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Since the 1980s many developing countries have implemented macro-economic policy reforms to curb inflation, reduce fiscal deficits and control foreign debt. The policy instruments used, such as exchange rate adjustment, budget cuts, trade policy reforms, public expenditure reviews and privatisation, have different and sometimes opposite consequences for agricultural land use. During the same period awareness was growing that deteriorating soil quality could become a limiting factor to increase or even sustain agricultural production. As a result, food availability and even accessibility for large population groups in developing countries may be jeopardised in the near future. Recently, quantitative models have made useful contributions to understanding the impact of economic policy reforms on the sustainability of land use. They provide a consistent analytical framework to deal with complex issues such as the direct and indirect effects of economic, agricultural, environmental and population policies, the role of market imperfections in transmitting economic policy signals, and the interactions between soil quality, agricultural production and household economic decision making. Different types of models can be distinguished: bio­ economic models, focussing on the link between farm household decisions and the agricultural resource base, household and village models, examining the impact of the socio-economic environment on farm household decisions, and more aggregate models, analysing interactions between sectors and their implications for sustainable land use.

Inhaltsverzeichnis

Frontmatter

1. Economic Policy Reforms and Sustainable Land Use in Developing Countries: Issues and Approaches

Abstract
An important factor in land degradation and farmers’ investment in soil conservation in developing countries are the changes in the socio-economic environment of farm households resulting from economic policy reform measures taken at higher levels. This chapter provides an overview of the mechanisms through which economic reforms may affect soil degradation and conservation investments,and discusses some recent developments in quantitative approaches that can be used for analysing these relationships. It starts with a discussion of the soil degradation problem and its effects on agricultural production. Next,the potential implications of economic policy reforms for the sustainability of agricultural land use are discussed. Relevant factors at the macro,meso, household and plot level,and the potential relationships between them,are reviewed. The resulting analytical framework takes into account the role of market imperfections and institutional factors in shaping the relation between economic policy instruments and farm household decision making. Recent developments in quantitative modelling may contribute to improving our understanding of the complex effects of economic policies on changes in soil quality. Major approaches in this respect, and their potential contributions,are briefly reviewed. The chapter ends with a discussion of the objectives of the book and a brief overview of its structure.
Nico Heerink, Arie Kuyvenhoven, Maarten S. van Wijk

2. Soil Degradation and Agricultural Production: Economic and Biophysical Approaches

Abstract
In this chapter we give an overview of a number of approaches used in the biophysical sciences to quanta the relationship between agricultural production and soil degradation. First the concept of soil degradation is discussed, and the various components detailed. Then the approaches are assessed in the context of bio-economic models in which biophysical processes are linked to decision making processes at household, village and regional levels. The main emphasis of the chapter is on the household level where the direct interaction between decision makers and the biophysical processes takes place. Different biophysical approaches are presented, used for generation of data for incorporation in bioeconomic models.
Gideon Kruseman, Herman van Keulen

3. Technical Options for Agricultural Development in the Ethiopian Highlands: A Model of Crop-Livestock Interactions

Abstract
The crop and livestock sectors in Ethiopia are closely interlinked. Oxen play a dominant role as draft animals. The oxen plough system has existed for thousands of years, but is currently under pressure due to reduced farm size and low availability and quality of fodder. There is a need therefore to develop alternative tillage systems like zero-tillage or cow traction. A model was developed to assess the resource constraints of the Ethiopian crop livestock system and to examine alternative technological options for improving the system. The model can be used to assess productive effects of fertiliser use, choice of livestock system and fodder quantity and quality. The data used to construct the model were derived from household surveys and established relationships between fodder quality and livestock production. The model results show fodder resources to be a critical factor in livestock production. An interesting option for improving the crop-livestock system is to introduce dairy goats. However, for such a change to take place, the quality of the fodder resources will have to be upgraded.
Ayele A. Abiye, Jens B. Aune

