Innovative agronomic practices for sustainable intensification in sub-Saharan Africa. A review

Africa's need to double food production and feed the burgeoning human population, without compromising its natural resource base, has raised the momentum for sustainable agricultural intensification on the continent. Many studies describe agronomic practices that can increase productivity on existing agricultural land without damaging the environment and without increasing the agricultural carbon footprint. However, there is limited information on specific practices with the greatest potential to contribute to sustainable intensification on smallholder farms in sub-Saharan Africa, while simultaneously keeping the carbon footprint low. The objectives of this review were to (1) identify good agronomic practices with potential for contributing to sustainable intensification across sub-Saharan Africa, (2) synthesize available information on benefits and synergies from these technologies, and (3) discuss bottlenecks in their adoption in order to obtain insights that inform the formulation of supportive policies. Agroforestry, cereal-legume intercropping, conservation agriculture, doubled-up legume cropping, fertilizer micro-dosing, planting basins, and push-pull technology were identified as key agronomic innovations widely promoted in sub-Saharan Africa. We show that these innovations can build synergies and increase resource use efficiency while reducing agricultural carbon footprint. We outline the benefits, trade-offs, and limitations of these practices and discuss their potential role in strengthening food sovereignty and climate change adaptation and mitigation

Contribution au Recensement des Plantes Médicinales au Togo : Cas de la Région Maritime

The ethnobotany survey conducted in nine markets of Togo maritime region leads to identification of 106 medicinal species in 61 families and 97 genera, including 90 dicotyledons, 6 monocotyledons, and one fern. These different species are used in the treatment of 63 pathologies, of which malaria and Gynecologic disorders are the most common. This vast array of therapeutic indications shows the important role that plants play in medical terms. The infusion and decoction appear as the most used methods of the traditional therapists. Several parts of plants fall into these different preparations. The leaves are the most used. These results of ethnobotanical survey will allow a possible orientation in the choice of target plants for given pathologies and the search for new molecules that are more active. L’enquête ethnobotanique menée sur neuf marchés de la région maritime du Togo a permis de recenser 106 espèces médicinales regroupées en 61 familles et 97 genres, dont 90 dicotylédones, 6 monocotylédones et une fougère. Ces différentes espèces interviennent dans le traitement de 63 pathologies, le paludisme et les troubles gynécologiques étant les plus fréquentes. Cette grande panoplie d’indications thérapeutiques montre le rôle important que les plantes jouent sur le plan médical. L’infusion et la décoction apparaissent comme les modes de préparation les plus utilisés par les tradithérapeutes. Plusieurs parties des plantes entrent dans ces différentes préparations. Les feuilles sont les plus utilisées. Ces résultats d’enquêtes ethnobotaniques pourront permettre une orientation éventuelle dans le choix des plantes cibles pour des pathologies données et la recherche de nouvelles molécules plus actives

Pantropical variability in tree crown allometry

Aim Tree crowns determine light interception, carbon and water exchange. Thus, understanding the factors causing tree crown allometry to vary at the tree and stand level matters greatly for the development of future vegetation modelling and for the calibration of remote sensing products. Nevertheless, we know little about large‐scale variation and determinants in tropical tree crown allometry. In this study, we explored the continental variation in scaling exponents of site‐specific crown allometry and assessed their relationships with environmental and stand‐level variables in the tropics. Location Global tropics. Time period Early 21st century. Major taxa studied Woody plants. Methods Using a dataset of 87,737 trees distributed among 245 forest and savanna sites across the tropics, we fitted site‐specific allometric relationships between crown dimensions (crown depth, diameter and volume) and stem diameter using power‐law models. Stand‐level and environmental drivers of crown allometric relationships were assessed at pantropical and continental scales. Results The scaling exponents of allometric relationships between stem diameter and crown dimensions were higher in savannas than in forests. We identified that continental crown models were better than pantropical crown models and that continental differences in crown allometric relationships were driven by both stand‐level (wood density) and environmental (precipitation, cation exchange capacity and soil texture) variables for both tropical biomes. For a given diameter, forest trees from Asia and savanna trees from Australia had smaller crown dimensions than trees in Africa and America, with crown volumes for some Asian forest trees being smaller than those of trees in African forests. Main conclusions Our results provide new insight into geographical variability, with large continental differences in tropical tree crown allometry that were driven by stand‐level and environmental variables. They have implications for the assessment of ecosystem function and for the monitoring of woody biomass by remote sensing techniques in the global tropics

