A Long-term Perspective on Environment and Development in the Asia-Pacific Region


Appendix 1 : Japan's experience

Project Objective

This project was designed to examine problems of land degradation in tropical Asian countries (China, the Philippines, Thailand, and Vietnam) and assess its consequences for sustainable rural development in this region. The objective was to clarify the nature of land degradation as a critical environmental problem in the developing countries of tropical Asia.


Degradation of land is increasingly recognized as a critical environmental problem in the Asia-Pacific region, especially in the developing countries of tropical Asia. For purposes of this study, land degradation is defined as changes in soil properties (e.g., nutrient availability, chemical composition, structure) that lower the productivity of agroecosystems on which rural populations depend for their survival.

According to the WRI World Resources Report (1992-1993), almost 20 percent of the vegetated land in Asia has already been degraded already by human activities. Deforestation is the leading cause of land degradation followed by agriculture (soil erosion and depletion of soil nutrients and damage to soil structure resulting from intensification of cropping, and the buildup of chemical toxicity resulting from improper application of chemical fertilizers and pesticides and improper irrigation management), overgrazing, and fuelwood collection.

Although land degradation occurs as the result of physical and biological forces working within specific agroecological systems, the character and intensity of the problem is determined by human management decisions and practices. The processes of land degradation, therefore, are driven by a complex of social forces, including population growth, commercialization and trade, adoption of new productive technologies, and changes in land tenure, which shape the relation of humans to the rural landscape. Understanding the ways in which Asian farmers actually use their land resources is thus a central concern of this investigation.

Project Description and Activities

This project was conducted as a collaborative study of the Program on Environment (ENV) of the East-West Center and the Task Group on Sustainable Land Use of the Southeast Asian Universities Agroecosystem Network (SUAN) in close cooperation with the ECO ASIA Long-term Project of the Japan Environment Agency. The project was implemented by research teams at Khon Kaen University (KKU) in northeast Thailand; the Center for Natural Resources and Environmental Studies (CRES) of the Vietnam National University, Hanoi; the Institute for Environmental Studies and Management (IESAM) of the University of the Philippines at Los Banos; the Nanjing Institute for Environmental Sciences, National Environmental Protection Agency, China; and the Department of Geography of the University of Hong Kong (UHK). The project was coordinated by Dr. A. Terry Rambo, ENV Director, and Dr. Aran Patanothai, Dean of the KKU Faculty of Agriculture and Coordinator of the SUAN Task Group on Sustainable Land Use. Administrative support for the project was provided by the East-West Center Program on Environment.

At a planning workshop held at Suranaree University of Technology in Khorat, Thailand, in February 1995 participating researchers designed a conceptual model that was used to analyze problems of land degradation in a variety of different types of agroecosystems in Asia. Figure 1 illustrates the conceptual framework that was employed in all of the case studies to assess the various inputs and outputs that influence the sustainability of land use in the different agroecosystems. Agroecosystems analyzed as part of this project include intensive irrigated wet rice systems (Red River Delta, Vietnam; Nanjing, China; Luzon, the Philippines), an extensive rainfed rice and field crop system (Khorat Plateau, northeastern Thailand), a composite swidden system (Da River Watershed, Vietnam), a rotational swidden system (Luzon, the Philippines), and grass-and brush-covered hillslopes in Hong Kong and southern China. Table 1 shows our research projects on the different agroecosystems in these countries. Map 1 illustrates the research sites for this project.

Following the planning workshop, each of the research teams collected the additional data needed to complete the analysis of land degradation and to prepare a draft report. These reports were reviewed at a synthesis workshop held at the Center for Southeast Asian Studies of Kyoto University in March 1996. At this workshop team reports were subjected to comparative analysis to provide the inputs to this final summary report. In addition, a volume containing all of the cases studies is being prepared.

Major Project Findings

1. Land degradation is a threat to the sustainability of all agroecosystems in tropical Asia.

It has often been assumed that land degradation was primarily a problem in marginal lands and poorly managed agricultural systems. Thus, much attention has been given to management of land in semi-arid zones where desertification and salinization are serious threats. Shifting cultivation systems on sloping lands were also seen as causing deforestation and soil erosion. Well-managed wet rice agroecosystems, which produce most of the staple food supply for tropical Asia, were believed to be both resilient and highly sustainable.

