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Rural societies in the face of climatic and environmental changes in West Africa

 | 
Benjamin Sultan
, 
Richard Lalou
, 
Mouftaou Amadou Sanni
, 
et al.

Part II. Impacts of the climate and environmental changes

Chapter 8. The forage constraint in pastoral and agropastoral livestock farming in the Sahel

Adaptation and prospects

Pierre Hiernaux, Mamadou Oumar Diawara, Laurent Kergoat et Éric Mougin

Texte intégral

Introduction: the forage question

1The forage question is involved in livestock farming practices in the Sahel and also in research conducted on the improvement of its profitability (Lhoste et al., 1993; Klein et al., 2014), animal husbandry development policies (Zoundi and Hitimana, 2008; CORAF/WECARD, 2010; Krätli et al., 2013) and finally discussion of the future of animal husbandry in the Sahel (Peyre de Fabrègue, 1984; Hesse and Thébaud, 2006; Jullien, 2006; Bassett and Turner, 2007). The availability and quality of forage would seem to be the main constraint for the development of livestock farming, and the constraint for pastoral livestock operations would be the carrying capacity of rangeland (Boudet, 1984; Breman et al., 1984, Le Houérou, 1989). However, at the same time the questions of forage and carrying capacity have been eluded substantially in development projects, as if the solutions were up to the judgements of farmers who, in their practices founded on knowledge that has been handed down, experience and the support of collective institutions, have always found a solution even during the worst situations of drought and access conflicts (De Bruijn and Van Djik, 1995; Thébaud and Batterbury, 2001; Krätli and Schareika, 2010). The definition and often the questioning of the livestock carrying capacity in the Sahel by technicians, scientists and political decision makers are revealing in this respect (Hiernaux, 1982; De Leeuw and Tothill, 1990; Sayre, 2008; Krätli et al., 2015).

2In fact the intuitive simplicity of the concept–the capacity of a pastoral resource consisting of rangeland and waterpoints to support a livestock operation in a sustainable manner (Boudet, 1984)—hides semantic duality. Indeed, the carrying capacity has ‘zootechnic’ meaning (Hiernaux, 1982) attached to the capacity of the pastoral resource to attain a livestock production objective: the maintaining of a certain level of fattening of livestock, of a certain level of milk production by lactating cows that give a certain reproduction level (age at first calving, fertility rate, limiting the death rate). The second meaning is described as being ‘ecological’ insofar as it is focused on the impact of livestock carrying capacity in rangeland, forage production capacity and, more broadly, the ecosystem services expected of the pastoral ecosystem: wood production, recycling of organic matter, infiltration of rain. The semantic duality results in confusion, especially as there is no obvious link between carrying capacities—each aspect depends on numerous conceptual variables such as the climate and fires—for forage production, species, breed and animal health for animal production capacity.

3In addition, both meanings of the concept run into the strength of the seasonal and inter-annual dynamics of Sahelian forage resources. The extreme seasonal contrast, with the alternation of green prairies lasting for the few weeks of the rainy season and stretches of dry straw and litter that gradually disappear during the long months of the dry season, is considered as being inherent to the Sahelian ecosystem (Hiernaux and Le Houérou, 2006). But what forage production reference should be used to estimate livestock production capacity or to judge the degradation of rangeland in an ecosystem governed by a monsoon climate marked by very large variations in forage production resulting from rainfall variations from one year to the next (Le Barbé and Lebel, 1997) and rainfall with very irregular geographic distribution (Ali et al., 2003), aggravated by runoff and flows (Breman and De Ridder, 1991)? The use of the ‘zootechnic’ meaning of the concept is complicated by the regional mobility of herds (Schlecht et al., 2001) that is generally multi-specific. Mobility organised within the framework of community use of pastoral resources means that forage balances, the ratio of consumption to the quantity of forage available, is only possible for very large geographic areas used for grazing by a group of farmers whose herds may display very varied performances (Colin de Verdière, 1994). The seasonal mobility of herds also complicates use of the ‘ecological’ meaning of the carrying capacity, especially as the impact of grazing on vegetation and soils depends on both the intensity and season of grazing (Hiernaux and Turner, 1996; Hiernaux, 1998). Do these objective difficulties of implication mean that the carrying capacity concept falls definitively through a technical trap door (Krätli et al., 2015)?

