Land And Soil Management

Technology, Economics, And Institutions

Alfredo Sfeir-Younis

• Publisher: CRC Press
• Year: 2019
• eBook ISBN: 9780429723223
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Soil erosion has become a problem of crisis proportions in developing countries around the globe, and better approaches to land management are desperately needed. This book provides analytical frameworks to guide the creation and appraisal of soil erosion control programs. The authors discuss a broad range of important issues involved in designing and implementing more effective soil conservation programs. The book begins with a discussion of the physical and economic dimensions of soil erosion and an estimation of the extent of the problem. It then explains how to improve the evaluation of soil conservation programs by integrating scientific knowledge with economic methods and procedures. A series of practical illustrations graphically demonstrates the application of the concepts derived from the theory. The most important organizational, institutional, technical, and macroeconomic aspects of soil and land management appraisal are outlined, and the major elements of project or program design are also pinpointed and illustrated. Finally, the book suggests areas most in need of future research.

Part One

1
Introduction

The chief purposes of this book are to create greater awareness of the magnitude of soil erosion and land management in developing countries, provide analytical frameworks for the preparation and appraisal of soil erosion control programs and discuss the broad range of important issues involved in the establishment of such programs.

The book has five parts. Part One is this introduction. Part Two discusses the physical and economic dimensions of soil erosion and estimates the overall magnitude of the soil erosion problem in developing countries. Part Three focuses on how to evaluate soil conservation programs by integrating scientific knowledge with economic methods and procedures -- and concludes with a series of illustrations of how different evaluation methods have been used. Part Four outlines the most important organisational, institutional, technical and macroeconomic issues involved in appraisal, presents the major elements of project or program design and suggests subjects for future research. The final part is the extensive bibliography.

Nature of the Erosion Process

Soil Erosion

Soil is one of the chief natural resources used in agriculture. Maintaining and if possible, increasing the productivity of existing soils is necessary to accomplish production and welfare goals in both the short and the long term. Despite its undisputed importance as a natural resource, soil is now suffering degradation of various kinds at such a high rate that future agricultural development may be severely limited. Soil erosion is the commonest form of land degradation today, but soil is also being degraded by such things as high salt and alkali levels, deposits of radioactive and inorganic wastes and saturation by chemicals.

Soil erosion is a three-stage process, the removal of soil particles (detachment), the transportation of these particles and their deposition in other areas. The chief agents of erosion are water and wind. An understanding of the entire process is essential not only for scientific purposes but also for understanding the costs and benefits of soil conservation programs.

The most important types of water-caused erosion are sheet erosion, rill erosion, gully erosion and stream bank erosion. Sheet erosion is the removal of thin layers of soil by raindrop splash and the subsequent flow of water over relatively flat surfaces. Rill erosion occurs along soil channels (that is, rills) that are small enough to be obliterated by normal tillage operations. Gully erosion, on the other hand, occurs in soil channels that are too large to be eliminated by ordinary tillage. Stream bank erosion occurs when soil is detached by water in permanent streams.

Erosion affects the potential productive capacity of soil by altering the medium for plant growth. Generally, the topsoil that is lost by erosion provides the most hospitable medium for root growth, water retention and nutrient storage. The erosion process is often difficult to detect by eyesight, it is selective and it is nonuniform. It is difficult to detect because erosion tends to occur slowly and reductions in productivity often manifest themselves only when serious damage has already occurred. It is selective in that the removed soil often contains more nutrients than the remaining soil, which has greater proportions of sand and clay. It is nonuniform in that it can result in a surface seal, or crusting, making farming difficult. This non-uniformity can lead to spotty crop maturities.

Erosion is a natural process. There is no doubt however, that human actions can have a strong effect on the process. These actions include deforestation, certain forms of intensive agriculture, unwise agricultural practices, shifting cultivation, overgrazing by livestock, forest fires, population resettlement and inadequate land tenure systems. Erosion is also exacerbated by human activities that take place outside the agricultural systems (for example, road construction).

To maintain soil productivity at acceptable levels, conservation practices must be carried out. These practices fall into two broad categories, biological and mechanical practices. Examples of biological practices are changes in crop rotation, afforestation, strip cropping, establishment of wind breaks and sand dune stabilisation. Examples of mechanical practices are construction of bench terraces, stormwater drains, artificial watercourses, contour bunds, ridges and furrows.

A Typology of Soil Erosion Effects

The physical nature of the erosion process provides the basis for a typology of erosion effects. Most of the effects of erosion are either "upstream effects," "downstream effects," or "worldwide effects." Little is said in this book about the last category, although recent research shows that erosion has important intercountry and intercontinental effects which policy makers should take into account.

