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GIS surveillance of nomads in Mali

By Thierry Metais, Amador Gomez and Carole Lambert, ACH

Thierry Metais is Technical Coordinator of Acción Contra el Hambre in Mali and Niger. He has been working in the Sahel region since 1997, supporting the technical strategy of ACH in water and sanitation, pastoralism and GIS.

Amador Gomez is Technical Director of Accion Contra el Hambre. Previously he spent several years working on nutrition and medical programmes in Angola, Somalia, Guinea, Nicaragua and Colombia.

Carole Lambert has worked in the field in diverse countries with ACF/ACH and since 1998 with Oxfam UK as a food security officer. She is now based in the ACH HQ Food Security Department.

In this article, Accion Contra El Hambre shares their experiences of applying a GIS tool to characterise pastoral vulnerability in Mali.

In the sahel north area of Mali, rainfall ranges from 400mm in the south to less than 100mm in the north. The resident populations are agro pastoral in the Niger river valley (the river extends for approximately 700 km), and nomads or transhumant1 in the vast surrounding area. The ethnic groups amongst the valley agro pastoralists are mainly the Songaï, Peulh, and Bozo while the pastoralists comprise the Tamasheq, Arab, Maure and Daoussak.

Vulnerability of these populations is mainly determined by factors linked to their ecosystem, in particular erratic rainfall which affects both availability and access to water and pastures for livestock. The defining ecological, geographic and social characteristics of the area do not easily allow application of classic vulnerability analysis tools. In particular, low population density, difficulty evaluating available resources at the end of the rainy season and population and livestock movements/displacements make vulnerability analysis problematic.

Traditionally, there are seasonal population movements in this area. Land areas are shared equitably, although several groups can use the same space together or separately. Stockbreeders always try to preserve resources where they stay during the dry and hot season (from March until June). Population movements/displacements are considered abnormal when the resources become so stretched that stockbreeders are forced to move long distances looking for land where there is adequate pasture. This usually requires that the 'newcomers' negotiate with those already present on issues of land area and length of stay.


Since 2002, Accion Contra El Hambre (ACH) has employed a geographical information system (GIS) in the Tombouctou, Gao and Kidal regions of Mali - an area of 800 000 km2. GIS has been applied in order to improve the understanding of vulnerability and risk in this nomadic population where classic analysis tools have failed to deliver. A particular challenge to understanding vulnerability has been interpreting information on rainfall and its impact on biomass (pastures) production and availability. One problem, in particular, was the limited data on rainfall available from the meteorological stations. However, a teledetection2 technique has helped quantify the biomass produced during the rainy season and consequently, the pasture stock available for stockbreeders. Examples of this are given in figures 1 and 2 on biomass production for Massif des Ifoghas and Haoussa Nord.

To implement the scheme, collaboration was established between ACH and a research group from the Centre for the biosphere spatial studies (CESBIO) in Toulouse, and with the IRD (Research Institute for Development ) in Mali. The IRD team had already been present in the field for several years, observing and analysing the development of vegetation at different sites in the Mali Gourma3. Ateam from the Toulouse centre developed a model that allows the quantification of biomass production using the images4 produced by the European Spot-Vegetation satellite. The use of such a technique has allowed the ACH team in Mali to follow biomass production in the Tombouctou, Gao and Kidal region from 1999 to the present day. While the results lack precision in absolute terms, they do allow a reasonably accurate trend analysis between different years.

Teledetection and rainfall deficit

During 2004, the locust invasion that affected the Sahel during that year attracted most media and aid attention at the time. However, analysis of vegetal production using teledetection, combined with recorded rainfall in some areas and the limnimetrique follow up (measurement of river level) from the large rivers, allowed ACH to determine and publicise that there was a rainfall deficit, in essence a 'drought', in early 2005. A comparison of primary vegetal production between 2002 (recognised deficit year) and 2004, confirmed that 2004 has been worse than 2002. More specifically, in 2002, primary production was equal to 77% of the average for the previous 5 years, compared with a 5 year average of 74% in 2004. (See figures 3-5 which display differences in primary production for 1999, 2002 and 2005).

To assess rainfall deficit, the Sahel pluviometry (rainfall) index5 was used, which is produced by IRD. This index is calculated from the figures of 20 meteorological stations in the Sahel and surveillance has been ongoing since 1895 (see figure 6). In this index, zero stands for the average rainfall, a deficit is reflected as negative figure and reflects degrees of risk of drought. It can be supposed that the pluviometry index for risk in 2004 was worse than in 2002 (-0.92)6, since biomass production was 77 % in 2002 and 74 % in 2004. To put this in context, during the 1973-74 and 1984 droughts, this index was close to - 1 and -1.35 respectively.

While it is difficult to absolutely confirm that rainfall has fallen over the years, these measures reflect that the Sahel countries are still experiencing rainfall equivalent to the drought years of the 1970s. It can also be deduced that since 1999, only one year can really be considered as 'good', (1999) and that other years have experienced average or bad rainfall.

