Land resources evaluation and the role of land-related indicators

W. G. Sombroek, Land and Water Development Division,
FAO, Rome, Italy

THE FRAMEWORK FOR LAND EVALUATION

Land quality assessment and land evaluation have been important programmes in FAO since its foundation in 1945. By 1970 many countries had developed their own systems of land capability classification and land evaluation, making international exchange and comparison of information difficult. Some form of standardization was obviously required. The International Institute for Land Reclamation and Improvement (ILRI) in Wageningen, which had traditionally concentrated on water issues, now wanted to pay more attention to "land" issues and sought contact with FAO for that purpose. This resulted in a joint project to develop a Framework for Land Evaluation, published in 1976.

The Framework drew substantially from earlier concepts and methodologies developed, e.g., in Brazil and Iran. It was subsequently applied in many countries in which FAO was active through UNDP-financed projects, and also in several bilaterally financed projects on natural resources inventories and evaluation.

In the years following publication of the Framework, detailed guidelines were published for its application for forestry, rainfed agriculture, irrigated agriculture, and extensive grazing (FAO, 1983; 1984; 1985; 1991). Guidelines for Land-use Planning were published as FAO Development Series 1 (FAO, 1993a).

During these years the concepts, principles and definitions of land, land utilization types, land qualities, land suitability classification and land evaluation procedures were already specified but in some circles the notion of a single, overall "land quality" in the sense of health-of-land has come to the fore.

Discussing differences in approach, and reconfirming or adapting existing concepts and definitions is one purpose of the present meeting. A second purpose is to raise awareness within FAO about interest in the World Bank (WB), United Nations Environment Programme (UNEP), United Nations Development Programme (UNDP) and the United Nations Commission on Sustainable Development in the use of indicators for sustainable agriculture and rural development. A third purpose is to inform these same organizations of FAO technical activities relevant to indicators.

ASSESSMENT OF LAND AND SOIL DEGRADATION

A second relevant historical development is the Global Assessment of Soil Degradation (GLASOD). The initiative was launched by UNEP, in 1987, in cooperation with the International Society of Soil Science (ISSS) and FAO. It resulted in the International Soil Reference and Information Centre (ISRIC) in Wageningen producing, at short notice and on the basis of admittedly incomplete knowledge, a credible global assessment of human-induced soil degradation. With the support of about 250 correspondents from all regions of the world this resulted in a world map (average scale 1:10M; 3 sheets and explanatory note: Oldeman, Hakkeling and Sombroek 1991; Oldeman 1992), showing causative factors, type, degree, rate and geographic extent of soil and land degradation. It was meant to be a quick and rough first attempt and did not deal with off-site effects, but it successfully raised public awareness of the problem of land degradation. The results were amply used, if not over-used, in the discussions related to the UN Conference on Environment and Sustainable Development in Rio de Janeiro, 1992; in the World Resources Institute's publications; in UNEP's World Atlas of Desertification (Middleton and Thomas, 1992), and in FAO's study Agriculture Towards 2010 (Alexandratos, 1995). It also illustrated the need for better, quantitative information and an assessment of the social and economic consequences of land degradation, and prompted the International Soil Conservation Organization (ISCO) to start with a World Overview of Conservation Approaches and Technologies (WOCAT).

AGENDA '21

The United Nations Conference on Environment and Development (UNCED) meeting in Rio resulted in a series of new initiatives on assessment of sustainability and resilience of land resources, by institutions such as the Commonwealth Agricultural Bureaux International (CABI) on soil resilience and sustainable land use (Budapest meeting: Greenland and Szabolcs, 1994); by the International Board of Soil Research and Management (IBSRAM) on an international Framework for Evaluating Sustainable Land Management (FESLM, FAO, 1993b) and on integrated soil-water-plant nutrient management research (SWNM, Greenland et al., 1994), and by the World Bank on land quality indicators. The latter initiative is based on two regional meetings (Cali, Colombia; Nairobi, Kenya) and an inter-agency meeting in Washington in June 1995 which resulted in concrete proposals for action.