4We seek here to answer the question in an empirical manner by trying to draw up a forage balance for a period of a few successive years at two locations in the Sahel: one where pastoral husbandry is the dominant economic activity at Hombori in the Gourma in Mali (Gallais, 1975; Boudet et al., 1977; Ag Mahmoud, 1992) and a location where it is combined with the growing of millet and cowpea and numerous non-agricultural activities at Dantiandou in the Fakara in Niger (Osbahr, 2001). But it must be specified first of all what livestock systems are examined and how sensitive they are to the forage constraint. Balances are then drawn up with the successive quantification of forage availability and the consumption of forage by livestock at the two locations. The balances are then compared to the decadal tendencies in plant production and to the performances of the livestock operations. To conclude, the results are set in the development perspective of Sahelian livestock farms.

The diversity and interrelations of livestock systems in the Sahel

5Livestock systems are very varied in the Sahel but generally pastoral insofar as the livestock feeds mainly or entirely by grazing in rangeland (Hiernaux and Diawara, 2014). The distinction made between pastoral and agropastoral livestock farming is more a reflection of the combining of crops and pastoral livestock rearing on the same family farm in the second case. The forms of regional mobility often used in pastoral operations are used to distinguish between sub-categories (Touré et al., 2012; Turner et al., 2014) depending on whether they involve the whole family (nomadism) or only the persons who move the livestock (transhumance) and the scale, regularity and even the direction of these movements. In contrast, the mobility of livestock in sedentary pastoral animal husbandry is limited to daily movements between resting places, watering and pasture suited to the season and the rights of access held by each livestock farmer (Turner et al., 2005). However, breeding livestock farms produce young animals for specialised rearing markets (Hiernaux and Diawara, 2014). In breeding operations, males are generally sold young, with the exception of a few kept for reproduction whereas females are kept until the end of their reproductive career and then sold off. This is seen in the composition of herds in terms of sex and age. Females are markedly dominant at 75 to 85% and two thirds of these are adult. This is the case of cattle herds and sheep and goat flocks at Hombori and also at Dantiandou, but with the exception of small cattle rearing units in which young bulls for fattening and draught oxen are dominant (Fig. 1). Breeding is accompanied by secondary milk production. Indeed, milking often accounts for only a fraction of milk production so as not to slow the growth of calves, which remains the main objective (Zezza et al., 2014). Milk and derived dairy products are for family consumption, with part being sold. The social issue of this is all the more important as this activity is generally reserved for women (Querre, 2003).

6The great majority of the pastoral and agropastoral units in the Sahel are breeding operations, but there are also pastoral and agropastoral units that are not devoted to this and that can be grouped as a ‘specialised’ category. They purchase stock—often young animals—and rear it for use as draught animals that are then sold off (this is the case of the operations with less than 5 head of cattle at Dantiandou, Fig. 1), or for fattening (Ayantunde et al., 2008) and finally but more rarely milk cows for dairy units that are generally in peri-urban zones (Sanogo, 2011). These specialised operations can be termed opportunist insofar as their economic success depends to a great extent on the market on which the livestock are purchased and then resold, dairy products are sold and inputs are also purchased—veterinary care and cattle feed.

Figure 1. Average composition by sex and age category of herds and flocks of graziers at Hombori, agropastoral farmers at Dantiandou, farmers and cattle rearers at Dantiandou (a single case of a herd of cattle of 5 animals or less). Livestock feeding young are shown as a separate category for Dantiandou.

7More dependent on market conditions, they are also more intensive as they require greater financial investment, often in equipment (stable, store) and more labour (foddering and minding the cattle). Specialised rearing operations aim at production that sells better on the market and for which grazing alone may be insufficient, especially as these holdings are run by sedentary, sometimes peri-urban farmers with limited access to forage. The operations are therefore more rarely pastoral and when they remain so they are less dependent on grazing; a complementary energy, protein and mineral ration is added. This is in the form of cowpea or groundnut stalks, bran and cereal stubble and other crop or processing residues that are thus used, but taken from community pastoral resources. On small specialised operations, the complements are produced on-farm but they are also purchased on the market and affect the profitability of the business.