Predicting the Potential Impact of Climate Change on Carbon Stock in Semi-Arid West African Savannas

West African savannas are experiencing rapid land cover change that threatens biodiversity and affects ecosystem productivity through the loss of habitat and biomass, and carbon emissions into the atmosphere exacerbating climate change effects. Therefore, reducing carbon emissions from deforestation and forest degradation in these areas is critical in the efforts to combat climate change. For such restorative actions to be successful, they must be grounded on a clear knowledge of the extent to which climate change affects carbon storage in soil and biomass according to different land uses. The current study was undertaken in semi-arid savannas in Dano, southwestern Burkina Faso, with the threefold objective of: (i) identifying the main land use and land cover categories (LULCc) in a watershed; (ii) assessing the carbon stocks (biomass and soil) in the selected LULCc; and (iii) predicting the effects of climate change on the spatial distribution of the carbon stock. Dendrometric data (Diameter at Breast Height (DBH) and height) of woody species and soil samples were measured and collected, respectively, in 43 plots, each measuring 50 × 20 m. Tree biomass carbon stocks were calculated using allometric equations while soil organic carbon (SOC) stocks were measured at two depths (0–20 and 20–50 cm). To assess the impact of climate change on carbon stocks, geographical location records of carbon stocks, remote sensing spectral bands, topographic data, and bioclimatic variables were used. For projections of future climatic conditions, predictions from two climate models (MPI-ESM-MR and HadGEM2-ES) of CMIP5 were used under Representative Concentration Pathway (RCP) 8.5 and modeling was performed using random forest regression. Results showed that the most dominant LULCc are cropland (37.2%) and tree savannas (35.51%). Carbon stocks in woody biomass were higher in woodland (10.2 ± 6.4 Mg·ha−1) and gallery forests (7.75 ± 4.05 Mg·ha−1), while the lowest values were recorded in shrub savannas (0.9 ± 1.2 Mg·ha−1) and tree savannas (1.6 ± 0.6 Mg·ha−1). The highest SOC stock was recorded in gallery forests (30.2 ± 15.6 Mg·ha−1) and the lowest in the cropland (14.9 ± 5.7 Mg·ha−1). Based on modeling results, it appears clearly that climate change might have an impact on carbon stock at horizon 2070 by decreasing the storage capacity of various land units which are currently suitable. The decrease was more important under HadGEM2-ES (90.0%) and less under MPI-ESM-MR (89.4%). These findings call for smart and sustainable land use management practices in the study area to unlock the potential of these landscapes to sequestering carbon

Burkina Faso – Land, climate, energy, agriculture and development: A study in the Sudano-Sahel Initiative for Regional Development, Jobs, and Food Security

In this working paper, the biophysical factors and socio-economic conditions that led to Land Use and Land Cover Changes (LULC) and land degradation in Burkina Faso are reviewed. It is found that the country is densely populated and population continues to rise at a rate of more than 3% a year. However, nearly half of the population still lives below the poverty line. The electrification relies heavily on fossil fuels as the country has limited hydropower potential and solar energy received little investment. The rate of electrification is still very low, triggering the use of other sources of energy derived from firewood in rural areas. In addition, Burkina Faso has experienced land degradation in the North as a consequence of the 1970s and 1980s droughts that struck all the Sahel. Subsequently, migration took place from the degraded areas to the central, western and southern regions of the country causing further LULC changes. Furthermore, the country suffers from the effects of climate change and climate variability through increasing temperature trends, highly variable precipitation regimes and intensification of extreme events. Projected changes reveal prevailing conditions that indicate an increased risk of disasters in the agriculture, water and health sectors, among others. Due to this situation, some technological responses and policy actions have been developed for sustainable land management and climate change adaptation and mitigation. The adopted technological approaches include, among others, irrigation expansion and efficiency, rainwater harvesting, crop diversification, adoption of drought-tolerant crop varieties and rotational grazing. Some policies have been put in place to facilitate the adoption of these technologies. They consist of carbon trading, land-use zoning and integrated landscape planning, payment for ecosystem services, providing access to markets and agricultural advisory services, securing land tenure and empowering women. These actions are part of broader programs and investment plans that include, but not limited to, the Strategic Framework for Poverty Reduction (SFPR), the Strategy for Accelerated Growth and Sustainable Development (SCADD), the National Rural Sector Program (PNSR), the Resilience and Support Plan for Vulnerable Population (RSPVP) and the Cereals Price Stabilization Program (CPSP) among others

