The designations employed and the presentation of material in this information product do not imp... more The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) or Biovision Foundation for Ecological Development concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO or Biovision in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO or Biovisioin.
The pan-African Great Green Wall (GGW) is an initiative that was initially meant to involve the p... more The pan-African Great Green Wall (GGW) is an initiative that was initially meant to involve the planting of a 15 km wide transcontinental forest belt running from Dakar to Djibouti. This major project is designed to combat desertifi cation. The band of vegetation is to be as continuous as possible, but it may be rerouted if necessary to skirt around obstacles (streams, rocky areas, mountains) or to link inhabited areas (see grandemurailleverte.org).
The Paris Agreement calls on parties to undertake ambitious efforts to combat climate change by e... more The Paris Agreement calls on parties to undertake ambitious efforts to combat climate change by engaging in appropriate policies and measures as put forward through Nationally Determined Contributions (NDCs), to strengthen transparency when reporting their greenhouse gas (GHG) emissions and to increase their mitigation contributions to climate action from 2020. It also calls for regular and transparent monitoring and reporting of the GHG emissions and on the NDCs implementation efforts. Biomass fires significantly affect the GHG atmospheric balance, with fire emissions representing more than 5% of total emissions from agriculture, forestry, and other land use (AFOLU), according to recent estimates produced by the Food and Agriculture Organization (FAO). We update previously published Tier 1 estimates of GHG emissions in FAOSTAT-which had been used in the IPCC AR5 analysis-by using new burned area activity data from the Moderate Resolution Imaging Spectroradiometer (MODIS) known as MCD64A1, Collection 6. The previous FAOSTAT estimates had used as input the Global Fire Emission Database v.4 (GFED4) burned area product, based on older MODIS Collection 5.1 burned area product. In line with differences between the input data used, the new FAOSTAT estimates indicate roughly 30% higher fire emissions globally than previously published. Our analysis also confirms that the FAOSTAT Tier 1 approach produces fire emissions estimates that are comparable to those computed at Tier 3 by GFED, and thus represent a useful complementary tool in support of country GHG reporting.
Adoption of no-till management on croplands has become a controversial approach for storing carbo... more Adoption of no-till management on croplands has become a controversial approach for storing carbon in soil due to conflicting findings. Yet, no-till is still promoted as a management practice to stabilize the global climate system from additional change due to anthropogenic greenhouse gas emissions, including the 4 per mille initiative promoted through the UN Framework Convention on Climate Change. We evaluated the body of literature surrounding this practice, and found that SOC storage can be higher under no-till management in some soil types and climatic conditions even with redistribution of SOC, and contribute to reducing net greenhouse gas emissions. However, uncertainties tend to be large, which may make this approach less attractive as a contributor to stabilize the climate system compared to other options. Consequently, no-till may be better viewed as a method for reducing soil erosion, adapting to climate change, and ensuring food security, while any increase in SOC storage...
