Tropical peatland carbon losses from oil palm plantations may be underestimated

A press release from the University of Minnesota: 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 thou
sands 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.

...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.

...Key findings of the study: The lower the water table, the higher the rate of carbon loss[, and m]ore studies in tropical peatland plantations are needed to reduce uncertainty about the global warming potential of peat drainage....

A palm oil plantation in  Cigudeg, Bogor, shot by Achmad Rabin Taim, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license