Identification of driving factors of land degradation and deforestation in the Wildlife Reserve of Bontioli (Burkina Faso, West Africa)

In Africa, protected areas can play an important role in mitigating the effects of climate change through carbon sequestration but they are threatened due to increasing land degradation and deforestation (LDD). The Total Wildlife Reserve of Bontioli (TWRB) in Burkina Faso is one of the country’s refuges with high biodiversity. This reserve is seriously threatened by human activities, and little information is available about the on-site causes of degradation extent. This study was carried out to investigate drivers and extent of LDD in the TWRB. Household surveys, focus group discussions and field observations were used to identify socio-economic factors that influence land use and land cover (LULC) changes. The socio-economic data were analyzed using rankings and binary logistic regression techniques. Logistic regression model was used to establish the relationship between socio-economic drivers and land cover change. Remote sensing and GIS techniques were used to analyze land use and LULC changes over 29 years, employing Landsat images of 1984, 2001 and 2013. We performed a supervised classification based on the maximum likelihood algorithm to derive vegetation maps. The results revealed significant (p <0.05) LULC change from one class of LULC to another. From 1984 to 2001, tree savannas, bare soils and agricultural lands increased by 17.55%, 18.79% and 21778.79%, respectively, while woodland, gallery forest, shrub savannas and water bodies decreased by 22.02%, 5.03%, 40.08% and 31.2%, respectively. From 2001 to 2013, gallery forests decreased by 14.33%, tree savannas by 22.30% and shrub savannas by 5.14%, while agricultural lands increased by 167.87% and woodlands by 3.21%. LDD occurred at a higher rate in areas bordering the reserve compared to the core-protected area and the inaccessible areas. Agricultural expansion and wood cutting activities were the main direct causes of LDD. Extensive land utilization for agriculture is a major threat to the conservation of biodiversity in this reserve. The research highlighted the soundness of GIS and remote sensing practical application to assess vegetation change extent in Burkina Faso. Understanding the signal extent of vegetation change is particularly important to support efforts by policy makers to halt or at least to slow down the deforestation in the country. There is a need to control the immediate causes of LULC dynamics by limiting agricultural land expansion and wood cutting in the study area

Predicting the Potential Impact of Climate Change on Carbon Stock in Semi-Arid West African Savannas

West African savannas are experiencing rapid land cover change that threatens biodiversity and affects ecosystem productivity through the loss of habitat and biomass, and carbon emissions into the atmosphere exacerbating climate change effects. Therefore, reducing carbon emissions from deforestation and forest degradation in these areas is critical in the efforts to combat climate change. For such restorative actions to be successful, they must be grounded on a clear knowledge of the extent to which climate change affects carbon storage in soil and biomass according to different land uses. The current study was undertaken in semi-arid savannas in Dano, southwestern Burkina Faso, with the threefold objective of: (i) identifying the main land use and land cover categories (LULCc) in a watershed; (ii) assessing the carbon stocks (biomass and soil) in the selected LULCc; and (iii) predicting the effects of climate change on the spatial distribution of the carbon stock. Dendrometric data (Diameter at Breast Height (DBH) and height) of woody species and soil samples were measured and collected, respectively, in 43 plots, each measuring 50 &times; 20 m. Tree biomass carbon stocks were calculated using allometric equations while soil organic carbon (SOC) stocks were measured at two depths (0&ndash;20 and 20&ndash;50 cm). To assess the impact of climate change on carbon stocks, geographical location records of carbon stocks, remote sensing spectral bands, topographic data, and bioclimatic variables were used. For projections of future climatic conditions, predictions from two climate models (MPI-ESM-MR and HadGEM2-ES) of CMIP5 were used under Representative Concentration Pathway (RCP) 8.5 and modeling was performed using random forest regression. Results showed that the most dominant LULCc are cropland (37.2%) and tree savannas (35.51%). Carbon stocks in woody biomass were higher in woodland (10.2 &plusmn; 6.4 Mg&middot;ha&minus;1) and gallery forests (7.75 &plusmn; 4.05 Mg&middot;ha&minus;1), while the lowest values were recorded in shrub savannas (0.9 &plusmn; 1.2 Mg&middot;ha&minus;1) and tree savannas (1.6 &plusmn; 0.6 Mg&middot;ha&minus;1). The highest SOC stock was recorded in gallery forests (30.2 &plusmn; 15.6 Mg&middot;ha&minus;1) and the lowest in the cropland (14.9 &plusmn; 5.7 Mg&middot;ha&minus;1). Based on modeling results, it appears clearly that climate change might have an impact on carbon stock at horizon 2070 by decreasing the storage capacity of various land units which are currently suitable. The decrease was more important under HadGEM2-ES (90.0%) and less under MPI-ESM-MR (89.4%). These findings call for smart and sustainable land use management practices in the study area to unlock the potential of these landscapes to sequestering carbon