8The great majority of Sahelian breeding and pastoral farms are closely dependent on the forage resources of rangeland for feeding their livestock. Specialised farms whose stock is supplied by breeding farms are less dependent on grazing but are in competition with breeding farms for cattle feed from rangeland. The rangeland forage balance thus concerns all categories of stock breeding either directly or indirectly.

Forage balances

9A forage balance is drawn up using the difference between the forage available—more precisely the potential forage fraction of the plant material available and the forage requirements of livestock during the annual cycle. Common access to rangeland and the seasonal mobility of herds and flocks mean that these balances can only be drawn up for areas that are large enough to cover the major part of the movements of the resident stock; possible stays by herds from elsewhere must also be incorporated. The size of these areas and the large number and broad diversity of farmers and herds makes estimating forage availability and the requirements of livestock very laborious. Two case studies illustrate the approach: that of a pastoral breeding farm in the Gourma (Mali) and that of breeding farms and specialised agropastoral rearing operations in the Fakara (Niger). In the Gourma, the territorial unit was defined by a set of waterpoints in the community area of Hombori and its surroundings from which the livestock of people in the area and some belonging to farmers from elsewhere graze the land of the commune and that adjoining it (3,000 km2). In the Fakara, the territorial unit is defined by the adjoining land of 12 villages and adjoining encampments, totalling 210 km2 (of the total of 845 km2 of the commune of Dantiandou).

Estimate of the forage resources of the land in the commune of Hombori and nearby areas

10The commune de Hombori is at the northern limit of rainfed millet growing, with cultivated fields covering only a few percent of the landscape (Cheula, 2009) and making only a very secondary contribution to forage resources. The latter are provided mainly by rangeland but in very distinct proportions and quality for the three main components of the landscape: deep sandy soil forming about 77% of the land at Hombori (Nguyen C. C., unpublished data), shallow soil on erosion glacis and rocky outcrops (15%) and the loam soils and clayey soils of the valleys and plains (8%). The areas of these soil categories were mapped by supervision classification of high-resolution Landsat images. Indeed, the hydric properties of surfaces and soils in the three landscape components govern the surface redistribution of rain and its infiltration, governing structure and plant production. These are also influenced by differences in the biochemical fertility of soils (Penning de Vries and Djiteye, 1982). Average maximum herbaceous mass measured in September at 12 pastoral sites, including vegetation monitored since 1984 (Mougin et al., 2009), is set out for each year and type of substrate. The averages are weighted by the relative areas of substrates to assess the amount of herbaceous forage available at the end of the growth season (Fig. 2). Erosion glacis and rocky outcrops display available forage of from a few tens to several hundred kilograms dry matter per hectare whereas availability on clayey and loamy rangeland is from 500 to 1,500 kg and that on sandy rangeland is between 1,000 and 2,500 kg/ha. Weighted forage availability for all the Hombori rangeland could be doubled between 2008, a dry year, and 2011, a more rainy one (Fig. 2). However, only a fraction of the amount of forage available is used by livestock, first because of difficult access to part of the area and above all because of the distance from waterpoints during the dry season, and also because grazing causes losses by trampling and biotic degradation which, without counting possible fires, causes two-thirds of straw degradation during the dry season (Hiernaux et al., 2012). Finally, it is estimated that useful grazing is a quarter of the total available.

Figure 2. Average by type of substrate weighted by the relative areas of substrates and of herbaceous masses at the end of the growth season in the commune of Hombori and adjoining areas. Measurements were made at 12 pastoral locations that are the subject of long-term monitoring (AMMA-CATCH network).

