The expansion of rubber plantations in Southeast Asia is not only destroying biodiversity but is a sub-optimal use of land, scientists say.

When one mentions “deforestation” in Southeast Asia, oil palm usually comes to mind. However, a study published in Global Environmental Change shows that rubber plantations also play a significant role, having increased by more than 50 percent since 2000.

Rubber (Hevea brasiliensis) originates from South America. Its history of cultivation in Southeast Asia can be traced back to the 22 seedlings that were sent to the Singapore Botanic Gardens in 1876 from Kew Gardens in London. The climate in tropical countries suited rubber cultivation and the industry expanded, particularly in Malaysia and Indonesia.

Governmental decisions to develop other sectors led to an interest in oil palm, which has since been in the limelight for to its negative impact on native ecosystems. However, demand for natural rubber has steadily increased, despite the invention of synthetic rubber as an alternative.

"The production of synthetic rubber has increased, but its production price is coupled with the crude oil price and can be high. Furthermore, it does not match some of the resistance properties of natural rubber,” explained Professor Antje Ahrends, Head of Genetics and Conservation at the Royal Botanic Gardens in Edinburgh.

In fact, 2013 data from the Food and Agricultural Organization of United Nations (FAO) showed that the rubber industry has expanded by 1,500 percent in the past 50 years on continental Southeast Asia (entire region excluding peninsula Malaysia).

In order to quantify the space occupied by rubber plantations and assess the consequences of expansion, Ahrends, along with Professor Xu Jianchu from the Chinese Academy of Sciences, conducted the following study.

"To our knowledge this is the first study that provides a quantitative region-wide overview of the extent and trends of rubber plantation expansion into biophysically marginal environments,” Ahrends told Asian Scientist Magazine.

Firstly, they identified areas where rubber occurs naturally, mapping out the areas of optimal and sub-optimal environments for rubber growth. By applying a model based on information on the types of land that have been converted so far, they were able to predict future land conversion patterns.

They found that the continued expansion of rubber plantations has eroded protected biodiversity areas in continental Southeast Asia. Of these expansions, 72 percent were planted in sub-optimal environmental areas, where reduced yields are likely to occur.

The situation is expected to worsen as climate change is likely to exacerbate low rubber yields. The Intergovernmental Panel for Climate Change estimates increased erosion and precipitation in the higher altitudes as well as an overall decrease in soil moisture across continental Southeast Asia.

Additionally, the authors found that 61 percent of the rubber plantation expansions were in protected areas and 70 percent were in key biodiversity areas. The trend for this expansion appears to be led by small-holdings farmers who are taking advantage of the lucrative activity while the prices are still high. If this trend continues, the study estimates 13,310 km2 of forest and 8,952 km2 of key biodiversity areas will be come under threat of land conversion.

Furthermore, 57 percent of the rubber plantation expansions were predicted to be in areas susceptible to drought, erosion, frost and wind damages. Destruction of these protected areas are likely to end up as a lose-lose situation, when protected land is destroyed and income of the people fall as a result of a fall in rubber prices.

So where do we go from here? The authors state that while schemes such as payment for ecosystem services and Reducing Emissions from Deforestation and Forest Degradation (REDD+) have the potential to reduce land conversion, these require time for market development and shifts in policy-making.

"We are in the process of providing this information to policy makers via our local partners. China is already paying farmers to convert plantations on steep slopes back to forests,” Ahrends said.

(Source: Asian Scientist Magazine; Photo: Dietrich Schmidt-Vogt/World Agroforestry Centre.)