|Soil Degradation - A Threat to Developing-Country Food Security by 2020? 2020 Vision for Food, Agriculture, and the Environment Discussion Paper 27 (IFPRI, 1999, 70 p.)|
The period since World War II has seen remarkable growth in agricultural production and productivity in the developing world. While in many farming areas this growth has apparently been sustainable, in others it derived from two unsustainable processes: the clearing of new lands of lower productive potential or higher vulnerability, and the intensification of production by mining or destroying the soil resource base. The challenge of feeding and supplying the much larger population projected to live in the developing countries by 2020 has to be met not only by raising production from current levels, but by substituting for supplies no longer available from land-clearing, by finding sustainable methods of intensive production on soils not previously used for this purpose, and by substituting for or rehabilitating degraded soils where there is continuing demand for their use.
Leaders in the economic and agricultural development communities, as well as environmentalists, must draw the attention of policymakers to soil degradation concerns and work with them to set priorities for public investment, farmer services, and policy. A necessary though not sufficient step is to provide supportive policies for broad-based agricultural development. Targeted policies and investments will also be needed to address many serious degradation problems. Better characterization and diagnosis of soil degradation effects will be needed to guide and support these efforts.
Support Policies for Broad-Based Agricultural Development
If the 2020 Vision policy agenda (IFPRI 1995) is seriously pursued, many soil degradation problems can self-correct to a considerable extent by 2020. Farmer investment in known land-husbandry technologies should increase where agricultural markets perform more effectively, reducing the costs of inputs and increasing farmgate output prices; where profitable farming opportunities raise the value of agricultural land; where technological change makes higher, sustainable yields possible; and where land tenure is secure. In some areas, in such a supportive policy environment, simply promoting information dissemination about good land husbandry practices and supporting research on technologies to reduce conservation costs may be sufficient for addressing degradation concerns.
Target Land-Improving Policies, Investments, and Research
It is doubtful, however, that indirect policies will be enough. Agricultural growth can have mixed effects on resources, due to widespread lack of information, institutional failures, and market failures. And many areas cannot count on having a dynamic economy or suitable technology. An integral element of development strategies to promote the 2020 Vision must be the policies, investment, and research that promote soil protection and rehabilitation where soil quality most affects agricultural supply, economic growth, rural welfare, or long-term national wealth.
Soil rehabilitation demands going well beyond simply applying fertilizer to replace chemical nutrients; it may involve restoring organic matter, improving soil structure and waterholding capacity, controlling the flow of water across fields, restoring soil flora and fauna, buffering acidity, and establishing vegetative cover. Community- and watershed-scale planning will often be needed in the transformation to more sustainable, higher-productivity landscapes.
However, efforts to improve soil quality must complement - not substitute for - other types of agricultural investments, and reflect economic realities and farmer resource constraints. Conservation efforts should maintain, stabilize, or increase productivity, not necessarily optimize soil condition. Direct action and research interventions must be designed to fit specific development pathways, farming systems, soil types, and degrees of degradation.
Densely Populated Marginal Lands
Policy action in densely populated marginal lands should focus explicitly on improving soil quality as a key element in increasing yields and reducing risk and yield variability. Nutrient depletion can be addressed by increasing nutrient inputs and improving nutrient use efficiency; reducing nutrient off-take (that is, reducing harvests) is not often a reasonable option. Chemical fertilizers will play an increasingly important role as marketing costs decline. However, few of the vulnerable soils on these lands can be managed intensively and sustainably over time with chemical nutrient applications alone. Organic matter management is critical for protecting the physical structure of soils and using nutrients efficiently (Sanchez et al. 1997). For soil types that cannot sustain continuous cultivation, economically productive perennials and cover crops must be incorporated into the farming rotation (Garrity 1998; Tengberg and Stocking 1997). For areas still not well integrated into markets in 2020 (much of Africa and the remote mountains) and for farmers who practice subsistence production, low-cost sources of plant nutrients must be found urgently to replace or supplement fertilizer use. Beyond nutrient maintenance, policies are needed to help farmers organize and finance investment in land improvements.
The research challenge is immense: to develop nutrient management systems for specific soils, low-cost soil rehabilitation techniques, and economical methods for incorporating more perennial plants in farming landscapes. Profitable systems to manage local forest and grazing lands are needed to justify good land husbandry. The more effective soil management practices from intensive farming systems need to be documented and shared with farmers working with similar soils elsewhere and who have only recently begun the transition to intensive systems.
The two priority policy actions to combat irrigated land degradation are fairly well known: improve system- and farm-level water management regimes and invest in proper drainage systems where this has not been done. Plans must be made to retire lands that are irreversibly degrading with minimal disruption to farm communities. Diversification to higher-value crops may help to justify reinvestments in irrigation systems and higher-priced water.
Priorities for research include exploring problems of micronutrient depletion and other soil-related factors that may lead to yield stagnation, identifying effective water management regimes, developing low-cost methods to control or reverse salinization, and utilizing saline lands.