4. Land Degradation as a Transformation Process in an Intertemporal Welfare Optimisation Framework

Abstract
An intertemporal social welfare optimisation framework proposed by Fischer et al. (1996) describes desirable scenarios of land use and land cover change in the future for China. This chapter intends to demonstrate that it is feasible to integrate a land degradation dimension into this framework, if the required quantitative data are available. We show how to incorporate the land degradation dimension into the profit maximisation process of a representative farm as part of resource management. Land units are categorised according to their soil and climate characteristics to represent the spatial heterogeneity. They can shift from higher quality classes to lower ones as a result of land degradation, while it is also possible to reverse this process by land conservation measures. Land degradation is treated as an integral element of an economic transformation function. The basic assumption is that users of the land farmers in particular notice the negative effect of land degradation on their production potentials. They are supposed to have opportunities to cancel these negative effects by investing in land and/or by increasing the volume of their input packages.
Peter J. Albersen, Laixiang Sun

5. Population Pressure and Land Degradation in the Ethiopian Highlands: A Bio-Economic Model with Endogenous Soil Degradation

Abstract
We apply a bio-economic modelling approach to trace important relationships between population pressure, poverty and management of land resources for a crop-livestock economy characterised by serious land degradation in the Ethiopian highlands. Our objective is to examine the interlinkages between population pressure and poverty, their impacts on household welfare and land management, and the consequent pathways of development in a low potential rural economy. Farm households are assumed to maximise their discounted utility over the planning horizon in a multi period model, where the management of the resource base has feedback effects on the stock and quality of the resource base. Market imperfections lead to non-separability of production and consumption decisions of farm households. The models trace the dynamic interactions between crop and livestock production, the resource base, consumption preferences, and partial integration of the household economy into markets. Simulation results indicate that under high population pressure, land becomes more expensive, relative to labour. This induces labour-intensive conservation investments when off-farm employment is limited and labour is not in scarce supply. Availability of credit and fertiliser, however, seem to discourage labour-intensive conservation efforts. When markets are imperfect, poverty in vital assets (e.g. oxen and labour) limits the ability or the willingness to invest in conservation.
Bekele Shiferaw, Stein Holden, Jens Aune

6. Imperfect Food Markets and Household Adoption of Soil Conservation Practices in the Dominican Republic Highlands: Household Probit and Duration Models

Abstract
This paper formalises the determinants of adoption and maintenance of soil conservation practices on peasant households’ food plots in the Dominican Republic highlands, where a local rural development project provides training, technical assistance and subsidies in the form of food-for-work. We model these decisions as an intertemporal labour allocation choice in the context of household-specific food markets imperfections. From the theoretical model, we derive consistent empirical models (probit and duration models). Results show, that food subsidies help bring marginal households into soil conservation. Households facing a higher return to their labour on the labour market tend nevertheless to abandon conservation practices once the subsidy stops. Large landholdings are also associated with less soil conservation. The main adopters are thus households strongly vested in agriculture, especially if they depend on own production for their consumption.
Bénédicte de la Brière

7. Soil Conservation and Imperfect Labour Markets in El Salvador: an Empirical Application of a Dynamic Control Model of Farm Production

Abstract
An important issue in the study of soil conservation is the impact that imperfect markets can have on farmers’ decisions regarding resource management. Rural areas in developing countries are characterised by high transaction costs and imperfect markets. Since soil conservation is labour-intensive, the functioning of agricultural labour markets and the availability of off-farm work opportunities are likely to affect soil conservation effort. In this paper I develop a dynamic control model of agricultural production in the context of lack of access to labour markets in order to analyse how soil management decisions are affected. An empirical application of the model is developed using data from a 1996 farm household survey in El Salvador. The results of the model are confirmed by the econometric estimation, showing that soil conservation is negatively affected by off-farm employment and smaller family labour force only for farmers who face a missing agricultural labour market. Soil degradation seems to be closely associated to conditions that prevent farmers from fully participating in rural markets. Moreover, rural policies that promote the non farm rural sector may have an unwanted negative impact on soil conservation and soil conservation programs would be more effective if they promoted labour-saving practices.
Claudia B. Romano

8. Assessing the Effects of Policy Measures on Household Welfare and Agro-Ecological Sustainability: an Overview of Farm Household Modelling Approaches

Abstract
Farm household modelling is a powerful tool to aid policy makers with the analysis of sustainable land use. This paper gives the methodological foundations for a farm household simulation approach encompassing the results from quantified agronomic models, based on parametric optimisation. The paper discusses shortcomings and advantages of different approaches underlying the methodology, and demonstrates how these can be integrated into a pragmatic framework. Starting with a basic farm household model extensions are made and methods described to make those extensions operational. While econometric analysis alone is an insufficient tool to fully explain all relevant household behaviour, it is an important element in the approach. The results of the optimisation model are used in metamodelling exercises that summarise the relationship between exogenous parameters and indicator variables, to account for endogenous prices at the regional level.
Gideon Kruseman

