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Chapter 1: The nature and principles of land evaluation
1.1 General
1.2 The aims of land evaluation
1.3 Land evaluation and land use planning
1.4 Principles
1.5 Levels of intensity and approaches
1.6 The nature of the framework
Decisions on land use have always been part of the evolution of human society. In the past, land use changes often came about by gradual evolution, as the result of many separate decisions taken by individuals. In the more crowded and complex world of the present they are frequently brought about by the process of land use planning. Such planning takes place in all parts of the world, including both developing and developed countries. It may be concerned with putting environmental resources to new kinds of productive use. The need for land use planning is frequently brought about, however, by changing needs and pressures, involving competing uses for the same land.
The function of land use planning is to guide decisions on land use in such a way that the resources of the environment are put to the most beneficial use for man, whiles at the same time conserving those resources for the future. This planning must be based on an understanding both of the natural environment and of the kinds of land use envisaged. There have been many examples of damage to natural resources and of unsuccessful land use enterprises through failure to take account of the mutual relationships between land and the uses to which it is put. It is a function of land evaluation to bring about such understanding and to present planners with comparisons of the most promising kinds of land use.
Land evaluation is concerned with the assessment of land performance when used for specified purposes. It involves the execution and interpretation of basic surveys of climate, soils, vegetation and other aspects of land in terms of the requirements of alternative forms of land use. To be of value in planning, the range of land uses considered has to be limited to those which are relevant within the physical, economic and social context of the area considered, and the comparisons must incorporate economic considerations.
1.2 The aims of land evaluation
Land evaluation may be concerned with present land performance. Frequently however, it involves change and its effects: with change in the use of land and in some cases change in the land itself.
Evaluation takes into consideration the economics of the proposed enterprises, the social consequences for the people of the area and the country concerned, and the consequences, beneficial or adverse, for the environment. Thus land evaluation should answer the following questions:
- How is the land currently managed, and what will happen if present practices remain unchanged?
- What improvements in management practices, within the present use, are possible?
- What other uses of land are physically possible and economically and socially relevant?
- Which of these uses offer possibilities of sustained production or other benefits?
- What adverse effects, physical, economic or social, are associated with each use?
- What recurrent input e are necessary to bring about the desired production and minimize the adverse effects? What are the benefits of each form of use?
If the introduction of a new use involves significant change in the land itself, as for example in irrigation schemes, then the following additional questions should be answered:
- What changes in the condition of the land are feasible and necessary, and how can they be brought about?
- What non-recurrent inputs are necessary to implement these changes?
The evaluation process does not in itself determine the land use changes that are to be carried out, but provides data on the basis of which such decisions can be taken. To be effective in this role, the output from an evaluation normally gives information on two or more potential forms of use for each area of land, including the consequences, beneficial and adverse, of each.
1.3 Land evaluation and land use planning
Land evaluation is only part of the process of land use planning. Its precise role varies in different circumstances. In the present context it is sufficient to represent the land use planning process by the following generalized sequence of activities and decisions:
i. recognition of a need for change;
ii. identification of aims;
iii. formulation of proposals, involving alternative forms of land use, and recognition of their main requirements;
iv. recognition and delineation of the different types of land present in the area;
v. comparison and evaluation of each type of land for the different uses;
vi. selection of a preferred use for each type of land;
vii. project design, or other detailed analysis of a selected set of alternatives for distinct parts of the area;
This, in certain cases, may take the form of a feasibility study.viii. decision to implement;
ix. implementation;
x. monitoring of the operation.
Land evaluation plays a major part in stages iii, iv and v of the above sequence, and contributes information to the subsequent activities. Thus land evaluation is preceded by the recognition of the need for some change in the use to which land is put; this may be the development of new productive uses, such as agricultural development schemes or forestry plantations, or the provision of services, such as the designation of a national park or recreational area.
Recognition of this need is followed by identification of the aims of the proposed change and formulation of general and specific proposals. The evaluation process itself includes description of a range of promising kinds of use, and the assessment and comparison of these with respect to each type of land identified in the area. This leads to recommendations involving one or a small number of preferred kinds of use. These recommendations can then be used in making decisions on the preferred kinds of land use for each distinct part of the area. Later stages will usually involve further detailed analysis of the preferred uses, followed, if the decision to go ahead is made, by the implementation of the development project or other form of change, and monitoring of the resulting systems.
