Fires in Indonesia, 1997: a Remote Sensing Perspective

Christopher A. Legg and Yves Laumonier

Fires in Indonesia, 1997: A Remote Sensing Perspective

This paper presents a study of the 1997 fires in Indonesia, which was undertaken during October and November 1997, partly to assess the extent and nature of fires during August and September, and partly to undertake real-time monitoring of the fires. Data, mainly in the form of satellite imagery and image products, was obtained from local receiving stations and through the Internet. The distribution of fires in time and space has been assessed, mainly using indicative “hot- spots” from NOAA AVHRR and ERS-2 ATSR imagery. A rough assessment of areas burnt in southern Sumatera up to the end of September 1997 has been undertaken using SPOT digital quicklook imagery, and vegetation classes burnt assessed by interpretation of pre-burn satellite imagery, where available. Major fires started in southern Sumatera and southern Kalimantan in early August 1997 and continued to burn until the second week of November, when they appear to have been extinguished by the arrival of substantial rain. Fires have also burnt for much of this period in southeastern Irian Jaya. The total area burnt in Sumatera Selatan and Lampung provinces of southern Sumatera alone is estimated to be about 1 mill.ha, and the total in all of Indonesia is in excess of 2 mill.ha. Most of this area was not forest, but scrub, grassland and agricultural lands. The most persistent fires, and the source of probably 90% of the smoke haze which blanketed parts of Indonesia and surrounding countries, were 7 clusters of fires along the edges of degraded peat- swamp forests in southern Sumatera and Kalimantan. Almost no fires occurred deep within undisturbed primary forest, and most were associated with land-clearing for new settlements or plantations, or with logging operations.

INTRODUCTION From early September 1997 it was apparent that the unusually dry weather consequent on a major El Niﬁo climatic event had initiated a serious ﬁre episode in Indonesia, especially in Sumatra and Kalimantan. Smoke haze covered large areas of Indonesia, and also affected parts of Malaysia and Singapore, as well as other neighboring countries. By the end of September 1997 smoke haze in parts of Sumatra and Kalimantan had reached extremely high densities, and many airports were closed. A major air crash in northern Sumatera, and a ship collision in the Malacca straits, were blamed, at least in part, on the poor visibility. The ambassadors of member countries of the European Union in Jakarta reacted by forming the European Union Fire Response Group (EUFREG) to report to member countries on the fire situation and on possible modes of international assistance, and at the beginning of October the authors were requested to use remote sensing and GIS techniques to analyze the fire situation and report to EUFREG. Fu11~time study continued through October, and part-time monitoring until mid-November, when the majority of major fires appeared to have ceased. This report summarizes the results of this study.

SOURCES OF DATA At the start of this study, it was anticipated that most data would come from local sources, in particular NOAA AVHRR (National Oceanographic and Atmospheric Administration Advanced Very High Resolution Radiometer) receiving stations in Palembang (Sumatera), Bogor (Java) and Samarinda (Kalimantan). It was also planned to use SPOT (Satellite Pour Observation de la Terre) and Landsat TM (Thematic Mapper) quicklook images, either in analogue or digital form. Within a short time an astonishing number of sites relating to the Indonesian fires appeared on the Intemet, many of them managed by national agencies or satellite receiving stations, but some started by individuals. Collectively these web-sites provided a huge range of timely information on the fires and associated smoke, and presented a shining example of the usefulness of the Internet in rapid response to a major emergency. Much of the data used in this project was obtained on a daily basis from many sites on the Internet. The main data sources are listed in Table 1.