Analysis of population movement

The spatial distribution of the rainfall deficit is of critical importance and practical relevance. Land use by the stockbreeders varies between times of the year and the concept of ecological zones is based on this use. An understanding of the complementarity of different ecological zones is also important. From an understanding of where the deficits are localised, it is possible to determine where the impact will be most pronounced on the nomadic system. This more qualitative analysis allows a better evaluation of the risks compared to using teledetection alone. Given the shortfall in primary vegetal production revealed through teledetection, further analysis of the data has identified the rainfall deficit areas since January 2005.

An analysis of the different types of population movement by stockbreeders and livestock further complements this information. A good background knowledge is needed for this analysis, which ultimately has to be verified in the field in consultation with the affected population. Movements or displacements are classified as 'normal', 'abnormal' or 'exceptional'7. In 2005, the analysis of movements, checked by the field missions, led to the definition of some areas as 'concentration areas' and other as 'abandoned' (see figures 7 and 8). The so-called 'concentration areas' are the geographical areas that, due to their ecological characteristics, have received an unusual number of stockbreeders and livestock. The 'abandoned areas' are those where the stockbreeders have left with their livestock.

Application of GIS tool to programming

From early 2005, ACH in collaboration with other national and international non-governmental organisations (NGOs), started market price surveillance in the drought affected areas. The main purpose was to determine the exchange rate between a bag of cereal and a small ruminant. This exchange rate, in turn, helps determine the population's access to staple foods. The analysis found the exchange rate, which is usually between 1 and 1.5, had reached 3, indicating an increased vulnerability of the population relying on livestock as their main livelihood. In April 2005, a new mission was dispatched to the field to verify and follow up developments. A nutritional screening using mid-upper arm circumference (MUAC) was carried out in the areas suspected of being the most vulnerable (abandoned areas) and for comparison, in concentration areas. Figure 9 displays the nutritional information and compares this with information from earlier years.

Timely interventions

When nobody was really talking about a food crisis in Mali and the Sahel, the use of the GIS tool allowed the ACH Mali mission to identify a problem, be the first to speak about the drought and to quantify its impact. Through collaboration with the WFP (World Food Programme) and Mali's Early Warning System, the concept and use of 'ecological zones' has facilitated the identification of sentinel sites inside the pastoral area of Mali where monitoring now takes place.

The quantification of the biomass deficit due to erratic rainfall and the analysis of its consequences have helped inform the international community about the urgent need faced by many vulnerable people and their need for aid.

Since May 2005, ACH teams have been operational in the field addressing acute malnutrition (wasting) in the 'abandoned areas', where unusually high rates of malnutrition were identified. A surveillance team follows nutritional trends, displacements, exchange rates and other indicators related to the present rainy season.

Furthering understanding of the mechanisms that produce a significant increase in vulnerability should facilitate planning for medium and long term preventive actions.


Characterisation of programming areas using GIS has allowed ACH to more truely assess the situation being experienced by the population. Today, ACH is convinced that application of GIS incorporating teledetection has strengthened the organisation's capacity to react to recurrent natural shocks in the Sahel. Nevertheless, efforts are still needed to develop a more integrated tool. This will help not only in providing better early warning of crisis in pastoral areas, but also assist in planning medium and longer term preventive initiatives in these structurally complex areas.

For further information, contact: Amador Gomez, email:

Show footnotes

1In nomadic populations, the majority of the family or clan members accompany herds during their displacement while, in the case of transhumant populations, only the shepherd accompanies the livestock. The nomadic systems mainly exploit the shelo-sahariens area bordering the north-sahelien area (rainfalls from 100 up to 300 mm/year) and, sometimes at the end of the dry season, the central sahelian area. In West Africa, the best known nomadic populations are the les Maures, Peuls Wodaabe, the Toubous, the Touareg, and the Mohida Arabs.The nomadic population travel less distance than tranhumant populations. (Bonfiglioli 1990).

2'Teledetection' is a technique by which measurements are taken at a distance, i.e. without direct contact between the measuring instrument and the detected object. It is used mostly to study the surface of the earth from air or space by measuring electromagnetic beams which carry information.

3Right bank of the Niger River in Songhaïe language

4The Spot Vegetation satellite has a quasi polar orbit, and picks up one image every ten days.


6The Sahel pluviometry (rainfall) index produced by the IRD was not available for the years 2003 and 2004.

7A normal movement denotes usual for the period of the year, abnormal is unusual and corresponds to a pattern typical of a bad year, exceptional means that the resources deficit has resulted in exceptionally unusual displacements which have been difficult to chart/and follow.

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Reference this page

Thierry Metais, Amador Gomez and Carole Lambert (). GIS surveillance of nomads in Mali. Field Exchange 27, March 2006. p24.



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