Contents - Previous - Next

This is the old United Nations University website. Visit the new site at

The need for integrated solutions in tropical land use

Tropical agriculture is not limited to the humid tropics; it also includes dry zones. However, it is in the humid tropics that the major challenges for eco-restructuring lie.

Humid tropic conditions are found over nearly 50 per cent of the tropical land mass and 20 per cent of the earth's total land surface an area of about 3 billion hectares. Tropical Central and South America contain about 45 per cent of the world's humid tropics, Africa about 30 per cent, and Asia about 25 per cent. As many as 62 countries are located partly or entirely within the humid tropics (NRC 1993).

Land transformation in temperate zones (such as Northern Europe) from its natural state to its present intensive agriculture and land use occurred over thousands of years. Changes in the tropics are occurring at a much faster rate; in some cases, areas are completely transformed and often degraded beyond economically feasible restoration within one generation.

Sustainable land use in the humid tropics will require an approach that recognizes the characteristic cultural and biological diversity of these lands, respects their complex ecological processes, involves local people at all stages of the development process, and promotes cooperation among biologists, agricultural scientists, and social scientists. The easing of rigid disciplinary boundaries is of special importance in the humid tropics.

Most public sector agricultural research and development programmes in the humid tropics have in the past used a commodity oriented approach, aiming to maximize the production of cereals and a limited number of root and pulse crops. This approach has led to striking increases in food production in areas with good soil and water resources. However, by focusing attention on particular crops and agro-ecosystem components, it has tended to neglect the range of physical and biotic interactions that influence crop production, the ecological impacts of intensive production practices, and broader social and economic aspects.

This commodity-oriented approach has also ignored lessons from the performance of traditional agricultural systems. Many traditional resource management techniques and systems, often dismissed as primitive, are highly sophisticated and well suited to the opportunities and limitations facing farmers in the tropics. Their durability, adaptability, diversity, and resilience often provide critical insights into the sustainable management of all tropical agro-ecosystems. Although many of these systems have been deeply modified or abandoned owing to economic, cultural, and social pressures, some could, with modification, contribute significantly to the sustainability and productivity of agriculture in many tropical countries (NRC 1993; Gallopín et al. 1991).

Agricultural systems and techniques that have evolved from ancient times to meet the special environmental conditions of the humid tropics include the paddy rice of South-East Asia, terrace, mound, and drained field systems, raised bed systems (such as the chinampas of Mexico and Central America), and a variety of agroforestry, shifting cultivation, home garden, and natural forest systems. Although diverse in their adaptations, these systems share common elements, such as high retention of essential nutrients, maintenance of vegetative cover, high diversity of crops and crop varieties, complex spatial and temporal cropping patterns, and the integration of domestic and wild animals into the system (NRC 1993). Many of the required activities are highly knowledge intensive, even if based on empirical knowledge. This diversified holistic, empirical knowledge, or socio-diversity as it is sometimes referred to, is being lost in the tropics as fast as, and often faster than, biodiversity. This is a precious resource receiving insufficient attention.

It is generally agreed that sustainable agriculture typically will require more information, more and better trained labour, and more diverse management skills per unit of production than conventional farming. This is because diversification into each additional crop and additional animal species requires additional and different skills. A diversified farm requires better production management and a different kind of labour resource than a similar-sized farm growing only one or two crops. This is one of the major limiting factors (Pesek 1994). In the case of integrated pest management (IPM), based on sound scientific principles, it is argued that, when problems arise in its practice, they are usually associated with the large amount of knowledge and expertise needed to develop, implement, and improve an IPM programme and with a tendency to rely too heavily on strategies developed from inadequate knowledge and without sufficient consideration of all the consequences of their use (Funderburk and Higley 1994). It is also recognized that sustainable agriculture must be based in large part on site-specific information and knowledge (White et al. 1994). It seems ironic that modern agriculture in many cases has lost (and, in the tropics, is still losing) site-specific skills for managing complex agro-ecosystems in its quest for standardization and commoditization, and that the same skill factor (albeit with the incorporation of modern scientific knowledge) is limiting the transition to sustainable agriculture.

Although traditional knowledge is not a panacea, it could contribute much to sustainable agriculture when combined with modern scientific knowledge, as will be discussed later.

