Suchergebnisse

Many peatlands in Europe and North America have been developed for agriculture for over a century, whilst in Southeast Asia development has largely occurred since 1990. Cultivation of drained peatlands now supports the livelihoods of large numbers of people, and the ongoing economic development of countries such as Indonesia and Malaysia. However, peat subsidence linked to plantation drainage represents both an environmental and a socio-economic challenge, associated with elevated CO2 emissions, impacts on adjacent forest habitat, and long-term changes in plantation drainability. Whilst the fundamental challenges presented by peat subsidence are broadly recognised, the long-term rates and the potential for mitigation or avoidance of subsidence remain uncertain. We analysed over 2000 site-years of subsidence measurements from 312 sites in Sumatra, Indonesia, collected under Acacia pulpwood plantation and adjacent native forest, representing the largest peat subsidence dataset published to date. Subsidence averaged 4.3 cm yr−1 in the Acacia plantations, and extended at least 300 m into adjacent forest. Mean water table depth (WTD) was the best predictor of subsidence rate in both plantation and forest areas. We did not find conclusive evidence that subsidence was intrinsically faster under Acacia plantation than under native forest or (by comparison with previous studies) oil palm plantations for the same level of drainage. Our results suggest that raising average WTDs to the Indonesian Government's 40 cm target could – if practically and economically viable means of achieving this can be developed – reduce current plantation subsidence rates by 25–30%. Whilst some degree of peat subsidence under any form of plantation management may be unavoidable, these reductions would – if achieved at scale – both increase the economic lifetime of the plantations, and simultaneously deliver reductions in CO2 emissions of national and global significance. ; CE, SP and AL undertook the analysis described in this paper as part of their contribution to the Independent Peat Expert Working Group (IPEWG), which was set up and funded by Asia Pacific Resources International Ltd. (APRIL) to provide objective science-based advice on peatland management. JW's contribution was also supported by APRIL via the IPEWG. YS and MFH are employees of APRIL, and FK and DI were separately commissioned by APRIL to provide an independent analysis of the subsidence dataset. All views expressed are the authors' own. ; Peer-reviewed ; Publisher Version

Many peatlands in Europe and North America have been developed for agriculture for over a century, whilst in Southeast Asia development has largely occurred since 1990. Cultivation of drained peatlands now supports the livelihoods of large numbers of people, and the ongoing economic development of countries such as Indonesia and Malaysia. However, peat subsidence linked to plantation drainage represents both an environmental and a socio-economic challenge, associated with elevated CO2 emissions, impacts on adjacent forest habitat, and long-term changes in plantation drainability. Whilst the fundamental challenges presented by peat subsidence are broadly recognised, the long-term rates and the potential for mitigation or avoidance of subsidence remain uncertain. We analysed over 2000 site-years of subsidence measurements from 312 sites in Sumatra, Indonesia, collected under Acacia pulpwood plantation and adjacent native forest, representing the largest peat subsidence dataset published to date. Subsidence averaged 4.3 cm yr−1 in the Acacia plantations, and extended at least 300 m into adjacent forest. Mean water table depth (WTD) was the best predictor of subsidence rate in both plantation and forest areas. We did not find conclusive evidence that subsidence was intrinsically faster under Acacia plantation than under native forest or (by comparison with previous studies) oil palm plantations for the same level of drainage. Our results suggest that raising average WTDs to the Indonesian Government's 40 cm target could – if practically and economically viable means of achieving this can be developed – reduce current plantation subsidence rates by 25–30%. Whilst some degree of peat subsidence under any form of plantation management may be unavoidable, these reductions would – if achieved at scale – both increase the economic lifetime of the plantations, and simultaneously deliver reductions in CO2 emissions of national and global significance.

The file associated with this record is under embargo until 6 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above. ; Peatlands are carbon-rich ecosystems that cover just three per cent of Earth's land surface1, but store one-third of soil carbon2. Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests2, 3. Here we present field measurements from one of the world's most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin4. We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene5. The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900–156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent2. We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 1015 grams) of carbon belowground (95 per cent confidence interval of 6.3–46.8 petagrams of carbon)—a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin6. Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by 36 per cent, to 104.7 petagrams of carbon (minimum estimate of 69.6 petagrams of carbon; maximum estimate of 129.8 petagrams of carbon2). This stored carbon is vulnerable to land-use change and any future reduction in precipitation 7, 8. ; We thank the Wildlife Conservation Society Congo Programme for logistical support and the villages that hosted our fieldwork: Bokatola, Bolembe, Bondoki, Bondzale, Ekolongouma, Ekondzo, Itanga, Mbala and Moungouma. We thank F. Twagirashyaka, T. F. Moussavou, P. Telfer, A. Pokempner, J. J. Loumeto and A. Rahïm (logistics); R. Mbongo, P. Abia (deceased), T. Angoni, C. Bitene, J. B. Bobetolo, C. Bonguento, J. Dibeka, B. Elongo, C. Fatty, M. Ismael, M. Iwango, G. Makweka, L. Mandomba, C. Miyeba, A. Mobembe, E. B. Moniobo, F. Mosibikondo, F. Mouapeta, G. Ngongo, G. Nsengue, L. Nzambi and J. Saboa (field assistance); M. Gilpin, D. Ashley and R. Gasior (laboratory assistance); D. Quincy (remote sensing and GIS support); D. Harris, J. M. Moutsambote (plant identification); P. Gulliver (radiocarbon analyses); F. Draper (access to Peruvian data); and T. Kelly and D. Young (discussions). The work was funded by Natural Environment Research Council (CASE award to S.L.L. and G.C.D.; fellowship to E.M.; NERC Radiocarbon Facility NRCF010001 (alloc. no. 1688.0313 and 1797.0414) to I.T.L., S.L.L. and G.C.D.); Wildlife Conservation Society-Congo (to G.C.D.), the Royal Society (to S.L.L.), Philip Leverhulme Prize (to S.L.L.), and the European Union (FP7, GEOCARBON to S.L.L.; ERC T-FORCES to S.L.L.). JAXA, METI, USGS, NASA and OSFAC are acknowledged for collecting and/or processing remote sensing data. ; Peer-reviewed ; Post-print