Decline of Sumatran Peat Swamp Forests since 1990
J. Miettinen*, S.C. Liew, L.K. Kwoh
Centre for Remote Imaging, Sensing and Processing, National University of Singapore
10 Lower Kent Ridge Road, Blk S17 level 2, Singapore 119076(crsjim, scliew, lkkwoh)@nus.edu.sg

Abstract – In this paper we highlight the dramatic declineof Sumatran peat swamp forests since 1990. Comparisonof three recently produced land cover maps (1990-20002010) revealed that the proportion of forested peatland inSumatra plunged from 75% to 28% between 1990 and2010, corresponding to over 30 000 km2 of deforested
peatland. These areas were primarily converted toplantations or taken over by secondary regrowth, withsome areas reduced to extremely degraded open fernland.
More detailed provincial level analysis on the three
primary peat provinces in Sumatra revealed that South
Sumatra province lost majority of its peat swamp forests
already by the year 2000, while the deforestation
continued on a very high level in Riau and Jambi
provinces between 2000 and 2010. This ongoing rapid
deforestation of peatlands not only jeopardizes theexistence of the entire peat swamp forest ecosystem inSumatra, but may have direct global consequences
through elevated levels of carbon emissions.
Keywords: Tropical peatland, Deforestation,emissions, Southeast Asia, Plantation development

Carbon1. INTRODUCTION
The approximately 70 000 km2 of peatlands in Sumatra
Island have been estimated to contain 19 Gt of carbon(Wahyunto et al. 2003), making them a globally considerable
surface carbon deposit. In addition, peatlands have valuableecological and hydrological functions. Peatlands e.g. regulate
water flow and thereby stabilize evaporation rates on localand regional level. Furthermore, the Sumatran peat swamp
forest ecosystems support unique flora and fauna partiallyendemic to insular Southeast Asia (Rieley and Page 2005).
Deforestation and land cover changes in peat swamp forest
ecosystems directly affect the balance of the entire peatlandarea and thereby have consequences also on the communities
surrounding the peatlands.
Large scale exploitation of peat swamp forests is a rather
recent phenomenon in Sumatra. Due to development in land
conversion technologies, diminishing forest areas on mineralsoils and escalating demand for forest and agricultural
products, exploitation and conversion of Sumatran peatswamp forests started to accelerate rapidly in the late 1980’s(Silvius and Diemont 2007). Since then, logging, drainage,
plantation development and conversion to small-holder
agricultural areas have taken place at high rate. These
activities not only disturb the ecosystem functions ofpeatland areas but invariably increase carbon emissions dueto the reduction of living biomass, surge in peat
decomposition and increase in fire activity.
Drainage connected to practically all peatland development
lowers the water table level in peatland areas. Low watertable level in turn induces fast decomposition of peat

releasing carbon into the atmosphere (Hooijer et al. 2010).
Moreover, drained peatland areas with degraded vegetation
become extremely vulnerable to yearly fire activity andincrease the risk of periodical severe fire episodes that may inthe worst case release immense quantities of carbon into theatmosphere (Page et al. 2002).
In this paper we highlight the dramatic decline of Sumatran
peat swamp forests since 1990. We use data from two recent
mapping projects (Miettinen and Liew 2010, Miettinen et al.
in press) to derive peat swamp forest extent in Sumatra forthe years 1990, 2000 and 2010. In addition to the total area
statistics, we analyse the spatio-temporal distribution ofpeatland deforestation over the past two decades between thethree main peatland provinces in Sumatra: Riau, Jambi andSouth Sumatra.
2. MATERIALS AND METHODS
2.1 Land cover maps
The 1990 land cover map was based on visual image
interpretation of high resolution (30m) Landsat 5 Thematic
Mapper (TM) satellite data (Miettinen and Liew 2010). The
2000 and 2010 land cover information was obtained fromtwo recently produced regional land cover maps (Miettinen etal. in press). These two maps were based on Moderate
Resolution Imaging Spectroradiometer (MODIS) satellite
sensor data. The classification was performed on a cloud free
250 m resolution composite image using a semi automaticclassification method (Miettinen et al. in press).
The land cover classes of the original land cover maps usedin this study (1990, 2000 and 2010) were simplified to enable
comparative analysis of the status of land cover in 1990,
2000 and 2010. The 1990 map was first converted fromvector to raster format in 250 m spatial resolution
corresponding to the spatial resolution of the 2000 and 2010
maps. Subsequently, the classification structure of theoriginal maps was simplified into six classes (Water, Forest,Plantation/regrowth, Mosaic, Open and Urban).
All degradation levels of the remaining peat swamp forests
were assigned into the Forest-class. The Plantation/regrowthclass included all natural and planted secondary vegetationfrom shrubland and secondary forest to industrial plantations.
The Mosaic-class included areas with a mixture of woody
vegetation and open areas. Typically this land cover classoccurred in either sparsely vegetated newly cleared areas or
small-holder farming areas. And finally, the Open-classincluded agricultural fields and areas that were either bare or
covered by ferns typically less than 2 m in height. All invalid
areas in any of the maps were masked out from all the maps,
thus creating the three maps used in the analysis in this study,
each covering the same valid areas and including the same
six land cover classes.