Soil provides ecosystem services, supports human health and habitation, stores carbon and regulat... more Soil provides ecosystem services, supports human health and habitation, stores carbon and regulates emissions of greenhouse gases. Unprecedented pressures on soil from degradation and urbanization are threatening agroecological balances and food security. It is important that we learn more about soil to sustainably manage and preserve it for future generations. To this end, we developed and analyzed a global soil visible-near infrared (vis-NIR) spectral library. It is currently the largest and most diverse database of its kind. We show that the information encoded in the spectra can describe soil composition and be associated to land cover and its global Earth-Science Reviews 155 (2016) 198-230
HAL (Le Centre pour la Communication Scientifique Directe), 2006
Soils represent a large carbon pool, approximately 1500 Gt, which is equivalent to almost three t... more Soils represent a large carbon pool, approximately 1500 Gt, which is equivalent to almost three times the quantity stored in terrestrial biomass and twice the amount stored in the atmosphere. Any modification of land use or land management can induce variations in soil carbon stocks, even in agricultural systems that are perceived to be in a steady state. Tillage practices often induce soil aerobic conditions that are favourable to microbial activity and may lead to a degradation of soil structure. As a result, mineralisation of soil organic matter increases in the long term. The adoption of no-tillage systems and the maintenance of a permanent vegetation cover using Direct seeding Mulch-based Cropping system or DMC, may increase carbon levels in the topsoil. In Brazil, no-tillage practices (mainly DMC), were introduced approximately 30 years ago in the south in the Paraná state, primarily as a means of reducing erosion. Subsequently, research has begun to study the management of the crop waste products and their effects on soil fertility, either in terms of phosphorus management, as a means of controlling soil acidity, or determining how manures can be applied in a more localised manner. The spread of no-till in Brazil has involved a large amount of extension work. The area under no-tillage is still increasing in the centre and north of the country and currently occupies ca. 20 million hectares, covering a diversity of environmental conditions, cropping systems and management practices. Most studies of Brazilian soils give rates of carbon storage in the top 40 cm of the soil of 0.4 to 1.7 t C ha-1 per year, with the highest rates in the Cerrado region. However, caution must be taken when analysing DMC systems in terms of carbon sequestration. Comparisons should include changes in trace gas fluxes and should not be limited to a consideration of carbon storage in the soil alone if the full implications for global warming are to be assessed. no-tillage / mulch / stocks / fluxes / greenhouse gas / Brazil
The designations employed and the presentation of material in this information product do not imp... more The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO.
What challenges for the South? A After being excluded, agriculture is gradually gaining a positio... more What challenges for the South? A After being excluded, agriculture is gradually gaining a position in climate policy negotiations. The IPCC Fifth Assessment Report assessed the potential reduction of GHG at between 20 and 60% in land-based sectors (agriculture, forestry and other land use) by 2030. The challenge to the sector is enormous. Greenhouse gas emission must be reduced in agriculture. The latter must also adapt to climate change while responding to food security imperatives. According to the FAO, agricultural production should at least double by 2050 to match population growth.
Quels défis pour le Sud ? A près en avoir été exclue, l’agriculture se fait progressivement une p... more Quels défis pour le Sud ? A près en avoir été exclue, l’agriculture se fait progressivement une place dans les négociations sur les politiques climatiques. Le 5e rapport du Giec a évalué entre 20 et 60 % le potentiel de réduction des émissions de GES par le « secteur des terres » (agriculture, forêt et sols) d’ici 2030. Le défi posé au secteur est gigantesque. L’agriculture doit réduire ses émissions de gaz à effet de serre. Elle doit aussi s’adapter au changement climatique, tout en répondant aux impératifs de sécurité alimentaire. Or, selon la FAO, la production agricole devrait au moins doubler d’ici 2050 pour faire face à la croissance démographique.
In the current context of climate change, oil palm plantations are much criticized because they r... more In the current context of climate change, oil palm plantations are much criticized because they replace large areas of tropical forests. In Benin Republic, located in the Sudano-Guinean region, smallholder's oil palm plantations do not replace forests but old and unproductive croplands. In some of these palm plantations, pruned leaves from the palm trees are deposited to the soil for recycling. A study was conducted in southeastern Benin to evaluate the effect of the input of pruned leaves on soil carbon sequestration in smallholders' plantations. The study area is characterized by a mean annual precipitation in the range 1300-1400 mm. Soils are slightly desaturated ferralsols. Young palm plantations (4-6 year-old), pre-adults (7-12 year-old) and adults (13-20 year-old) were selected. In the young plantations, the leaves pruning is not occurring yet. In the pre-adults and adults plantations, the leaves have been cut down and recycled during respectively 4 years and 10 years,...
Land degradation and regeneration are complex processes that greatly impact climate regulation, e... more Land degradation and regeneration are complex processes that greatly impact climate regulation, ecosystem service provision, and population well‐being and require an urgent and appropriate response through land use planning and interventions. Spatially explicit land change models can greatly help decision makers, but traditional regression approaches fail to capture the nonlinearity and complex interactions of the underlying drivers. Our objective was to use a machine learning algorithm combined with high‐resolution data sets to provide simultaneous and spatial forecasts of deforestation, land degradation, and regeneration for the next two decades. A 17,000‐km2 region in the south of Madagascar was taken as the study area. First, an empirical analysis of drivers of change was conducted, and then, an ensemble model was calibrated to predict and map potential changes based on 12 potential explanatory variables. These potential change maps were used to draw three scenarios of land chan...