Certain principles are fundamental to the approach and methods employed in land evaluation. These basic principles are as follows:
i. Land suitability is assessed and classified with respect to specified kinds of use
This principle embodies recognition of the fact that different kinds of land use have different requirements. As an example, an alluvial flood plain with impeded drainage might be highly suitable for rice cultivation but not suitable for many forms of agriculture or for forestry.The concept of land suitability is only meaningful in terms of specific kinds of land use, each with their own requirements, e.g. for soil moisture, rooting depth etc. The qualities of each type of land, such as moisture availability or liability to flooding, are compared with the requirements of each use. Thus the land itself and the land use are equally fundamental to land suitability evaluation.
ii. Evaluation requires a comparison of the benefits obtained and the inputs needed on different types of land
Land in itself, without input e, rarely if ever possesses productive potential; even the collection of wild fruits requires labour, whilst the use of natural wilderness for nature conservation requires measures for its protection. Suitability for each use is assessed by comparing the required input e, such as labour, fertilizers or road construction, with the goods produced or other benefits obtained.iii. A multidisciplinary approach is required
The evaluation process requires contributions from the fields of natural science, the technology of land use, economics and sociology. In particular, suitability evaluation always incorporates economic considerations to a greater or lesser extort. In qualitative evaluation, economics may be employed in general terms only, without calculation of costs and returns. In quantitative evaluation the comparison of benefits and inputs in economic terms plays a major part in the determination of suitability.It follows that a team carrying out an evaluation require a range of specialists. These will usually include natural scientists (e.g. geomorphologists, soil surveyors, ecologists), specialists in the technology of the forms of land use under consideration (e.g. agronomists foresters, irrigation engineers, experts in livestock management), economists and sociologists. There may need to be some combining of these functions for practical reasons, but the principle of multidisciplinary activity, encompassing studies of land, land use, social aspects and economics, remains.
iv. Evaluation is made in terms relevant to the physical economic and social context of the area concerned
Such factors as the regional climate, levels of living of the population, availability and cost of labour, need for employment, the local or export markets, systems of land tenure which are socially and politically acceptable, and availability of capital, form the context within which evaluation takes place. It would, for example be unrealistic to say that land was suitable for non-mechanized rice cultivation, requiring large amounts of low-cost labour, in a country with high labour costs. The assumptions underlying evaluation will differ from one country to another and, to some extent, between different areas of the same country. Many of these factors are often implicitly assumed; to avoid misunderstanding and to assist in comparisons between different areas, such assumptions should be explicitly stated.v. Suitability refers to use on a sustained basis
The aspect of environmental degradation is taken into account when assessing suitability. There might, for example, be forms of land use which appeared to be highly profitable in the short run but were likely to lead to soil erosion, progressive pasture degradation, or adverse changes in river regimes downstream. Such consequences would outweigh the short-term profitability and cause the land to be classed as not suitable for such purposes.This principle by no means requires that the environment should be preserved in a completely unaltered state. Agriculture normally involves clearance of any natural vegetation present, and normally soil fertility under arable cropping is higher or lower, depending on management, but rarely at the same level as under the original vegetation. What is required is that for any proposed form of land use, the probable consequences for the environment should be assessed as accurately as possible and such assessments taken into consideration in determining suitability.
vi. Evaluation involves comparison of more than a single kind of use
This comparison could be, for example, between agriculture and forestry, between two or more different farming systems, or between individual crops. Often it will include comparing the existing uses with possible changes, either to new kinds of use or modifications to the existing uses. Occasionally a proposed form of use will be compared with non-use, i.e. leaving the land in its unaltered state, but the principle of comparison remains. Evaluation is only reliable if benefits and inputs from any given kind of use can be compared with at least one, and usually several different, alternatives. If only one use is considered there is the danger that, whilst the land may indeed be suitable for that use, some other and more beneficial use may be ignored.
1.5 Levels of intensity and approaches
Certain groups of activities are common to all types of land evaluation. In all cases evaluation commences with initial consultations, concerned with the objectives of the evaluation, assumptions and constraints, and the methods to be followed. Details of subsequent activities and the sequence in which they are carried out, vary with circumstances. These circumstances include the level of intensity of the survey and which of two overall approaches is followed.
1.5.1 Levels of Intensity
Three levels of intensity may be distinguished: reconnaissance, semi-detailed and detailed. These are normally reflected in the scales of resulting maps.
Reconnaissance surveys are concerned with broad inventory of resources and development possibilities at regional and national scales. Economic analysis is only in very general terms, and land evaluation is qualitative. The results contribute to national plans, permitting the selection of development areas and priorities.
