July 27th, 2009
Written by Michael Ricciardi
Eco Worldly Unrestricted expansion of rubber tree plantations in South East Asia could lead to “devastating environmental effects”, according to authors Ziegler, Fox and Xu writing in a May, 2009 perspective article in Science.
Throughout the “montane” (foot hill and low mountainous) mainland of South East Asia (inclusive of Thailand, Vietnam, Cambodia, Laos, Myanmar, and China), rubber plantations are expanding. So far, an estimated half million hectares have been planted, and by 2050, that land mass area could triple. This expansion will come at a cost to broad leaf, evergreen forests and “swidden” areas (with vegetation from older slash and burn efforts).
Replacing both primary and secondary forests, the authors assert, will have an impact on long-term bio-diversity (creating “permanent monocultures”) and reduced total carbon biomass (note: forests derived much of their carbon biomass from uptake of atmospheric CO2).
Much of the current planting of rubber trees (Hevea brasiliensis, aka Para Rubber trees, whose sap is pure latex) is along sloping land areas and on foot hill and mountain sides (often converted to step agriculture) which naturally channel water into streams and lakes at lower elevations. The danger and risks from this expanding agricultural effort are many, and include: accelerated erosion of soil cover, excess stream sedimentation m(due to repeat cultivation on slope without adequate conservation), increased landslide risks (due to permanent conversion and road building), depletion of streams and lakes (due to irrigation needs), and decreased water quality (from pesticides and fertilizer runoff). Many of these risks and hazards–including permanent loss of forest cover–have already been encountered by farmers growing palm oil mono-cultures further into the interior of this region.
Perhaps ironically, these risks come on with a near half-century effort to mitigate, diminish swidden, slash-and-burn practices that were believed to be at the time quire environmentally destructive. Although these older practices did have some environmental and ecological consequences, over the years it has become clear from observation and studies that these consequences (in this region) were not as negative as once expected. Collectively, these various nation’s policies to move away from these practices (which are also less industry-efficient ones) and establish more productive cultivation systems, is resulting in far more harm, according to the authors, than the previous swidden agriculture base.
Scientists now must focus their research on studies of evapo-transpiration and hydrology (total water use) in these forests to determine real environmental impacts. The governments of Cambodia and Thailand are currently conducting such studies and it is hope that other nations will follow suit. Also, efforts are underway to expand reserve areas to preserve biodiversity and carbon biomass. Some have sugested paying farmers not to cut down the evergreen forests. The authors cited here also suggest encouraging “diversified agro-forestry systems” which permits extensive planting of rubber and palm oil trees, but not as monocultures. These systems represent a sort of “hybrid” compromise between total preservation of all forested areas and the creation of monoculture plantations, which produce a myriad of negative ‘eco’ and ‘enviro’ effects.