11In Mamadou Diawara’s thesis work, forage availability was also plotted spatially in the territory of the commune of Hombori to compare the evolution of forage in the areas served by waterpoints during the 2010-2011 dry season with the evolution of stocking levels by head counts at the waterpoints (Fig. 3). The map of available forage was plotted using a linear regression between the peak MODIS/Terra NDVI (index maximums for 16-day periods at 250 m resolution) during the rainy season and the herbaceous plant mass measured at 12 monitoring sites in and around the commune of Hombori: mass (kg ha-1) = 9 979,4*NDVImax–738.09 (r = 0.75, rmse = 12.5, n = 21) (Diawara, 2015)

12The average available forage mass derived from this function for the territory of the commune was 1,844,9 ± 747.9 kg ha-1. This estimate is a little lower than that based on averages (2,027 kg ha-1), but spatialisation makes it possible to analyse the balance by the areas served by waterpoints.

Figure 3. Forage availability map for the commune of Hombori (Mali) at the end of the 2010 rainy season (kg DM/ha).
Source: Diawara (2015)

Estimate of available forage in the areas of 14 villages in the commune of Dantiandou

13Millet fields cover a little less than half of the area of the commune of Dantiandou and make a considerable contribution to forage resources (Fig. 4a). Forage availability is therefore estimated using the areas of three types of land use in the pastoral zones of 14 villages in the commune with a cumulated area of 210 km2 (of the 845 km2 of the commune). The area is estimated from land use maps plotted each year from 2009 to 2011 by supervised classification of Spot multispectral images (Fig. 4a). Available forage mass was calculated for each of the three land use types by ground measurements at 24 sites (72 were monitored but destructive measurements were applied to a 24-site sub-sample). Only herbaceous plant organs with forage value were taken into account, that is to say herbaceous plants in rangeland or fallows, weeds and millet straw leaves in the fields (Fig. 4b). Land use types are not independent of topo-geomorphological positions: uncultivable rangeland is on indurated (hardpan in the intermediate area) and the bordering scarp but also the upper part of slopes where weathered and decayed Continental Terminal sandstone outcrops and on the hardpan soils at the base of the slope (piedmont hardpan). Millet fields and fallows are in the sandy soil found on a few fixed dunes above the plateau and above all on sandy deposits on valley slopes and on the alluvial deposits in valley bottoms. Sampling of sites was performed with care taken to show the diversity of these positions (Hiernaux et al., 2009 a).

14Total herbaceous forage resources in the 210 km2 of the 12 agropastoral areas were estimated at 13,597 t DM in 2009; the figure increased to 16 293 t in 2010 before falling to 13 401 t in 2011. A kind of compensation is seen in the fluctuations recorded for each type of land use. Only a fraction of the forage available is of practical use for livestock whose grazing is selective (Ayantunde et al., 1999) and that avoids grazing certain species that are abundant unfortunately at Dantiandou (Mitracarpus scaber and Sida cordifolia are very common). Grazing causes losses by trampling and biotic degradation which, without counting possible fires, causes two-thirds of straw degradation during the dry season (Hiernaux et al., 2012). Finally, the useful fraction of grazing is estimated to be a quarter of the forage available, as at Hombori.

Figure 4. a) Evolution of use for farming in the land (210 km2) of 12 villages in the commune of Dantiandou, Niger, from 2009 to 2011. b) Average annual forage by land use measured at 24 sites where plant cover and average available forage are recorded (kg DM)/ha.

The forage balance in the commune of Hombori

15Assuming that stocking varies little from one year to the next in both numbers and composition, forage requirements are calculated for the numbers counted from March 2010 to June 2011 taking into account the structure of stock by sex and age category (Table 1) and the evolution of average weights and forage digestibility over the seasons. Monthly livestock counts are performed at the main waterpoints in the commune—about 50 ponds, sumps, wells and tanks are grouped in 20 waterpoints (Diawara, 2010). This count underestimates stocking as it does not cover livestock that drinks in small, unlisted ponds during the rainy season. Stocking is calculated from the numbers observed from October to June in order to correct this under-estimate (Table 1).

16The herbaceous forage intake of this stock is estimated from the average daily intake calculated for each animal category using an intake rate of 98 g per kilogram of metabolic weight (live weight to the power of 0.75). The fraction of ingested forage consisting of herbaceous forage is then deducted from total ingested forage, considering that the ration of cattle and donkeys is mainly herbaceous (95%), that of sheep 85% herbaceous and that of goats and that of camels 60% with the complement consisting of grazed foliage of ligneous plants.