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Agriculture, and the patterns of land use change that are associated with it, have a high environ... more Agriculture, and the patterns of land use change that are associated with it, have a high environmental footprint and contribute to climate change, as the sector accounts for about one-quarter of anthropogenic greenhouse gas (GHG) emissions globally. However, improved land management practices can play an important role in mitigating GHG emissions by removing substantial volumes of carbon from the atmosphere and sequestering them in soils and plant tissues. We can't fix what we do not measure, which is why quantifying greenhouse gas emissions is a necessary step for climate-smart agriculture and sustainable land management. Greenhouse gas accounting can provide the numbers and data that are important to decision making in adopting less carbon-intensive practices, guiding low-emissions development, assessing product supply chains, certifying sustainable agriculture practices, and informing consumers on the carbon footprint of their choices. This Quick Guidance on Greenhouse Gas Accounting for Sustainable Land Management provides an overview of SLM activities subject to greenhouse gas appraisal, guidance in the selection of tools, data needs for the application and final use of the greenhouse gas accounting tools It complements the more comprehensive Carbon Accounting Tools for Sustainable Land Management report, and it is targeted at leading resource managers and project developers to proficiency in the independent use of greenhouse gas accounting tools.
Greenhouse gas (GHG) emissions from the surface soils and surface water receiving animal excreta ... more 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 km² 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 (CO 2), nitrous oxide (N 2 O) and methane (CH 4) 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-CO 2 eq/(hm²•a) (CO 2 : 82%, N 2 O: 15%, and CH 4 : 3%), but detailed results revealed notable spatial heterogeneity of GHG emissions. CO 2 fluxes ranged from 1148.2 (±91.6) mg/(m²•d) in rangelands to 97,980.2 (±14,861.7) mg/(m²•d) in surface water in the vicinity of the borehole. N 2 O fluxes ranged from 0.6 (±0.1) mg/(m²•d) in forest plantations to 22.6 (±10.8) mg/(m²•d) in the vicinity of the borehole. CH 4 fluxes ranged from-3.2 (±0.3) mg/(m²•d) in forest plantations to 8788.5 (±2295.9) mg/(m²•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.
Abstract In the context of climate change, studies have focused on the temperature dependence of ... more Abstract In the context of climate change, studies have focused on the temperature dependence of soil CO 2 emissions. Although calcareous soils cover over 30% of the earth's land surface, few studies have considered calcareous soils where soil inorganic carbon (SIC) makes the analysis of the C fluxes at the soil to air interface more complex. This study tested how temperature could affect the contributions of soil organic carbon (SOC) and SIC to the CO 2 emitted from a calcareous soil. The soil pH, CO 2 emissions and δ 13 C signatures of CO 2 were measured after soil incubations at 4 temperatures (20 °C, 30 °C, 40 °C and 50 °C). The CO 2 emissions and the δ 13 C signature of the emitted CO 2 increased with temperature. The proportion of SIC-derived CO 2 in these emissions seemed to be stimulated by temperature. Three processes were discussed: (1) isotopic fractionations, (2) temperature impacts on SIC- and SOC-derived CO 2 , and (3) isotope exchanges between SIC- and SOC-derived CO 2 . The use of δ 13 C signature analysis to determine the contribution of SIC and SOC to the total CO 2 emissions from soil is not straightforward. An increase in the SIC signature of emitted CO 2 does not directly imply an increase in SIC as a source of CO 2.
