Source: ASEAN Today
Date: 10 June 2020

New research documents how clearing and drainage of peat forests in Southeast Asia are driving carbon emissions. Using a new remote sensing technique, researchers showed that peatland across the region is sinking—not just on large-scale plantations but also on small farms and in degraded areas.

A new study by researchers in Singapore from the Massachusetts Institute of Technology (MIT) uses satellite data to show just how rapidly Southeast Asia's vital peat forests are being cleared, drained and dried out.

The paper, published in the journal Nature Geoscience, uses remote sensing to document how peatlands across Indonesia and Malaysia are sinking, leading to massive carbon emissions.

The study looked at 2.7 million hectares of forest—more than 10% of Southeast Asia's peatland—and found that 90% of that land was sinking at an average of 2.2 centimetres per year. The research indicates that destruction of peatland is widespread, rather than limited to large-scale plantations.

Until now, studies of peatland draining and drying have required time consuming, point-by-point manual measurements, using poles stuck into the ground. According to study author Alison Hoyt of the Max Planck Institute for Biogeochemistry, the new research represents "the first time that we can make measurements across many different types of land uses rather than just plantations, and across millions of hectares."

Southeast Asia is losing its carbon-dense peat forests

Peatlands are permanently flooded forests that hold thousands of years of dead plant matter. In peat forests, dead leaves, branches, tree trunks and other plant life settle and decay into layer-on-layer of organic carbon, in some cases forming deposits that go up to 19 metres deep. The ground in peatland forests is wetter than in most forests, and the water normally holds the carbon in place instead of allowing it to disperse as carbon dioxide.

The carbon reserves in peat forests resemble the ancient carbon deposits that eventually became the coal we burn today. The Global Peatlands Initiative estimates that 42% of the planet's soil carbon sits in peat reserves. These carbon-dense wetland areas are natural carbon sinks, but when they're drained or burned—which is increasingly common in Southeast Asia—they emit damaging amounts of greenhouse gasses. The burning of dry peatlands is a major driver of forest fires and haze across the region every year.

In Southeast Asia, the primary driver of peat forest degradation is agriculture—oil palm plantations. Especially in Indonesia and Malaysia, swaths of peat forest are drained and cleared to make room for palm oil estates—or in some cases, rice paddies. The pulp, paper and timber industries are also major drivers of peat forest clearing.

In Indonesia, a far-fetched scheme for a new capital city in East Kalimantan further threatens Borneo's peat bogs, and the largest country in the region is already losing its forests at an unnerving rate. At some points in recent years, Indonesia was losing an area of rainforest the size of a football field every 25 seconds.

"Thirty years ago, or even 20 years ago, this land was covered with pristine rainforest with enormous trees," says Professor Charles Harvey, one of the authors and principal investigator at the Singapore-MIT Alliance for Research and Technology. Charles began researching forests in Southeast Asia over a decade ago. "Unfortunately in 13 years, I've seen almost all of these rainforests removed. There's almost none at all anymore, in that short period of time," he said.

New research shows the extent of damage to peatlands and carbon emissions

The new study also shows that peatlands are sinking and emitting carbon, regardless of how the land is being used.

The research team, composed of scientists from Singapore, Brunei and MIT, used a new type of satellite measurement that can precisely detect changes in surface elevation down to the level of centimetres or millimetres. Based on these measurements, the team was able to see what percentage of the study area in Indonesia and Malaysia was subsiding and how fast it was sinking.

Because peat bogs and forests are so carbon-dense, this data gives a good indication of how much carbon the degraded peat was emitting into the atmosphere—and how much the changes in the landscape are contributing to climate change.

"It's not just compaction. It's actually mass loss. So measuring rates of subsidence is basically equivalent to measuring emissions of carbon dioxide," said Harvey.

The data showed that peatland continues to sink and release carbon long after it's been drained and cleared.

Professor David Wardle of Nanyang Technological University in Singapore, another regional forest ecology expert, said the new research points to the consequences that come from damaging peatlands. According to Wardle, the study shows "the serious environmental problems that have emerged from peat forest clearing and its conversion and degradation, and, alarmingly, highlights that the problems are worse than we thought they were."