9. Agricultural Prices and Land Degradation in Koutiala, Mali: a Regional Simulation Model Based on Farmers’ Decision Rules

Abstract
To enhance sustainability of agricultural production and food supply, insight is required in the relevant agro-ecological and socio-economic processes at farm and regional level. In this chapter a modelling approach is presented that is suitable to provide a qualitative insight in the dynamics of agricultural development. The approach is used to develop a model of the Koutiala region in southern Mali that allows simulating the development of different farm types and their interactions. It is demonstrated how the model may help to identify discontinuities in agricultural development when conditions change, and how it may serve to explore effects of price policies on,for example, soil organic matter content.
Tjark Struif Bontkes

10. Integrating Site-Specific Biophysical and Economic Models to Assess Trade-offs in Sustainable Land Use and Soil Quality

Abstract
In this paper we describe the sustainability of a production system in terms of trade-offs between present and future outcomes such as crop productivity. Based on the observed site-specificity of the relationship between soil characteristics and productivity, we hypothesise that to accurately assess the sustainability of an agricultural production system we must measure the interactions between farmers’ management decisions and soil quality on a site-specific basis and then aggregate the resulting relationships. The analysis of linked, site-specific economic and biophysical models shows that soil quality at a point in space and time depends on both fixed site characteristics and on the history of farmers’ management decisions. Aggregation then shows that both on farm productivity and potential productivity are functions of parameters that define the distributions of physical and economic variables in a region. Using this result, we show that measurements of sustainability based on ‘representative’ data such as mean soil characteristics will generally be biased and thus may lead to inaccurate assessment of a system’s productivity and sustainability.
John M. Antle, Jetse Stoorvogel

11. Effects of Land Degradation in a Diversified Economy with Local Staple and Labour Markets: A Village-Town CGE Analysis from Mexico

Abstract
Land degradation has potentially complex effects on diversified economies typical of rural areas in less-developed countries. Market linkages transmit the impacts from the directly affected households to others in the economy. When high transactions costs inhibit trade in food,labour, capital,or other goods,shifts in consumer or input demands influence prices and unleash general-equilibrium effects in local economies. These effects are missed by the extensive research on first-round effects of agricultural policies on household farms including those in imperfect market environments. Economy-wide models including computable general equilibrium (CGE) models are designed to capture the second and higher-round feedback of exogenous shocks to the macro economy. Our research uses an adaptation of CGE techniques presented in Taylor & Adelman (1996) to explore the impacts of land degradation on village economies and on migration for an area in rural Mexico characterised by local markets for staples and labour. Our village-town CGE blends microeconomic household farm models with economy-wide modelling. Results suggest that second round effects,which are not captured by household models can be important.
George Dyer, Antonio Yunez-Naude, J. Edward Taylor

12. Agricultural Production and Erosion in a Small Watershed in Honduras: a Non-Linear Programming Approach

Abstract
This paper describes a multi period non-linear programming model of agricultural production that includes soil erosion and its effect on crop production within a small watershed. The purpose of the model is to predict the likely effect of different decisions taken by the local community of the watershed on land uses, soils and incomes. The model has been applied to a small watershed in the hillsides of Central Honduras. Results show how erosion will affect local production in the long term. It also shows how farmers are likely to cope with the problem. In the model, the effect of erosion is calculated as a function of soil loss through decreasing soil depth. To better describe the spatial dimension of the problem, the watershed is divided in homogenous land units of different sizes. These land units are specified according to altitude, slope and farm type. The land units are inter-related through transport time, access to road, and water transfer. The main actual agricultural activities are available to the model, including land conservation techniques. Each land unit starts with a different stock of soil volume, land use area, crop productivity, and human population. These variables are modified over time by both natural and human activities.
Bruno Barbier

13. Alternative Approaches to the Economics of Soil Nutrient Depletion in Costa Rica: Exploratory, Predictive and Normative Bio-Economic Models