Table 1. Sources of data for 1997 fire study. Data Type Coverage Area Source Access Dates NOAA AVHRR Sumatra EU FFMCP Jaz Drive via Daily for all of imagery, all bands Palembang, courier September and Sumatra October NOAA AVHRR Sumatra and NOAA, USA Internet, noaa.gov October and imagery, band 3 Kalimantan November NOAA AVHRR Irian Jaya DOLA, Perth, Internet Daily for all of Imagery. Quick- Australia www.rss.dolawa.g August, looks ov.au September and October Processed NOAA Kalimantan and Singapore www.gov.sg/metsi Daily from mid- GAC images, with Sumatra Meteorological n September to mid- “Hot-spots” Office November NOAA ‘Hot- Sumatra EU FFMCP Email Daily for spots" Palembang, September, Sumatra October NOAA ‘Hot- Sumatra and JICA/PHPA, Courier Daily for August spots” Kalimantan Bogor, Java and September NOAA “Hot- Kallmantan and GT2, Samarinda, E-mail Daily for all of spots” W. Sulawesi Kalimantan September ERS-2 ATSR Kalimantan and ESA/ESRIN pooh.esrin.esa.it:8 October and ‘Hot-spots” and Sumatra “Earth-Watching" 080/ew/ November images DMSP processed Kalimantan and NOAA DMSO www.ngclc.noaa.g October and images Sumatra site ov/dmsp November TOMS haze All of SE Asia NASA GSFC site jwocky.gsfc.nasa.g Daily from 3 product ov September to 16 November Interpreted maps Parts of US Forest Service www.fs.fed.us/eng Regularly updated of fires Kalimantan and Washington DC /indofire from early Sumatera October to early November SPOT digital Parts of CRISP, National www.crisp.nus.ed Mainly mid- quick-look images Kalimantan, University, u.sg September to mid- Sumatera and Singapore October Sulawesi Landsat TM Irian Jaya ACRES, Alice www.auslig.gov.a September and digital quick-look Springs, Australia u/acres October images Landsat TM Parts of LAPAN, Courier August and analogue quick- Kalimantan and Indonesia September took images Sumatera THE DETECTION AND MONITORING OF FIRES BY REMOTE SENSING So-called “hot-spots” derived from thermal imagery from the AVHRR sensor on NOAA satellites and from the ATSR (Along Track Scanning Radiometer) sensor on ERS-2, are widely used in the detection of fires (1-4). A range of processing techniques permit automated extraction of “hot-spots” in near real-time, which should permit monitoring and rapid response to fires. Hot-spot” extraction techniques normally depend on initial thresholding of AVHRR band 3 imagery (3.5 micron atmospheric window) at pre-set temperature levels, with later filtering of possible fire pixels using data from other wavebands as well as surrounding pixels. All extraction and filtering techniques are strongly dependent for their success on calibration to local land-cover types (5). Errors of omission and commission are common. Fires may not be detected by automated “hot-spot” extraction techniques because they are wholly or partially masked by cloud or smoke. Dense cloud or smoke cover will render the surface completely invisible, while relatively thin cover will tend to attenuate the signal, reducing band 3 pixel values below the threshold value. Spurious “hot-spots” can result from a wide range of circumstances, of which high soil temperatures in areas of sparse vegetation, specular reflectance of sunlight from water, and reflectance from high clouds are the most significant. The three main local sources of AVHRR “hot-spot” data used different algorithms for “hot-spot” extraction. The EU Palembang station used a threshold of 320K, sometimes with contextual filtering. The J ICA (Japan International Cooperation Agency) Bogor station used 3 threshold levels, 310, 315 and 320K, always with contextual filtering. The GTZ (Gesselschaft fur Technische Zusammenarbeiten) Samarinda station used a 310K threshold, but also included albedo levels for bands 1 and 2, as well as band 3 and band 4 temperatures. This would havenabled further filtering if suitable constants for the local environment were known. The algorithm used for extraction of ATSR hot-spots by ESRIN is not known, but is probably also based on thresholding of 3.7 micron band imagery.

A totally different “fire product” became available during October. Processed imagery from the US DMSP (Defense Meteorological Satellite Program) satellite was made available on the Intemet. The main sensor used observed the earth’s surface at visible wavelengths during night, and detected light emissions from ﬁres rather than heat. Archive imagery is used to remove continuous light sources associated with human settlements and other artifacts such as oilfields. Fire locations in this imagery were found to duplicate many of the fires observed in thermal imagery.

