Jefferson Fox

The Rubber Juggernaut

The demise of swidden cultivation in Southeast Asia may have devastating environmental consequences. Rubber plantations are expanding rapidly throughout montane mainland Southeast Asia (1–3). More than 500,000 ha may have been converted already in the uplands of China, Laos, Thailand, Vietnam, Cambodia, and Myanmar (see the figure, panel A). By 2050, the area of land dedicated to rubber and other diversified farming systems could more than double or triple, largely by replacing lands now occupied by evergreen broadleaf trees and swidden-related secondary vegetation (2). What are the environmental consequences of this conversion of vast landscapes to rubber?

Policies, Political-Economy, and Swidden in Southeast Asia

For centuries swidden was an important farming practice found across the girth of Southeast Asia. Today, however, these systems are changing and sometimes disappearing at a pace never before experienced. In order to explain the demise or transitioning of swidden we need to understand the rapid and massive changes that have and are occurring in the political and economic environment in which these farmers operate. Swidden farming has always been characterized by change, but since the onset of modern independent nation states, governments and markets in Southeast Asia have transformed the terms of swiddeners’ everyday lives to a degree that is significantly different from that ever experienced before. In this paper we identified six factors that have contributed to the demise or transformation of swidden systems, and support these arguments with examples from China (Xishuangbanna), Laos, Thailand, Malaysia, and Indonesia. These trends include classifying swiddeners as ethnic minorities within nation-states, dividing the landscape into forest and permanent agriculture, expansion of forest departments and the rise of conservation, resettlement, privatization and commoditization of land and land-based production, and expansion of market infrastructure and the promotion of industrial agriculture. In addition we note a growing trend toward a transition from rural to urban livelihoods and expanding urban-labor markets.

The Demise of Swidden in Southeast Asia? Local Realities and Regional Ambiguities

Abstract Swidden farmers throughout Southeast Asia are rapidly abandoning traditional land use practices. While these changes have been quantified in numerous local areas, no reliable region-wide data have been produced. In this article we discuss three linked issues that account for at least some of this knowledge gap. First, swidden is a diverse, complex, and dynamic land use that data gatherers find difficult to see, define and measure, and therefore often relegate to a “residual category” of land use. Second, swidden is a smallholder category, and government authorities find it difficult to quantify what is happening in many dynamic and varied smallholdings. Third, national policies in all countries of Southeast Asia have tried to outlaw swidden farming and to encourage swiddeners to adopt permanent agriculture land use practices. Drawing on specific, local examples from throughout the region to illustrate these points, we argue that an accurate assessment of the scale and pace of changes in swidden farming on a regional level is critically important for identifying the processes that account for these shifts, as well as evaluating their consequences, locally and regionally.

Expansion of rubber (Hevea brasiliensis) in Mainland Southeast Asia: what are the prospects for smallholders?

The rubber tree is native to the humid tropics and has traditionally been cropped in the equatorial zone between 10°N and 10°S; in mainland Southeast Asia this includes portions of southern Thailand, southeastern Vietnam, and southern Myanmar. In the early 1950s, the Chinese government began to invest in growing rubber in environments perceived to be ecologically marginal and eventually established state rubber plantations in areas that lie as far north as 22° north latitude. Chinas success in growing rubber in these ‘non-traditional’ environments expanded the habitat in which rubber could be planted and pushed it further north. Today entrepreneurs from China, Vietnam, Malaysia, and Thailand are investing in rubber plantations in areas of Laos, Cambodia, and Myanmar, northwest Vietnam, northeast Thailand, and Yunnan, China. The impact of rubber on smallholders, however, is not yet clear. Experiences in Xishuangbanna, Yunnan, China and northeast Thailand clearly show that smallholder rubber production is a viable and effective proposition in moving households and communities out of poverty. By contrast in countries such as Laos, Cambodia and Myanmar many farmers are struggling to maintain their lands and forests in the face of growing pressures from investors and government institutions to impose concession arrangements.

