Land quality indicators: aspects of land use, land, soil and plant nutrients

R. Brinkman, Land and Water Development Division,
FAO. Rome, Italy

The UN Commission on Sustainable Development (CSD) in its work programme indicated the need for indicators of sustainability linked to each issue discussed in Agenda 21. Among the well over 100 indicators defined, two refer to Agenda 21 Chapter 10, the Integrated Planning and Management of Land Resources. These are Land Use Change and Land Condition Change (change in the aggregate of the land qualities). Their descriptions, in the form of standard CSD methodology sheets, are provided at the end of this chapter.

It will be clear that the land condition indicator subsumes everything that is being discussed in the present Consultation on Land Quality Indicators. Here lies the core problem of the CSD effort. Unlike the relatively narrow economic indicators traditionally used by governments, central banks and the World Bank and regional development banks, which can summarize various aspects of the economy in a single, monetary variable, the land condition indicator is essentially multi-dimensional (as is the land use indicator).

The monitoring of broad changes in land use and in general land conditions will enable governments to report on the general improvement or deterioration of the state of the natural resources in their countries, using standard methods that allow comparisons between countries and between years. However, such broad, very highly aggregated indicators will not be useful in support of policy development, either national or at more detailed scale.

For practical purposes of policy advice or management advice, much more detailed, disaggregated indicators will be needed. In fact, the more detailed and specific the information requirements, the less the concept of land quality indicators makes sense, and the more evident is the need for actual observations on specific land use changes and on specific aspects of land condition, of physical, biological and chemical soil conditions, and of plant nutrient stocks and availability of plant nutrients in soils.

LAND USE

Is land use change an indicator of a driving force, state or response? Land use changes are generally conscious, volitional responses by humans or human societies to changes in biophysical or societal conditions. It is a response indicator, therefore, reflecting how and to what extent society is responding to meet its changing needs and goals or to adapt to changing environmental conditions. This does not exclude the possibility that some land use changes may, in turn, constitute a driving force for changes in the state of the environment. That is in the very nature of the complex causal network (not a simple causal chain), including a number of feedback loops, that is society's relationship with its environment.

As suggested in the brief description in the standard format, it is virtually impossible to aggregate land use changes into a single, scalar indicator. The rates or extent of land use changes can be represented in the form of a transition matrix of land uses, showing the transition between each pair of uses as extent or proportion of area per unit time. An example of such a transition matrix can be found in the Forest Resources Assessment 1990 (FAO, 1995 pp. 35-36) for different kinds of forest and woodland versus broad categories of non-forest.

In the absence of a widely accepted, systematic set of land use definitions, it was not possible to compare land uses between countries or continents except in the most general terms. The concept of land use as a sequence of management activities in relation to a given area of land (Sims, 1986 and Terms of Reference for Land Use Description Systems, unpublished, 1990) has enabled FAO, jointly with several partners, to embark on a computer-aided system of land use description usable at several levels of detail, and on an effort to arrive at a system of land use classification that serves as a standard translator between different local or regional land use information sources.

It is now possible to map and report on land uses in a consistent manner across countries and regions. Part of the needed information can be obtained by translation or interpretation of existing local land use data as indicated above. A major part can be obtained by interpretation of remote sensing data with limited ground verification to produce land cover maps (land cover is the physical vegetation or crop cover resulting from natural processes or human activities). The land cover data then need to be complemented through more detailed field work with the more specific land use information (the management activities that characterize the system of use) to arrive at a land use map.

LAND

As is the case for land use change, it is doubtful whether a single, aggregate measure of land condition or land condition change would be feasible. What is feasible in principle is an estimation of the change in the different land qualities that influence the suitability of the land for one use or another, or for conservation - for example, of biodiversity. (Land qualities are discussed in FAO, 1976.)