Increasing soil organic matter (SOM) is of primary importance for maintaining soil fertility and ... more Increasing soil organic matter (SOM) is of primary importance for maintaining soil fertility and mitigating climate change. Leaving crop residues on top of soil is not always an efficient means of increasing SOM because (i) of the high mineralization of the crop residues, (ii) crop residues may increase the mineralization of existing SOM (priming effect) and (iii) wetting-drying cycles may increase mineralization of SOM and crop residues. Little research has been carried out into these mechanisms under Sudano-Sahelian conditions where the rainfall is mostly irregular with wetting-drying cycles during the transition between the wet and the dry season. To evaluate the effect of wetting-drying cycles on the mineralization of SOM and crop residues and the priming effect, an agricultural soil from the North Region of Cameroon with or without (controls) 13 C-labeled rice straw amendment as crop residues was either subjected to five wetting-drying cycles or maintained at constant water potential after a single rewetting event. Soil samples were incubated for 70 days at 28°C and the CO 2 and 13 CO 2 emissions and mineral N were monitored. Adding straw (+833 μg C g −1 soil) increased the cumulative CO 2 emissions from the soil (+921 μg C-CO 2 g −1soil). A positive priming effect was observed (+92 μg C-CO 2 g −1 soil). Only the first wetting cycle created a mineralization flush of the SOM and the straw. This flush did not recur probably because of a lack of labile SOM. However an extra addition of straw after 28 days increased CO 2 emissions but did not result in further mineralization flushes after re-wetting while SOM mineralization was not limited by N availability. We conclude that SOM depletion under Sudano-Sahelian conditions was not explained by SOM mineralization enhancement due to multiple rewetting events or to priming effect following crop residues addition. Indeed, SOM depletion could rather be explained by a high level of mineralization of both, SOM and crop residues, when the soil reached its water retention capacity.
Aims This study evaluated a framework for modelling the continuous exchange of carbon (C) between... more Aims This study evaluated a framework for modelling the continuous exchange of carbon (C) between the atmosphere, plants, humus, and microorganisms, proposing a plant C model coupled to MOMOS, an existing microbial C model. Methods C data were collected on low fertility cereallegume cropping systems. Plant C and microbial C were modelled simultaneously and the growth parameters of plants and nitrogen-fixing microorganisms were fitted to the data. Results All C exchanges were successfully predicted using the same weather correction for plant and microbial processes. Most of the photosynthetic production was allocated to the roots, reducing yields. The C losses were found modelled mainly by root respiration for cereals, probably as an energy source for nutrient explorings, and by root mortality for legumes as a growth source for decomposers and symbiotic nodules. The effect of root-nodule activity on shoot growth was found non-linear. The system was modelled as a sink of 4.2 Mg C ha-1 year −1 in the soil's labile C reserve. Conclusions This paper coordinates theoretical bases for modelling the processes regulating plant productivity associated with plant C losses. The tool appears to be robust and is now available for calculating the essential parameters of agro-ecology and climate change.
21èmes Rencontres autour de la Recherche sur les Ruminants (Journées 3R), Paris, France, 3 et 4 décembre 2014, 2014
RESUME Les systèmes pâturant extensifs d'Afrique sub-saharienne sont responsables de hauts niveau... more RESUME Les systèmes pâturant extensifs d'Afrique sub-saharienne sont responsables de hauts niveaux d'émissions de Gaz à effet de Serre (GES) par unité de produits animaux, dû à la faible productivité du bétail et à des rations fortement méthanogènes. Ce travail propose un bilan GES original à l'échelle d'un écosystème sylvo-pastoral caractérisé par un élevage extensif de bovins, d'ovins et de caprins dans la zone semi-aride au nord du Sénégal, au Ferlo. Les principales sources d'émission sont la fermentation entérique (56%) et la déposition de fèces des ruminants (18%). Le feu et les termites sont également d'importantes sources d'émissions. Ils représentent à eux deux environ 20% des émissions. Le bilan GES ramené au kg de produit est de 39,6 kg eq.CO2/kg de poids vif et 9,8 kg eq.CO2/kg de lait corrigé en protéines et matières grasses (FPCM) pour les bovins et environ 15,8 kg eq.CO2/kg de poids vif et 7,7 kg eq.CO2/kg FPCM (Fat and Protein Corrected Milk) pour les petits ruminants. Si l'on tient compte de l'accumulation annuelle de carbone (C) dans le sol et les arbres, l'écosystème présente globalement un bilan GES net négatif de-0,1 t.eq.CO2/ha/an. Autrement dit, les émissions liées au troupeau sont compensées par la séquestration de carbone dans l'écosystème pris dans son ensemble.
