More rubber, more money, less of everything else?
By Xu Jianchu and Edward Grumbine
Rapid land-use transformations are occurring in the Mekong Region, especially in Xishuangbanna, Yunnan province, in southwestern China, thanks primarily to the spread of monocultural rubber plantations.
Our team at the World Agroforestry Centre’s East Asia Node in Kunming, China, has discovered that the rapid spread of mostly rubber plantations has led to structural and functional biodiversity being reduced, increased habitat fragmentation, reduced carbon sequestration in natural forests, and altered hydrological systems in Xishuangbanna with implications for the whole region. For humans in Xishuangbanna, while incomes have risen, food insecurity has also grown.
Using a new map derived from Landsat and RapidEye imagery that tracked the spread of monoculture rubber plantations from 1992 to 2010, along with a literature review and interviews with key local experts and officials, we created a general overview of the extent, causes and consequences of landscape transformation in Xishuangbanna.
These changes have been characterized by two broad, interactive trends. The first is ecological—the reduction of native forest cover—while the second is primarily socioeconomic: the replacement of a variety of subsistence shifting-cultivation systems with plantation monocultures of cash crops (rubber, tea, oil palm etc.).
There are both costs and benefits to these transformations. Rubber now covers more than 21% of Xishuangbanna, replacing swidden practices that have played significant roles in creating, maintaining and conserving genetic resources of upland rice for many centuries. The Jinuo people alone have cultivated 71 rice varieties; now, many of these are at risk.
As lowland and upland ecosystems have undergone major land-use changes, biodiversity, as measured by the number of species found, is decreasing. Ecosystem diversity has also felt the impact: from 1976 to 2003, forest cover in Xishuangbanna was reduced from 69% to less than 50%, and the important tropical seasonal rainforest was reduced from 10.9% to 3.6% of the landscape.
Fragmentation of the landscape is a major concern as the overall number of forest patches has increased, average patch size and amount of core habitat have decreased, and both amount of edge habitat and average distance to other forest patches have increased.
These data reflect conditions for all forest types in the region. Across much of the landscape, there is little to virtually no natural forest of any kind left outside Xishuangbanna’s nature reserves. Some areas of plantation can even be found inside reserve boundaries.
Functionally, compared to primary and secondary natural forests, rubber plantations have decreased concentrations of soil organic carbon and total soil and inorganic nitrogen. Old forests in Xishuangbanna sequester much more carbon than rubber plantations both above and below the ground. Conversion to rubber leads to a substantial net release of carbon dioxide. Annual carbon emissions owing to land-use change have been estimated at 0.37 ± 0.03 Tg C/year between 1976 and 1988 and 0.13 ± 0.04 Tg C/year from 1988 to 2003.
Land clearance starts with burning the local forest, which provides a nutrient pulse for young rubber trees and intercropped pineapples but, within a few years, chemical fertilizers are required. Heavy application of fertilizers has led to eutrophication of water bodies, and the combination of herbicide use and reduced natural filtering has contaminated drinking water.
Rubber plantations also have an impact on water supplies. Watershed services are deteriorating as streams dry up. Rubber uses more water than other crops or native vegetation, particularly in the period of leaf flushing during the hottest and driest season. In comparison to rainforest, leaf-litter decomposition rates and nutrient-use efficiency are lower in rubber plantations.
Tropical rainforest has persisted at its northern latitudinal limit in Xishuangbanna owing to a combination of pronounced cold foggy season, high subsurface water and adequate soil moisture with diverse soil fauna and flora. In effect, these influences prolong the monsoon season, but with rubber plantations creating a longer hotter and drier season, the degradation of ecosystem services is inevitable.
Overall, it is important to note that almost all of the above ecological studies are based on forest cover as it stood before 2003, that is to say, prior to the dramatic expansion (over 100%) of rubber from 2002 to the present. Since then, there have been no further studies to update ecological conditions on the ground that would capture the loss of another 186 000 hectares of habitat to rubber plantations. In particular, new peer-reviewed regional hydrology and landscape connectivity studies that assess rubber’s impact on wildlife and species’ migration have yet to be done.