Table 10.1 Summary of the three major types of agriculture



Green Revolution

Resource poor
Main locations Industrialized countries and specialized enclaves in the third world Irrigated and stable rainfall, high-potential areas in the third world Rain-fed areas, hiterlands, most of sub-Saharan Africa, India, Burma, Bangladesh, Indo-China
Main climatic zone Temperate Tropical Tropical
Major type of farmer plantations Highly capitalized farms and Large and small Smallholders
Use of external inputs Very high High Low
Farming systems, relatively: Simple Simple Complex
Environmental diversity, relatively: Uniform Uniform Diverse
Production stability Moderate risk Moderate risk High risk
Current production as percentage of sustainable production Far too high Near the limit Low
Priority for production Reduce production Maintain production Raise production

Source: Chambers et al. (1989).

Tropical agriculture includes two of the three major types of agriculture (see table 10.1). These two types can be illustrated by the following extreme situations.2

- The robust and fertile tropical agro-ecosystems. These are characterized by relative homogeneity of the natural resource base. A realistic production objective in those agro-ecosystems may be to maximize yields subject to environmental constraints. The major inputs for production are chemical and genetic. Because these are mostly appropriable technologies, the private sector might undertake a large portion of the research effort, with the state playing a subsidiary and regulatory role. Ecological unsustainability is mainly reflected in the overuse of agro-chemicals (generating pollution), inadequate water management (leading to salinization and alkalinization), genetic erosion, and overexploitation (leading to loss of soil fertility). Production has a relatively stable market. One of the major economic instruments for regulation is the pricing policy.

Appropriate measures for moving towards sustainability include solving the basic genetic problems, managing crop rotations, establishing regulatory policies for the use of inputs, using integrated pest and nutrient management, etc. An economic objective should be the internalization of the real costs by producers. In terms of organizational requirements, a stimulus to private enterprises and horizontal cooperation between producers are particularly relevant.

In other words, owing to the essentially commercial nature of the activity, these agro-ecosystems can be made sustainable through adjustments optimizing the functioning of the system.

- The fragile and resource-poor tropical agro-ecosystems. A common feature is their great heterogeneity in terms of the natural resource base. A major objective is to reduce risk and sustain productive capacity. This requires a new technological pattern for the management of diversity and heterogeneity. Information and management are more important for production than agricultural inputs. These technologies are not easily appropriable by the private sector. This highlights the need for a strong role for public institutions and civil society (non-governmental organizations, unions, cooperatives, etc.). The major negative impact upon natural resources is degradation and physical destruction. Integrated approaches are essential here. Some policy problems are related to the fact that the market for the products is practically unknown and often unstable. One major economic policy instrument is the discount rate. The development of this technological pattern requires horizontal cooperation between international and national agricultural research centres but also vertical coordination involving the political decision makers, the makers of technology, and the agricultural producers.

This differentiation between two extreme situations illustrates the point that there is no single technological pattern for sustainable tropical agriculture, but rather a constellation of patterns corresponding to different agro-ecological situations. Furthermore, the role of integrated approaches, although important in all types of agriculture, becomes absolutely essential in the case of fragile, resource poor, and heterogeneous tropical agro-ecosystems.

Where resources and inputs are scarce and crop failure might be fatal, diverse and complex cropping systems dominated by long-lived plants are appropriate. However, the very attributes that make forest mimics attractive - recycling of nutrients, freedom from dependence on large inputs of agro-chemicals, reduced risk, and effective use of available resources - seem to have biological costs that are incompatible with high yield. A plant's photosynthetic energy may be allocated either to harvestable products or to the ecological functions that sustain complex ecosystems, but not to both simultaneously (Ewel 1986). On the other hand, the development of new technologies (particularly biotechnology) may change the picture drastically, by allowing the making of useful food and non-food products from the biomass that is now considered non-harvestable.

The above-ground net primary productivity of natural ecosystems (biomass production per hectare per year) may be used as a rough indicator of the aggregated potential supply of ecological resources provided by an ecosystem. A study for Latin America (Gómez and Gallopín 1995) compares estimated natural above-ground net primary productivity with estimated potential yields of rain-fed agriculture in the same area. Tropical ecosystems tend to cluster in two groups, both with high potential agricultural yield: the first (including a number of savanna types and dry and open tropical forests) has relatively low net ecological productivity, and the second has much higher net primary productivity (this includes the tropical lowland and montane moist forests, mangrove forests, tropical deltas, and Amazonian forests). In a sense, agricultural food production in the first group has a comparative advantage, because it allows high agricultural yields in relation to natural ecological productivity. In the second group, the reverse is true. This comparison between ecological productivity and potential agricultural yields suggests that tropical savannas and grasslands should be the priority for classical agriculture, whereas tropical and subtropical forests (although they too have good agricultural potential under suitable technologies) would be best considered (from the productive viewpoint) as areas for the development of new eco-technologies allowing the tapping of the enormous natural biomass.

