Seite - 22 - in options, Band winter 2014/2015

africa 22 options + winter 2014/2015 www.iiasa.ac.at regional focus Scientists from IIASA’s Ecosystems Services and Management (ESM) Program have been studying ways of increasing yields of staple food crops in sub-Saharan Africa, which has some of the lowest crop yields in the world. Researchers projected potential climate change impacts on maize yields under three different intensification options using the GIS-based EPIC (GEPIC) agronomic model—one with a high mineral nitrogen (N) supply and rotating with bare fallow, and two with a moderate N supply and rotating with the fast-growing nitrogen-fixing tree Sesbania sesban or the herbaceous N-fixing crop, cowpea. They found that to the 2040s the Sesbania sesban option would lead to increased maize yields due to increased soil N, enhanced water infiltration, and better soil water holding capacity; intensive cultivation with a bare fallow or rotation with cowpea, however, would result in lower yields and increased soil erosion. Spatially, though, the conventional intensification appeared more suitable in arid regions, while cowpea was the most efficient option in the humid tropics. Yields in all scenarios would decrease by 2100, should temperatures exceed critical thresholds. Eco-intensification in sub-Saharan Africa as a sole means of adapting agriculture to climate change was thus limited. Highly adverse temperatures would require introduction of heat-tolerant cultivars, while strongly adverse precipitation decreases would necessitate expanding irrigation where feasible. The scientists recommended further detailed studies at field and regional scale to analyze how changes in agro-environmental variables like soil organic carbon, erosion, and soil humidity might influence the field crop’s resilience to climate change. KP Further info Folberth C, Yang H, Gaiser T, Liu J, et  al (2014). Effects of ecological and conventional agricultural intensification practices on maize yields in sub-Saharan Africa under potential climate change. Environmental Research Letters 9(4):044004 [doi:10.1088/1748-9326/9/4/044004]. Christian Folberth folberth@iiasa.ac.at IIASA has contributed to a paper on global methane (CH4) emissions from pit latrines. The research aims to provide policymakers with a comprehensive understanding of how emissions from on-site sanitation systems can best be limited, the appropriate mitigation technologies, and relative costs. The UN has targeted universal access to adequate sanitation by 2030 for 2.5 billion people who currently lack improved sanitation services. However, this could also significantly increase CH4 from wastewater in previously underserved areas of South Asia and sub-Saharan Africa. The new analysis demonstrates that the problem of CH4 emissions from pit latrines can be reframed as an opportunity to incentivize progress up the sanitation ladder to the use of composting toilets, or more advanced systems, with co-benefits for both greenhouse gas mitigation and water and sanitation development. The paper uses a global hydrological model to estimate water table depths, and combines this with characteristics of various sanitation and composting technologies. A key ingredient in a sustainable sanitation system is more fully aerobic disposal. The use of well-maintained composting toilets, where the solids decompose aerobically to a nutrient-rich compost within a few months, is an excellent option. It would avoid groundwater contamination and provide an opportunity for nutrient recycling; it is also price-competitive with other CH4 mitigation measures in organic waste sectors. However, direct measurements of CH4 and N2O from pit latrines and composting toilets are not available in the literature. Scientists emphasize that these are needed to validate and improve emissions factors and inventories. KP Further info Reid MC, Guan K, Wagner F, Mauzerall DL (2014). Global methane emissions from pit latrines. Environmental Science & Technology 48(15):8727–8734 [doi:10.1021/es501549h]. Fabian Wagner wagnerf@iiasa.ac.at Curbing CH4 from pit latrines Solving the maize? A urine-diverting dry toilet (UDDT) in Botswana. The walls of the superstructure are made of old beer cans. Photo: Stefanie Lorenz | SuSanA (flickr.com CC BY 2.0)