Der Klimawandel und der damit verbundene Meeresspiegelanstieg bedrohe ganz besonders Südostasien, schrieb das Potsdam-Institut für Klimafolgenforschung (PIK) in einem Bericht für die Weltbank. Dabei hatte das PIK jedoch nicht nur die Ozeanzyklen übersehen, die den Meeresspiegel in der Region mal schneller und mal langsamer ansteigen lassen, sondern auch unbequeme Folgen der Palmölgewinnung. Die Energiewende und der damit verbundene hohe Bedarf an Palmöl gibt Grund zu großer Sorge: Küstennahe Sumpflandschaften in Südostasien werden unter einem grünen Deckmäntelchen im großen Maßstab entwässert, um lukrative Palmöl-Pflanzungen anzulegen. Dazu gibt es oft dann noch grüne, blaue und sonstwiefarbene Öko-Engel aufgestempelt, die die Maßnahmen im Ausland scheinheilig als nachhaltig ausgeben.
In Wahrheit lässt die massive Entwässerung das Land absinken, was bei Sturmfluten dem salzigen Meerwasser Tür und Tor öffnet. In den kommenden Jahrzehnten wird so der Lebensraum der Menschen versalzen und zerstört, die wirtschaftliche Grundlage der Region geraubt und die Biodiversität untergraben. Durch die Entwässerung gelangen zudem größere Mengen an zusätzlichem CO2 in die Atmosphäre, was den grünen Anstrich des Palmöls weiter abblättern lässt. Die Erkenntnisse wurden im Rahmen einer Studie gewonnen, die kürzlich von Deltares im Rajang-Delta in Malaysia im Auftrag von Wetlands International durchgeführt wurde.
Das Thema scheint die deutsche Presse jedoch nicht im Geringsten zu interessieren. Eine Google-News-Suche ergab, dass offenbar keine einzige Redaktion über die Studie berichtete. Wir wollen die Nachrichtenlücke zu diesem wichtigen Thema gerne füllen. Im Folgenden die Pressemitteilung von Wetlands International vom 6. Juli 2015:
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Peatlands of South East Asia are heading towards a socio-economic disaster
Agricultural production in vast regions of South East Asia will be lost in the coming decades as a result of flooding of extensive lowland landscapes due to unsustainable development and management of peat soils. About 82% of the Rajang Delta in Sarawak (East Malaysia) will be irreversibly flooded within 100 years and substantial areas are already experiencing drainage problems. This will increasingly impact local communities, the economy and biodiversity and will develop over time into disastrous proportions unless land-use on the region’s peatlands is radically changed. Therefore Wetlands International calls for conservation and sustainable management of peatlands in South East Asia.
A study commissioned by Wetlands International and executed by Deltares suggests that extensive drainage of peatlands for oil palm cultivation in the Rajang river delta results in such massive land subsidence that this will lead to extensive and devastating flooding incidents in the coming decades. The study analysed an area of 850,000 hectares of coastal peatlands in Sarawak, and produced a model which demonstrates that in 25 years 42% of the area will experience flooding problems. In 50 years the percentage affected will increase to 56% while the nature of flooding becomes more serious and permanent, and in 100 years 82% of the peatlands will be affected.
Such extensive flooding is due to massive conversion of peat swamp forests to agriculture, mainly oil palm plantations: currently only 16% of Sarawak’s natural peat forests remain. These valuable crops require drainage in order to be profitable. “The results of the model clearly shows the need for a radical change in peatland landuse not only in Sarawak but in all peat landscapes in the region”, said Lee Shin Shin, Senior Technical Officer of Wetlands International – Malaysia.“Current trends whereby vast areas of peatlands are opened up for drainage-based activities will render these areas unproductive and useless and this will adversely impact communities, industries and biodiversity that rely on such areas for their very survival and existence.”
Peat soils are made up of 10% accumulated organic material (carbon) and 90% water. When water is drained from the peat soil, the carbon in the peat soil is turned into CO2 and emitted into the atmosphere causing climate change. This carbon loss reduces the peat volume and thus causes the peat soil to subside. This process continues as long as drainage is continued and until the soil surface reaches sea or river levels constraining the outflow of water and thus leading to flooding. In tropical conditions, peat drainage causes the soil to subsidence at a rate of 1 to 2 metres in the first years of drainage, and 3 to 5 centimetres per year in subsequent years. This results in the subsidence of the soil by up to 1.5 metres within 5 years and 4 to 5 metres within 100 years.
“The study results are very relevant to Indonesia as well, where we observe the same patterns of peat swamp forest conversion, drainage and expansion of oil palm and Acacia for pulp wood plantations”, said Nyoman Suryadiputra, Director of Wetlands International – Indonesia. “Thousands of square kilometres in Sumatra and Kalimantan may become flooded in the same way as the Rajang delta, affecting millions of people who depend on these areas for their livelihoods”.
“Highly developed countries or regions in temperate areas, such as the Netherlands, cope with soil subsidence by building dykes and pump-operated drainage systems, but this is impossible in Malaysia or Indonesia”, explained Marcel Silvius, Programme Head for Climate Smart Land Use at Wetlands International. “The predominantly rural economy along thousands of kilometres of coastline and rivers, combined with the intense tropical rainfall makes it economically and practically impossible to implement such costly water management measures in the Southeast Asian region”.