The use of data from night satellite passes can eliminate most of the spurious hot-spots observed in NOAA AVHRR imagery. The number of “hot-spots” detected in night imagery is almost always much less than from day passes. This is partly due to the elimination of many of the causes of spurious daytime hot-spots, but may also result from the diumal nature of many short-duration ﬁres. Fires started deliberately to burn agricultural or land-clearing debris will normally be started during the day, and may already have burnt themselves out before the night satellite overpass. In some climates, cloud cover may be more pervasive at night than during the day, obscuring many fire pixels.

Locations of fires can be interpreted visually by on-screen examination of suitably enhanced imagery. A combination of bands 1, 2 and 3 of AVHRR, displayed as blue, green, and red, with band 3 thresholded at about 310K, shows hot pixels as well as smoke plumes. If a fire is defined as only hot pixels with visible smoke emission, many spurious “hot-spots” can be eliminated. With practice, fires in an area covering the whole of southem Sumatera can be interpreted in less than 1 hour. This technique also permits identification of fires partially obscured by smoke or haze, which might not be identified by automated techniques.

For this study it was decided after initial experimentation to use mainly night-pass AVHRR hot- spots for the months of August and September. Data from the JICA Bogor and GTZ Samarinda stations included many night passes, while the EU Palembang station did not routinely archive night pass data. Night-pass hot spots from ATSR, available through the Internet, were used to continue monitoring through October and November, since this data was more readily accessible on a daily basis than data from NOAA receiving stations in Indonesia. While it is recognized that night data may not detect many short-duration ﬁres, it soon became apparent that most of the smoke-haze was generated by long-duration fires, mainly in areas of peat or degraded peat forest. Fires of this type are readily detected by night-pass imagery. As a further check on automatically-generated “hot- spots”, fire locations were interpreted manually from enhanced AVHRR imagery covering Jambi, Sumatera Selatan and Lampung provinces in southern Sumatera for every day in September. Pixels or groups of up to four pixels which are anomalously hot in AVHRR band 3, and which have smoke plumes associated with them, were interpreted as individual ﬁres.

A total of 4450 fires were observed during the whole month. On most days the number of interpreted fires was significantly less (often by a factor of five) than the number of computer- generated “hot-spots” (a result of selecting only those hot pixels with associated smoke), although many interpreted fires in Jambi Province were not detected as “hot-spots” due to attenuation of the signal by haze, which reduced the apparent temperature of pixels to below the automatic detection threshold. Many fires persist for more than a single day, and new fires may start close to previous fire locations. As an indication of fire persistence, and in order to highlight the greatest concentrations of fires, fire locations were grouped in grid-cells 6 km square. This also allows for possible positioning errors of interpreted fires due to poor geo-location of the satellite imagery. Each grid cell was then classified according to the number of days of observed fire. Persistent fires often coincide with known locations of peat and peat forest fires, which are also seen in the NOAA imagery to be the main sources of smoke.

THE 1997 FIRES IN TIME AND SPACE

Sumatera Small scattered fires occur in southern Sumatera throughout the year, but the first major concentrations of fires of the present fire episode appeared in the second week of August in west— central Sumatera Selatan, in and around the extensive Pendopo pulp-wood plantations; along the Jambi - Sumatera Selatan border northwest of Palembang; in north-central Jambi; and in the Berbak National Park, Jambi. By the third week of August fires in these areas had increased in number, and additional fires had appeared in the Pampangan area southeast of Palembang; west of Palembang; between Palembang and the Jambi border; in south-central Sumatera Selatan; in northern Lampung; and in eastem J ambi outside the Berbak National Park. By the end of August, an additional concentration of fires had appeared in northwest Sumatera Selatan. Fires continued in all these areas through September, the greatest concentrations being in four areas: Pampangan; between Palembang and the Jambi border; Pendopo in west central Sumatera Selatan; and eastern Jarnbi close to the Berbak National Park. Fires around Pendopo appear to have been mainly in secondary forest and scrub, but the remaining 3 concentrations were all in areas of degraded peat forests, within the boundaries of logging concessions. The fires appear to have reached their peak in the last week of September, and fires around Pendopo appear to have largely ceased after this. Burning in Pampangan, north of Palembang and eastern Jambi continued through the whole of October, with other scattered fires in south-central and northwestern Sumatera Selatan, and within the Berbak and Way Kambas (Lampung) National Parks. The number of fires decreased slightly at the end of October, and then, within a period of two to three days starting from November 6, all major fires ceased, apparently following torrential rain.

