Livestock in sub-Saharan Africa is a major contributor to greenhouse gas emissions, particularly enteric methane (eCH4), with emissions intensities and yield often elevated. In this region, wet-season rangeland fodder is the primary feed source for livestock. This study evaluated the effects of fodder growth stage and feed allowance on feed intake, digestibility, average daily gain (ADG), feed conversion ratio (FCR), and eCH4 emissions in cattle. Over a 112-day period, including a 14-day adaptation and a 98-day data collection phase, ten Sudanese Fulani zebu bulls (52 ± 1.2 months of age, 195 ± 14.6 kg body weight) were fed green rangeland fodder. They were divided into two groups of five animals each: one received fodder at a high allowance level of 4.5% of body weight (BW) dry matter (DM) basis (4.5ING), while the other received 2.5% of BW (2.5ING). Voluntary intake, digestibility, and eCH4 (GreenFeed®) were measured daily across three fodder growth stages: vegetative stage (VeS), reproductive stage (ReS), and mature stage (MaS). ADG and FCR were assessed fortnightly. DM intake decreased progressively from VeS to MaS with the highest values recorded for 4.5ING (P<0.05). Digestibility was affected only by growth stage, decreasing from VeS to MaS (P<0.05). Both ADG and FCR were influenced by fodder growth stage and feed level. The lowest eCH4 yield and intensity were observed in VeS (P<0.05). Fodder level influenced eCH4 intensity (P<0.05). Intra-wet season fodder growth stage significantly affected intake, digestibility, growth, and eCH4 emissions in cattle, while feed allowance influenced performance and eCH4 intensity. Significant interactions effects were observed between fodder growth stage and feed allowance for all parameters except digestibility. The best animal performance, along with the lowest eCH4 yield and intensity were observed in 4.5ING animals during VeS. These findings suggest that optimizing feed availability at the beginning of the wet season is an effective feeding strategy to enhance productivity while mitigating methane emissions in extensive livestock systems.

Estimating the daily diet of grazing cattle from available feed resources in pastoral and mixed crop-livestock systems in tropical West Africa remains a challenge. The objective of this study was to describe the relevance of cattle diet monitoring across the seasons to better assess the livestock-resources interactions in its local environment in the region. We analyzed seasonal profiles of the diet of grazing cattle in five sites distributed along the Sudano-Sahelian climate gradient from an arid to a sub-humid bioclimate. In the five sites (ranked from the driest to the wettest: Widou, Dahra, Niakhar, Koumbia, Kolda), the feeding behavior of grazing cattle was monitored and feces were collected monthly for one year to estimate dietary intake and digestibility. All the conserved dry samples (n = 1,186) underwent near infrared spectroscopy (NIRS) analyses. The resulting spectral data were compared with a large set of spectral reference data (n=4,138) to predict dry matter intake (DMvi_Fnir DM; g.kgMW-1) and digestibility (dMO_Fnir,%OM) using an updated NIRS “local calibration” procedure. Daily fodder intake ranged from 38.90 ± 6.35 in the hot dry season to 83.86 ± 8.73 gDM.kgMW-1.d-1 in the late wet season. Estimated diet organic matter digestibility ranged from 53.6 ± 8.51% in the hot dry season to 74.3 ± 3.52% in the early wet season. Estimated by aggregation, the total annual intake of a tropical livestock unit (TLU, i.e. a standard 250 kg live weight animal) ranged from 1,236 ± 255 kgDM.TLU-1.year-1 in Dahra to 1,560 ± 142 kgDM.TLU-1.year-1 in Widou. This was well below the 2,281 Kg.DM annual estimate derived from a standard intake of 2.5% LW in DM. Taking digestibility into account, the summed annual metabolizable energy (ME) intake values ranged from 9,858 ± 2,077 Mj.TLU-1.year-1 in Dahra to 13,929 ± 2,345 Mj.TLU-1.year-1 in Koumbia. While important gaps appear during the dry season in some locations, this covered the annual basal maintenance requirements of a TLU, which, based on international standards, are estimated at 7,819 Mj.TLU-1.year-1 (21.4 Mj.day-1). This leaves ME at varying extend, to cover the needs for growth, milk production and reproduction. Tested in a GLM, the variations in in the dependent variables (the daily DM intake, diet digestibility, and ME intake) were analyzed in relation to the independent factors location (study site) and season, as well as their interaction. Results showed that, seasonal effects largely explained the observed variability across the five sites, while differences in herd management practices modulated these effects.