Land use change: complexity and comparisons

Research on the determinants of land use change and its relationship to vulnerability (broadly defined), biotic diversity and ecosystem services (e.g. Gullison et al. 2007), health (e.g. Patz et al. 2004) and climate change (e.g. van der Werf et al. 2004) has accelerated. Evidence of this increased interest is demonstrated by several examples. Funding agencies in the US (National Institutes of Health, National Science Foundation, National Aeronautics and Space Administration and National Oceanic and Atmospheric Administration) and around the world have increased their support of land use science. In addition to research papers in disciplinary journals, there have been numerous edited volumes and special issues of journals recently (e.g. Gutman et al. 2004; Environment & Planning B 2005; Environment & Planning A 2006; Lambin and Geist 2006; Kok, Verburg and Veldkamp 2007). And in 2006, the Journal of Land Use Science was launched. Land use science is now at a crucial juncture in its maturation process. Much has been learned, but the array of factors influencing land use change, the diversity of sites chosen for case studies, and the variety of modeling approaches used by the various case study teams have all combined to make two of the hallmarks of science, generalization and validation, difficult within land use science. This introduction and the four papers in this themed issue grew out of two workshops which were part of a US National Institutes of Health (NIH) ‘Roadmap’ project. The general idea behind the NIH Roadmap initiative was to stimulate scientific advances by bringing together diverse disciplines to tackle a common, multi-disciplinary scientific problem. The specific idea behind our Roadmap project was to bring together seven multi-disciplinary case study teams, working in areas that could be broadly classified as inland frontiers, incorporating social, spatial and biophysical sciences, having temporal depth on both the social and biophysical sides, and having had long-term funding. Early in our Roadmap project, the crucial importance of modeling, particularly agent-based modeling, for the next phase of land-use science became apparent and additional modelers not affiliated with any of the seven case studies were brought into the project. Since agent-based simulations attempt to explicitly capture human behavior and interaction, they were of special interest. At the risk of oversimplification, it is worth briefly reviewing selected key insights in land use science in the past two decades to set the stage for the papers in this themed issue. One of the earliest realizations, and perhaps most fundamental, was accepting the crucial role that humans play in transforming the landscape, and concomitantly the distinction drawn between land cover (which can be seen remotely) and land use (which, in most circumstances, requires in situ observation; e.g. Turner, Meyer and Skole 1994). The complexity of factors influencing land use change became apparent and led to a variety of ‘box and arrow’ diagrams as conceptual frameworks, frequently put together by committees rarely agreeing with one another on all details, but agreeing among themselves that there were many components (social and biophysical) whose role needed to be measured and understood. A series of case studies emerged, recognizing the wide array of variables that needed to be incorporated, and typically doing so by assembling a multidisciplinary team (Liverman, Moran, Rindfuss and Stern 1998; Entwisle and Stern 2005). The disciplinary make-up of the team strongly influenced what was measured and how it was measured (see Rindfuss, Walsh, Turner, Fox and Mishra 2004; Overmars and Verburg 2005), with limited, if any, coordination across case studies (see Moran and Ostrom 2005 for an exception). In large part, the focus on case studies reflected the infancy of theory in land use science. Teams combined their own theoretical knowledge of social, spatial and ecological change with an inductive approach to understanding land use change – starting from a kitchen sink of variables and an in-depth knowledge of the site to generate theory on the interrelationships between variables and the importance of contextual effects. This lack of coordination in methods, documentation and theory made it very difficult to conduct meta-analyses of the driving factors of land use change across all the case studies to identify common patterns and processes (Geist and Lambin 2002; Keys and McConnell 2005). Recognizing that important causative factors were affecting the entire site of a case study (such as a new road which opens an entire area) and that experimentation was not feasible, computational, statistical and spatially explicit modeling emerged as powerful tools to understand the forces of land use change at a host of space–time scales (Veldkamp and Lambin 2001; Parker, Manson, Janssen, Hoffmann, and Deadman 2003; Verburg, Schot, Dijst and Veldkamp 2004). Increasingly, in recognition of the crucial role of humans in land use change, modeling approaches that represent those actors as agents have emerged as an important, and perhaps the dominant, modeling approach at local levels (Matthews, Gilbert, Roach, Polhil and Gotts 2007). In this introductory paper we briefly discuss some of the major themes that emerged in the workshops that brought together scientists from anthropology, botany, demography, developmental studies, ecology, economics, environmental science, geography, history, hydrology, meteorology, remote sensing, geographic information science, resource management, and sociology. A central theme was the need to measure and model behavior and interactions among actors, as well as between actors and the environment. Many early agent-based models focused on representing individuals and households (e.g. Deadman 1999), but the importance of other types of actors (e.g. governmental units at various levels, businesses, and NGOs) was a persistent theme. ‘Complexity’ was a term that peppered the conversation, and it was used with multiple meanings. But the dominant topic to emerge was comparison and generalization: with multiple case studies and agent-based models blooming, how do we compare across them and move towards generalization? We return to the generalization issue at the end of this introductory paper after a brief discussion of the other themes.

EFFECTS OF SWIDDEN CULTIVATION, STATE POLICIES, AND CUSTOMARY INSTITUTIONS ON LAND COVER IN A HANI VILLAGE, YUNNAN, CHINA

A study of air photographs and satellite imagery of a Hani village (Mengsong) in southwestern Yunnan between 1965 and 1993 showed that swidden cultivation did not lead to permanent conversion of forest land to agriculture but rather a conversion of a fairly homogeneous secondary closed-canopy forest into a highly heterogeneous land cover of different stages of forest succession. An analysis showed a direct correlation between government policies on producing food from hilly lands and the destruction of forest cover. This analysis also showed that since the Household Responsibility System was introduced in late 1979, allowing farmers the right to decide where, what, and how much to plant, farmers have decreased the amount of land farmed and intensified their farming methods.