The designations employed and the presentation of material in this information product do not imp... more The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) or Biovision Foundation for Ecological Development concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO or Biovision in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO or Biovisioin.
The pan-African Great Green Wall (GGW) is an initiative that was initially meant to involve the p... more The pan-African Great Green Wall (GGW) is an initiative that was initially meant to involve the planting of a 15 km wide transcontinental forest belt running from Dakar to Djibouti. This major project is designed to combat desertifi cation. The band of vegetation is to be as continuous as possible, but it may be rerouted if necessary to skirt around obstacles (streams, rocky areas, mountains) or to link inhabited areas (see grandemurailleverte.org).
The Paris Agreement calls on parties to undertake ambitious efforts to combat climate change by e... more The Paris Agreement calls on parties to undertake ambitious efforts to combat climate change by engaging in appropriate policies and measures as put forward through Nationally Determined Contributions (NDCs), to strengthen transparency when reporting their greenhouse gas (GHG) emissions and to increase their mitigation contributions to climate action from 2020. It also calls for regular and transparent monitoring and reporting of the GHG emissions and on the NDCs implementation efforts. Biomass fires significantly affect the GHG atmospheric balance, with fire emissions representing more than 5% of total emissions from agriculture, forestry, and other land use (AFOLU), according to recent estimates produced by the Food and Agriculture Organization (FAO). We update previously published Tier 1 estimates of GHG emissions in FAOSTAT-which had been used in the IPCC AR5 analysis-by using new burned area activity data from the Moderate Resolution Imaging Spectroradiometer (MODIS) known as MCD64A1, Collection 6. The previous FAOSTAT estimates had used as input the Global Fire Emission Database v.4 (GFED4) burned area product, based on older MODIS Collection 5.1 burned area product. In line with differences between the input data used, the new FAOSTAT estimates indicate roughly 30% higher fire emissions globally than previously published. Our analysis also confirms that the FAOSTAT Tier 1 approach produces fire emissions estimates that are comparable to those computed at Tier 3 by GFED, and thus represent a useful complementary tool in support of country GHG reporting.
Adoption of no-till management on croplands has become a controversial approach for storing carbo... more Adoption of no-till management on croplands has become a controversial approach for storing carbon in soil due to conflicting findings. Yet, no-till is still promoted as a management practice to stabilize the global climate system from additional change due to anthropogenic greenhouse gas emissions, including the 4 per mille initiative promoted through the UN Framework Convention on Climate Change. We evaluated the body of literature surrounding this practice, and found that SOC storage can be higher under no-till management in some soil types and climatic conditions even with redistribution of SOC, and contribute to reducing net greenhouse gas emissions. However, uncertainties tend to be large, which may make this approach less attractive as a contributor to stabilize the climate system compared to other options. Consequently, no-till may be better viewed as a method for reducing soil erosion, adapting to climate change, and ensuring food security, while any increase in SOC storage...
Soil provides ecosystem services, supports human health and habitation, stores carbon and regulat... more Soil provides ecosystem services, supports human health and habitation, stores carbon and regulates emissions of greenhouse gases. Unprecedented pressures on soil from degradation and urbanization are threatening agroecological balances and food security. It is important that we learn more about soil to sustainably manage and preserve it for future generations. To this end, we developed and analyzed a global soil visible-near infrared (vis-NIR) spectral library. It is currently the largest and most diverse database of its kind. We show that the information encoded in the spectra can describe soil composition and be associated to land cover and its global Earth-Science Reviews 155 (2016) 198-230
HAL (Le Centre pour la Communication Scientifique Directe), 2006