CONTEXT: Agricultural intensification to ensure food security and limit rural exodus is a major issue in subSaharan Africa. The potential of livestock farming to improve the sustainability of farming systems has been studied but rarely at the landscape level. However, because the herds move about in the landscape, thereby creating horizontal biomass and nutrient flows between plots and households, the landscape is the only level where all the interactions between the different components of the agroecosystem (animals, crops and trees) can be considered. OBJECTIVE: Our objective was to develop a methodology that uses territorial metabolism for multicriteria assessment of sustainability to compare contrasted livestock systems.METHODS: We compare two neighboring village terroirs in the former groundnut basin of Senegal. One village (Diohine), has kept a "traditional extensive system" based on fallow, free grazing and night corralling, while the other (Barry) uses a "modern semi-intensive system" based on livestock fattening in which the livestock is stall -fed with feed concentrate and crop residues. During the survey, village households were asked to describe their practices and to quantify biomass and nitrogen (N) flows to enable us to calculate sustainability indicators (productivity, balance, efficiency, dependency, profitability) at plot, household and village terroir levels.RESULTS AND CONCLUSIONS: At village terroir level, introducing livestock fattening increased the livestock stocking rate (0.96 TLU ha-1 in Diohine and 2.31 TLU ha-1 in Barry) and spreading of solid manure on crop fields (respectively 337 and 482 kgDM ha-1). Fattening livestock requires large imports of feed concentrate, 23.67 kgN ha-1 in Barry versus 3.39 kgN ha-1 in Diohine. The improved livestock productivity of fattening (+217 kgLW ha-1) produces higher financial returns (+432euro household-1 year-1) that enable the use of more mineral fertilizers (6.28 kgN ha-1 in Barry versus 1.09 kgN ha-1 in Diohine). The additional N inputs in Barry enable increased yields of the main staple crop (millet) (+101 kgDM ha-1). The population density of Barry village is +78% higher (320 capita km-2 in Barry versus 180 capita km-2 in Diohine). The village nitrogen balance (24.88 kgN ha-1 in Barry versus 8.51 kgN ha-1 in Diohine) and N use efficiencies (respectively 0.64 and 0.15) demonstrate that nutrient cycling and soil fertility management are more sustainable in Barry. SIGNIFICANCE: We propose a methodology to rebuild territorial metabolism from surveys. Territorial metabolism is used to calculate a set of multi-criteria sustainability indicators. This methodology will be particularly useful in sub-Saharan Africa where data on agricultural systems are lacking.

In Benin, adaptation to climate change in the livestock sector has led cattle farmers to develop different livestock practices. Most research has focused on evaluating the effects of these practices on livestock productivity. However, information on the effect of these practices on carbon (C) sequestration in farmland soils is lacking. Soil C sequestration has been identified as a potential strategy to offset greenhouse gas emissions. Thus, the present study aimed at filling this gap. The calculation was one hand based on inventory data obtained from literature sources (excrement production of each cattle category, moisture content of each crop, ratio of crop residue to main product, and C content of the main product and excrement) and on the other hand on activity data (cattle herd size, manure applied, land use area, crop yield, and crop residues management) obtained from surveys carried out among 360 cattle farmers belonging to 3 cattle farming types. The results revealed that whatever the cattle farming type, annual C input from manure was higher (p<0.05) than C input from crop residues. Annual C sequestration in farmland soil of farms integrating livestock with cereal-legume and forage crops was significantly higher (Type 2: 158.07 +/- 1.79 kg C ha(-1) year(-1)) followed by farms integrating livestock with cereal-legume crops (Type 1: 99.51 +/- 0.95 kg C ha(-1) year(-1)), which in turn had a higher value than farms practicing pastoral mobility (Type 3: 78.46 +/- 0.70 kg C ha(-1) year(-1)). These results highlight the potential for climate change mitigation through these farming practices. This is justified because the quantity of C sequestered in farmland soil of all cattle farming types was significant. Thus, for future research, it is necessary to include soil C sequestration in the calculations of farms' carbon footprint.