Kalimantan A few scattered fires appeared in the second week of August, mainly in central Kalimantan, northeast of Pangkalanbun and east of Palangkaraya. The number of fires increased greatly during the third week of August, the main concentrations being east of Katopang in west Kalimantan, near Sampit on the south coast, within the ‘Million Hectares” transmigration scheme east of Palangkaraya, and extending west of Palangkaraya towards Pangkalanbun. A new concentration appeared southeast of Kotapang in the fourth week of August, and burning continued in all these sites through September. A new cluster of fires appeared southwest of Sampit in the second week of September, and in southwest Central Kalimantan and on the south coast between Sampit and Banjarmasin in the fourth week of September. Sporadic fires within the Tanjung Puting National Park in Central Kalimantan occurred from the middle of September onwards, reaching a peak in mid-October. Fires in the area south-east of Kotapang appear to have ceased at the end of September, but fires within the “Million Hectares” scheme, north and east of Sampit, and north-west of Palangkaraya appear to have continued throughout October. As in the case of Sumatera, all significant fires seem to have ceased abruptly at the end of the first week of November.

Sulawesi NOAA “hot-spot” data was only available for west-central Sulawesi, but within this area there were no long-duration fires. Most “hot-spots” were checked on SPOT quick-look images, and were found to represent small ﬁres associated with areas of human settlement. Although the data available was by no means comprehensive, it appears that fire damage in Sulawesi was minor in comparison to Kalimantan and Sumatera.

Irian Jaya Irian is outside the reception range of any NOAA station used in this study, and is also beyond the range of the Singapore SPOT receiving station. The only data available were Landsat digital quicklook images from the Australian ground station in Alice Springs, NOAA quicklooks from DOLA in Perth and processed TOMS (Total Ozone Mapping Spectrometer) images from NASA- GSFC. Landsat imagery obtained covered about 60% of Irian Jaya with dates ranging from late August to early October, while daily NOAA passes from September 1 to October 21 were also downloaded. Extensive fires were observed in the lowland savannahs along the southeastern coast. These varied in intensity, with peak fire activity in mid-September, few fires at the end of the month, and a resurgence of buming at the end of the first week of October. There were also fires in the area of the Lorenz National Park in south-central Irian in early September, with renewed activity at the beginning of November. Sporadic fires were observed in the central highlands, particularly between September 6 and September 12, and relatively small fires were seen along the north coast between September 18 and 20. It is understood that seasonal burning is common in the savannah areas of southeastern Irian, to the north and west of Merauke, where there are large transmigrant settlements. The fires this year were almost certainly worse than usual, and resulted in large volumes of smoke, most of which dissipated over the sea to the west and south.

DISTRIBUTION OF SMOKE HAZE Data from the TOMS sensor on the NOAA satellites provides information on the distribution and density of atmospheric aerosols. Goddard Space Flight Centre in the USA, a NASA centre, provided daily images processed from TOMS data, indicating smoke haze distribution in the Indonesian area, from 3 September 1997 until mid-November 1997. An example of the imagery is shown in Figure 3. Visual interpretation of the relative area and density of smoke haze over Sumatera, Kalimantan, and Irian Jaya into 8 classes on a daily basis results in the graph shown in Figure 4. This supports interpretations from “hot-spot” data. Smoke haze was present over Sumatera and Kalimantan at the beginning of September, and increased in area and density until the last week of September. Smoke generation in both areas declined during early October, with renewed peaks of activity in the third week of October and the first week of November before a decline to zero from November 11. There appears to be a time lag of three or four days between disappearance of “hot-spots” and elimination of smoke haze. Smoke generation in Irian Jaya appeared to start only in early September, with peaks of activity in the second and fourth weeks of September, the third week of October and the first and second weeks of November. There appeared to be no smoke between October 1 and 9, and some smoke was still present in the last TOMS image received November 16. _

The TOMS images show that a significant change of mean wind direction at the end of September from southeasterly to easterly reduced the amount of smoke haze over Singapore and Malaysia. Even though buming in Sumatera, Kalimantan, and Irian Jaya continued until early November, the easterly winds restricted most of the air pollution to Indonesia itself, although the pollution in parts of Kalimantan and Sumatera remained extremely serious during this time. Air pollution resulting from fires in Irian Jaya has been little noticed by the international community, since most of the smoke has dissipated over the sea before reaching any major population centers.