Soil Health Changes Over a 25-Year Chronosequence From Forest to Plantations in Rubber Tree (Hevea brasiliensis) Landscapes in Southern Côte d'Ivoire: Do Earthworms Play a Role?

The agro-ecological drawbacks of the spread of rubber tree plantations in Côte d'Ivoire since the 1990's are obvious even though they have not been properly investigated. They consist of biodiversity loss, land degradation and food insecurity, which have extended into the existing cocoa-led degraded areas whose rehabilitation have unfortunately not started. This situation increases not only the threat on soil health status but also undermines the capability of soils to deliver ecosystem services that are key to sustainable agricultural production. The current study took advantage of a chronosequence in rubber tree landscapes to assess soil health deterioration in general and possibly earthworm-mediated role in soil health changes. The hypothesis underpinning this study was that earthworms contribute to mitigate soil health deterioration in rubber-dominated landscapes due to their key role in soil functioning. This study confirmed that the conversion of forest to rubber tree plantations significantly impaired all soil biological, physical, and chemical parameters at the beginning (7 years) of the chronosequence; followed further by a restorative trend taking place beneath the plantations from 12 years. However, this study failed to find evidence of a direct role of earthworms in soil health rehabilitation over time. Mesoscale studies along with the use of appropriate models could help unravel this “black box” and shed some light on the contribution of earthworms as key soil ecosystem engineers

Analyse spatiale des différentes formes de pressions anthropiques dans la réserve de faune de l’Oti-Mandouri (Togo)

La présente étude a permis de relever dans 126 placeaux 116 espèces ligneuses (dbh ≥ 10 cm) réparties en 84 genres et 33 familles. Les familles les plus représentées sont les Rubiaceae, les Mimosaceae et les Combretaceae. Cette aire protégée est soumise à de fortes pressions dues à l’influence des populations dont les principales sont : les installations liées aux activités agricoles et pastorales, le prélèvement illégal du bois, les feux de brousse. Eu égard à l’adoption de la nouvelle méthode de gestion, la réserve de l’Oti-Mandouri devrait être préservée au maximum pour ce qui reste, car sa proximité avec le complexe d’aires protégées appelé WAP (Parc W au Niger, le parc Arly au Burkina Faso et la réserve de biosphère de Pendjari au Bénin) laisse ouverte la possibilité d’un repeuplement ultérieur naturel depuis ces zones et la possibilité de maintenir un corridor vers le parc national d’Oti-Kéran.This study was carried out in 126 plots. 116 woody species (dbh ≥ 10 cm) were identified, including 84 genera and 33 families. The Rubiaceae, Combretaceae and Mimosaceae are the most represented families. This protected area is subject to strong human pressures, including agricultural and pastoral activities, the illegal harvesting of timber, brush fires. The new management rules should aim to preserve to the maximum the Oti-Mandouri natural reserve. Its proximity to the WAP complex leaves open the possibility of a) a subsequent natural repopulation and b) maintaining a corridor to the Oti- Keran national Park