UNCED's Agenda 21 itself (1993), as agreed upon by participating governments, specifies desired actions on environmental protection and sustainable development, including the land-cluster of chapters 10 to 14. Chapter 10, called "An integrated approach to land resources planning and management", is meant to provide the over-arching approach to the more sectoral land-use issues (on mountains, forests, deserts, rainfed agriculture, etc.). FAO is Task Manager for most of these chapters, and the Land and Water Development Division (AGL) is the focal point for Chapter 10. It resulted in a progress report by the UN Secretary-General during the second Substantive Session of the UN Commission for Sustainable Development (CSD) in April 1995, and also in a background publication by FAO itself, with substantial input by other FAO staff and correspondents of other UN organizations such as UNEP and Habitat (FAO, 1995). This, in turn, led to a joint UNEP/FAO project on promoting integrated land-use planning at national and local level in developing countries, with special attention to socio-economic issues and participatory approaches.

CONCEPTS, DEFINITIONS AND PRINCIPLES

"Land", the "functions of land", "land evaluation", "land qualities", "sustainability", "resilience", etc. need to be defined carefully to avoid confusion and to assure effective cooperation between international institutions and national planning entities that deal with the assessment of changes in land conditions.

The holistic concept of Land was already recognized in the Framework for Land Evaluation (FAO 1976), repeated implicitly in UNCED's chapter 10 of 1993, and formally described in FAO 1995. It reads:

"Land is a delineable area of the earth's terrestrial surface, encompassing all attributes of the biosphere immediately above or below this surface, including those of the near-surface climate, the soil and terrain forms, the surface hydrology (including shallow lakes, rivers, marshes and swamps), the near-surface sedimentary layers and associated groundwater reserve, the plant and animal populations, the human settlement pattern and physical results of past and present human activity (terracing, water storage or drainage structures, roads, buildings, etc.)."

The many functions of Land: · production function · biotic environmental function · climate-regulative function · hydrologic function · storage function · waste and pollution control function · living space function · archive or heritage function · connective space function

The various functions of land are also described in FAO's 1995 background paper:

¤ land is the basis for many life support systems, through production of biomass that provides food, fodder, fibre, fuel, timber and other biotic materials for human use, either directly or through animal husbandry including aquaculture and inland and coastal fishery (the production function);

¤ land is the basis of terrestrial biodiversity by providing the biological habitats and gene reserves for plants, animals and micro-organisms, above and below ground (the biotic environmental function);

¤ land and its use are a source and sink of greenhouse gases and form a co-determinant of the global energy balance - reflection, absorption and transformation of radiative energy of the sun, and of the global hydrological cycle (the climate regulative function);

¤ land regulates the storage and flow of surface and groundwater resources, and influences their quality (the hydrologic function);

¤ land is a storehouse of raw materials and minerals for human use (the storage function);

¤ land has a receptive, filtering, buffering and transforming function of hazardous compounds (the waste and pollution control function);

¤ land provides the physical basis for human settlements, industrial plants and social activities such as sports and recreation (the living space function);

¤ land is a medium to store and protect the evidence of the cultural history of humankind, and source of information on past climatic conditions and past land uses (the archive or heritage function);

¤ land provides space for the transport of people, inputs and produce, and for the movement of plants and animals between discrete areas of natural ecosystems (connective space function).

Land has attributes, characteristics, properties and qualities (or limitations/conditions):

¤ an attribute, or variable, is a neutral, over-arching term for a single or compound aspect of the land;

¤ a characteristic is an attribute which is easily noticed and which serves as a distinguishing element for different types of land; it may or may not have a practical meaning (e.g., soil colour or texture, or height of forest cover are characteristics without giving direct information on land quality);

¤ a property is an attribute that already gives a degree of information on the value of the land type;

¤ a land quality (or limitation) is a complex attribute of land which acts in a manner distinct from the actions of other land qualities in its influence on the suitability of land for a specified kind of use.