The need for integrated solutions to tropical land use is not limited to agriculture in fragile, resource-poor ecosystems. On the one hand, many interlinkages exist among the components of all tropical farming systems or types (Beets 1990). On the other hand, at a broader resolution level, the interlinkages between economic, social, and ecological factors in the unsustainability of land use are also clearly visible (fig. 10.1)

Fig. 10.1 Interlinkages between ecological, economic, and social factors in tropical land use in Latin America (Source: Gallopín et al. 1991)

As discussed above, the search for new technologies and production systems (contributing to the availability of sustainable solutions) in the tropics requires a high degree of integration. Beyond the issue of availability, that of the replicability of solutions is crucial. To ensure that sustainable agricultural technologies are adopted and generalized it is clearly necessary to take a broad view including social, economic, and cultural aspects in an integrated manner. Examples of a framework for comparing the attributes and potential contributions to the sustainability of land-use systems in the humid tropics appear in tables 10.2,10.3, and 10.4 (NRC 1993).

Table 10.2 indicates a number of biophysical attributes directly associated with ecological sustainability, including the nutrient cycling capacity (understood as the capacity to cycle nutrients from the soil to economically useful plants or animals and replenish them without significant losses to the environment), the capacity of the system to conserve soil and water, the resistance of the system to pests and diseases (defined as its natural ability to maintain pests and diseases below economic threshold levels), the level of biological diversity within the system (referring to the diversity of plant and crop species, which, in turn, fosters diversity of flora and fauna both above and below ground), and the carbon flux and storage capacity of the system. Together, these attributes help to characterize the relative complexity, efficiency, and environmental impacts of the various land uses.

In terms of the total set of biophysical attributes considered, and assuming the best technologies available or under experimentation, the forest reserves rank highest, followed by the mixed tree systems (also known as forest or home gardens and mixed tree orchards), the regenerating and secondary forests, natural forest management, and modified forests. Intensive cropping, low-intensity shifting cultivation, and cattle-ranching rank lowest.

This is in direct contrast with the ranking of land uses according to social attributes (table 10.3): the highest values correspond to intensive cropping in both resource-rich and resource-poor areas, and agro-pastoral systems, and the lowest to regenerating and secondary forests, and forest reserves. Only mixed tree systems rank high in both biophysical and social attributes.

Table 10.3 shows the social attributes considered. Health and nutritional benefits (to farms and their local communities) reflect the capacity of a system to offset problems associated with intensive agro-chemical use, heavy metal contamination, degraded water resources, high disease vector populations, and other public health concerns, as well as the capacity to provide local people with a diversity of food products at adequate levels. Cultural and communal viability indicates the capacity of production systems to be adapted to local cultural traditions and to enhance community structures, making optimum use of local resources and encouraging acceptable levels of local equity. The final social attribute is political acceptability, here taken as the system being politically desirable at levels above the local community (country, region, province, state, or national level).

Table 10.2 Comparison of the biophysical attributes of land-use systems the humid tropics


Biophysical attributes


Nutrient cycling capacity

Soil and water conservation capacity

Stability toward pests and diseases

Biodiversity level

Carbon storage

Land-use system L M H L M H L M H L M H L M H
Intensive cropping: high-resource areasa   Xc Xd   X   X O   X     X    
Intensive cropping: low-resource areas X O   X O   X O   X O   X    
Low-intensity shifting cultivation X     X O   X       X   X O  
Agro-pastoral systems   X     X O   X     X     X  
Cattle-ranching Xb     X O     X   X Oe   X O  
Agro-forestry   X     X         X O     X  
Mixed tree systems     X   X O         X     X O
Perennial tree crop plantations     X   X O X     X       X  
Plantation forestry     X   X O X O   X       X O
Regenerating and secondary forests     X   X O   X     X     X O
Natural forest management     X     X   X     X     X O
Modified forests     X     X   X     X       X
Forest reserves     X     X     X     X     X

Source: modified from NRC (1993), pp. 140-141.
Note: The letters L (low), M (moderate), and H (high) refer to the level at which a given land use would reflect a given attribute. In this assessment, "X" denotes results using the best widely available technologies for each land-use system. "O" connotes the results of applying the best technologies currently under limited location research or documentation. The systems could have the characteristics denoted by "O" given continued short-term (5 10-year period) research and extension.
a. Those areas having fertile soils with little slope and few, if any, restrictions on agricultural land use. They have adequate rainfall or irrigation during much of the year for crop growth.
b. High efficiency of recycling but low levels of nutrient removal through harvesting.
c. Present technologies may develop high flow with high crop production, but they often involve high nutrient loss. Future technologies hold promise for greater containment and efficiency.
d Lowland, flooded rice production has both high nutrient flow and very high efficiency of recycling and of nutrient containment.
e Assumes diversity of plant species under well-managed grazing systems, which may include tree species in silvipastoral systems.