17The forage requirement of livestock on the Hombori rangeland is estimated to be 50,964 tonnes of herbaceous forage (average 170 kg/ha). Compared to the available herbaceous forage in the 3,000 km2 of the commune and the surrounding area, this use is low, reaching 78.5% of the usable fraction in 2008, a drought year, and between 33 and 46% in the three following years (Fig. 5). These overall statistics would thus seem to show that there is not a forage problem at Hombori. However, the livestock feed situation was critical at the end of the 2008-2009 dry season, with exceptional migrations and the provision of supplementary feed. The apparent contradiction is explained on examination at a more local scale of the areas supplied by waterpoints. The straw and litter degradation model for the dry season according to livestock density using the resources working outwards from the water points (Mougin et al., 1995), calibrated using observations and measurements made in three waterpoint supply areas in the commune reveals very different rates of use of resources from one area to another (Fig. 6).

Table 1. Head of livestock counted once a month at drinking at some 20 waterpoints in the commune of Hombori. Monitoring from March 2010 to June 2011.

Table 1. Head of livestock counted once a month at drinking at some 20 waterpoints in the commune of Hombori. Monitoring from March 2010 to June 2011.

Figure 5. Inter-annual variations of the annual herbaceous forage available, of the fraction that can be used by livestock, of the estimate of forage ingestion and of the ratio of ingestion to the usable forage in the territory of the commune of Hombori and the surrounding area from 2008 to 2011.

18Two of the main waterpoints—perennial ponds with public access—reach the theoretical maximum of 33% while the rates of use of the resource are lower in the other areas with an overall average is 9.4%. It is therefore possible even in a fairly favourable year to observe livestock in a situation of seasonal under-nutrition (Fernàndez-Rivera et al., 2005). This contributes to poor reproductive performance and the high losses observed in the major droughts of 1972-1973 and 1983-1984 (Dawalak, 2009).

Figure 6. Grazing intensity around pastoral waterpoints: rate of use of forage by livestock during the 2010-2011 dry season.
Source: Diawara (2015)

Forage balance at Dantiandou

19An exhaustive survey of family livestock in 12 villages and associated encampments in 2010-2011 documents the livestock by species, sex and age category, with distinction made between unweaned young animals, weaned young animals, adults and lactating female adults (Table 2).

20The ingestion of herbaceous forage by this livestock is estimated using average daily ingestion calculated on the same basis as for Hombori: ingestion of 98 g per kg metabolic weight. For this, a standard weight was used by category of age and sex for each species (Table 3), and the forage ingestion calculation was performed by sex and age category for each species.

21As at Hombori, the herbaceous forage fraction of ingestion is deduced from forage ingestion using the same average forage selection coefficients. Annual forage ingestion by the livestock in the 12 areas is thus estimated to be 5,046 t DM, of which 4,521 t consists of herbaceous material, including millet straw (Table 4).

22This total is only a fraction of the forage mass available (average 14,430 t from 2009 to 2011). However, it exceeds the proportion of available forage considered as being usable by the livestock (3,608 t) as a result of losses by trampling, herbivores and decomposition and also because of the large contribution of non-forage species (including Mitracarpus scaber that is dominant in fallows). The ratio of ingested forage to the usable quantity is thus always greater than 100% (Fig. 7), underlining the acuteness of the question of forage at Dantiandou.

Table 2. Sedentary livestock in 12 villages and encampments in the commune of Dantiandou in 2011, by species, sex and age category.

Table 2. Sedentary livestock in 12 villages and encampments in the commune of Dantiandou in 2011, by species, sex and age category.

Table 3. Unit weight standards for livestock by species, sex and age category and the corresponding average forage ingestion calculated using metabolic weight.

Table 3. Unit weight standards for livestock by species, sex and age category and the corresponding average forage ingestion calculated using metabolic weight.

Table 4. Estimated annual ingestion of forage by the resident livestock in 12 villages and encampments of the commune of Dantiandou. The proportion of herbaceous forage including millet straw is estimated separately.