Defined as such, land qualities are not absolute values, but have to be assessed in relation to the functions of the land and the specific land use that one has in mind. Some examples:

i. land recently cleared from forest has a positive quality in respect of arable cropping (clearing, as "development costs", adding to the value of potential agricultural land), but has a negative quality in respect of sustainable use of the natural vegetative cover;

ii. land with a high degree of short-distance variation in soil and terrain conditions has a positive quality for biodiversity, is a large drawback to large-scale mechanized arable farming, but has a smaller limitation - or even an advantage - for smallholders' mixed farming;

iii. the presence of scattered clumps of trees or shrubs in an open savannah area with harsh climatic conditions is a positive quality for extensive grazing (shelter against cold, heat or wind) but may be less important, or negative, for arable farming;

iv. the presence of small land parcels, of woody or stony hedgerows and terraces, or of archaeological remains, is a positive quality in relation to the archival function of the land, but can conflict with its production function;

v. the propensity of the soil surface to seal and crust is a negative quality for arable farming (poor seedbed condition; reduced moisture intake of the soil), but is an asset of the land as regards water harvesting possibilities for crop growing in lower parts of the landscape wherever rainfall is submarginal.

A listing of the various land qualities in relation to crop growth, animal production, forest productivity and inputs/management levels is already given in the Framework for Land Evaluation of 1976 as shown in Table 1.

TABLE 1. Examples of land qualities

LAND QUALITIES RELATED TO PRODUCTIVITY FROM CROPS OR OTHER PLANT GROWTH
	Crop yields (a resultant of many qualities listed below).
	Moisture availability.
	Nutrient availability.
	Oxygen availability in the root zone.
	Adequacy of foothold for roots.
	Conditions for germination.
	Workability of the land (ease of cultivation).
	Salinity or sodicity.
	Soil toxicity.
	Resistance to soil erosion.
	Pests and diseases related to the land.
	Flooding hazard (including frequency, periods of inundation).
	Temperature regime.
	Radiation energy and photoperiod.
	Climatic hazards affecting plant growth (including wind, hail, frost).
	Air humidity as affecting plant growth.
	Drying periods for ripening of crops.
LAND QUALITIES RELATED TO DOMESTIC ANIMAL PRODUCTIVITY
	Productivity of grazing land (a resultant of many qualities listed under "Atmospheric qualities" in Table 2).
	Climatic hardships affecting animals.
	Endemic pests and diseases.
	Nutritive value of grazing land.
	Toxicity of grazing land.
	Resistance to degradation of vegetation.
	Resistance to soil erosion under grazing conditions.
	Availability of drinking water.
LAND QUALITIES RELATED TO FOREST PRODUCTIVITY
The qualities listed may refer to natural forests, forestry plantations, or both.
	Mean annual increments of timber species (a resultant of many qualities listed under "Atmospheric qualities" in Table 2).
	Types and quantities of indigenous timber species.
	Site factors affecting establishment of young trees.
	Pests and diseases.
	Fire hazard.
LAND QUALITIES RELATED TO MANAGEMENT AND INPUTS
The qualities listed may refer to arable use, animal production or forestry.
	Terrain factors affecting mechanization (trafficability).
	Terrain factors affecting construction and maintenance of access-roads (accessibility).
	Size of potential management units (e.g. forest blocks, farms, fields).
	Location in relation to markets and to supplies of inputs.

Another listing, related to the vertical components of a natural land unit, is given in FAO (1995), and shown in Table 2. A similar one can be developed for horizontally defined qualities.