High-Quality Rainfed Lands
Policy action for high-quality rainfed lands must seek to better integrate technology development and extension for productivity growth with good soil husbandry through tillage practices, agricultural machinery use, and agrochemical management. Market-based mechanisms should be developed to improve distribution systems for fertilizers that reduce cost, improve nutrient balance, and encourage complementary use of organic nutrients. Recommendations will vary with changing ratios of output to nutrient prices.
Research priorities must develop recommendations and technologies for fertilizer and organic nutrient management for specific soils, climates, and crops and identify or develop low-cost organic nutrient sources for smallholder producers. New biotechnology and other technical advances should be designed for integration into sustainable resource management systems.
Urban and Peri-Urban Agricultural Lands
Much of the policy action needed to promote better soil quality in urban and peri-urban agriculture is institutional. Zoning rules, land access, controls on agricultural land conversion, and regulation of agrochemicals and livestock waste disposal need to be changed to improve the security of urban farming. Community gardening opportunities on public and unutilized private land should be protected and promoted.
Research priorities need to focus on designing technologies to improve the use of urban waste products in soil nutrient management and livestock feed and minimize toxic agrochemical use. Studies are needed to understand the patterns and strategies for controlling livestock disease in urban environments. Physical and institutional barriers to protect farmland from urban soil pollutants also need to be developed.
Extensive Agriculture in Marginal Lands
In extensive agricultural systems, policy action should aim to limit the environmental damage of farming practices at a minimal cost to farmers and help farmers make the transition to more sustainable short-fallow or permanent cultivation systems. Extensive farming can only be regulated or prohibited economically in a small number of strategic sites. Farmers need support from extension services to farm lightly on the land using technologies that do not require high labor use or purchased inputs. Mosaic patterns of land-clearing and controlled burning can be encouraged on cropland and rotational grazing and grazing reserves on rangeland, in order to maintain more natural vegetation. In areas with vulnerable soils, policies that raise the value of forest and tree products can reduce land clearing, raise local incomes, and initiate a long-term transition to an economy based on permanent crops. Improved employment opportunities for the landless outside agriculture, in other farming areas, or in forest management can reduce farmer incentives to clear new lands. Infrastructure investments need to be concentrated in areas of existing settlement.
Research should focus on technologies for low-input farming, higher-value products that encourage spatial concentration of production, and perennial crops. Crop, forest, or range management systems will ideally meet both local economic and broader environmental objectives, justifying the transfer of re sources from outside the region to help finance this dual agenda.
Identify Priority Soil Degradation Problems
Currently available data are insufficient to guide and prioritize such targeted policy action. Accurate information is needed on the actual areas and farming communities where serious soil degradation - and soil improvement - are taking place, and the nature of the effects on agricultural supply, economic growth, rural poverty, and soil wealth. Analysis should focus on the subnational level, where soil quality change and its effects can be meaningfully measured and interpreted, and where policies need to be implemented. National and international priorities can best be developed by aggregating this subnational information.
The design of sampling frames and the collection of agricultural production, farm income, and rural poverty data need to be made spatially explicit, or at least the different land classes, agroclimatic zones, land use intensities, market environments, and types of producers should be distinguished from each other. For the design of specific interventions, more detail is needed on type of soil, resilience from and sensitivity to degradation, and management history. Advances in remote sensing methods (for example, in spectrome-try) will soon offer the potential for monitoring key soil characteristics on a large scale. International support is needed to expand resource characterization and monitoring systems such as the international soil and terrain database (SOTER), the Land Quality Indicator program (Pieri et al. 1995), and the global database on farmer use of conservation technologies (WOCAT 1997), which draw on a mix of information from remote sensing, spatially informed agricultural and household surveys, and key informants.
Geographic information systems can be used to integrate and manage databases of various types and spatially analyze the economic effects of soil quality change. Time-series data can be used to explore the relationships between soil quality change over time and farm management, local economic and social conditions, and the policy environment. Soil quality indicators can be incorporated into economic and policy modeling of agricultural trends at subregional and national scales. Where adequate information about the links among soil quality, degradation, and productivity and the geographic location of problems exists, models can help identify priorities for action. Where information is sparse, modeling can help identify priority data needs and encourage dialogue among soil, agricultural, and environmental experts, policymakers, and the larger agricultural community.
Economists need to use more creative methods to analyze the effects of soil degradation on agricultural supply, in order to reflect the geographic structure of production, the price effects, and the consumer and producer responses to those effects in different geographic regions. Studies of the effects of soil degradation on agricultural income (including multiplier effects) and rural poverty similarly require more systematic design and analysis. More conceptual work is still needed to determine appropriate methods for evaluating soil wealth.
We should not take lightly the long-term economic threat of accelerating soil degradation. Historical evidence suggests that the economic decline of empires in Mesopotamia and the Indus Valley was due, at least in part, to widespread salinization and waterlogging of irrigated lands, while decline in ancient Israel, Lebanon, Greece, and Rome was due to topsoil loss in the rainfed uplands of the Mediterranean (Hillel 1991). We have more knowledge and tools at our disposal today, but the output demands and pace of change in soil resource management have also vastly accelerated. The difficulties of measuring and valuing soil quality changes and their effects mean we must approach the challenge with care. However, this should not deter economists and policymakers, but rather inspire them to focus greater attention on soil quality management as a central natural resource issue for sustainable agriculture in the developing world.