But more rubber means more money
The biggest gain has been financial: villagers’ incomes have risen as people have switched from swidden agricultural practices to rubber cultivation. For rural people, rubber is providing a path out of poverty.
Over the decades in the Mekong, primarily in response to various government policies and the expansion of regional, national and international markets, there have always been transitions in farmers’ swidden strategies. But the region has never before seen such large-scale changes as are taking place today.
A farmer can make more money using less labour by cultivating rubber, especially if plantation work is supplemented with off-farm labour. As long as the global price for rubber remains high, farmers will continue to benefit throughout the region.
Financial gains, however, have come with certain costs. While incomes have increased, villagers now have fewer livelihoods’ options, less opportunities to collect non-timber forest products and, arguably, less food security.
With the reduction of diverse swidden agricultural systems, the traditional exchange of forest products between indigenous groups has been disrupted. With less overall natural forest cover and farther distances from villages to remaining patches of forest, people derive less income from the collection of non-timber forest products. Traditional ecological knowledge and aesthetic and cultural practices have been eroded, with farmers more dependent on crops that are priced on the world market that local people have little knowledge of and no control over. If the global price of rubber goes down, so will farmers’ incomes. Similarly, when Xishuangbanna experiences cold weather that causes losses in rubber trees, as it has on average about every eight years since the 1960s, farmers’ incomes will be affected, too.
At the regional scale in the Mekong, rural food security is predicted to become more tenuous. A 2% annual increase in food production to 2025 will be necessary, according to some estimates, accounting only for population growth. Such agricultural yields would be unprecedented in the region and therefore it is likely that more cash crops are inevitable.
Rubber, rubber everywhere?
While these transitions are not occurring at the same rate everywhere across the region, the overall trend is unmistakable: the region is becoming developed and therefore more integrated into regional and global economies, with the all-too-familiar environmental casualties.
These land-use trends are set to continue and possibly even speed up. States throughout the region are busy implementing socioeconomic developments that will continue to bring new construction of transportation and communication infrastructure into the Mekong Region. A host of new roadways, railways and pipelines for fossil-fuel energy transfer are being constructed.
Recent debates among Mekong countries have focused on the commercial exploitation of the region’s natural resources rather than the need to promote sustainable ecosystems. Insufficient attention has been given, either in scientific studies or policy discussions, to the current and long-range ecological consequences of the overall rate and scale of local and regional land-use changes.
In general, solving land-use problems requires a transboundary, multi-scale perspective. One way to begin this work is to search for ‘win/win’ solutions. In Xishuangbanna, for example, there was no a priori reason why monoculture rubber had to be chosen over diverse agroforestry rubber systems. Using a ‘green’ rubber approach, local peoples’ incomes would still have risen without losing so much ecosystem structure, functional diversity and resilience of human livelihoods. Now, the state is faced with the significant costs of ‘greening’ the rubber plantations if it is to support sustainable livelihoods.
Read the research article
Xu J, Grumbine RE. Landscape transformation through the use of ecological and socioeconomic indicators in Xishuangbanna, Southwest China, Mekong Region. Ecological Indicators 2012.
Part of the funding for this work was generously provided by Deutsche Gesellschaft für Internationale Zusammenarbeit and Bundesministerium Für Wirtschaftliche Zusammenarbeit’s project, ‘Making the Mekong Connected’, as well as by the Commonwealth Scientific and Industrial Research Organization’s ‘Exploring Mekong Region Futures 2009–2010’ project. Funding during the latter stages of this research was generously provided by the Chinese Academy of Sciences’ visiting professorship for senior international scientists.
This work is part of the CGIAR Research Program on Forests, Trees and Agroforestry.
Edited by Robert Finlayson