Previous long-term experiments conducted more than 10 years ago, showed that long-term application of organic fertilizer increased soil organic carbon (SOC) of grasslands. However, it was usually assumed that, independent of the successive additions of fertilizer, soils have an upper limit to their SOC due to the inability of the soil mineral phase to fix additional carbon. Andosols of the volcanic Reunion Island are typically very rich in carbon and are usually considered as saturated in SOC. To assess the long-term effect of different types of fertilization on SOC in these soils, SOC concentrations were recorded at yearly intervals for 15 years in one arenosol site and in two andosols sites across a topo-sequence. The types of fertilization tested included inorganic, organic, and a mix of inorganic and organic nutrient sources. The addition of organic fertilizers increased soil carbon in the top (0-15 cm) horizon in both the arenosol and the two andosols (up to +250% in the arenosol and up to +41% in the andosol), whereas inorganic fertilizers and the control treatment did not always result in a significant in-crease in SOC. After 15 years, no plateau was reached in C stocks even with the highest fertilization rates. Our results suggest that the increase in SOC was mainly caused by direct carbon inputs, while the effect of the in-crease in litter resulting from the increase in yield caused by fertilization, remained uncertain. In the andosol, all the fertilization treatments led to higher concentrations of carbon in the deeper layers. This suggests that SOC inputs lead to downward migration of OC to deep horizons. For C-rich soils like andosols, assessing the variations in carbon in the deep horizon is thus critical in estimating the effects of soil management on carbon sequestration.

Since the discovery in the early 1950s of fixation of industrial atmospheric nitrogen through physico-chemical processes, mineral fertilisation has become the main means of fertilising cultivated land. However, several studies have shown that continued use of mineral fertilisers can accelerate soil acidification and reduce cation exchange capacity, water-holding capacity, and soil microbial activity, thereby reducing soil fertility. Other studies have underlined the importance of a nutrient balanced fertilisation protocol to sustain high grass yields. On the other hand, by recycling livestock manure, the use of organic fertiliser has been shown to lead to high soil productivity and to provide economic and environmental benefits to farmers. Our study focused on the short-and long-term effects of several types of fertilisers, (mineral, organic, and mixed organic-mineral), and several doses (ranging from 440 to 1,260kgN/ha/year) in a 15-year experiment on highly productive grassland. We showed that, in contrast to organic fertilisation, although the mineral treatments maintained soil nitrogen content, these treatments did not increase phosphorous and potassium concentrations, and in addition, led to soil acidification. Furthermore, although mineral fertilisation led to rapid increases in grass yield, its fertilisation effect weakened over time whereas some of the organic fertilisation treatments resulted in a gradual increase in grass yields. Significant differences in grassland productivity were observed between the effects of liquid manure and compost, liquid manure being more immediately effective while compost had a longer-term positive effect on grass yield. The mixed organic-mineral treatments were shown to be a good compromise, with a significant short-term increase in grass yields plus sustained grass production over time.

In Northern Senegal, traditional cattle management systems (TRAD) which depend on natural forages coexist with intensified systems (INT) which rely on periodic supplementation with crop residues and local concentrates. This study aims to estimate the effects of seasons and management systems on the methane emissions of Gobra zebu, in relation to the diet’s chemical composition and feed intake. Six Gobra zebu cows per management system were individually monitored over 10 months, diet and faeces were sampled each season and their chemical composition and dry matter intake (DMI) were predicted by near infrared spectroscopy. Each diet was fermented in vitro to assess methane production and volatile fatty acid concentration. The DMI and digestible organic matter intake (DOMI) decreased (P < 0.0001) during the dry seasons for both systems in the same range, but INT improved the crude protein of the diets (P < 0.0001). Enteric methane production (mmol.g−1 dry matter) was lower for TRAD than INT, except during the rainy season when TRAD cows experienced a higher increase (P = 0.002). The methanogenic potential (methane production in vitro × DMI) varied with the seasons and the system with more accentuated variations for TRAD (P < 0.0001). Methanogenic potential shows true reflection of the effects of the seasons and management systems. The results highlight that enteric methane emissions varied with seasonal changes and that intensifying the diet induced no mitigating effect.