Governments and industry should therefore immediately stop the conversion of remaining peat forests to agricultural or other use, and actively promote peatland conservation and restoration. Industry will need to phase out drainage-based plantations on peatlands, as these areas will be increasingly subject to flooding and eventually become unsuitable for any form of productive land-use. Effective policies should be drawn up, implemented and enforced to conserve and ensure the wise use of peatlands. There are many crops that can be cultivated on peatlands without drainage. Over 200 commercial local peat forest tree species have been identified, such as Tengkawang (Shorea spp.) which produces an edible oil and Jelutung (a latex producing species). These can provide alternative and sustainable livelihood opportunities for local communities but require piloting, improvement of varieties and up-scaling for industrial plantations.
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Eine weitere aktuelle Studie zeigt deutlich auf, dass die früher behauptete Klimabilanz des Palmöls viel schlechter ausfällt als lange gedacht. Die University of Minnesota gab am 9. Juli 2015 in einer Pressemitteilung bekannt, dass die CO2-Emissionen im Rahmen der Entwässerung der Palmölplantagen wohl knapp doppelt so hoch sind wie vom IPCC im letzten Klimabericht angenommen. Hier die Pressemitteilung in Vollversion (deutsche Zeitungen ignorierten auch die Studie bislang):
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Tropical peatland carbon losses from oil palm plantations may be underestimated
New study uncovers limitations in past carbon calculations, suggests improved strategies
Draining tropical peatlands for oil palm plantations may result in nearly twice as much carbon loss as official estimates, according to a new study by researchers from the University of Minnesota Institute on the Environment and the Union of Concerned Scientists in the journal Environmental Research Letters.
Peatlands — waterlogged, organic soils — have developed over thousands of years as carbon storage systems. In Southeast Asia, peat swamp forests cover about 250,000 square kilometers, a land area about the size of Michigan. In the past 15 years, peatland forests have been rapidly drained and cleared to make way for oil palm and pulpwood plantations. Draining exposes the upper peat layer to oxygen, raising decomposition rates and soil carbon losses. Most of that carbon is emitted to the atmosphere, speeding up climate change.
Kimberly M. Carlson, a postdoctoral research scholar with IonE’s Global Landscapes Initiative, and UCS researchers Lael K. Goodman and Calen C. May-Tobin designed their research to support site-specific greenhouse gas emissions assessments in tropical plantations. “We wanted to know whether water table depth could be used as a proxy for soil carbon loss in peatland plantations,” Carlson explained.
Major international companies that buy and sell products sourced from peatland plantations have committed to reducing their climate footprints. These companies can now trace a product through the supply chain back to its source. Consequently, specific information about the carbon balance of a producing plantation helps companies and consumers better understand the climate implications of purchasing choices.
The study, a comprehensive analysis of scientific literature on tropical plantation peatland carbon balance, found a correlation between long-term water table depth (the distance from the soil surface to the water surface) and soil carbon loss rate. This finding suggests that peat water table monitoring could help companies more accurately measure their greenhouse gas emissions.
The researchers compared two measurements of carbon loss: subsidence and mass balance. To find the subsidence rate, scientists measure how much the land has sunk over time and how much carbon is stored in the soil. Subsidence models alone cannot inform the global warming potential of peatland drainage.
Mass balance models estimate carbon emissions from the balance of carbon gains such as leaf decomposition and losses such as soil carbon dioxide emissions. With this method, both carbon dioxide and methane — a much more potent greenhouse gas — can be measured, permitting more accurate global warming potential assessments.
Carbon losses calculated from mass balance and subsidence methods differed substantially for oil palm plantations. At plantation drainage depths of 70 centimeters, the annual rate of carbon loss determined from the subsidence method is about 20 tons of carbon per hectare per year. This is almost twice the rate of 12 tons of carbon per hectare per year that the International Panel on Climate Change uses to calculate emissions from oil palm land use. This rate, as put forth in the 2013 Supplement to the 2006 Guidelines for National Greenhouse Gas Inventories: Wetlands, is partly based on the mass balance method.
The researchers caution that additional field studies are needed to reconcile these estimates. “While our calculations take advantage of an exciting set of newly published data, a serious lack of research in tropical peatlands means that such estimates of peat carbon loss from plantation systems remain uncertain, and are frequently based on assumptions rather than empirical measurements,” Carlson said.
Water table depth is only one of many factors, such as fertilizer application, that should be considered when quantifying carbon losses from cultivated peatlands.
Key findings of the study:
- The lower the water table, the higher the rate of carbon loss.
- More studies in tropical peatland plantations are needed to reduce uncertainty about the global warming potential of peat drainage.
The authors emphasize that reducing greenhouse gas emissions from peat requires preventing plantation expansion into intact peat swamp forests. “Our findings lend weight to the idea that draining peat soils should be avoided at all costs, due to the impact on global climate,” Goodman said.
The article, “Modeling relationships between water table depth and peat soil carbon loss in Southeast Asian plantations,” was written with support from the Gordon and Betty Moore Foundation, National Academies Keck Futures Initiative, and the European Federation for Transport & Environment.