Soils represent a large carbon pool, approximately 1500 Gt, which is equivalent to almost three t... more Soils represent a large carbon pool, approximately 1500 Gt, which is equivalent to almost three times the quantity stored in terrestrial biomass and twice the amount stored in the atmosphere. Any modification of land use or land management can induce variations in soil carbon stocks, even in agricultural systems that are perceived to be in a steady state. Tillage practices often induce soil aerobic conditions that are favourable to microbial activity and may lead to a degradation of soil structure. As a result, mineralisation of soil organic matter increases in the long term. The adoption of no-tillage systems and the maintenance of a permanent vegetation cover using Direct seeding Mulch-based Cropping system or DMC, may increase carbon levels in the topsoil. In Brazil, no-tillage practices (mainly DMC), were introduced approximately 30 years ago in the south in the Paraná state, primarily as a means of reducing erosion. Subsequently, research has begun to study the management of the crop waste products and their effects on soil fertility, either in terms of phosphorus management, as a means of controlling soil acidity, or determining how manures can be applied in a more localised manner. The spread of no-till in Brazil has involved a large amount of extension work. The area under no-tillage is still increasing in the centre and north of the country and currently occupies ca. 20 million hectares, covering a diversity of environmental conditions, cropping systems and management practices. Most studies of Brazilian soils give rates of carbon storage in the top 40 cm of the soil of 0.4 to 1.7 t C ha-1 per year, with the highest rates in the Cerrado region. However, caution must be taken when analysing DMC systems in terms of carbon sequestration. Comparisons should include changes in trace gas fluxes and should not be limited to a consideration of carbon storage in the soil alone if the full implications for global warming are to be assessed. no-tillage / mulch / stocks / fluxes / greenhouse gas / Brazil
The designations employed and the presentation of material in this information product do not imp... more The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO.
What challenges for the South? A After being excluded, agriculture is gradually gaining a positio... more What challenges for the South? A After being excluded, agriculture is gradually gaining a position in climate policy negotiations. The IPCC Fifth Assessment Report assessed the potential reduction of GHG at between 20 and 60% in land-based sectors (agriculture, forestry and other land use) by 2030. The challenge to the sector is enormous. Greenhouse gas emission must be reduced in agriculture. The latter must also adapt to climate change while responding to food security imperatives. According to the FAO, agricultural production should at least double by 2050 to match population growth.
Quels défis pour le Sud ? A près en avoir été exclue, l’agriculture se fait progressivement une p... more Quels défis pour le Sud ? A près en avoir été exclue, l’agriculture se fait progressivement une place dans les négociations sur les politiques climatiques. Le 5e rapport du Giec a évalué entre 20 et 60 % le potentiel de réduction des émissions de GES par le « secteur des terres » (agriculture, forêt et sols) d’ici 2030. Le défi posé au secteur est gigantesque. L’agriculture doit réduire ses émissions de gaz à effet de serre. Elle doit aussi s’adapter au changement climatique, tout en répondant aux impératifs de sécurité alimentaire. Or, selon la FAO, la production agricole devrait au moins doubler d’ici 2050 pour faire face à la croissance démographique.
In the current context of climate change, oil palm plantations are much criticized because they r... more In the current context of climate change, oil palm plantations are much criticized because they replace large areas of tropical forests. In Benin Republic, located in the Sudano-Guinean region, smallholder's oil palm plantations do not replace forests but old and unproductive croplands. In some of these palm plantations, pruned leaves from the palm trees are deposited to the soil for recycling. A study was conducted in southeastern Benin to evaluate the effect of the input of pruned leaves on soil carbon sequestration in smallholders' plantations. The study area is characterized by a mean annual precipitation in the range 1300-1400 mm. Soils are slightly desaturated ferralsols. Young palm plantations (4-6 year-old), pre-adults (7-12 year-old) and adults (13-20 year-old) were selected. In the young plantations, the leaves pruning is not occurring yet. In the pre-adults and adults plantations, the leaves have been cut down and recycled during respectively 4 years and 10 years,...
Land degradation and regeneration are complex processes that greatly impact climate regulation, e... more Land degradation and regeneration are complex processes that greatly impact climate regulation, ecosystem service provision, and population well‐being and require an urgent and appropriate response through land use planning and interventions. Spatially explicit land change models can greatly help decision makers, but traditional regression approaches fail to capture the nonlinearity and complex interactions of the underlying drivers. Our objective was to use a machine learning algorithm combined with high‐resolution data sets to provide simultaneous and spatial forecasts of deforestation, land degradation, and regeneration for the next two decades. A 17,000‐km2 region in the south of Madagascar was taken as the study area. First, an empirical analysis of drivers of change was conducted, and then, an ensemble model was calibrated to predict and map potential changes based on 12 potential explanatory variables. These potential change maps were used to draw three scenarios of land chan...
