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Monitoring and of desertification
1. Present situation
There is no specific operational programme for the monitoring and mapping of desertification. However, the situation can be partially assessed on the basis of a large number of programmes that can be grouped as follows:
observation programmes involving the production and dissemination of seasonal, and therefore short-term, geo-referenced data on agricultural and pastoral resources and production in arid and semi-arid regions. This mainly involves the estimation and monitoring of rainfall; assessment of risk of famine; agricultural statistics; control of locusts and other pests; monitoring of floods; monitoring of bush fires; evaluation of livestock density. Observation is mainly based on data from low-resolution meteorological satellites, particularly NOAA/AVHRR and Meteosat, combined with ground data on rainfall, agricultural yield, population location, markets and commodity prices.
Long-term monitoring programmes for the production of detailed geographic maps and databases on the state and changing pattern of land resources. These actions are, however, relatively location-specific, comprising: (i) land base inventories; land use maps, pastoral resource maps, forest and agricultural inventory maps, water resource inventories; (ii) exercises in the detection and monitoring of changes: changes in pasture, physical and chemical land degradation, changes in land use; monitoring of sand dune movement. The long-term monitoring programmes mainly use high-resolution satellite data (Landsat, SPOT) and, increasingly, the geographic information systems, particularly for the studies on resource degradation and potential.
The technical implementation of the observation and long-term monitoring programmes is carried out by a wide range of national and regional institutions. Most countries and development agencies involved agree that standardized instruments are needed to integrate the findings of the various programmes.
2. Possibilities of action
Desertification could be evaluated and monitored on the basis of a series of specific physical and socio-economic parameters, that are sometimes grouped under the term "ecosystem": (i) for the physical data, the climate and its effects such as agro-ecological zoning, type of soil, present state of soil and risk of physical, chemical and biological degradation, soil structure, land use, agricultural, forest and pastoral cover and level of degradation; (ii) for the socio-economic data, population pressure, the predominant agroforestry/pastoral system. Multi-disciplinary teams of experts familiar with the area in question will be required to evaluate the interaction and respective importance of these parameters and estimate the level of desertification as reliably and objectively as possible.
The evaluation and mapping of these various parameters should be based on a judicious concurrent utilization of:
(a) Remote-sensing data
high-resolution satellites are essential for the production of reference maps on land use, vegetation and level of degradation, soil structure and, in many cases, predominant agro-pastoral system. These data will have to be updated every 3 to 5 years using representative samples or priority zones.
data from the environment satellites are unique for a complete daily, weekly or monthly monitoring of meteorological conditions and vegetation changes. However, these data can only be examined on a scale of 1:2 000 000 to 1:10 000 000, so their interpretation must be carefully aligned to reference maps from high-resolution satellite data, or even sample aerial photographs.
(b) Data from measuring stations and ground observation and posts. These mainly comprise data from meteorological stations, but also from soil research stations, ecological or pastoral monitoring posts, etc.
(c) Maps, statistics, databases and summary reports on the various desertification parameters, available at local, national or regional level.
The integration of these three levels of information and the modelling of the trend can be facilitated and rendered more accessible to users with the use of the geographic information systems.
The information already on hand and the potential of observation instruments point to an urgent need for a specific programme to monitor and map desertification, and integrate the various instruments. The technical design of this programme could comprise:
a. The regional and subregional collection and standardization on geographic information systems (GIS) of existing geo-referenced desertification data.
b. The exhaustive mapping of the main physical and socio-economic parameters of desertification, on the basis of national-level high-resolution data (scale of 1:500 000).
c. The preparation of a national-level geo-referenced programme of action against desertification
d. The introduction of a regional- and national-level drought and desertification monitoring system based on sample sites and environment satellite data.
4. FAO programme
FAO implements a number of programmes that arc directly relevant to any desertification surveillance system. In terms of the four above activities these include, respectively:
a. Regional and sometimes national databases established on geographic information systems concerning land cover, agro-ecological zones and numerous agricultural and forest indicators.
b. Projects for national resource reference maps conducted by the Remote Sensing Centre in arid and semi-arid areas.
c. Desertification expertise available in each of the technical services and coordinated by the working group on desertification.
d. Ongoing agrometeorology monitoring programmes and early warning programmes, particularly in the Sahel, that produce regular bulletins on desertification parameters. There is also the ARTEMIS remote sensing programme that monitors rainfall and vegetative growth in the whole of Africa and the Middle East.
|Additional information on the ongoing monitoring of desertification can be obtained from the Remote Sensing Centre, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome (Italy) - Fax (39.6) 5797 5137|
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