Table 4. Estimated annual ingestion of forage by the resident livestock in 12 villages and encampments of the commune of Dantiandou. The proportion of herbaceous forage including millet straw is estimated separately.

Figure 7. Estimated annual forage availability with the usable proportion and that ingested by livestock during an annual cycle (t dry matter) in the pastoral area of 12 villages in the commune of Dantiandou (210 km2) from 2009 to 2011. The curve of the ingested proportion of usable forage is shown in%.

Comparison of the forage balances drawn up for Hombori and Dantiandou

23It might seem paradoxical that the forage question is more acute at Dantiandou where rainfall (565 ± 142 mm at Niamey during the period 1905-2012) is more abundant and regular than at Hombori (376 ± 107 mm during the period 1935-2012). However, available herbaceous forage per unit of surface area is less on average at Dantiandou, even if it is less variable from one year to the next (Figs. 2 and 4). The reason is mainly the fact that nearly half of the land is used for growing millet, whose only pastoral resource is leaf straw (the stems are not eaten, unlike those of sorghum) and weeds. It is also caused by poor herbaceous production on rangeland on the indurated plateaux and their borders subjected to very strong grazing pressure during the rainy season when livestock is kept out of crop fields (Turner et al., 2005).

24Furthermore, stocking over the year is slightly greater at Dantiandou with 8.4 TLU/km2 (2,108 kg live weight per km2) exerting grazing pressure with forage consumption of 215 kg/ha whereas average stocking at Hombori is 7.0 TLU/km2 (1,742 kg live weight per km2) and grazing pressure corresponds to average herbaceous forage consumption of 169 kg/ha. However, more detailed estimates at the scale of the areas served by waterpoints at Hombori show that this average figures hides very contrasted realities with consumption close to the maximums possible (a third) near the most frequent waterpoints while the standing forage reserves are little exploited when they are at some distance from the waterpoints. But this is part of the security margin used by certain livestock farmers during crisis situations (Benoit, 1984).

25These forage balances are just a guide as the chronic forage shortage at Dantiandou renders the situation impossible without the adaptive practices of livestock farmers that are not included in these balances. For example, Dantiandou livestock farmers address the forage deficit by organising the seasonal migration out of the commune of part of the livestock. During the rainy season, livestock is driven to pastoral areas 300-400 km further north, near the frontier with Mali (Turner et al., 2006). When they return at the time of the millet harvest, part of the herds are driven about 50 kilometres to the east in the neighbouring Dallol and, if necessary, some also go south at the end of the dry season (Brottem et al., 2014). The other solution is to supplement pasture with feed given to livestock in enclosures and resting and milking sites (Ayantunde et al., 2008). This feed is produced partly on the farm—millet bran, stems of cowpea, groundnut, Bambara groundnut and residues of roselle. Part of this is harvested in rangeland (Zornia glochidiata straw, millet straw, particularly appetible weeds such as Alysicarpus ovalifolius, Eragrostis tremula, Jacquemontia tamnifolia and acacia seed pods) and—more rarely—purchased on markets (bran, oilseed cake). It should be noted that the harvesting (or setting aside) of feed such as straw and stubble competes directly with grazing.

Forage balances and livestock productivity

26Do the differences in forage balances between Hombori and Dantiandou result in a difference in livestock productivity? Surveys of livestock farmers were performed at the two sites, focusing on the size and composition of flocks and herds, demographic parameters (deaths, losses, sales, births, purchase and gifts) and the reproduction parameters of females (age at first birth, reproduction career, age at disposal). These data are used in Dynmod, a matrix model of the dynamics of livestock populations (Lesnoff, 2010) to make a projection of flock and herd dynamics and production with the hypothesis of the maintaining of the initial structure of the herd or flock (steady state option). A single type of livestock farming—pastoral—was considered at Hombori, whereas at Dantiandou distinction is made between livestock farming by Peul families living in encampments and where numbers are greater and who practice more regional transhumance and the Djerma agro-livestock farmers living in the villages (Hiernaux and Turner, 2002). And in the latter case, cattle operations with fewer than 5 head are excluded from the analysis as they do not qualify as breeding operators and the simulation is therefore not suitable for judging their performance.