Surveys at the semi-detailed, or intermediate, level are concerned with more specific aims such as feasibility studies of development projects. The work may include farm surveys; economic analysis is considerably more important, and land evaluation is usually quantitative. This level provides information for decisions on the selection of projects, or whether a particular development or other change is to go ahead.
The detailed level covers surveys for actual planning and design, or farm planning and advice, often carried out after the decision to implement has been made
1.5.2 Two-stage and parallel approaches to land evaluation
The relationships of resource surveys and economic and social analysis, and the manner in which the kinds of land use are formulated, depend on which of the following approaches to land evaluation is adopted (Fig. 1):
- a two-stage approach in which the first stage is mainly concerned with qualitative land evaluation, later (although not necessarily) followed by a second stage consisting of economic and social analysis;
- a parallel approach in which analysis of the relationships between land and land use proceeds concurrently with economic and social analysis.
The two-stage approach is often used in resource inventories for broad planning purposes and in studies for the assessment of biological productive potential. The land suitability classifications in the fires stage are based on the suitability of the land for kinds of land use which are selected at the beginning of the survey, e.g. arable cropping, dairy farming, maize, tomatoes. The contribution of economic and social analysis to the fires stage is limited to a check on the relevance of the kinds of land use. After the first et age has boon completed and its results presented in map and report form, these results may then be subject to the second et ego, that of economic and social analysis, either immediately or after an interval of time.
FIG. 1 TWO-STAGE AND PARALLEL APPROACH TO LAND EVALUATION
In the parallel approach the economic and social analysis of the kinds of land use proceeds simultaneously with the survey and assessment of physical factors. The kinds of use to which the evaluation refers are usually modified in the course of the study. In the case of arable farming, for example, this modification may include selection of crops and rotations, estimates of the inputs of capital and labour, and determination of optimum farm size. Similarly, in forestry it may include, for example, selection of tree species, dates of thinning and felling and required protective measures. This procedure is mostly favoured for specific proposals in connection with development projects and at semi-detailed and detailed levels of intensity.
The parallel approach is expected to give more precise results in a shorter period of time. It offers a better chance of concentrating survey and data-collection activities on producing information needed for the evaluation.
However, the two-stage approach appears more straightforward, possessing a clear-cut sequence of activities. The physical resource surveys precede economic and social analysis, without overlap, hence permitting a more flexible timing of activities and of staff recruitment. The two-stage approach is used as a background in the subsequent text except where otherwise stated.
1.6 The nature of the framework
The Framework does not by itself constitute an evaluation system. The range of possible uses of land and purposes of evaluation is so wide that no one system could hope to take account of them. Besides such obvious contrasts as those of climate, differences in such matters as the availability and cost of labour, availability of capital, population density and levels of living will all cause differences of detail and emphasis in the evaluation of land.
It was recognition of this situation, coupled with the need for some degree of standardization or compatibility, which led to the concept of the Framework for Land Evaluation. The Framework is a set of principles and concepts, on the basis of which local, national or regional evaluation systems can be constructed. Thus the Framework is not an evaluation manual; it does not, for example, specify such matters as limiting slope angles or soil moisture requirements for particular kinds of land use, since such values can never have universal applicability. Instead, the Framework sets out a number of principles involved in land evaluation, some basic concepts, the structure of a suitability classification and the procedures necessary to carry out a land suitability evaluation.
The principles and procedures given in the Framework can be applied in all parts of the world. They are relevant both to less developed and developed countries. At the one extreme, they can be applied to areas where development planning is being applied to the more or less unaltered natural environment; at the other, to densely populated lands where the main concern of planning is to reconcile competing demands for land already under various forms of use. The Framework can be used to construct systems applicable at all levels of intensity ranging from, at one extreme, national, continental or world-scale assessments, and at the other to detailed local studies. The Framework covers all kinds of rural land use: agriculture in its broadest sense, including livestock production, together with forestry, recreation or tourism, and nature conservation. Engineering aspects involved in rural land use, such as foundation suitability for roads or small structures, are also included.
The Framework is not intended for the distinct set of planning procedures involved in urban land use planning, although some of its principles are applicable in these contexts. Nor does the Framework take account of the resources of the seas. Water on and beneath the surface of the land is, however, of relevance in land evaluation.
This Framework is written mainly for those actively involved in rural land evaluation. Since most land suitability evaluations are at present carried out for purposes of planning by national and local governments, this is the situation assumed in references to decision-making, but the evaluation can also be applied to land use planning by firms, farmers or other individuals. The principles and procedures which are set out can be applied either to land evaluation for individual land development projects or to the construction of local or national evaluation systems.