Our case studies reveal that none of the agroecosystems are being managed in a wholly sustainable manner. The upland systems are being degraded by extraction of nutrients in the crops, fodder, and fuel that are exported to the lowlands or even abroad as well as by heavy loss of soil to erosion. The lowland wet rice systems are also not in balance. In most cases, more nutrients are removed in the harvest than are replaced by natural and artificial means. In the case of the very heavily fertilized wet rice system in Nanjing, China, an excessive quantity of nutrients is applied, which can lead to toxicity and pollution of groundwater.

2. Transport of soil nutrients across system boundaries is an important aspect of land degradation.

Most previous studies of land degradation have been conducted at the site (field) level and have focused on maintenance of nutrient balances within the site. Our case studies have also examined the movement of nutrients within the larger environment, including the landscape and macro-levels. They reveal that transboundary flow of nutrients is a major aspect of land degradation.

At the landscape level, productivity of lowland wet rice fields is found to be quite dependent on in-flow of nutrients eroded from swiddens and other fields on hillslopes. Successful reforestation of hillslopes may thus reduce the productivity of lowland rice fields.

At the macro-level, the export of cash crops to national and international markets results in the depletion of nutrients in the source fields. Thus, cassava grown on rainfed upland fields in northeastern Thailand is exported to Europe for use as livestock feed. Given the very low price paid for cassava chips, the income received by the Thai farmers may not even equal the value of the nutrients exported in the cassava (if the farmers were to try to replace these nutrients with chemical fertilizer at current market prices).

Reliance on chemical fertilizers to replace nutrients lost in export crops can also create and reinforce local and national dependencies on external sources of supply. Nitrogen can be successfully produced in virtually all countries, including by the farmers themselves by the use of nitrogen-fixing species in their cropping cycles. Phosphorous and potassium have only a relatively few sources of supply and must be imported by most Asian countries.

3. Policy changes are needed to reduce the rate of land degradation to enhance the sustainability of tropical Asian agroecosystems.

The current rapid rate of land degradation is, at least in large part, the result of policy shortcomings and market failures.

Land tenure systems that do not give individual farmers a strong vested interest in the long-term productivity of the plots they are exploiting are particularly at risk. This is clearly the case in many swidden systems in which the farmer clearing the field only retains control over it for one cropping cycle. Once put back into fallow, the field becomes an open access resource that may be re-cleared by any other individual who chooses to claim it. Thus, there is no incentive for the initial cultivator to invest extra effort to reduce soil erosion or to accelerate the regeneration of the plot since there is no assurance that he will benefit from this investment. Share cropping and other forms of insecure tenancy suffer from similar disincentives for farmers to invest in measures to ensure sustainability.

In situations where farmers do have long-term control over their land, they may lack adequate knowledge about how to manage it sustainably. Many traditional agroecosystems were relatively sustainable under conditions of low population pressure. This was especially true when crops were produced primarily for subsistence purposes. Increased population pressure and, especially, the shift to production of cash crops that export nutrients from the local system tend to upset this equilibrium. Existing agricultural research and extension systems, on the whole, have not proven to be very effective in providing new technology to poor farmers on marginal lands. Particularly neglected are the many millions of upland farmers, often members of ethnic minorities, who depend on swidden agriculture for their meager subsistence.

Even in those situations where farmers have clear long-term title to their land, and have access to the necessary information and inputs to maintain soil quality, they may fail to take necessary measures to replace nutrients lost in the cropping process. This is particularly a problem in agroecosystems producing cash crops for export. This reflects the fact that the present pricing of agricultural commodities does not reflect the true cost of production because market prices do not fully incorporate the costs of land degradation. No allowance is made for the depreciation of soil quality in the process of agricultural production. The result is that farmers "mine" the soil for short-term gain with little concern for its long-term sustainability.

Figure 1 Model for Nutrient Input-Output analysis

Table1:Research Projects on
Land Degradation and Sustainable Land Use
in Tropical Asia

Country Location/Institution
Lowland Upland
Thailand Khon Kaen(KKU)
rainfed wet rice
Khon Kaen(KKU)
rainfed field crops
nutrient depletion
soil erosion
nutrient depletion
Vietnam Thai Binh(CRES)
irrigated wet rice
Hoa Binh(CRES)
composite swidden
nutrient depletion
nutrient accumulation
soil erosion
nutrient depletion
Philippines Laguna(IESAM)
irrgated wet rice
nutrient depletion
soil erosion
China Nanjing(NIES)
intensive rice/fruit cropping
Hong Kong(HKU)
degraded hillslopes
excessive nutrient accumulation
energy,pesticide use
soil erosion

Map 1 Research Sites for the Project on Land Degradation in Tropical Asia

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