Upstream effects are chiefly the effects of erosion on agriculture within a project area (however this is defined) or in the upper portion of a watershed, while downstream effects are effects on activities elsewhere in the economy. Examples of upstream effects are on-farm losses in productivity and inter-farm damages to irrigation terraces, roads, bridges and other capital assets. Examples of downstream effects are sedimentation of rivers, siltation of reservoirs, floods, contamination of drinking water supplies, constraints on water navigation and hydroelectric power production and damage to environmental services and activities (for example, fisheries and wildlife).

Magnitude of the Erosion Problem

Erosion is very widespread and the upstream and downstream effects of erosion are reaching alarming levels in the developing world. While the data are far from complete, statistics at the national and local levels are comprehensive enough to support the assertion that soil erosion should be an issue of public concern at all levels of decision making in both developed and developing countries. If erosion continues, we can expect a constant diminution in available land assets.

This book groups and analyses data on upstream and downstream effects. Because there are very large numbers of effects, both upstream and downstream, a subset of effects was analysed. The upstream effects include farm-level soil erosion, water runoff and losses in plant nutrients. The downstream effects include sediment loads in major river basins, the effects of sedimentation on water reservoirs and the effects of floods on human lives, livestock and infrastructure.

Erosion at the Country Level

Estimates of the extent of erosion in a number of developing countries are given in Part Two. It is estimated, for example, that land degradation affects nearly 150 million of India's 328 million hectares of land. Of this, 90 million hectares are affected by water (rainfall) erosion. An additional 7 million hectares are seriously affected by salinity and 20 million hectares are affected by floods, some of which can be traced to erosion effects. It has also been estimated that farmers in India are losing 6 million tonnes a year of nitrogen, phosphorus and potash due to the high rate of erosion. Annual replacement of these nutrients would require an expenditure of up to approximately US$6 billion at 1984 prices. Soil erosion is an even more critical problem in certain other developing countries. In Guatemala, for example, 40 percent of the production capacity of the land has been totally lost due to erosion. Farmers in several regions of Guatemala have abandoned their farms because it has become uneconomic to carry out agricultural activities. In Nepal, where many areas have been cleared for subsistence cultivation, losses of topsoil average 35 to 75 tonnes per hectare per year. Erosion in some gullied areas is reported to range from 200 to 500 tonnes per hectare per year. Given the "threshold level" of 5 to 10 tonnes per hectare per year (as established in the United States), erosion rates in Nepal are between seven and one hundred times higher. The World Food Programme reports that more than 2,000 tonnes of soil per square kilometre are lost every year in Ethiopia. This soil, otherwise, would be sufficient to produce food for 12,000 families.

Erosion and Land Productivity

Many factors determine land productivity and research studies that show a clear and convincing relationship between erosion and productivity are few. The FAO Agricultural Department is now conducting an extensive study of this particular question. This book presents evidence on how erosion rates are affected by crop management and other environmental conditions, on how erosion depletes nutrients in the soil and in a few instances, on the effects of erosion on crop yields. Reference is also made to the apparent effectiveness of soil conservation practices in sustaining productivity.

This book shows that erosion rates in developing countries are often very high and that the amount of plant nutrients lost because of erosion is extremely large. Consequently, there are bound to be important effects on land productivity. A few studies have been carried out to determine the relationship between changes in soil depth and crop yields. One study in the United States showed that a loss of 10 inches of topsoil could reduce corn yields by nearly 40 percent.

This book also presents data on the effectiveness of specific erosion control practices. It is clear that, other things being equal, these practices can greatly reduce erosion rates. The acceptance and success of these practices depend on economic, social and environmental conditions.

Downstream Effects

The book focuses first on sediment loads in the major river basins of the world. Except for geologic erosion, these sediments are "produced" upstream by many economic activities, of which agriculture is only one. Sediment loads were converted into an approximate average erosion rate for each basin where data were available. The data systematically show that erosion rates in these river basins are very high compared with "normal" rates and that the rates are independent of the size of the drainage area. The data show that the highest erosion rates are registered in Asia.

Much of the sediment resulting from soil erosion is deposited above major dams or in river beds, often causing severe economic and environmental damage. This book includes data on estimated and actual rates of sedimentation for a large sample of major dams in developing countries. These data show that actual sedimentation rates are several times higher than the rates that had been predicted prior to dam construction. In some cases the actual rate has been more than 20 times the estimated rates. In other words, water reservoirs are literally becoming soil traps. A study of nearly 70 dams in India estimated that the total capacity already lost due to sedimentation was more than 21% Thus, the economic life of very expensive infrastructural assets is being impaired at a rather fast rate. Several other examples of high sedimentation rates are given on a country-by-country basis.

