SINGAPORE — Oil palms and rice plantations have been identified as key drivers of mangrove deforestation in South-east Asia in recent times, alongside the traditional culprit, aquaculture.

About 100,000 hectares of mangroves in South-east Asia were lost between 2000 and 2012, and a recent study by researchers linked to the National University of Singapore (NUS) found that about 22 per cent of that area was converted to rice agriculture, while 16 per cent was converted to oil palm plantations.

Rice agriculture expansion in Myanmar, especially in Rakhine state, as well as expansion of oil palm plantations in Malaysia, Sumatra and Borneo, are under-recognised threats to mangrove ecosystems, which offer coastal protection, are highly biodiverse and store disproportionately large amounts of carbon, said the researchers.

While the study confirmed aquaculture — the farming of fish and other aquatic creatures — as the main driver of mangrove destruction in the region, responsible for about 30 per cent of mangrove forests lost, its role was smaller than in previous decades.

During the 1980s and 1990s, as much as double the percentage of mangrove forest destroyed was estimated to be for fish or shrimp ponds, wrote researchers Daniel Richards and Daniel Friess in their paper published last month in the journal, Proceedings of the National Academy of Sciences of the United States of America.

Mangrove conversion to aquaculture now occurs mainly in Kalimantan and Sulawesi in Indonesia.

Assistant Professor Friess is from NUS’ geography department; his former colleague Dr Richards is now with the University of Sheffield.

The pair used global forest-change datasets and satellite imagery in their analysis, supported by Singapore’s Ministry of Education.

“This is the first study to systematically quantify the conversion of mangroves to different land use types in South-east Asia and identify the key drivers of mangrove deforestation over the past decade,” said Asst Prof Friess.

Available data potentially shows mangrove destruction slowing down, but the problem remains substantial, he said.

South-east Asia lost its mangrove forests at a rate of 0.18 per cent a year between 2000 and 2012, with the highest rates of loss found in Myanmar, Malaysia, Cambodia and Indonesia.

Singapore, whose mangrove forests make up about 0.5 per cent of its total land area from an estimated 13 per cent in the 1820s, did not suffer any mangrove loss from 2000 to 2012.

In future, mangroves will probably continue to be under siege in Myanmar and Indonesia — given few environmental safeguards for mangrove forests and the importance of rice production for food security in the Indochinese country, and future oil-palm expansion slated for Papua, said the researchers.

Besides mangrove loss, oil palm expansion has also been blamed for the drainage of carbon-rich peatlands, which has contributed to haze-causing forest fires.

The study could aid decision makers in formulating targeted, evidence-based policies to conserve mangrove forests, said the researchers.