In late June 2013, smoke billowed from
thousands of fires on the Indonesian island of Sumatra and blew across the
Strait of Malacca to Malaysia and Singapore. Haze-darkened skies have become
all too normal during the tropical dry season in this region; but this year,
air quality degraded more than ever before in Singapore. On June 21, the
nation’s air quality index reached a record 400. The maximum level for good
health is 100.
A close look at Riau—the Sumatran
province closest to Singapore and site of most of the fires—reveals the cause
of the fires: land use. The Operational Land Imager on the Landsat 8 satellite
acquired the top image on June 25, 2013, at the height of the burning episode.
The image was made with a combination of visible (green) and infrared light so
that fires and freshly burned land would stand out. The blue smudge across the
scene is smoke, while higher clouds are white. Fires glow orange, and newly
burned land is dark red. Bare soil or older burn scars are a lighter shade of
red. The fires burn within well-defined, rectangular fields, showing that they
were deliberately set to clear the land for farming.
The lower image, taken by Landsat 8 on
May 24, 2013, shows the same area before the burning started. The grids and
lines indicate that the area is almost entirely devoted to agriculture.
According to land-use maps from the Indonesian government, the dark green
fields are mature forest, likely palm oil and timber plantations. Paler green
areas are either less-mature trees or other crops, and red fields are bare soil
or burned land. The contrast between the two images shows that both mature
forest and other types of land cover burned in June.
The trend of burning for agriculture
holds true throughout Sumatra. Between June 1 and June 25, the Moderate
Resolution Imaging Spectroradiometer (MODIS) sensors on NASA’s Aqua and Terra
satellites counted thousands of fires in Sumatra. Fifty-two percent of the
fires burned in areas zoned for palm oil or pulpwood plantations. Two-thirds of
the fires burned on fertile peat land, where the dense, organic soil burns for
days to weeks and generates more smoke, haze, pollutants, and greenhouse gases
than other types of fire. Unusual wind patterns pushed the smoke toward Singapore
and Malaysia, creating an air quality disaster.
In an effort to curb such burning, the
Indonesian government declared a temporary moratorium on new permits for land
development in primary forest and peat land between 2011 and 2013. The
moratorium has had little impact, according to the U.S. Department of
Agriculture’s Foreign Agricultural Service. Palm oil plantations alone have
increased by an average 630,000 hectares per year between 2011 and 2013, up
from a growth rate of 500,000 hectares per year in the previous decade. This
growth can continue for up to a decade at this rate without breaching the
moratorium because palm oil producers already hold six to seven million
hectares of undeveloped land.
Palm oil production is highly
profitable, and the commodity is an important export for Indonesia, the world’s
largest producer. (Crop analysts forecast a record palm oil harvest of 31
million tons this year.) When converting forest to a palm oil plantation,
growers harvest the timber, and then burn the remaining brush and trees before
planting new seedlings. This means that as palm oil production expands, the
annual fires and associated air quality issues are likely to continue.
References
Borneo Post (2013,
June 21) Singapore haze PSI reads record high of 400 as of 11 am. Accessed July
22, 2013.
Center for
International Forestry Research (2013, July 2) Forests News: New data on Riau
fires generate important insights. Accessed July 22, 2013.
Foreign Agricultural
Service, U.S. Department of Agriculture (2013, June 26) Indonesia: Palm oil
expansion unaffected by forest moratorium. Accessed July 22, 2013.
World Resources
Institute Insights (2013, July 2) How Singapore can help clear the air on haze.
Accessed July 22, 2013.
World Resources
Institute Insights (2013, July 17) Indonesia haze risk will remain high unless
ministers keep promises. Accessed July 22, 2013.
World Resources
Institute Insights (2013, June 25) New data shows Indonesian forest fires a
longstanding crisis. Accessed July 22, 2013.
World Resources
Institute Insights (2013, June 24) WRI releases updated data on the fires in
Indonesia. Accessed July 22, 2013.
NASA Earth Observatory image by Jesse
Allen and Robert Simmon, using Landsat data from the U.S. Geological Survey.
Caption by Holli Riebeek.
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