Long-term organic fertilizer (OF) application on agricultural soils is known to induce soil Cu and Zn contamination, along with pH and organic matter changes, which in turn alter the soil Cu and Zn availability. Our study was aimed at assessing Cu and Zn availability in long-term OF-amended soils by distinguishing the importance of increased contamination levels versus pH and organic matter changes in soil. Seventy-four soil samples were collected over time from fields corresponding to three soil types upon which no, mineral, or organic fertilization had been applied over a decade, and thus exhibited a gradient of Cu and Zn contamination, pH, and organic matter concentration. Soil Cu and Zn contamination (i.e. total and DTPA-extractable Cu and Zn concentration), soil solution chemistry (i.e. pH and dissolved organic matter concentration and aromaticity) and Cu and Zn availability (i.e. total concentration and free ionic activity in solution and DGT-available concentration in soil) levels were measured. The Windermere humic aqueous model (WHAM) was used to estimate Zn2+ activity and dissolved organic matter (DOM) binding properties in soil solution. Regardless of the soil type, organic fertilization increased Cu and Zn contamination in soil, in addition to the pH and the DOM concentration, aromaticity and binding properties in soil solution. The pH increase prompted a decrease in the total Zn concentration and Zn2+ activity in soil solution. The concomitant pH increase and DOM concentration, aromaticity and binding properties boosted the total Cu concentration but decreased the Cu2+ activity in soil solution. DGT-available Cu and Zn varied very little between the three fertilization modalities. Our results suggest that pH and DOM changes were able to regulate Cu and Zn availability in long-term OF amended soils by exerting a protective effect that offset the concomitant increase in soil Cu and Zn contamination.

Agriculture development in sub-Saharan Africa is characterized by two important tendencies: (1) a strong degradation of the natural forage resources exploited by pastoralism due to excess and uncontrolled stocking density linked to increasing demographic pressure and (2) development and intensification of arable cropping sectors within large irrigated perimeters based on mono-cropping systems directly linked with market pressure but leading to important negative impacts on environments. In between these two systems, there is space for development of more integrated crop-livestock systems based on a network of smallholder farms and susceptible to profit from synergies provided by diversification of production systems. The development of a local dairy production along the Senegal River, based on milk collection from a network of poor smallholder producers, is a relevant example of the accuracy of such a local integration across specialized sectors. The development of a pivotal forage resource based on alfalfa associated with arable cropping system should allow strong local synergies for (1) improving nutrition quality of local peoples by both nutritional complement production with leaf extracts and local dairy industry expansion and (2) improving agronomic and environmental performances of arable cropping systems. But beyond the technological, agronomic, and environmental benefits potentially provided by this integrated system, the socioeconomic conditions for its emergence and adoption have to be analyzed and promoted, which require further important studies.

Au Sahel, l’elevage pastoral valorise un milieu extreme. Alors qu’il est accuse d’emettre trop de gaz a effet de serre par kilogramme de lait ou de viande produit, une recherche menee au Senegal montre que les territoires pastoraux peuvent en realite avoir un bilan carbone neutre : les emissions d’origine animale sont compensees par la sequestration de carbone dans les sols et la vegetation. Ces resultats ont ete obtenus par une methode d’evaluation originale, dite ecosystemique : elle integre l’utilisation du territoire pastoral dans son ensemble, en fonction des saisons et des lieux investis par les troupeaux. Ces resultats incitent a revoir a la baisse les normes actuelles de calcul du comportement alimentaire et des emissions de methane issu de la digestion des ruminants. D’autres implications sont envisageables, comme ameliorer le bilan carbone par des pratiques locales specifiques et valoriser ces espaces sur le marche du carbone. Preserver ce mode d’elevage est aussi une des voies pour generer du developpement et contribuer a securiser ces regions.