Table 1. Development of land cover distribution from 1990 to 2010 in Sumatran peatlands.

Water
Peat swamp forest
Plantation/regrowth
Mosaic
Open
Urban
Total

1990
km2%
146
0.2
49216
75.8
2953
4.57258
11.2
5327
8.2
40.064905

1990-2000
km2%/year-1-0.1-18431
-4.6
18803
22.1
442
0.6
-813
-1.6
0-0.9

The overlapping valid area of the 1990, 2000 and 2010 maps
totalled in 65 000 km2, providing 90% coverage of Sumatran
peatlands. Due to the strong simplification of the 1990
classification which had been based on visual interpretationof high resolution satellite images and the over 90% accuracyof the 2000 and 2010 maps in forest/non-forest level, thesimplified land cover maps used in this study were expected
to provide reliable data for the analysis of deforestation rates
1990-2010 and for the analysis of spatial distribution of
deforestation between the three main peatland provinces in
Sumatra Island: Riau, Jambi and South Sumatra. It is
important to remember, however, that the areas considered asforest in these maps include a range of degradation levels.
Thus, the results presented in this can be considered to givean overly optimistic impression on the status peat swamp
forests in Sumatra Island.
2.2 Fire data
Two active fire (i.e. hotspot) datasets were used to visualize
the connection between fire and deforestation in Sumatra
during the past two decades. For the 1990’s, Along Track
Scanning Radiometer (ATSR) active fire detections wereused. The data was produced by European Space Agency(ESA) and downloaded from the ATSR World Fire Atlas(ATSR 2010). This fire dataset was used from its
commencement (July 1996) to the end of 1999. Most
importantly, this dataset covered the exceptionally strong fire
episode in 1997-1998 (Page et al. 2002, Field et al. 2009)induced by extraordinarily strong El Niño conditions.
Moderate Resolution Imaging Spectroradiometer (MODIS)
hotspot data detected by the sensor on board Terra satellite
was used from November 2000 onwards. The data wereproduced and provided by the MODIS Rapid Response
System (Davies et al. 2009). Altogether the ATSR and
MODIS active fire datasets were expected to deliver a good

2000
km2%
145
0.2
30785
47.4
21756
33.5
7700
11.9
4514
7.0
4
0.0
64905

2000-2010
km2%/year18
1.2-12716
-5.2
7654
3.1
1230.24917
7.6
47.42010km2%
1630.3
18069
27.8
29411
45.3
7823
12.1
9432
14.5
80.064905