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Agriculture, and the patterns of land use change that are associated with it, have a high environ... more Agriculture, and the patterns of land use change that are associated with it, have a high environmental footprint and contribute to climate change, as the sector accounts for about one-quarter of anthropogenic greenhouse gas (GHG) emissions globally. However, improved land management practices can play an important role in mitigating GHG emissions by removing substantial volumes of carbon from the atmosphere and sequestering them in soils and plant tissues. We can't fix what we do not measure, which is why quantifying greenhouse gas emissions is a necessary step for climate-smart agriculture and sustainable land management. Greenhouse gas accounting can provide the numbers and data that are important to decision making in adopting less carbon-intensive practices, guiding low-emissions development, assessing product supply chains, certifying sustainable agriculture practices, and informing consumers on the carbon footprint of their choices. This Quick Guidance on Greenhouse Gas Accounting for Sustainable Land Management provides an overview of SLM activities subject to greenhouse gas appraisal, guidance in the selection of tools, data needs for the application and final use of the greenhouse gas accounting tools It complements the more comprehensive Carbon Accounting Tools for Sustainable Land Management report, and it is targeted at leading resource managers and project developers to proficiency in the independent use of greenhouse gas accounting tools.
Greenhouse gas (GHG) emissions from the surface soils and surface water receiving animal excreta ... more 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 km² 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 (CO 2), nitrous oxide (N 2 O) and methane (CH 4) 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-CO 2 eq/(hm²•a) (CO 2 : 82%, N 2 O: 15%, and CH 4 : 3%), but detailed results revealed notable spatial heterogeneity of GHG emissions. CO 2 fluxes ranged from 1148.2 (±91.6) mg/(m²•d) in rangelands to 97,980.2 (±14,861.7) mg/(m²•d) in surface water in the vicinity of the borehole. N 2 O fluxes ranged from 0.6 (±0.1) mg/(m²•d) in forest plantations to 22.6 (±10.8) mg/(m²•d) in the vicinity of the borehole. CH 4 fluxes ranged from-3.2 (±0.3) mg/(m²•d) in forest plantations to 8788.5 (±2295.9) mg/(m²•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.
Abstract In the context of climate change, studies have focused on the temperature dependence of ... more Abstract In the context of climate change, studies have focused on the temperature dependence of soil CO 2 emissions. Although calcareous soils cover over 30% of the earth's land surface, few studies have considered calcareous soils where soil inorganic carbon (SIC) makes the analysis of the C fluxes at the soil to air interface more complex. This study tested how temperature could affect the contributions of soil organic carbon (SOC) and SIC to the CO 2 emitted from a calcareous soil. The soil pH, CO 2 emissions and δ 13 C signatures of CO 2 were measured after soil incubations at 4 temperatures (20 °C, 30 °C, 40 °C and 50 °C). The CO 2 emissions and the δ 13 C signature of the emitted CO 2 increased with temperature. The proportion of SIC-derived CO 2 in these emissions seemed to be stimulated by temperature. Three processes were discussed: (1) isotopic fractionations, (2) temperature impacts on SIC- and SOC-derived CO 2 , and (3) isotope exchanges between SIC- and SOC-derived CO 2 . The use of δ 13 C signature analysis to determine the contribution of SIC and SOC to the total CO 2 emissions from soil is not straightforward. An increase in the SIC signature of emitted CO 2 does not directly imply an increase in SIC as a source of CO 2.
