Land rewetting can restore tropical peatlands without affecting farmers

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Image credit: Wikipedia Commons.

Southeast Asia’s tropical peatlands are huge underground carbon sinks, while peat swamp forests have unique and currently threatened biodiversity. Conserving these two environments and restoring them is an important part of our climate change efforts as well as our efforts to preserve unique ecosystems. However, vast amounts of peat forests have been cleared and peatlands drained for cultivation, leading to a combination of carbon emissions, biodiversity loss and land subsidence.

Now, a new study has found a possible route. Researchers studied tropical peatland restoration efforts in Indonesia and found that draining peatlands for cultivation affected oil palm viability as well as bird species diversity. Instead, restoring the natural flow of water (a process called ‘rewetting’) can conserve both biodiversity and farmers’ livelihoods.

“Tropical peatlands in Indonesia have been drained to allow farmer access and improve crop yields, but we found no trade-off between drainage depth, yields, and bird diversity in small palm palm farms. oil,” explain the authors of the new study. “Current restoration initiatives aimed at re-wetting peat can benefit farmers by reducing fire risk.”

Bogs and fires

This study was part of a larger project focusing on the restoration of tropical peatlands in Indonesia, led by University of York researchers at the Indonesia Center for Agricultural Land Resources Research and Development (ICALRRD). This work was initiated in response to the fires and pollution crisis which affected Indonesia and the wider region in 2015, driving peatland restoration efforts in the country.

“In our research project, we sought to assess how peat restoration efforts that aimed to raise water levels in drained peatlands had affected the livelihoods of people cultivating the peatlands, as well as the biodiversity of the peatlands. bog habitats, either on farms or in remaining natural bogs. habitat,” Eleanor Warren-Thomas, the study’s lead author, told ZME Science.

Indonesia has almost 50% of the world’s tropical peatlands, mainly on the islands of Borneo and Sumatra. Forests covered 76% of Sumatra’s peatlands in 1990, but in 2015, 66% was covered with plantations, mainly oil palm. Drainage is considered necessary to maintain oil palm yields, as prolonged flooding reduces fruit production because the roots cannot breathe under prolonged flooding.

However, draining peatlands mean that Sumatra is currently a hotspot for peat fires, and agricultural practices have caused more fires in the zone. Peatland restoration activities are currently underway, primarily focused on re-wetting cultivated areas by blocking drainage channels to reduce fire risk, driven by the introduction of new requirements. Mandates of law average water table depth of -40 cm in cultivated peatlands.

Warren-Thomas and the research team investigated smallholder oil palm farms in Jambi Province, Sumatra, in hopes of finding out whether the water levels in the farms (the water table in the soil bogs, under the ground) had an effect on the yield of oil palm on the farms, on the vegetation that grows between the oil palms on the farms, and then in turn, the birds living on these farms.

Overall, the study showed that there was no apparent difference in oil palm yields in the water table depth range between the studied farms (from -3 cm to -50 cm under the ground). Water levels also did not appear to affect vegetation much, nor birds living on farms, meaning that higher water levels should reduce the risk of peat fires without negatively impacting yields.

The researchers also found that the area of ​​remaining peat swamp forest next to the farms contained over ninety species of birds of species almost completely different from those found at the oil palm farms (where they found 48 species). This means that this forest is important for the conservation of birds and other wildlife living in the landscape. In other words, rewetting peatlands would help local ecosystems at no cost to farmers.

“We also know that in the longer term, cultivation on peatlands may not be possible, because due to drainage the peat slowly decays and subsides to the permanent water table and the clay under the peat. Once that happened, the land would be completely flooded and it would no longer be possible to cultivate it,” Warren-Thomas told ZME Science.

Despite these findings, researchers recognize the big challenges ahead. People have strong economic interests related to the cultivation of peatlands, and currently it mainly depends on drainage. Some crops can be grown on fully re-wetted bogs, such as jelutong, but currently there is not a big market for it. Changing that could require strong financial incentives, the researchers conclude.

The study was published in the Journal of Applied Ecology.

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