Quantifying the environmental consequences of the spread of rubber plantations in Southeast Asia
Originally published in NUS’s publication Knowledge Enterprise
The sprawling rubber plantations of around a million hectares in Montane Mainland Southeast Asia (MMSEA) pose a danger to the environment because there is a potential threat to the loss of biodiversity – these findings were highlighted by NUS Geography Department’s Assoc Prof Alan Ziegler and his colleagues in the prestigious Science journal.
Rubber could also contribute to a decrease in carbon stocks and deplete ground water resources, but until recently, no one stopped to question the environmental consequences of the rubber juggernaut.
The research team found that much of the land converted to rubber plantations in the region were historically associated with swidden cultivation. Dr. Ziegler said: “Swiddening, which also refers to slash-and-burn and shifting cultivation, involves clearing and burning of forest plots for cultivation of subsistence crops, such as upland rice. It has been practiced throughout Southeast Asia perhaps since rice was domesticated a few thousand years ago. When mountain populations are low and forested lands are abundant, traditional swiddening practices are environmentally friendly because very little of the landscape is actively cultivated at any one time.”
“Once the traditionally long fallow periods are reduced and fields are cultivated for several years in succession, negative impacts on environmental systems emerge,” continued Dr. Ziegler. “The consequences can be even higher for intensive permanent forms of agriculture, such as those that have been replacing swiddening over the last few decades as new markets opened for crops that could be grown in the cool mountain climates. These systems are often plagued by accelerated erosion, increased probability of landslides, degradation of water quality, and changes in stream flow patterns.”
Assoc Prof Ziegler explained that loss of biodiversity was one of the potential dangers associated with the expansive rubber plantations in MMSEA – the upland region that includes parts of Cambodia, China, Laos, Myanmar, Thailand and Vietnam. By 2050, the area dedicated to rubber and other diversified farming systems could increase by more than two or three-fold, largely by replacing lands currently occupied by evergreen broadleaf trees and swidden-related secondary vegetation.
While others have used the term “water pumps” to describe rubber trees, Assoc Prof Ziegler is cautious. He said: “Sufficient research has not yet been done to evaluate the extent of the hydrological threat or the effect conversion to rubber could have on carbon fluxes”. To address these issues, he and his colleagues are currently conducting experiments in Thailand and Cambodia along with local scientists. “These new data should provide the answer soon.”