Version française de l'article In the Sahel, pastoralism capitalises on an extreme environment. Although it is accused of producing excessive amounts of greenhouse gases per kilogram of milk or meat produced, a research study conducted in Senegal shows that pastoral landscapes can actually have a neutral carbon balance: emissions from animals are offset by carbon sequestration in soils and plants. These findings were obtained using an original evaluation method, known as ecosystem assessment, which integrates the use of the pastoral landscape as a whole, according to the seasons and the areas grazed by herds. These findings indicate that current standards for calculating feeding behaviour and methane emissions from ruminant digestion need to be revised downwards. Other implications are possible, such as improving the carbon balance through specific local practices and promoting these areas on the carbon market. Preserving this livestock system is also one way of fostering development and ensuring greater security in these regions.

Domestic species such as cattle (Bos taurus taurus and B. t. indicus) represent attractive biological models to characterize the genetic basis of short-term evolutionary response to climate pressure induced by their post-domestication history. Here, using newly generated dense SNP genotyping data, we assessed the structuring of genetic diversity of 21 autochtonous cattle breeds from the whole Mediterranean basin and performed genome-wide association analyses with covariables discriminating the different Mediterranean climate subtypes. This provided insights into both the demographic and adaptive histories of Mediterranean cattle. In particular, a detailed functional annotation of genes surrounding variants associated with climate variations highlighted several biological functions involved in Mediterranean climate adaptation such as thermotolerance, UV protection, pathogen resistance or metabolism with strong candidate genes identified (e.g., NDUFB3, FBN1, METTL3, LEF1, ANTXR2 and TCF7). Accordingly, our results suggest that main selective pressures affecting cattle in Mediterranean area may have been related to variation in heat and UV exposure, in food resources availability and in exposure to pathogens, such as anthrax bacteria (Bacillus anthracis). Furthermore, the observed contribution of the three main bovine ancestries (indicine, European and African taurine) in these different populations suggested that adaptation to local climate conditions may have either relied on standing genomic variation of taurine origin, or adaptive introgression from indicine origin, depending on the local breed origins. Taken together, our results highlight the genetic uniqueness of local Mediterranean cattle breeds and strongly support conservation of these populations.

This paper explores an original approach in which greenhouse gas (GHG) emissions and carbon (C) accumulation are assessed monthly and at landscape scale to account for the highly seasonal monsoon climate and the mobility of pastoral herds that characterize West African pastoral ecosystems. The study was conducted in northern Senegal, in the service area of the Widou Thiengoly borehole, a circular zone of 706 km(2) centered on the borehole. The C balance was calculated using an ecosystem approach, i.e. taking all main sources of GHG emissions and C sinks of the ecosystem, not only anthropogenic sources, into account. The annual C balance of the pastoral ecosystem was -0.04 +/- 0.01 tC-eq.ha(-1).year(-1), showing that total GHG emissions were mitigated by C accumulation in trees, soil and livestock. The C balance varied considerably with the seasons, with a positive monthly balance in the wet season, from July to October (+ 0.58 tC-eq.ha(-1).month(-1)) and a negative monthly balance in the cold dry season from November to February and the hot dry season from March to June (- 0.57 and -0.05 tC-eq.ha(-1).month(-1) respectively). Care should be taken when generalizing these results, which were obtained in a dry year, because of strong inter-annual variations in rainfall.

Ruminant livestock systems are significant sources of greenhouse gases (GHG). Livestock farming in regions with extreme climatic events have to face both scarcity and variability in feed resources. Herd mobility is a known major adaptation strategy to address seasonal availability of forage resources: it allows an increase in herd size, thereby improving labor productivity. The present study quantifies enteric methane (CH4) emissions from French Mediterranean sheep farming systems, focusing on the use of diversified pastoral feed resources, and developing a calculator (Diversity of feed REsources and Enteric Methane emissions, DREEM). The DREEM calculator was developed to estimate at the animal level enteric CH4 emissions (g/day) from empirical equations and be subsequently integrated, as a sub-table, into an economic and GHG (kg/year) balance model (Outil de Simulation du TRoupeau ovin ALaitant, OSTRAL) at the whole farm level. Several equations were taken from the literature to estimate enteric CH4 emissions in DREEM calculator. Nature of forage and feed, animal feeding levels and performance were referenced according to the animal feeding system and tables in France and taking into account the French Mediterranean area studied. DREEM was used to estimate enteric CH4 emissions from four sheep farming systems covering the main contrasting mobility and situations, from sedentary to highly mobile pastoral systems, in the French Mediterranean area. At the individual level, enteric CH4 emissions (g/ day) of ewes in the sedentary system were slightly higher than those of ewes in other systems. These differences were due mainly to differences in animal feeding level (intake / body weight) and feed resources characteristics. Overall, enteric CH4 emissions of ewes and rams were slightly lower than French national inventory estimates. When enteric CH4 emissions of lambs were expressed in g/kg of carcass, were lower in the less pastoral farming systems than in the other systems, because lambs' average daily gains were higher. In double transhuming farming systems, lambs late slaughtering age led to lamb's CH4 contribution of 15% vs 2-5% in the other systems. Flock management, which depends on land use and ownership, greatly contributed to these results.

