-use history. The six sites include an old growth forest, a selectively logged old growth forest, and four secondary forests: either located on abandoned agricultural lands or in abandoned villages, and either isolated or adjacent to old growth forests. We found that the old growth forest had significantly higher species density of ants and termites than any other site. Rarefaction curves showed that ant and termite species richness were highest in the old growth forest followed by the selectively logged forest albeit these results were not significantly different from other sites. Ant species composition changed along a gradient of fragment isolation. Termite community composition in the old growth forest shared a higher proportion of species with the adjacent secondary forest, than with the selectively logged old growth forest, suggesting that the species pool of adjacent habitats is important for species re-colonisation of regenerating habitats. Our results suggest, albeit without replications, that secondary forests differ in conservation value and that disturbed habitats in continuous forest fragments recover more rapidly than isolated ones. Further, we emphasise the importance of old growth forest fragments within man-made ecosystems as sources of original biodiversity.

Bait station preferences in two Macrotermes species

Baiting is considered to be a relatively environmentally benign termite control method; however, all commercial baiting systems are designed for species in the Rhinotermitidae and are used primarily in temperate countries. Fungus-growing termites in the Macrotermitidae can be important pests in tropical countries; they can be difficult to control using all available methods, and there are no baiting systems designed for them. We tested bait station size, an important component of bait station design, against two Macrotermes species in Singapore. Macrotermes gilvus recruited to small stations (0.35 L) very poorly and medium stations (3.6 L) poorly (both similar in size to various commercial stations), but they recruited to large stations (11.5 L) well. Macrotermes carbonarius followed a similar pattern but recruited to fewer stations overall. In the occupied stations, M. gilvus ate the bait wood, sometimes creating a fungus garden inside the stations, and brought little soil into the stations. In comparison, M. carbonarius ate no wood at all, but filled stations with soil. There was significantly less leaf litter around M. carbonarius mounds compared with M. gilvus mounds, although there were no obvious differences in habitat, which suggested that M. carbonarius eats leaf litter only and is not a pest species. Our study shows that stations much larger than current commercial options may provide a useful means for controlling pest wood-eating, fungus-growing termites in tropical countries.

Peat soil bulk density important for estimation of peatland fire emissions.

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/gcb.13364 This article is protected by copyright. All rights reserved. Received Date : 08-May-2016 Accepted Date : 09-May-2016 Article type : Letters to Editor

Carbon emissions from South-East Asian peatlands will increase despite emission-reduction schemes

Carbon emissions from drained peatlands converted to agriculture in South-East Asia (i.e., Peninsular Malaysia, Sumatra and Borneo) are globally significant and increasing. Here, we map the growth of South-East Asian peatland agriculture and estimate CO2 emissions due to peat drainage in relation to official land-use plans with a focus on the reducing emissions from deforestation and degradation (REDD+)-related Indonesian moratorium on granting new concession licences for industrial agriculture and logging. We find that, prior to 2010, 35% of South-East Asian peatlands had been converted to agriculture, principally by smallholder farmers (15% of original peat extent) and industrial oil palm plantations (14%). These conversions resulted in 1.46-6.43 GtCO2 of emissions between 1990 and 2010. This legacy of historical clearances on deep-peat areas will contribute 51% (4.43-11.45 GtCO2 ) of projected future peatland CO2 emissions over the period 2010-2130. In Indonesia, which hosts most of the regions peatland and where concession maps are publicly available, 70% of peatland conversion to agriculture occurred outside of known concessions for industrial plantation development, with smallholders accounting for 60% and industrial oil palm accounting for 34%. Of the remaining Indonesian peat swamp forest (PSF), 45% is not protected, and its conversion would amount to CO2 emissions equivalent to 0.7%-2.3% (5.14-14.93 Gt) of global fossil fuel and cement emissions released between 1990 and 2010. Of the peatland extent included in the moratorium, 48% was no longer forested, and of the PSF included, 40%-48% is likely to be affected by drainage impacts from agricultural areas and will emit CO2 over time. We suggest that recent legislation and policy in Indonesia could provide a means of meaningful emission reductions if focused on revised land-use planning, PSF conservation both inside and outside agricultural concessions, and the development of agricultural practices based on rehabilitating peatland hydrological function.