The data needed for interpretation of changes in land qualities can be derived in part from remote sensing, complemented by ground survey observations. These should be combined with more frequent and thorough monitoring at selected permanent benchmark sites and long-term land productivity trial sites. Information is needed on aspects such as nature and density of vegetation or nature and productivity of crops (partly overlapping data with land use); conditions of the land surface (slope, runoff and erosion rates, sediment transport by wind, surface salinity); hydrological conditions (flooding incidence, groundwater dynamics); and physical, biological and chemical conditions (toxins, nutrients) of the soil. Such monitoring information, superimposed on a baseline soils and terrain database, will allow the estimation of potential productivity changes of land under different main uses and of suitability changes for different purposes such as conservation of native vegetation or animal populations. The institutional framework that would make such systematic, repetitive monitoring feasible does not yet exist in many countries.

SOIL

The soil, as a major subsystem of land, is changing with time consequent on changes in its environment (e.g., rainfall) or in management (grazing intensity, crops, irrigation, inputs, etc.). Land use or management decisions at any scale, from individual farm family to nation, need information about the soil system and its relationships with the environment and with management options. These relationships, as in the case of land use, are complex, with feedbacks providing different metastable situations and non-linear, sometimes delayed, responses to change. This implies that some changes in external conditions may not cause a perceptible change in the soil condition, while others may cause acute, or gradual, degradation or improvement.

Figure 1 shows the complex of processes that may lead to more biologically active and productive soils with a gradual rise in concentration of atmospheric carbon dioxide, as has started in the last century and is expected to continue for at least several decades. Clearly, a simple soil condition indicator cannot capture such processes. That will require both modelling and monitoring of a range of variables.

Even in a less complex system, in which monitoring shows increasing runoff and consequent gully formation in sloping soils, for example, such a change in soil condition cannot by itself be used to diagnose the proximate or underlying causes and does not contribute to identification of the most appropriate responses. These might be as diverse as advising the land users to change crop rotations or plant dense contour lines of permanent crops, or improving access roads or markets in the area, or enabling the users to obtain secure, long-term land tenure.

In every case, the system as a whole will need to be understood rather than one possibly diagnostic or indicative element, before sound responses can be identified and put into practice.

PLANT NUTRIENTS

Descending another step, into the plant nutrients or soil fertility subsystem of soil, one finds similar complexity. Nitrogen deficiency, for example, may be caused by a low content of decomposable organic matter in the soil, or by a high groundwater table, and remedied by applications of manure or appropriate fertilizer or green manuring, or by land drainage. Similarly, zinc deficiency in wetland rice may be caused by an absolute zinc deficiency, or by poor availability of zinc due to fixation in the presence of calcium carbonate, or by very gradual, but strong fixation where soils remain continuously wet and reduced for long periods, without drying between rice crops. So even at this level of detail, single indicators may be meaningless until the related factors in the system are known and the system as a whole is clearly understood.

FIGURE 1. Qualitative relationships between gradually increasing atmospheric CO₂ concentration ¹, soil characteristics and medium-term processes in soils ², and biomass or crop productivity ³

1 Gradually rising CO₂ as in this century and in transient global change scenarios.
² Soils with some weatherable minerals at least in the subsoil or substratum within rooting depth.
³ Extreme weather events may disrupt some relationships in the figure, so any major increase in their frequency or intensity may counteract positive effects shown.
⁴ Species composition adjusts, or choices indicated are made to adjust, to the newly attainable biomass or crop production under increased atmospheric CO₂, compensating for shortened growth cycles of existing species or crops. The figure does not include the positive effects of higher temperatures on length of growing periods in temperate or boreal climates.

CONCLUSION

In brief, land quality indicators may in future have a useful function on a world scale and for national reporting, for example to UN CSD. But for any more detailed or specific purposes, such as policy advice at national level, or management or planning advice in provinces or districts or smaller farming areas, indicators would not provide the sound, process-based information needed. That can only be derived from investigations using real data, interpreted for the purpose rather that aggregated a priori using a predetermined procedure.

REFERENCES

FAO. 1976. A framework for land evaluation. Soils Bulletin 32. FAO, Rome.