The book contains a scenario analysis of what would happen to reservoir capacity by the year 2000, using different assumptions about sedimentation rates. The first scenario assumes that the "live" storage areas of major reservoirs have not been affected since 1940 and will not be affected between now and the year 2000. The second scenario assumes an across-the-board sedimentation rate of 2% of live storage per year. The third scenario assumes a 1% rate of sedimentation per year for the 1940-50 period, a 2% rate for 1950-60, a 3% rate for 1960-70 and a 4% rate for 1970-80. In the case of the second scenario, it is estimated that the world will lose nearly one-third of total reservoir capacity by the year 2000. The third scenario would mean that two-thirds of total reservoir capacity would be lost by the year 2000.

The data show that while the number of dams increased in earlier decades, it decreased slightly between 1970 and 1980. This may indicate that the number of potential dam sites has declined. On the other hand, the data on total capacity in the different decades show that total capacity has been growing since 1940. This may mean that countries are building dams of greater capacity.

The facts have great implications for the design and implementation of sediment management schemes. In particular, they suggest that where only a small part of the drainage area of a river basin is located in a given country, efforts to control the effects of sedimentation will require action by other countries bordering the rivers.

This book also attempts to estimate an average erosion rate for developing countries. On the basis of data on the sediment loads of rivers and on various analytical assumptions, the book concludes that, on average, developing countries are losing 53 tonnes of topsoil per hectare every year, or more than five times the threshold level of 10 tonnes per hectare per year. Some of this topsoil is deposited elsewhere in the watershed, causing siltation problems, but much is irrevocably lost to the ocean. Soil erosion rates vary from one continent to another. In Asia, soil losses average more than 138 tonnes per hectare per year, compared to 6 tonnes per hectare per year in Africa and 12 tonnes per hectare per year in Latin America.

The emphasis in this book is on the negative effects of erosion and sedimentation. It is important to note however, that these natural processes may also have beneficial effects. Certain ancient civilisations built dams for the sole purpose of trapping sediments. Once the reservoir area was filled with sediments, often with a very high nutrient content, the area was used for cultivation. Some of the most fertile valleys in the world owe their fertility to sediment deposition from upstream.

Economic Nature of Soils

Part Two of this book includes a chapter that discusses the economic nature of soils. This chapter develops a framework for resource management policies, outlining the meaning of conservation and the nature of policy decisions on conservation. The book suggests that the "Safe Minimum Standard of Conservation" (SMSC) should be a guiding policy principle. Given the class of natural resources under consideration -- that is, renewable resources with "critical zones" -- the SMSC is a standard that avoids irreversible damage to the resources.

In assessing the merits of decisions on soil erosion control, a distinction is made between private or farmers' decision making and national or social decision making. While farmers will make decisions which tend to maximise their profits, society's decisions should involve maximisation of the welfare of present and future generations. Farmers make their decisions on an environment where economic factors are usually changing. Some of these are market factors (for example, prices, taxes, subsidies), while others are nonmarket factors (for example, tenure, property rights). Changes in this institutional environment may emphasise either conservation or depletion of soil resources.

Investment decisions are the central topic of this book. It is often contended that the rationale for using Benefit-Cost Analysis (BCA) to make decisions on soil conservation cannot be the same rationale for using BCA to judge other investment projects. What makes soil erosion control projects so unique that they require new or modified BCA procedures? The following reasons seem to be important.

1. Soil conservation decisions have an impact on equity (farm equity compared to equity in other enterprises) and an impact across generations.
2. These projects also have external effects (outside project areas).
3. Valuation of such projects is difficult because of the importance of nonmarket factors.
4. Such projects have very long-term effects.
5. The risk and uncertainty of such projects is large.
6. Soil conservation programs are multiproductive in nature (thus, forestry programs are often designed to control erosion as well as to supply fuel wood energy).
7. Economic evaluation is affected by the presence of ecological irreversibilities.

Economic Evaluation of Soil Conservation Programs

Economic analysis of soil conservation programs often suffers from three shortcomings. These relate to:

1. The identification of benefits and costs.
2. The valuation in monetary terms of goods and services that are not directly traded in markets.
3. Discounting procedures.

Part Two of this book should provide appraisal teams with enough material to identify the benefits and costs of soil conservation projects.Part Three focuses on the problem of valuation, while the problems associated with discounting procedures are discussed in one of the chapters of Part Four.

The quality of the valuation process depends upon the ability of the economist to understand the technical relationships necessary to conceptualise the physical effects of erosion and on proper definitions of the environmental effects of erosion. An adequate system for the valuation of benefits and costs must take account of the principles of welfare economics, particularly the notions of consumer surplus and rent. Part Three of the book presents the most important principles of project evaluation and also the corresponding procedures for estimating the necessary parameters to be used by the economist to assess changes in welfare "with" and "without" a soil conservation project (changes...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Dedication
• Contents
• Tables and Figures
• Acknowledgments
• PART ONE
• PART TWO
• PART THREE
• PART FOUR
• Bibliography
• About the Book and Authors