Le recyclage de la biomasse végétale et animale joue un rôle central dans le fonctionnement des systèmes agro-sylvopastoraux. En Afrique de l’Ouest, la variabilité des précipitations impacte les pratiques de gestion de cette biomasse pour nourrir les hommes, le bétail, le sol et les plantes. Cette étude décrit un modèle d’action conceptuel basé sur des règles ≪ si-alors-sinon » qui représentent les décisions de gestion de la biomasse des ménages agricoles. L’étude souligne les conséquences en cascade d’un aléa pluviométrique sur le calendrier des activités agricoles, les quantités et la nature des biomasses mobilisées. Les activités les plus directement impactées sont le semis et la récolte des cultures, l’alimentation animale et, indirectement, la fertilisation des sols et la gestion des stocks alimentaires. Le modèle d’action regroupe les principales règles et modalités de gestion constituant les pratiques des ménages agricoles. Il est défini pour quatre types de ménages agriculture-élevage selon leurs activités dominantes : agricultureversusélevage et vivrierversusvente. Les ménages vivriers et élevage sont plus sensibles aux variations pluviométriques. Ils présentent une gestion plus adaptative car ils sont davantage dépendants de leur propre production. Ce modèle d’action a été conçu en vue de son intégration dans un modèle à base d’agents pour simuler les conséquences de l’aléa pluviométrique sur les flux de biomasses résultant des interactions entre les ménages agricoles d’une communauté villageoise en Afrique de l’Ouest.

The feeding behavior and fodder intake of cattle, sheep and goats grazing semi-arid sub-Saharan Africa rangelands in Senegal was studied over a one-year cycle. The objective of the study was to improve the assessment of fodder intake by livestock grazing rangelands in semi-arid sub-Saharan Africa, The study was conducted in the service area of a borehole that includes 354 pastoral settlements and a total of 11,000 cattle and 1800 small ruminants. The grazing behavior of five steers was monitored monthly. Their forage intake was estimated every month from hand plucking simulations of all the bites of forage taken by the steers 24 h out of 48. The feces they excreted during the day were collected in fecal bags. Near infrared spectrum (NIRS) images were used to analyze 80 samples of these feces, and the data were then added to an existing reference data set to predict fodder intake and digestibility using NIBS. The complete and contextualized data base was then used to predict the daily fodder intake and its digestibility by cattle, sheep and goats whose fresh feces were systematically and randomly sampled every month in the study area (768 samples). Annual means of the daily dry matter fodder intake were 68.4 +/- 6.4 g/kg LW0.75 or 17.2 +/- 1.7 g/kg LW for cattle, 73.1 +/- 5.3 g/kg LW07.5 or 34.3 +/- 2.8 g/kg LW for sheep, and 74.7 +/- 8.7 g/kg LW0.75 or 37.1 +/- 4.4 g/kg LW for goats. The annual mean organic matter digestibility of grazed fodder was higher for goats (67.4 +/- 3.9%) than for sheep (64.1 +/- 3.2%) and cattle (59.3 +/- 3.8%). The seasonal variations in diet digestibility were bigger for cattle than for sheep, and smaller for goats. The standard reference used to assess livestock fodder intake in tropical Africa relies on a fixed daily intake rate per unit live weight of 25 g/kg LW. Our results show that this method overestimates (+ 45%) intake by cattle, especially in the dry season, and underestimates intake by small ruminants (-24%). Alternative assessment methods are proposed either relying on a single standard annual intake per metabolic weight unit for all ruminant species, 73 g/kg LW0.75 per day, or on separate annual intake norms per live weight unit for cattle (18 g/kg LW per day) and small ruminants (34 g/kg LW per day). In both cases, modulations (+/- 12%) of the norm are proposed for use in the wet and dry season.