PRELIMINARY INDICATIONS OF AREAS AND VEGETATION TYPES BURNT In order to obtain a rapid indication of the areas burnt, digital SPOT quicklook images were used. These can be downloaded from the Centre for Remote Imaging and Processing (CRISP) at the National University of Singapore. The digital quicklooks are sub-sarnpled SPOT scenes, with every sixth pixel and row, and an effective resolution of 120 meters. Coordinates of scene corners are provided on the Internet, permitting rough geolocation. Approximately 150 SPOT-XS quicklook images acquired during late September and early October were downloaded and geolocated. Most covered areas in southern Sumatera, especially Sumatera Selatan and Lampung provinces, but some images covering areas in Kalimantan and Sulawesi were also processed. An example of this imagery is shown in Figure 5.

Geolocated images were then displayed as color composites, and contrast-stretched so as to enhance the darkest areas, thought to be bum-scars. In wet seasons, large areas of very low reflectance can indicate certain types of swamps, but the unusual dry season which permitted the fires has left very little surface water in southern Sumatera, and most of the very low reflectance areas visible in imagery are interpreted as burn-scars. The interpretation of burnt areas was assisted by the simultaneous display of hot spot locations from dates preceding the SPOT images. Only those dark areas including August and September hot-spots were accepted as bum-scars. Margins of interpreted scars were digitized on-screen, and the vector files exported to a GIS. SPOT quick-look images covering a total of 68% of Sumatera Selatan and Lampung, acquired between September 17 and October ll, were studied. The total area of 590 bum-scars in the cloud-free portions of these scenes is 690 000 hectares. If this is extrapolated, simply on the basis of relative areas, to the whole of Sumatera Selatan and Lampung provinces, the total area burnt is estimated at about one million hectares. Since the mean density of “hot-spots” in the area covered by cloud-free SPOT quicklooks is of the same order of magnitude as the density in the remainder of the two provinces, this extrapolation appears justified.

It would be useful to have information on the pre-bum vegetation in each bum-scar. This could best be obtained from recent medium-resolution (Landsat TM or SPOT) imagery. At the time of this rapid study, only June 1994 TM imagery was available in geo-coded form, although some April 1996 imagery was purchased during October 1997. The available imagery only covered about 30% of the area of bum-scars interpreted from SPOT. The relative proportion of each burn~scar occupied by each of 7 broad vegetation/land-use types (types selected for ease of visual interpretation) was estimated by overlaying bum-scars on geocoded 1994 imagery. Preliminary examination of 1996 TM imagery indicates that there has been a decline in areas of disturbed primary forest and secondary forest and an increase in plantations during the period 1994 to 1996. An indication of the proportions of different 1994 land-cover types bumt is given in Table 2.

CONCLUSIONS AND RECOMMENDATIONS FOR FURTHER STUDY This study has shown how near-rea1-time data from the wide range of operational satellites currently available can be used to monitor major fire episodes such as those which occurred in 1997 in Indonesia. Integration of “hot-spots” and other fire indicators within a geographic information system permits early recognition of the most serious fires, in terms of local and regional environments. Digital quicklook images, especially those from the SPOT multispectral sensor, have proved a very useful data source for rapid assessment of bumed areas. The study has also demonstrated the value of the Intemet in rapid dissemination of information on a major intemational environmental disaster, especially when this disaster occurs in a region where information flow is often restricted and slow.