FAO. 1995. Forest resources assessment 1990; global synthesis. Forestry Paper 124. FAO, Rome.

Sims, D. 1986. META: A New Approach, AGL Land and Water Newsletter No. 26, August, 1986.

APPENDIX 1

UNDPCSD/FAO METHODOLOGY SHEETS
UNCED AGENDA 21, CHAPTER 10: PLANNING AND MANAGEMENT OF LAND RESOURCES

LAND USE CHANGE

1. INDICATOR

(a) name of the indicator: Land use change.
(b) brief definition of the indicator: Change with time of distribution of land uses within country.
(c) unit in which the indicator is measured: Proportion of change of given land use per unit time.

2. PLACEMENT IN THE FRAMEWORK

(a) chapter of Agenda 21: Chapter 10, Planning and management of land resources.
(b) type of indicator (Driving Force, State or Response): Response (mainly).

3. SIGNIFICANCE

(a) purpose of the indicator (the phenomenon it is meant to represent): Highlight changes in productive or protective uses of the land resources.
(b) policy relevance: Consequent changes in volume of produce available; and in scope for providing services such as tourism or environment.
(c) relevance of the phenomenon to sustainable/unsustainable development (interpretation, value, movement): Evident from 3(b).
(d) close linkages between this indicator and other indicators in the list e.g. is this indicator better interpreted if paired or combined with (an) other indicator (s)?: With land condition change (Chapters 10 and 14).
(e) targets (do international targets exist? does the indicator lend itself to the establishment of national targets? how does this indicator relate to existing targets?): No. Except for establishing certain minimal contiguous extent, or proportions of total, for certain needed or desirable land uses.
(f) reference to international conventions or agreements:

4. METHODOLOGICAL DESCRIPTION OF THE INDICATOR AND THE UNDERLYING DEFINITIONS

(a) underlying definitions and concepts description of the elements of the indicator, concept availability (are the concepts readily available? does the indicator need further work? are the concepts lacking? from where are the concepts available?): AGL and partners in and outside FAO developing:
¤ computerized land use database structure;
¤ broadly accepted structure of land use classifications.

(b) measurement methods (how is the indicator measured and computed?): By periodic mapping and monitoring land uses, partly on the basis of land cover information from remote sensing, partly by ground check; also, relation with land use aspects of agricultural census.
(c) description of the indicator in relation to the DSR framework: A response indicator. The response is the resultant of several driving forces, both past and current. These include demands for produce and services from within the country and from abroad, as modulated by price relationships, terms of trade and non-financial barriers to trade, domestic and international; by rural population growth as modified by immigration; by national and customary law and policy environment; by infrastructure and services available; and by the biophysical potentials and qualities of the land (soils, landforms, agroclimate, water availability...).
(d) limitations of this indicator: Does not by itself help identify nature of causes (driving forces).
(e) alternative definitions of the indicator and possible consequences of variations in the definition: -------

5. ASSESSMENT OF AVAILABILITY OF DATA FROM NATIONAL AND INTERNATIONAL SOURCES

(a) which data are needed to compile the indicator: Dependable agricultural census data on land uses and dependable land use maps, (updated at intervals).
(b) are the data available? (most countries? some countries? a few countries? on both a national and sub-national level? on a regular basis?): For only few countries to date.
(c) data sources: National governments.

6. AGENCIES INVOLVED IN THE DEVELOPMENT OF THE INDICATOR

(a) lead agency, including contact point: FAO; AGL (D. Sims), UNEP.
(b) other organizations. Governments or major groups which have been involved: None.

7. FURTHER INFORMATION

(a) further readings: Documents under development.
(b) other references for additional information (including document citation): Documents under development.
(c) and contact points: ITC Enschede Netherlands (International Institute for Aerospace Survey and Earth Sciences); ITE, UK. (Institute for Terrestrial Ecology).
(d) indication as to whether or not methodology has already been agreed upon by an intergovernmental fora and if it has the status of (1) recommendations, (2) guidelines, or (3) a technical report: No.

LAND CONDITION CHANGE