TABLE 2. Land qualities related to vertical components of a natural land unit

ATMOSPHERIC QUALITIES
	Atmospheric moisture supply: rainfall, length of growing season, evaporation, dew formation.
	Atmospheric energy for photosynthesis: temperature, daylength, sunshine conditions.
	Atmospheric conditions for crop ripening, harvesting and land preparation: occurrence of dry spells.
LAND COVER QUALITIES
	Value of the standing vegetation as "crop", such as timber.
	Value of the standing vegetation as germ plasm: biodiversity value.
	Value of the standing vegetation as protection against degradation of soils and catchment.
	Value of the standing vegetation as regulator of local and regional climatic conditions.
	Regeneration capacity of the vegetation after complete removal.
	Value of the standing vegetation as shelter for crops and cattle against adverse atmospheric influences.
	Hindrance of vegetation at introduction of crops and pastures: the land "development" costs.
	Incidence of above-ground pests and vectors of diseases: health risks of humans and animals.
LAND SURFACE AND TERRAIN QUALITIES
	Surface receptivity as seedbed: the tilth condition.
	Surface treatability: the bearing capacity for cattle, machinery, etc.
	Surface limitations for the use of implements (stoniness, stickiness, etc.): the arability.
	Spatial regularity of soil and terrain pattern, determining size and shape of fields with a capacity for uniform management.
	Surface liability to deformation: the occurrence or hazard of wind and water erosion.
	Accessibility of the land: the degree of remoteness from means of transport.
	The presence of open freshwater bodies for use by humans, animals or fisheries.
	Surface water storage capacity of the terrain: the presence or potential of ponds, on-farm reservoirs, bunds, etc.
	Surface propensity to yield run-off water, for local water harvesting or downstream water supply.
	Accumulation position of the land: degree of fertility renewal or crop damaging by overflow or overblow.
SOIL QUALITIES
	Physical soil fertility: the net moisture storage capacity in the rootable zone.
	Physical soil toxicity: the presence or hazard of waterlogging in the rootable zone (i.e. the absence of oxygen).
	Chemical soil fertility: the availability of plant nutrients.
	Chemical soil toxicity: salinity or salinization hazard; excess of exchangeable sodium.
	Biological soil fertility: the N-fixation capacity of the soil biomass; and its capacity for soil organic matter turnover.
	Biological soil toxicity: the presence or hazard of soil-borne pests and diseases.
	Substratum (and soil profile) as source of construction materials.
	Substratum (and soil profile) as source of minerals.
	Biological soil toxicity: the presence or hazard of soil-borne pests and diseases.
SUBSTRATUM OR UNDERGROUND QUALITIES
	Groundwater level and quality in relation to (irrigated) land use.
	Substratum potential for water storage (local use) and conductance (downstream use).
	Presence of unconfined freshwater aquifers.
	Substratum (and soil profile) suitability for foundation works (buildings, roads, canals, etc.)

A land utilisation type (FAO, 1976) is a kind of land use described or defined in a higher degree of detail than that of a major kind of land use (such as rainfed agriculture or forestry), as an abstraction of actual land-use systems (which may be single, compound or multiple).

Land evaluation is the process of assessment of land performance when used for specific purposes, involving the execution and interpretation of surveys and studies of land forms, soils, vegetation, climate and other aspects of land in order to identify and make a comparison of promising kinds of land use in terms applicable to the objectives of the evaluation.

Land evaluation should combine the various qualities/limitations of the land in relation to the envisaged use or non-use. Obviously, the relative value of all land qualities has to be weighted for each of such uses. For the physico-chemical qualities of the land, such as the net soil moisture storage capacity, the availability of plant nutrients, or the land surface arability, this weighting can be done quantitatively. For a number of the bio-environmental qualities such as biodiversity or archival values a qualitative assessment is necessary which may be non-tangible in an economic sense. For instance, "wetlands" may have an important ecological value, but if one has a thousand or more small wetland units in a country such as Rwanda, then their individual value depends on whether all these wetlands are of the same type or whether they are all different. Also, the upland forests of central Amazonia may have a "surplus" value of biodiversity, but all or most of them may still be necessary to ensure their climate- or hydrology-regulative function.

Finally, regarding sustainability of land "quality" or land "health", again land health depends on the function or functions that one considers from an environmental point of view, or for sustained use by an increasing human population in relation to food security and their well-being in an intergenerational context.

