The truth about oil palms and carbon sinks

Dr Lulie Melling tells OOI TEE CHING about the importance of peat soil research FORESTS are often called “the lungs of the world” — huge carbon sinks absorbing carbon dioxide emitted by the industrialised world, and producing the oxygen we need to breathe.

At the same time, agriculture is seen as “polluting” in the sense that land clearing and development release greenhouse gas into the atmosphere, contributing to global warming. Environmental organisations such as Greenpeace, Friends of the Earth and Wetlands International as well as their local affiliates take this view further by lobbying for a moratorium on planting oil palm on peat soil and the imposition of greenhouse gas criteria on palm oil exports.

In 2007, Wetlands and the Netherlands-based consultancy Alterra issued a report titled PEAT-CO2 Assessment of CO2 Emissions from Drained Peatlands in Southeast Asia alleging the region’s peatlands are going up in smoke, emitting tonnes of carbon dioxide and causing global warming.

Kuching-based Tropical Peat Research Laboratory (TPRL) director Dr Lulie Melling argues that if such a claim is true, then millions of Sarawakians would have choked to death.

In reality, Sarawak’s oil palm plantations have been sequestering carbon dioxide and generating oxygen that goes back into the atmosphere while creating carbon sinks and stocks.

“People tend to forget that oil palms are trees and that they absorb carbon dioxide in the air, only to release oxygen and in the same process, convert solar energy into biomass,” says Melling in an interview in Kuching.

“Trees are trees, they function the same whether they are part of the forest or plantations.

“Since tree plantations are perennial, they are more efficient carbon sequesters than seasonal oilseeds like soy, rapeseed and sunflower. Oil palms can feed on year-round tropical sun and rainfall to create biomass, i.e. carbon stock, without any soil disturbance compared with seasonal oilseeds.” When peer-reviewed studies by soil scientists were adduced at the Round-table on Sustainable Palm Oil (RSPO) meetings, it became evident that reports containing alarmist predictions were founded on calculations riddled with statistical bias and lacking in real evidence.

Last year, Brinkmann Consultancy’s recommendation to include greenhouse gas emission from peatland as a criterion for RSPO certification was rejected. TPRL’s findings had, in part, showed soil respiration at oil palm estates planted in peat had lower greenhouse gas emissions than that of untouched peatland.

This is one instance where soil research allows you to differentiate facts from mistaken assumptions about planting crops on peat soil. Good soil management, be it peat or mineral-based, is the basis for sustainable food production.

Melling says that many of the current assumptions about tropical peatland were based on the understanding of temperate peatland research.

“Tropical peat is different from temperate peat. First and foremost, tropical peat is mainly woody material, whereas temperate peat is made up of spaghnum and sedges.” The woody nature of tropical peat means there is higher lignin content. Lignin, being a more “recalcitrant” carbon than labile carbon of cellulose materials in temperate peat, highly influences the peat decomposition rate.

Furthermore, the acidic condition of tropical peat inhibits microbial population, indirectly slowing the breakdown rate and therefore greenhouse gas emissions. Heavy and frequent rainfall in Sarawak, which helps to maintain moisture content in the peat soil, also decelerates decomposition and carbon dioxide emission.

Melling goes on to explain that unlike the northern hemisphere where temperate peatland is developed for energy and horticulture, oil palm plantations in the tropical countries only use the peatland as a planting medium.

On current understanding that drainage of peatland for agriculture leads to large carbon losses from oxidation, Melling says it is “not entirely correct”. “Peat subsidence is also due to compaction, consolidation and shrinkage.

“Water management and compaction is a prerequisite to any agriculture development on tropical peatland. Consolidation of the peat increases bulk density and capillary rise, resulting in higher water-filled pore space of the peat. This leads to a more anaerobic condition, which results in a lower decomposition rate and less carbon dioxide emission.” Over the years, Melling has found that people, who are ill-informed, jealous or have vested interests, tend to get offended when she speaks out on issues. At such highly-charged meetings, it helps to stick to a simple rule: “I just do my job; I don’t try to do someone else’s job, and I don’t let anyone else do my job.” She takes a sip of tea and leans back on her office swivel chair.

“When I say I do my job, it also means I do not do someone else’s job. This is because scientists are not in the business of saving the world, nor are we vegetable oil salesmen. Science is about the process, not the purpose.” On not letting anyone else try to do her job, Melling attributes it to the highly politicised topic of climate change, especially on greenhouse gas emissions.

In many international conferences on tropical peatland management and greenhouse gas, she has witnessed how some activists and politicians, skilful at straw man arguments, were quick to label people they disagree with as “taking sides with greedy oil palm tycoons who do not care about the environment” and are “likely to condone widespread forest destruction”.

While most local scientists become silent when debates heat up and arguments get louder, Melling rises to the occasion.

Soon after she presents her data, it becomes apparent that the critics’ claims are full of speculations. Until today, these environmental activists and politicians continue to claim expertise in tropical peat despite having never waded into Sarawak’s itch-inducing and acidic peat swamps.

As early as 1995, Melling has been studying tropical peat. Despite escalating citations of her peer-reviewed research papers, she remains humble and says there is still much to learn. Recently, Melling and her team at TPRL set out to verify whether a national park, logged-over forest and oil palm plantation absorb more greenhouse gas than they emit.

Three 40m-tall Eddy Covariance towers were set up in an oil palm plantation in Sibu, a logged-over forest and Maludam National Park in Betong division. They have built-in lightning protection and the sensors are fully powered by solar panels. These instruments measure carbon flux and concentration, wind, moisture, sunshine hours, rainfall, humidity, soil moisture and water table.

When asked to comment on Malaysia’s aspiration to become a knowledge-based economy, Melling says the government needs to allocate more funds for peat soil research.

“Through Science, farmers are able to carry out sustainable agriculture that satisfies both the economic and environmental needs of food production.”

Source: The truth about oil palms and carbon sinks