general impression of fire situation in Sumatra, including
both spatial and temporal distribution.
3. RESULTS AND DISCUSSION
The peat swamp forest cover in Sumatran peatlands dropped
from 75% to 28% between 1990 and 2010 (Table 1). This
corresponds to deforestation of over 31 000 km2 or more than
60% of the peat swamp forest cover in 1990. Regardless ofthe decrease in absolute deforested area from the 1990’s to
the 2000’s, the average yearly rate of deforestation in factincreased from 4.6%/a to 5.2%/a due to the rapidly
diminishing area of remaining forest cover.
Table 1 also reveals that an overwhelming proportion (85%)
of all deforested peatland turned into plantations andsecondary regrowth by 2010. While these areas covered lessthan 5% of peatlands in 1990, they had reached 45%
coverage by 2010. Another significant change in the land
cover distribution in peatland areas was the increase of theproportion of open land from 8% to nearly 15% over the past
two decades. These areas may be new clearances for landdevelopment (e.g. large scale industrial plantations or smallholder farming). However, in many cases they are extremely
degraded areas that have been reduced to open fern land.
Comparison between the three main peatland provinces Riau, Jambi and South Sumatra - revealed significant
variation in temporal distribution of peatland deforestation
within Sumatra. South Sumatra experienced clearly thestrongest deforestation during the 1990’s. It had lost 74% of
its year 1990 peat swamp forest cover by the year 2000. Thislarge scale destruction is expected to have happened largely
through fires that raged in degraded forests during the last
three years of the decade, most notably during the 1997-1998
fire episode (Figure 1b).

Table 2. Development of peat swamp forest cover from 1990 to 2010 in the three main peat provinces of Sumatra.

Riau
Jambi
South Sumatra
Other provinces
Total

1990
km2
%
30962
80.8
4368
78.0
8404
61.9
5481
73.7
49216
75.8

1990-2000
km2%/year
-7726
-2.8
-1757
-5.0
-6189
-12.5
-2759
-6.8
-18431
-4.6

2000
km2
%
23236
60.7
2612
46.6
2215
16.3
2721
36.6
30785
47.4

2000-2010
km2%/year
-9357
-5.0
-994
-4.7-1015-5.9-1350-6.6-12716
-5.2

2010
km2%
13879
36.2
1618
28.9
1200
8.8
1371
18.4
18069
27.8

Figure 1. Deforestation on the peatlands of (a) northern Riau between 2000 and 2010 and (b) South Sumatra and Jambi between
1990 and 2000. Note the concentration of active fire detections (marked as red dots) on deforested peatland areas. The land covertypes refer to decadal changes: e.g. Forest-class refers to areas that remained forest over the entire decade and Deforested-class refersto areas that were deforested during the decade etc.

Since the year 2000, fire has continued to be tightly
connected to peatland deforestation in Sumatra (Figure 1a).
However, it is believed that large proportion of the fire
activity that occurred during the past decade was deliberate
land clearance burning. No region wide episode of wild fires
comparable to the one that took place under theextraordinarily strong El Niño conditions in 1997-1998 took
place during the past decade.
Over the first decade of the new millennium, especially Riau
province experienced dramatic increase in peatland
deforestation (Table 2). This increase is expected to belargely driven by plantation development (based on furtheranalysis of the deforested areas in high resolution satellitedatasets) and fire is believed to have been widely used as atool in land clearance and preparation (Figure 1). Apart fromRiau, both the absolute areas deforested and the yearly
deforestation rates decreased from the 1990’s to the 2000’s inSumatra.
4. CONCLUSION
The figures reported in this paper powerfully highlight thedramatic destruction of Sumatran peat swamp forests over thepast two decades. As a result of all the deforestation revealedin this paper, Sumatran peatlands are now constantly emittinghigh amounts of carbon into the atmosphere due to peat
decomposition (Hooijer et al. 2010), they are extremely
vulnerable to repeated annual fire occurrence further
degrading the area and releasing carbon dioxide into theatmosphere (Langner and Siegert 2009) and they aresusceptible to catastrophic fire events comparable or worse to
the 1997-1998 fires (Page et al. 2002, Field et al. 2009) when
exceptionally strong El Niño conditions arise.

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ACKNOWLEDGEMENTS

D.K. Davies, S. Ilavajhala, M.M. Wong and C.O. Justice,“Fire Information for Resource Management System:Archiving and Distributing MODIS Active Fire Data”, IEEE
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The authors would like to thank the MODIS Rapid Response
Project at the University of Maryland for providing theMODIS active fire data and the European Space Agency forproviding the ATSR active fire data. The authors also
acknowledge financial support from the Agency for Science,Technology and Research (A*STAR) of Singapore for theCentre for Remote Imaging, Sensing and Processing (CRISP)
where this study was conducted.