Abstract
This chapter discusses three methodologies to analyse land use with respect to income generation and sustainability in the Atlantic Zone of Costa Rica: the explorative SOLUS methodology,the predictive UNA-DLV methodology,and a normative optimal control approach. Each methodology may be classified as bioeconomic; the first two are single period optimisation models at the regional and farm level,respectively,while the third is a dynamic model at the plot level. The SOLUS and UNA-DLV methodologies incorporate a multi-market structure for commodities produced by a wide spectrum of land use systems with specified technologies. For each of these systems,technical coefficients are generated related to discounted benefits and costs,and to sustainability indicators,including soil nutrient depletion. The optimal control model is confined to a pasture plot with cattle,property of a single farmer,and analyses the inter-temporal trade-off between soil nitrogen depletion and net benefits. Apart from assessing the ‘economic benefit - sustainability’ trade-off,all methodologies are capable of analysing the effects of technological change. After providing some example results,the chapter concludes with a comparison of the relative merits of each methodology.
Hans G. P. Jansen, Robert A. Schipper, Peter Roebeling, Erwin H. Bulte, Huib Hengsdijk, Bas A. M. Bouman, André Nieuwenhuyse

14. Effects of Economic Policies on Farmers, Consumers and Soil Degradation: a Recursively Dynamic Sector Model with an Application for Burkina Faso

Abstract
In this paper, a bio-economic model is described to support the process of policy formulation. The model incorporates the results of crop growth simulation models (with detailed information on the process of soil erosion) within the framework of an economic model designed to represent farmers’, herders’ and consumers’ behaviour at the agricultural sector level. It consists of three interacting and recursive modules: production, a regional optimisation model that simulates the individual decisions about crop allocation based on expected prices; marketing/consumption, a partial equilibrium model where ‘real’ prices are estimated as a result of the confrontation between marketed production and urban demand; and macro-economic context, in which the general economic variables affecting farmers and consumers are defined. The production choices and their effects on soil degradation influence the future choices of farmers within the model, allowing to take into account explicitly the dynamic recursive impact. The model gives indications on the way different actors might probably respond to the simulated policies and the influence of these responses on production, income, and consumption. Also, part of the positive and negative effects on soil quality is estimated. The use of these variables allows to compare the results of the simulation of different policies and facilitates the choice for the policy maker.
Daniel Deybe

15. Soil Degradation in Macro CGE Models

Abstract
Soil degradation is a widespread and serious threat to poor developing countries. The large contribution of agriculture to the national economies of these countries makes partial analysis of soil degradation insufficient. Soil productivity loss affects the urban economy through food prices, demand for farm inputs and consumer goods. Also, general economic policies create incentives that influence farm practices and the pressure on soil resources. To focus these interactions, soil degradation has been incorporated in macro CGE models. Two approaches are presented in this paper. One incorporates soil productivity with nitrogen as limiting factor in a CGE model for Tanzania, forecasting inputs of fertiliser, land and output by eleven crops. The use of fertiliser and amount of recycled crop residues determine the rate of soil productivity loss. Deforestation for subsistence agriculture has been modelled in a CGE for Nicaragua. Migration to the agricultural frontier is encouraged by the imputed income from producing their own diet, and serves as an alternative to rural/urban employment or urban unemployment. Policy simulations show that economic reforms like devaluation have significant impacts on land use and nutrient mining. Deforestation for subsistence agriculture is sensitive to income distribution and changes in food prices. High economic growth does not guarantee forest conservation.
Solveig Glomsrod

16. The Effect of Soil Degradation on Agricultural Productivity in Ethiopia: a Non-Parametric Regression Analysis

Abstract
The paper estimates the effect of soil degradation on crop yields for dominant cereals in Ethiopia at a nation-wide level and analyses its relation with population density and fertiliser use. A soil degradation index is derived from an ordered qualitative classification on the degree of soil degradation and the area extension. Biophysical variability is incorporated by using, as dependent variable,the yield ratio (actual/potential yield) to correct for agro-climatic and crop genetic differences,and by including soil fertility as explanatory variable. The data set is cross sectional and obtained from gridded overlays on soil degradation,climate,soil,land form,population (and cattle) density. The relationships are estimated via non parametric (kernel density) regression and the estimation results are depicted in 3-D graphs. It appears that the relationship between yield ratio,land degradation and soil fertility is not very strong. Yet, three stylised facts can be identified. First,land degradation has its major impact on soils of lower fertility, where population levels are low. Secondly,on fertile soils,land degradation is largely compensated by fertiliser application. Finally,most people can be found on the slope facing a deep and dangerous precipice. A spatial representation of the elasticity of crop productivity with respect to soil degradation indicates that most vulnerable areas are located in the northern part of the country.
Michiel A. Keyzer, Ben G. J. S. Sonneveld