27Livestock numbers vary considerably (Table 5). They are higher in pastoral operations; then come crop and livestock operations and are limited to 5 small ruminants and 13 cattle in sedentary crop and livestock systems. Annual rates of disposal (sale/stock) are similar in the livestock systems and at the two sites: 10 to 13% for cattle and 30 to 33% for small ruminants. In contrast, the performances of livestock systems differ in their growth rate, with the best being those of the crop and pastoral systems at Dantiandou. Those of the Hombori pastoralists are very irregular and even negative for sheep and finally those of the sedentary crop and livestock farms of Dantiandou are very weak and close to the viability point (Lesnoff et al., 2012), confirming the farm trajectories described by several crop and livestock farmers (Bonnet and Guibert, 2014). Thus the forage advantage of Hombori livestock farming does not result in better performance. But management by agropastoralists, and especially the use of mobility, results in distinctly better performances than those of the crop and livestock farmers who live alongside them at Dantiandou. This finding calls into question the application of the concept of carrying capacity in the zoological sense as the viability of the livestock operation does not depend in a major manner at least on the rangeland used.

28Furthermore, the agreement between measurements of plant production on the rangeland at the two sites and estimates by satellite remote sensing confirms the increase in plant production on the Gourma rangeland over the last three decades and its decrease in the Fakara (Dardel et al., 2014 a; see Chapter 6). But this does not indisputably support the concept of ecological carrying capacity. Indeed, the regreening of the Gourma is explained is explained to a considerable degree by more abundant rainfall since the major droughts of the 1970s and 1980s and by the resilience of the vegetation in the sandy soils that are dominant in the landscape (Dardel et al., 2014 b). In contrast, the deterioration of plant cover in shallow soils on erosion glacis and rocky outcrops should continue after the years of drought (Hiernaux et al., 2009 b), causing a deep-seated change in the hydrologic system (Gardelle et al., 2010; see Chapter 9). The apparent degradation of the Dantiandou agro-ecosystem may be partly a result of the impact on the vegetation index of the increase in areas under millet at the expense of fallow (Hiernaux et al., 2015). The degradation of rangeland seen in the field would seem to have a negligible impact on the satellite index.

Table 5. The results of the Dynmod model simulating the dynamics of livestock populations (Lesnoff, 2010) for cattle, sheep and goats in pastoral livestock operations in Hombori (Mali), and agropastoral and crop and livestock farms at Dantiandou (Niger).

Table 5. The results of the Dynmod model simulating the dynamics of livestock populations (Lesnoff, 2010) for cattle, sheep and goats in pastoral livestock operations in Hombori (Mali), and agropastoral and crop and livestock farms at Dantiandou (Niger).

Conclusion: prospects for the development of livestock farming in the Sahel

29Can Sahelian livestock systems adapt to the rapid development of the market for livestock products accompanying the demographic and urban growth of the sub-region and to the globalisation of trade (Zoundi and Hitimana, 2008)? With the exception of poultry, the response is often expected from special livestock operations—fattening units and dairy farms—that are frequently in peri-urban zones and with close links to markets (Williams et al., 1999; Corniaux, 2005; Coulibaly, 2008; Sanogo, 2011). However, their productivity is restrained by access to high-quality forage and when they do not use grazing their viability depends on access to cattle feed and its cost.

30Part of their economic viability is linked with purchases at low prices and on a steady base of young animals—especially males—produced by pastoral rearing operations. But pastoral breeding has only limited capacity for increasing the production of young livestock because of the forage constraint. Availability, related to climatic events, is still irregular. Both local and regional pastoral mobility is the major adaptation used by breeders to variations in forage availability, but the latter is increasingly limited because of the spread of crops and infrastructure, the increased scarcity of qualified labour, risks of landholding legislation favouring private ownership at the expense of community land (Lavigne-Delville, 1998; Oxby, 2011) and increased civil insecurity (Bonnet, 2013). It is therefore urgent for all the sectors of livestock farming for water resources and grazing land to be made secure and for suitable infrastructure for education, health and communications to be developed in pastoral regions (Plateforme pastorale tchadienne, 2013).