Sustainability does not necessarily imply a continuous stability of productivity level, but rather a resilience of the land; in other words: the capacity of the land to recover quickly to former levels of productivity - or to resume the trend to increased productivity - after an adverse influence such as drought, floods, or human abandonment or mismanagement (Figure 1).

FIGURE 1. Some concepts of resilience of land and its productivity, comparing the situation in some industrialized countries (A) with that of most developing countries (B). Source: Sombroek, 1 993

Degradation of land has to be considered in the same context. The GLASOD criteria for degrees of land degradation tried to specify resilience as follows:

1. Light degradation: The terrain has somewhat reduced agricultural suitability, but is suitable for use in local farming systems. Restoration to full productivity is possible by modifications of the management system. Original biotic functions are still largely intact.

2. Moderate degradation: The terrain has greatly reduced agricultural productivity but is still suitable for use in local farming systems. Major improvements are required to restore productivity. Original biotic functions are partially destroyed.

3. Strong degradation: The terrain is non-reclaimable at farm level. Major engineering works are required for terrain restoration. Original biotic functions are largely destroyed.

4. Extreme degradation: The terrain is unreclaimable and beyond restoration. Original biotic functions are fully destroyed.

REFERENCES

Alexandratos, N. (ed.), 1995. World Agriculture: towards 2010. An FAO study. FAO, Rome, and John Wiley, Chichester, UK.

FAO. 1976. A framework for land evaluation. Soils Bulletin 32, FAO, Rome. 72 p. Also, Publication 22, (R. Brinkman and A. Young (eds.)), ILRI, Wageningen, The Netherlands.

FAO. 1983. Guidelines: land evaluation for rainfed agriculture. Soils Bulletin 52. FAO, Rome. 237 p.

FAO. 1984. Land evaluation for forestry. Forestry Paper 48, FAO, Rome. 123 p.

FAO. 1985. Guidelines: land evaluation for irrigated agriculture. Soils Bulletin 55. FAO, Rome. 231 p.

FAO. 1991. Guidelines: land evaluation for extensive grazing. Soils Bulletin 58. FAO, Rome. 150 p.

FAO. 1993a. Guidelines for land-use planning. Development Series 1, FAO, Rome. 96 p.

FAO. 1993b. FESLM: an international framework for evaluating sustainable land management, Smyth, A.J. and Dumanski, J. (eds.). World Soil Resources Report 73, FAO, Rome. 74 p.

FAO. 1995. Planning for sustainable use of land resources: toward? a new approach, W.G. Sombroek and D. Sims. Land and Water Bulletin 2, FAO, Rome.

Greenland, D.J. and Szabolcs, I. (eds.). 1994. Soil Resilience and Sustainable Land Use. CAB International, Wallingford, UK. 561 p.

Greenland, D.J., Bowen, G., Eswaran, H., Rhoades, R. and Valentin, C. 1994. Soil, water and nutrient management research - a new agenda. IBSRAM Position Paper. IBSRAM, Bangkok.

Middleton, N.J. and Thomas, D.S.G. 1992. World Atlas of Desertification. UNEP, Nairobi.

Oldeman, L.R., Hakkeling, R.T.A. and Sombroek, W.G. 1991. World Map of the Status of Human-induced Soil Degradation (GLASOD). 3 map sheets and explanatory note. UNEP, Nairobi, and ISRIC, Wageningen, The Netherlands.

Oldeman, R.L. 1992. Global extent of soil degradation. pp. 19-36. In: Bi-annual Report 1991-1992, ISRIC, Wageningen, The Netherlands.

Sombroek, W.G. 1993. Agricultural use of the physical resources of Africa: achievements, constraints and future needs. pp. 12-30. In: Sustainable Food Production in Sub-Saharan Africa 2. Constraints and Opportunities. IITA, Ibadan, Nigeria.

UNCED. 1993. Agenda 21: Programme of Action for Sustainable Development. United Nations, New York. 294 p.