Table 10.3 Comparison of the social attributes of land-use systems in the humid tropics


Social attributes

Health and nutritional benefits

Cultural and communal viability

Political acceptability

Land-use system L M H L M H L M H
Intensive cropping: high-resource areas   X O     X     X
Intensive cropping: low-resource areas   X O   X O   X O
Low-intensity shifting cultivation     X   X     X  
Agro-pastoral systems   X O   X O   X O
Cattle-ranching X O     X O     X
Agro-forestry   X     X     X O
Mixed tree systems X O     X     X O
Perennial tree crop plantations X       X       X
Plantation forestry X       X       X
Regenerating and secondary forests X       X     X  
Natural forest management X       X O   X O
Modified forests X O     X     X  
Forest reserves X       X     X  

Source: modified from NRC (1993), pp. 140-141.
Note: The letters L, M, H. X, and O are defined in table 10.2.

Finally, table 10.4 shows the ranking of land-use systems according to three economic attributes. The first is the level of external inputs (such as fertilizer and equipment) required to maintain optimal production. These levels may not be environmentally sustainable in the long term. The second and third attributes are the amount of employment and income generated per land unit. The ranking according to economic attributes is fairly similar to the one based on social attributes, with the highest values given to intensive cropping in high resource areas, followed by perennial tree crop plantations.

Table 10.4 Comparison of the economic attributes of land-use systems in the humid tropics


Economic attributes

Required external inputs

Employment per land unit


Land-use system L M H L M H L M H
Intensive cropping: high-resource areas     X     X     X
Intensive cropping: low-resource areas   X     X O X O  
Low-intensity shifting cultivation   X       X   X  
Agro-pastoral systems   X     X O   X  
Cattle-ranching   X   X       X  
Agro-forestry   X   X O   X O  
Mixed tree systems X O   X O   X O  
Perennial tree crop plantations     Xa   X       X
Plantation forestry   X Xa   X     X  
Regenerating and secondary forests X     X     X    
Natural forest management   X     X     X  
Modified forests X O     X   X    
Forest reserves X     X     X    

Source: modified from NRC (1993), pp. 140-141.
Note: The letters L, M, H. X, and O are defined in table 10.2.
a. Includes capital investment for establishment.

Regenerating and secondary forests, forest reserves, modified forests, and cattle-ranching have the lowest ranks.

However, if one gives the highest ranking to the lowest levels of required external inputs (given that lower inputs are better than higher, both economically and environmentally), then the highest ranking land-use systems are intensive cropping in both high- and low-resource areas, low-intensive shifting cultivation, and agro-pastoral systems, while the lowest ranking become cattle-ranching, plantation forestry, regenerating and secondary forests, modified forests, and forest reserves.

Comparing the three types of attributes indicates that there is no single "best" land-use system for the humid tropics. Each system entails positive and negative attributes that must be assessed in the context of local ecological, social, and economic opportunities and limitations. Different systems may be sustainable in different places, ecologies, and cultures.

But perhaps more than the kind of land-use system adopted, access to the best available technologies may be the strongest factor affecting progress towards sustainability. In the case of the Latin American tropics, for instance, technologies exist for the sustainable management of many agro-ecosystems, but these are not generally used (Gallopín and Winograd 1995). Prevailing land use is generally environmentally unsustainable and economically inefficient.

Agriculture is a strongly regulated social activity and very much dependent upon the laws and policies established to govern it (White et al. 1994). It is clear that, in most cases, policies and institutions are greater determinants of agricultural methods of production than the availability of technologies. This is true even in industrial countries such as the United States, where the National Research Council Committee concluded that their laws and policies governing agriculture, especially their commodity policies, are among the major culprits interfering with alternative methods of production (NRC 1989). This is clearly shown on the left side of figure 10.1, where the major determinants of unsustainable exploitation of the land are indicated as the use of inadequate (or marginal) land and inadequate technologies (due to speculation and short-term planning horizons on the one hand, and to needs for survival associated with demographic growth and poverty, on the other), changes in the market and in consumption patterns, and institutional and legal deficiencies. Most of these factors are amenable to improvement through policy.

Contents - Previous - Next