17. Between Free Riders and Free Raiders: Property Rights and Soil Degradation in Context

Abstract
This paper aims at a reorientation of the assumptions and perspectives with which the significance of property rights for more or less sustainable land use is viewed. The conventional four property categories do not offer a useful guidance into the complexity of property relationships. Generalisations over relations between categorical types of property rights and environmental consequences are dangerous and do not seem to be warranted given the empirical evidence. Rather, characteristics of property rights seem to play a dominant role for land use, relatively independent of the legal status of the land, such as the time horizon of land users, their dependence on the resource and the kind of dependence, and the spatial proximity/distance to the resource. In particular, actual constellations of property rights, in other words the distribution of wealth, over people and resources are important characteristics. Institutions should be approached from a post-institutionalist perspective which problematises the relationships between the normative-legal institutional framework, the social relationships that develop in their context and the social practices these rules purport to regulate, and which maintain or change the relationships and the normative institutional framework.
Franz von Benda-Beckmann

18. Land Rights, Farmers’ Investment, and Sustainable Land Use: Modelling Approaches and Empirical Evidence

Abstract
Secure land rights are generally acknowledged as a major incentive to increase agricultural yields and farm investments. In practice, however, tenure policies easily fail due to the persistence of a large number of market imperfections. This chapter provides a review of the literature on the role of land rights in farm household resource allocation decisions, and the dynamic effects of improved land property or transfer rights on labour use, input applications and capital investments. Special attention is given to the importance of land rights for enhancing (non)attached investments in sustainable production systems and the incentives for increasing labour and material input use as components of more sustainable land management practices. Different aspects of land rights are discussed in order to provide insight in the dynamics of rural land markets under multiple market imperfections. Basic components for a generic modelling framework that addresses the impact of tenure status on access to credit and farmers’ willingness to invest are presented. Empirical results derived from studies that assess the implications of land rights for fixed investment, material input use and labour use still provide rather mixed evidence. Differences in modelling approaches and empirical settings prove to be of fundamental importance for the understanding of the implications of land rights for resource management practices.
Ruerd Ruben, Marrit van den Berg, Tan Shuhao

19. Assessing Social Factors in Sustainable Land-Use Management: Social Capital and Common Land Development in Rajasthan, India

Abstract
Performance with respect to common land development is compared among 64 villages in north India, all of which participated in a government funded program, beginning in 1991. Results vary considerably even though the same level of technical and financial support was provided to all participating villages, and even though these villages share similar agro-ecological condition. Three social factors, literacy, extent of political competition, and level of social capital —measured with the help of a locally-relevant scale — are all significantly associated with program performance. Purposive action to enhance the levels of these three variables can go a long way toward improving performance in common land development and other collective enterprises.
Anirudh Krishna, Norman Uphoff

20. Modelling Economic Policy Reforms and Sustainable Land Use in Developing Countries: Key Issues

Abstract
Four key issues emerge,from the models presented in this book,in quanting the effects of economic policy reforms on sustainable land use in developing countries: (1) conceptualisation of household objectives,market imperfections,agricultural production relationships,and sustainability,(2) specification of interactions between agricultural inputs,agricultural activities,spatially dispersed land units,household objectives,and economic agents,(3) method of aggregating micro-relationships to regional or higher levels,and (4) incorporation of a time dimension in the relationships. The way in which the various models presented in this volume incorporate these four key issues is reviewed. Based on this review,it is recommended that future quantitative research should concentrate on (1) incorporating the institutional environment of rural households,(2) testing the validity of basic assumptions,such as separability of household decision making,and/or the sensitivity of model outcomes to changes in these assumptions,and (3) addressing the aggregation bias in regional or higher-level models resulting from non-linear micro relationships and from off-site effects of soil erosion.
Marijke Kuiper, Nico Heerink, Herman van Keulen

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