Acknowledgements

31The authors are grateful to numerous persons for the data used to estimate forage availability and to document the livestock systems in the commune of Hombori (Mali) and that of Dantiandou (Niger). This work was carried out within the framework of the projects ‘Élevage, Climat et Société’ (Eclis, ANR-AA-VULNS-003) and ‘Changements environnementaux et sociaux en Afrique: passé, présent et futur’ (ESCAPE, ANR-10-CEPL-005) and the AMMA CATCH observation service.

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Table des illustrations

Légende Figure 1. Average composition by sex and age category of herds and flocks of graziers at Hombori, agropastoral farmers at Dantiandou, farmers and cattle rearers at Dantiandou (a single case of a herd of cattle of 5 animals or less). Livestock feeding young are shown as a separate category for Dantiandou.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-1.jpg
Fichier image/jpeg, 267k
Légende Figure 2. Average by type of substrate weighted by the relative areas of substrates and of herbaceous masses at the end of the growth season in the commune of Hombori and adjoining areas. Measurements were made at 12 pastoral locations that are the subject of long-term monitoring (AMMA-CATCH network).
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-2.jpg
Fichier image/jpeg, 83k
Légende Figure 3. Forage availability map for the commune of Hombori (Mali) at the end of the 2010 rainy season (kg DM/ha).Source: Diawara (2015)
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-3.jpg
Fichier image/jpeg, 271k
Légende Figure 4. a) Evolution of use for farming in the land (210 km2) of 12 villages in the commune of Dantiandou, Niger, from 2009 to 2011. b) Average annual forage by land use measured at 24 sites where plant cover and average available forage are recorded (kg DM)/ha.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-4.jpg
Fichier image/jpeg, 120k
Titre Table 1. Head of livestock counted once a month at drinking at some 20 waterpoints in the commune of Hombori. Monitoring from March 2010 to June 2011.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-5.jpg
Fichier image/jpeg, 165k
Légende Figure 5. Inter-annual variations of the annual herbaceous forage available, of the fraction that can be used by livestock, of the estimate of forage ingestion and of the ratio of ingestion to the usable forage in the territory of the commune of Hombori and the surrounding area from 2008 to 2011.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-6.jpg
Fichier image/jpeg, 109k
Légende Figure 6. Grazing intensity around pastoral waterpoints: rate of use of forage by livestock during the 2010-2011 dry season.Source: Diawara (2015)
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-7.jpg
Fichier image/jpeg, 114k
Titre Table 2. Sedentary livestock in 12 villages and encampments in the commune of Dantiandou in 2011, by species, sex and age category.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-8.jpg
Fichier image/jpeg, 190k
Titre Table 3. Unit weight standards for livestock by species, sex and age category and the corresponding average forage ingestion calculated using metabolic weight.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-9.jpg
Fichier image/jpeg, 148k
Titre Table 4. Estimated annual ingestion of forage by the resident livestock in 12 villages and encampments of the commune of Dantiandou. The proportion of herbaceous forage including millet straw is estimated separately.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-10.jpg
Fichier image/jpeg, 120k
Légende Figure 7. Estimated annual forage availability with the usable proportion and that ingested by livestock during an annual cycle (t dry matter) in the pastoral area of 12 villages in the commune of Dantiandou (210 km2) from 2009 to 2011. The curve of the ingested proportion of usable forage is shown in%.
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-11.jpg
Fichier image/jpeg, 98k
Titre Table 5. The results of the Dynmod model simulating the dynamics of livestock populations (Lesnoff, 2010) for cattle, sheep and goats in pastoral livestock operations in Hombori (Mali), and agropastoral and crop and livestock farms at Dantiandou (Niger).
URL http://books.openedition.org/irdeditions/docannexe/image/12346/img-12.jpg
Fichier image/jpeg, 186k

Auteurs

Agroecologist, Université Paul-Sabatier (Toulouse III)-Université de Bamako (Mali)

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