Greenhouse gas (GHG) emissions from the surface soils and surface water receiving animal excreta may be important components of the GHG balance of terrestrial ecosystems, but the associated processes are poorly documented in tropical environments, especially in tropical arid and semi-arid areas. A typical sylvo-pastoral landscape in the semi-arid zone of Senegal, West Africa, was investigated in this study. The study area (706 kmA(2) of managed pastoral land) was a circular zone with a radius of 15 km centered on a borehole used to water livestock. The landscape supports a stocking rate ranging from 0.11 to 0.39 tropical livestock units per hectare depending on the seasonal movements of the livestock. Six landscape units were investigated (land in the vicinity of the borehole, natural ponds, natural rangelands, forest plantations, settlements, and enclosed plots). Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes were measured with static chambers set up at 13 sites covering the six landscape units, and the 13 sites are assumed to be representative of the spatial heterogeneity of the emissions. A total of 216 fluxes were measured during the one-year study period (May 2014 to April 2015). At the landscape level, soils and surface water emitted an average 19.8 t C-CO2 eq/(hm(2).a) (CO2: 82%, N2O: 15%, and CH4: 3%), but detailed results revealed notable spatial heterogeneity of GHG emissions. CO2 fluxes ranged from 1148.2 (+/- 91.6) mg/(m(2).d) in rangelands to 97,980.2 (+/- 14,861.7) mg/(m(2).d) in surface water in the vicinity of the borehole. N2O fluxes ranged from 0.6 (+/- 0.1) mg/(m(2).d) in forest plantations to 22.6 (+/- 10.8) mg/(m(2).d) in the vicinity of the borehole. CH4 fluxes ranged from-3.2 (+/- 0.3) mg/(m(2).d) in forest plantations to 8788.5 (+/- 2295.9) mg/(m(2).d) from surface water in the vicinity of the borehole. This study identified GHG emission "hot spots" in the landscape. Emissions from the surface soils were significantly higher in the landscape units most frequently used by the animals, i.e., in the vicinity of the borehole and settlements; and emissions measured from surface water in the vicinity of the borehole and from natural ponds were on average about 10 times higher than soil emissions.

Pastoral farming systems have always adapted to the seasonal availability of forage resources and climate variability by moving animals. However, the role of animal mobility as a possible mitigating strategy in response to climate change has not been clearly documented. To understand this role, we investigated (i) the major methodological challenges linked to the diversity of grazing areas and other forage resources exploited by these systems and enteric emissions of methane; (ii) the impacts of grazing practices (carbon sequestration/emission) on soil and biomass carbon fluxes. We developed an approach based on two existing models (OSTRAL: Outil de Simulation du TRoupeau ovin ALlaitant and CASA: Carnegie Ames Stanford Approach) that we adapted and used in combination. This approach was applied to three French Mediterranean sheep and crop farming systems with different degrees of flock mobility (sedentary, single transhumance and double transhumance). The preliminary results produced by the whole farm model OSTRAL showed that two systems (sedentary and double transhumance) causing low carbon emissions. In the sedentary system, higher animal productivity offsets the increase in GHG emissions (in CO(2)eq) caused by feed production. In the pastoral system, grazing reduced total GHG emissions (in CO(2)eq). The CASA model proved to be useful to simulate the carbon balance under dynamic land cover in natural environments, whether used for grazing or not. This model can help assess the impact of grazing practices and carbon fluxes in systems linked to natural environments. The results of the first application showed that seasonal mobility of livestock increases the contribution of rangeland to feeding systems and improves the non-renewable energy balance of the system. It is thus extremely important to include the specificities of animals grazing in rangelands outside the structural limits of the farm when evaluating GHG emissions.