Increasing soil organic matter (SOM) is of primary importance for maintaining soil fertility and ... more Increasing soil organic matter (SOM) is of primary importance for maintaining soil fertility and mitigating climate change. Leaving crop residues on top of soil is not always an efficient means of increasing SOM because (i) of the high mineralization of the crop residues, (ii) crop residues may increase the mineralization of existing SOM (priming effect) and (iii) wetting-drying cycles may increase mineralization of SOM and crop residues. Little research has been carried out into these mechanisms under Sudano-Sahelian conditions where the rainfall is mostly irregular with wetting-drying cycles during the transition between the wet and the dry season. To evaluate the effect of wetting-drying cycles on the mineralization of SOM and crop residues and the priming effect, an agricultural soil from the North Region of Cameroon with or without (controls) 13 C-labeled rice straw amendment as crop residues was either subjected to five wetting-drying cycles or maintained at constant water potential after a single rewetting event. Soil samples were incubated for 70 days at 28°C and the CO 2 and 13 CO 2 emissions and mineral N were monitored. Adding straw (+833 μg C g −1 soil) increased the cumulative CO 2 emissions from the soil (+921 μg C-CO 2 g −1soil). A positive priming effect was observed (+92 μg C-CO 2 g −1 soil). Only the first wetting cycle created a mineralization flush of the SOM and the straw. This flush did not recur probably because of a lack of labile SOM. However an extra addition of straw after 28 days increased CO 2 emissions but did not result in further mineralization flushes after re-wetting while SOM mineralization was not limited by N availability. We conclude that SOM depletion under Sudano-Sahelian conditions was not explained by SOM mineralization enhancement due to multiple rewetting events or to priming effect following crop residues addition. Indeed, SOM depletion could rather be explained by a high level of mineralization of both, SOM and crop residues, when the soil reached its water retention capacity.
Aims This study evaluated a framework for modelling the continuous exchange of carbon (C) between... more Aims This study evaluated a framework for modelling the continuous exchange of carbon (C) between the atmosphere, plants, humus, and microorganisms, proposing a plant C model coupled to MOMOS, an existing microbial C model. Methods C data were collected on low fertility cereallegume cropping systems. Plant C and microbial C were modelled simultaneously and the growth parameters of plants and nitrogen-fixing microorganisms were fitted to the data. Results All C exchanges were successfully predicted using the same weather correction for plant and microbial processes. Most of the photosynthetic production was allocated to the roots, reducing yields. The C losses were found modelled mainly by root respiration for cereals, probably as an energy source for nutrient explorings, and by root mortality for legumes as a growth source for decomposers and symbiotic nodules. The effect of root-nodule activity on shoot growth was found non-linear. The system was modelled as a sink of 4.2 Mg C ha-1 year −1 in the soil's labile C reserve. Conclusions This paper coordinates theoretical bases for modelling the processes regulating plant productivity associated with plant C losses. The tool appears to be robust and is now available for calculating the essential parameters of agro-ecology and climate change.
21èmes Rencontres autour de la Recherche sur les Ruminants (Journées 3R), Paris, France, 3 et 4 décembre 2014, 2014
RESUME Les systèmes pâturant extensifs d'Afrique sub-saharienne sont responsables de hauts niveau... more RESUME Les systèmes pâturant extensifs d'Afrique sub-saharienne sont responsables de hauts niveaux d'émissions de Gaz à effet de Serre (GES) par unité de produits animaux, dû à la faible productivité du bétail et à des rations fortement méthanogènes. Ce travail propose un bilan GES original à l'échelle d'un écosystème sylvo-pastoral caractérisé par un élevage extensif de bovins, d'ovins et de caprins dans la zone semi-aride au nord du Sénégal, au Ferlo. Les principales sources d'émission sont la fermentation entérique (56%) et la déposition de fèces des ruminants (18%). Le feu et les termites sont également d'importantes sources d'émissions. Ils représentent à eux deux environ 20% des émissions. Le bilan GES ramené au kg de produit est de 39,6 kg eq.CO2/kg de poids vif et 9,8 kg eq.CO2/kg de lait corrigé en protéines et matières grasses (FPCM) pour les bovins et environ 15,8 kg eq.CO2/kg de poids vif et 7,7 kg eq.CO2/kg FPCM (Fat and Protein Corrected Milk) pour les petits ruminants. Si l'on tient compte de l'accumulation annuelle de carbone (C) dans le sol et les arbres, l'écosystème présente globalement un bilan GES net négatif de-0,1 t.eq.CO2/ha/an. Autrement dit, les émissions liées au troupeau sont compensées par la séquestration de carbone dans l'écosystème pris dans son ensemble.
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Papers by Martial Bernoux