Climate change to severely impact West African basin scale irrigation in 2 °C and 1.5 °C global warming scenarios

Abstract West Africa is in general limited to rainfed agriculture. It lacks irrigation opportunities and technologies that are applied in many economically developed nations. A warming climate along with an increasing population and wealth has the potential to further strain the region’s potential to meet future food needs. In this study, we investigate West Africa’s hydrological potential to increase agricultural productivity through the implementation of large-scale water storage and irrigation. A 23-member ensemble of Regional Climate Models is applied to assess changes in hydrologically relevant variables under 2 °C and 1.5 °C global warming scenarios according to the UNFCCC 2015 Conference of Parties (COP 21) agreement. Changes in crop water demand, irrigation water need, water availability and the difference between water availability and irrigation water needs, here referred as basin potential, are presented for ten major river basins covering entire West Africa. Under the 2 °C scenario, crop water demand and irrigation water needs are projected to substantially increase with the largest changes in the Sahel and Gulf of Guinea respectively. At the same time, irrigation potential, which is directly controlled by the climate, is projected to decrease even in regions where water availability increases. This indicates that West African river basins will likely face severe freshwater shortages thus limiting sustainable agriculture. We conclude a general decline in the basin-scale irrigation potential in the event of large-scale irrigation development under 2 °C global warming. Reducing the warming to 1.5 °C decreases these impacts by as much as 50%, suggesting that the region of West Africa clearly benefits from efforts of enhanced mitigation

Grain legumes and dryland cereals contribute to carbon sequestration in the drylands of Africa and South Asia

Grain legumes and drylands cereals including chickpea (Cicer arietinum), common bean (Phaseolus vulgaris), cowpea (Vigna unguiculata), groundnut (Arachis hypogaea), lentil (Lens culinaris), pigeon pea (Cajanus cajan), soybean (Glycine max), finger millet (Eleusine coracana), pearl millet (Pennisetum glaucum) and sorghum (Sorghum bicolor) are the leading sources of food grain in drylands of Africa and South Asia. These crops can help smallholder agriculture to become more resilient, productive, and profitable, but their quantitative impact on carbon sequestration is unknown. The aim of this review study was to quantify their contribution to carbon sequestration across the drylands of Africa and South Asia based on 437 publications with 1319 observations in studies conducted across 32 countries. Cropping systems with grain legumes showed the greatest increase in soil organic carbon (SOC) concentrations, while cereals (and pigeon pea) gave the largest amount of aboveground carbon stock (>2 Mg C ha 1). Estimated carbon stock in post-harvest residues of these crops was 1.51 +/- 0.05 Mg C ha 1 in Africa and 2.29 +/- 0.10 Mg C ha 1 in South Asia. These crops produced more aboveground carbon, and significantly increased SOC, when grown as intercrops. Soils with low initial SOC (32%) showed the greatest potential for carbon sequestration when cropped with grain legumes and dryland cereals. This study is the first of its kind to provide evidence that grain legumes and drylands cereals improve carbon sequestration across Africa and South Asia

Climate change to severely impact West African basin scale irrigation in 2 °C and 1.5 °C global warming scenarios

Abstract West Africa is in general limited to rainfed agriculture. It lacks irrigation opportunities and technologies that are applied in many economically developed nations. A warming climate along with an increasing population and wealth has the potential to further strain the region’s potential to meet future food needs. In this study, we investigate West Africa’s hydrological potential to increase agricultural productivity through the implementation of large-scale water storage and irrigation. A 23-member ensemble of Regional Climate Models is applied to assess changes in hydrologically relevant variables under 2 °C and 1.5 °C global warming scenarios according to the UNFCCC 2015 Conference of Parties (COP 21) agreement. Changes in crop water demand, irrigation water need, water availability and the difference between water availability and irrigation water needs, here referred as basin potential, are presented for ten major river basins covering entire West Africa. Under the 2 °C scenario, crop water demand and irrigation water needs are projected to substantially increase with the largest changes in the Sahel and Gulf of Guinea respectively. At the same time, irrigation potential, which is directly controlled by the climate, is projected to decrease even in regions where water availability increases. This indicates that West African river basins will likely face severe freshwater shortages thus limiting sustainable agriculture. We conclude a general decline in the basin-scale irrigation potential in the event of large-scale irrigation development under 2 °C global warming. Reducing the warming to 1.5 °C decreases these impacts by as much as 50%, suggesting that the region of West Africa clearly benefits from efforts of enhanced mitigation

Landsat-8 vs. Sentinel-2: examining the added value of sentinel-2’s red-edge bands to land-use and land-cover mapping in Burkina Faso

The availability of freely available moderate-to-high spatial resolution (10–30 m) satellite imagery received a major boost with the recent launch of the Sentinel-2 sensor by the European Space Agency. Together with Landsat, these sensors provide the scientific community with a wide range of spatial, spectral, and temporal properties. This study compared and explored the synergistic use of Landsat-8 and Sentinel-2 data in mapping land use and land cover (LULC) in rural Burkina Faso. Specifically, contribution of the red-edge bands of Sentinel-2 in improving LULC mapping was examined. Three machine-learning algorithms – random forest, stochastic gradient boosting, and support vector machines – were employed to classify different data configurations. Classification of all Sentinel-2 bands as well as Sentinel-2 bands common to Landsat-8 produced an overall accuracy, that is 5% and 4% better than Landsat-8. The combination of Landsat-8 and Sentinel-2 red-edge bands resulted in a 4% accuracy improvement over that of Landsat-8. It was found that classification of the Sentinel-2 red-edge bands alone produced better and comparable results to Landsat-8 and the other Sentinel-2 bands, respectively. Results of this study demonstrate the added value of the Sentinel-2 red-edge bands and encourage multi-sensoral approaches to LULC mapping in West Africa

Priority area for sustainable Cashew (Anacardium occidentale L.) growing in Togo: Economic implications and conservation areas

Understanding a species’ current and future potential habitat is crucial to design its policy for management and cultivation practices that are more resilient in the face of climate change. This study assessed the present-day distribution and predicted the potential effect of climate change on the distribution of Anacardium occidentale’s habitat in Togo under two Representative Concentration Pathways (RCP4.5 and RCP8.5) by 2055. Maximum Entropy algorithm, 2538 species occurrence records, and a combination of 23 climate- and soil-related variables were used. Soil, isothermality, temperature seasonality, and annual precipitation are the most significant environmental factors affecting the distribution of the species in Togo. Based on the current model, 54.45% of the Togolese landscape is favourable for cashew development, mainly in the plains of Guinean and Sudanese savannahs. Unfavourable areas (15.20%) are in the southern mountainous areas of Togo and coastal areas. An increase in favourable areas and a slight decrease in unfavourable and moderately favourable areas are predicted by 2055, considering the two scenarios