European Indicators of Desertification Risks
J. L. Rubio, E. Bochet
Topic Centre on Soil (European Environmental Agency)
Centro de Investigaciones sobre Desertificación - CIDE (CSIC, Universitat de València, Generalitat Valenciana)
Camí de la Marjal S/N
46470 Albal (Valencia)
Spain
Introduction
Although the seriousness of the environmental and socio-economic impact of desertification, not many efforts have been made to devise diagnostic techniques and criteria for appraising the status and trend of desertification.
The existing studies have been oriented in a global perspective (FAO, 1977; Berry & Ford, 1977; Dregne, 1983; UNEP, 1994) and most of them were mainly directed to range land conditions. Moreover, the areas usually considered, included developing countries with cultural background and socio-economic conditions quite different to the prevailing in European countries (Rubio, 1991).
For these reasons, the European Centre on Soils (ETC of the EEA) is planning to develop an evaluation system of environmental indicators, with a special attention paid to desertification in the European countries. A brief presentation of a methodological approach and diagnosis criteria for desertification risk assessment in Europe is described hereafter.
At present, different methods exist for the evaluation of desertification, such as direct observations and measures, mathematical models and parametric equations, estimates, remote sensing, and indicators. However, there is no satisfactory evaluation system of desertification adapted to the biological history and specific characteristics of Mediterranean ecosystems, which are those more exposed to desertification problems.
Indicators have the advantage of being synthetic and simplified information that is useful in order to determine the state and tendency (prediction) of complex processes such as desertification. Moreover, they can be used as an easy synthetic information in geographic information systems (GIS), in order to determine spatial extension and geographic distribution of degraded areas, and to relate human actions (causes) to environmental conditions (effects).
Methodological approach
With the intention of developing an evaluation system of desertification by means of indicators, a methodological approach, based on the one described by Hunsacker and Carpenter (1990), will be used for the selection and evaluation of satisfactory indicators.
Several general requirements have to be taken into account before selecting potential indicators. In this respect, indicators should be
- desirably quantitative
- sufficiently sensitive to provide an early warning of change
- distributed over a broad geographical area (widely applicable)
- relatively independent of sample size
- easy and cost-effective to measure, collect, assay, and/or calculate
- able to assess the present status
- able to assess the trend
- able to differentiate between natural cycles or trends and those induced by anthropogenic stress
- relevant to ecologically significant phenomena
- adapted to European conditions
Different potential indicators will be listed on the basis of bibliographic information and with reference to a large amount of available data on desertification studies carried out during several years in our Research Centre. A preliminary list of possible desertification indicators is presented in table 1. Biophysical indicators related to soil, vegetation and water, and socio-economic indicators linked for example to land use, wood supply, human health and response, will be taken into consideration at that stage.
Table 1: European desertification indicators (J.L. Rubio, E. Bochet)
|
Criteria |
Indicators |
|
Soil
Water
Vegetation
Topography
Socio-economic (human) |
Water and wind erosion (runoff, sediment transport, splash, types of erosion, gully and rill density,...) Salinization-alcalinization (electrical conductivity, absorption by Na) Acidification (Al, H) Contamination (heavy metals) Structural degradation (compaction, infiltration, bulk density, aggregate stability, stoniness, water content, carbonates, temperature,...) Biological degradation (organic matter content, cations) Soil depth (available soil depth fro roots, texture) Fertility Rainfall aggressivity (rainfall amount, frequency and intensity, USLE's K index of erosivity, Fournier's index of rainfall variability, Bagnouls-Gaussen's index of aridity) Evapotranspiration (temperature) Climate change Water redistribution (runoff,
infiltration) Percentage of cover Biomass (net primary productivity, root biomass/canopy biomass ratio) Aridification of vegetation (structure,
composition, asymmetrical morphology, spatial pattern,
biological types, C3/C4 plants, root system, germination
rates,...) Slope (length, angle) Abandonment of marginal land (and practices of conservation) Unreliable regional planning Risk of forest fires (frequency, duration, temperature) Unsuitable agricultural practices (intensity, type) Inappropriate use of the land |
The process of selection and evaluation of indicators will consist of different steps that have been summarized in the following diagram, inspired by EMAP's methodological approach on environmental state indicators (Hunsacker and Carpenter, 1990).
Table 2: Indicator selection, prioritization and evaluation approach (EMAP, 1990)
|
CANDIDATE INDICATORS | |
|
IDENTIFY AND PRIORITIZE |
Expert Knowledge Literature Review Peer Review |
|
RESEARCH INDICATORS | |
|
EVALUATE EXPECTED PERFORMANCE |
Analysis of Existing Data Simulations Limited-Scale Field Peer Review |
|
DEVELOPMENTAL INDICATORS | |
|
EVALUATE ACTUAL PERFORMANCE |
Regional Demonstration Projects Peer Review |
|
CORE INDICATORS | |
|
PERIODIC REEVALUATION |
|
|
IMPLEMENT REGIONAL AND NATIONAL MONITORING |
|
Available and new field data collected preferentially in the experimental sites specially designed by our Research Centre team for desertification studies (erosion plots, fire simulations, different types of vegetation and soils, automatic meteorological station, ...) will be used in the selection and evaluation of indicators. On the one hand, measurements in control and degraded areas will allow the determination of desertification state, and on the other hand, measurements obtained at different time in given place will give a suitable information on the evolution and time-scale at which the processes act.
Information resulting from the process of definition, selection and evaluation described above, will be interpreted and validated. Indicators chosen after different steps of selection and evaluation will be then checked in field areas.
Ranges of status and trend values will be determined, and thresholds and critical values will be defined. By combining several indicators, possible desertification indices will be evaluated in order to increase the discriminant capacity of single indicators.
The environmental health of studied areas will be predicted by means of the set of indicators selected.
Bibliography cited
Berry, L. and Ford, R.B. 1977. Recommendations for a system to monitor critical indicators in areas prone to desertification. Program for International Development, Clark University, Worcester, Massachusetts, USA
Dregne, H.E. 1983. Desertification of arid lands. Texas Tech. University.
FAO/UNESCO/WMO 1977. World Map of Desertification. United Nations Conference on Desertification. Nairobi, 29 August - 9 September 1977, Document A/CONF.74.2.
Hunsaker, C.T. and Carpenter, D.E. (Eds.) 1990. Ecological Indicators for the Environmental Monitoring and Assessment Program. EPA 600/3-90/060. U.S. Environmental Protection Agency, Office of Research and Development, Research Triangle Park, NC.
UNEP, 1994. United Nations convention to combat desertification in those countries experiencing serious drought and/or desertification particularly in Africa. Text with annexes. U. N. Environmental Programmes for the Convention to Combat Desertification. (CCD).
Rubio, J.L. 1991. European Desertification Indicators. Symposium on Desertification in the Mediterranean Area, C.E.E. (DG XII), Firenze (Italy), June 1991 (CIDE's Report).