Dry-season radiation balance of land covers replacing forest in northern Thailand

The results of numerous general circulation model (GCM) experiments of climatic effects of extensive tropical deforestation include significant reductions in regional precipitation. However, the simulated precipitation decrease is highly dependent on the large albedo shift associated with the assumed conversion of forest into grassland. Land cover change surveys of the Amazon and Thailand suggest that secondary vegetation at various growth stages, rather than grassland, is the dominant feature of deforested land. In this paper, we present field measurements, taken during the dry season, of radiative characteristics of various deforested land surfaces in montane northern Thailand, including secondary vegetation. Dry-season albedo at nine sites in the village of Pang Khum, Chiang Mai Province, ranged from 0.085 for irrigated bare soil to 0.171 for 3year secondary vegetation. As a result of increased albedo and higher daytime surface temperature at exposed dry soil sites, net radiation is reduced substantially. Regional mean dry-season albedo is estimated to have increased from 0.13 to 0.144 by 1980 for all of northern Thailand, and from 0.13 to 0.14 by 1983 for the southern portion of Sam Mun watershed, the 10 000 ha area immediately surrounding the study site. Continuing significant upward trends in regional albedo at both spatial scales are suggested by the estimates. However, our measurements suggest a maximum deforestation-induced albedo increase of about 0.04, half that used to simulate the effects of deforestation in most GCM experiments. It is likely, therefore, that simulated reductions in precipitation in the region due to deforestation will not be seen in model runs using more realistic scenarios of post-deforestation land cover characteristics. # 1999 Elsevier Science B.V. All rights reserved.

Integrating Mahalanobis typicalities with a neural network for rubber distribution mapping

Accurate rubber distribution mapping is critical to the study of its expansion and to provide a better understanding of the consequences of land-cover and land-use change on carbon and water cycles. Employing Mahalanobis typicalities as inputs to a hard classifier to enhance the capability of generalization has not previously been explored. This letter presents a novel approach by integrating Mahalanobis typicalities with the multi-layer perceptron (MLP) neural network for mapping of rubber. A case study from the Thai–Lao and Sino–Lao borders was conducted using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Different combinations of the nine ASTER bands including Visible and Near Infrared (VNIR) and Short-wave Infrared (SWIR), Normalized Difference Vegetation Index (NDVI) and Mahalanobis typicalities were used as input variables to the MLP. Results indicate that including Mahalanobis typicalities as input variables can improve the MLPs performance and increase the users accuracy of rubber mapping.

The problem of scale in community resource management

Scale is a fundamental variable in most community resource management programs. This is true both in terms of scale as a management concept (i.e., local, regional, and national level management) as well as a mapping concept (i.e., units on the map per unit on the ground). Julian Steward, the father of human ecology, recognized as early as 1950 that social scientists have failed to develop methods for incorporating the effect of scale in their work. This article seeks to determine whether methods used in plant and animal ecology for assessing the effects of scale are applicable to community resource management. The article reviews hierarchy theory and multiple scales, two methods (one theoretical and the other practical) for dealing with problems that span many scales. The application of these methods to community resource management programs is examined by way of an example.

Evapotranspiration of rubber (Hevea brasiliensis) cultivated at two plantation sites in Southeast Asia

To investigate the effects of expanding rubber (Hevea brasiliensis) cultivation on water cycling in Mainland Southeast Asia (MSEA), evapotranspiration (ET) was measured within rubber plantations at Bueng Kan, Thailand, and Kampong Cham, Cambodia. After energy closure adjustment, mean annual rubber ET was 1211 and 1459 mm yr(-1) at the Thailand and Cambodia sites, respectively, higher than that of other tree-dominated land covers in the region, including tropical seasonal forest (812-1140 mm yr(-1)), and savanna (538-1060 mm yr(-1)). The mean proportion of net radiation used for ET by rubber (0.725) is similar to that of tropical rainforest (0.729) and much higher than that of tropical seasonal forest (0.595) and savanna (0.548). Plant area index (varies with leaf area changes), explains 88.2% and 73.1% of the variance in the ratio of latent energy flux (energy equivalent of ET) to potential latent energy flux (LE/LEpot) for midday rain-free periods at the Thailand and Cambodia sites, respectively. High annual rubber ET results from high late dry season water use, associated with rapid refoliation by this brevideciduous species, facilitated by tapping of deep soil water, and by very high wet season ET, a characteristic of deciduous trees. Spatially, mean annual rubber ET increases strongly with increasing net radiation (R-n) across the three available rubber plantation observation sites, unlike nonrubber tropical ecosystems, which reduce canopy conductance at high R-n sites. High water use by rubber raises concerns about potential effects of continued expansion of tree plantations on water and food security in MSEA.