Table 2. Percentage areas of pre-fire land-cover classes, parts of Southern Sumatera. Disturbed Secondary Scrub Plantations Agriculture Grass Swamp Primary Forest Forest 5.1% 31.3% 25% 5.9% 11.5% 16.4% 4.8%

The total area affected by fire between August and November 1997 in Indonesia appears to have been in excess of 2 mill. ha. Most of the fires were apparently associated with agricultural and land- c1earing operations, with probably less than 20% in forest of any kind and less than 3% in primary forest. It appears that most of the smoke, probably in excess of 90%, originated from a relatively small proportion of the fires. These were long-duration fires in degraded peat forest and in deforested areas of peat soils. The main areas of fires were in southern Sumatera and southern Kalimantan, although serious ﬁres also occurred in Irian J aya. These latter fires were 1ittle-noticed because the smoke from them did not affect countries outside Indonesia, and the area was out of range of the main satellite receiving stations used for fire monitoring in Indonesia.

More information is required on the types of Vegetation burnt in these fires, and on human activities in the burnt areas, so as to better plan future fire control programs. It is suggested that studies be undertaken of test areas in Sumatera and Kalimantan, mapping burn-scars using high-resolution satellite imagery, and assessing pre-burn land cover in the burnt areas using satellite imagery acquired before August 1997. Studies should also be continued on the use of NOAA AVHRR imagery for estimation of burnt areas on a national scale, extrapolating outwards from detailed study areas. Communication between existing NOAA AVHRR receiving stations in Indonesia should be improved, and methods for “hot-spot” extraction should be standardized. One additional NOAA receiving station in eastern Indonesia could provide coverage of currently poorly observed areas.

References and Notes

1. Lee, TF. and Tag, P.M. 1990. Improved detection of hotspots using the AVHRR 3.7 micron channel. Bull. Amer. Meteorol. Soc. 71, 1722-1730.

2. Justice, C. and Dowty, P. (eds). 1994. IGBP-DIS satellite ﬁre detection algorithm work- shop technical report. IGBP-DIS working paper No. 9. 88 pp.

3. Malingreau, J.P., Stephens, G. and Fellows, L. 1985. Remote sensing of forest fires: Kalimantan and North Borneo in 1982-83. Ambio 14, 314321.

4. Malingreau, J.P., Jones, S.H., Dwyer, E. and Pinnock, S. 1996. Regional vegetation ﬁre patterns in south and south-east Asia. A satellite based assessment. Conference on Transboundary Pollution and the Sustainability of Tropical Forests. Asean Institute of Forest Management, Malaysia, December 1996. 5. Kennedy, P.J., Belward, AS. and Gregoire, J.-M. 1994. An improved approach to fire monitoring in West Africa using AVHRR data. Int. J. Remote Sensing 15, 2235-2255.

6. The assistance of staff from the EU Forest Fire Prevention and Control Project in Palembang, the JICA NOAA receiving station in Bogor and the GTZ receiving station in Samarinda is gratefully acknowledged. Counterpart staff in the Ministry of Forestry assisted with downloading and geometric correction of SPOT digital quick-look images. N. Jewell of the ODA Indonesia Forest Management Project assisted with initial processing of NOAA data. Numerous web-sites on the Internet, listed in Table l of this paper, provided extremely valuable multi-sensor data during October and November 1997,

7. First submitted 23 March 1998. Accepted for publication after revision 12 November 1998.

Christopher Legg studied geology at Royal School of Mines, London, and has worked as an economic geologist in Zambia, Kenya and Saudi Arabia. He became increasingly involved in satellite remote sensing from 1974, and moved from geology to full-time remote sensing applied to environmental studies. Since 1995 he has worked in Indonesia developing the Integrated Forest Resources Information System, a geographic information system for management of natural forests. His address: EU-FIMP, P. O. Box 7612, JKP 10076, Jakarta, Indonesia. E-mail: [email protected]

Yves Laumonier studied biogeography and vegetation, tropical ecology at University of Toulouse, France, and has worked as a vegetation cartographer and botanist in Indonesia. He graduated from Toulouse University with a PhD on the vegetation of Sumatra Island. Since 1995 he has worked in developing the biodiversity data aspects of the Integrated Forest Resources Information System, a geographic information system for management of natural forests. His address: EU- FIMP, P.O. Box 7612, JKP 10076, Jakarta, Indonesia. , E-mail: y|[email protected]