Estes L.D.,Civil and Environmental Engineering |
Searchinger T.,Woodrow Wilson School |
Spiegel M.,Civil and Environmental Engineering |
Tian D.,Civil and Environmental Engineering |
And 8 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2016
Rapidly rising populations and likely increases in incomes in sub-Saharan Africa make tens of millions of hectares of cropland expansion nearly inevitable, even with large increases in crop yields. Much of that expansion is likely to occur in higher rainfall savannas, with substantial costs to biodiversity and carbon storage. Zambia presents an acute example of this challenge, with an expected tripling of population by 2050, good potential to expand maize and soya bean production, and large areas of relatively undisturbed miombo woodland and associated habitat types of high biodiversity value. Here, we present a new model designed to explore the potential for targeting agricultural expansion in ways that achieve quantitatively optimal trade-offs between competing economic and environmental objectives: total converted land area (the reciprocal of potential yield); carbon loss, biodiversity loss and transportation costs. To allow different interests to find potential compromises, users can apply varying weights to examine the effects of their subjective preferences on the spatial allocation of new cropland and its costs. We find that small compromises from the objective to convert the highest yielding areas permit large savings in transportation costs, and the carbon and biodiversity impacts resulting from savannah conversion. For example, transferring just 30% of weight from a yield-maximizing objective equally between carbon and biodiversity protection objectives would increase total cropland area by just 2.7%, but result in avoided costs of 27–47% for carbon, biodiversity and transportation. Compromise solutions tend to focus agricultural expansion along existing transportation corridors and in already disturbed areas. Used appropriately, this type of model could help countries find agricultural expansion alternatives and related infrastructure and land use policies that help achieve production targets while helping to conserve Africa’s rapidly transforming savannahs. This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
Legg J.P.,International Institute Of Tropical Agriculture |
Shirima R.,International Institute Of Tropical Agriculture |
Tajebe L.S.,University of Catania |
Guastella D.,University of Catania |
And 5 more authors.
Pest Management Science | Year: 2014
Cassava mosaic disease and cassava brown streak disease are caused by viruses transmitted by Bemisia tabaci and affect approximately half of all cassava plants in Africa, resulting in annual production losses of more than $US 1 billion. A historical and current bias towards virus rather than vector control means that these diseases continue to spread, and high Bemisia populations threaten future virus spread even if the extant strains and species are controlled. Progress has been made in parts of Africa in replicating some of the successes of integrated Bemisia control programmes in the south-western United States. However, these management efforts, which utilise chemical insecticides that conserve the Bemisia natural enemy fauna, are only suitable for commercial agriculture, which presently excludes most cassava cultivation in Africa. Initiatives to strengthen the control of B. tabaci on cassava in Africa need to be aware of this limitation, and to focus primarily on control methods that are cheap, effective, sustainable and readily disseminated, such as host-plant resistance and biological control. A framework based on the application of force multipliers is proposed as a means of prioritising elements of future Bemisia control strategies for cassava in Africa. © 2014 Society of Chemical Industry.
Vincent K.,Kulima Integrated Development Solutions Pty Ltd |
Vincent K.,University of Witwatersrand |
Cull T.,Kulima Integrated Development Solutions Pty Ltd |
Hamazakaza P.,Zambia Agricultural Research Institute |
And 3 more authors.
Climate and Development | Year: 2013
Southern Africa has a history of climate variability, and thus is an ideal setting to analyse responses to past and current climate variability by farmers. This paper presents original qualitative research undertaken in five southern African countries (Malawi, Mozambique, South Africa, Zambia and Zimbabwe) to determine farmers' responses and whether they can be classified as coping or adaptation. Farmers were both subsistence- and commercially oriented, operating on a variety of scales, from small-scale through to large-scale, and growing a wide variety of crops, from cereals to vegetables and cash crops. A wide range of strategies have been adopted in order to respond to climate variability and change. These strategies include crisis responses, modifying farming practices, modifying crop types and varieties, resource management and diversification. Coping typically refers to short-term strategies designed to maintain survival, but the long-term nature of many of the responses suggests that they do, in fact, constitute adaptations to current variability and change. However, determining whether or not the observed strategies are examples of coping or adaptation is dependent on the particular context in which they were observed, and also requires a consideration of the scale of interest. This has implications for how policies and programmes are designed to support adaptation in the future. © 2013 Copyright Taylor and Francis Group, LLC.
Mapila M.A.T.J.,University of Pretoria |
Njuki J.,International Center for Tropical Agriculture |
Delve R.J.,International Center for Tropical Agriculture |
Zingore S.,International Center for Tropical Agriculture |
Matibini J.,Zambia Agricultural Research Institute
Agrekon | Year: 2012
Farm surveys in Malawi, Zambia and Mozambique were carried out to assess the determinants of fertiliser use given continued low yields, low organic matter and general poor soil health in southern African soils. Regression modelling showed that fertiliser use was influenced by household and farm characteristics. In addition, it was also influenced by social and human capital and farmers perceptions of the effect of fertilisers on soil fertility. Farmers who perceived fertilisers as bad for their soil were less likely to adopt their use. This is a key result, as the emerging discussions on a green revolution for Africa, as well as the continued food crisis discussion, are prompting increased fertiliser use as an immediate intervention for increasing nutrient inputs into agriculture in the developing world. Increased policy efforts should be placed not only on increasing access to fertilisers but also on evolving farmers perceptions and attitudes towards fertiliser use. © 2012 Copyright Agricultural Economics Association of South Africa.
PubMed | Humboldt University of Berlin, Princeton University and Zambia Agricultural Research Institute
Type: Journal Article | Journal: Philosophical transactions of the Royal Society of London. Series B, Biological sciences | Year: 2016
Rapidly rising populations and likely increases in incomes in sub-Saharan Africa make tens of millions of hectares of cropland expansion nearly inevitable, even with large increases in crop yields. Much of that expansion is likely to occur in higher rainfall savannas, with substantial costs to biodiversity and carbon storage. Zambia presents an acute example of this challenge, with an expected tripling of population by 2050, good potential to expand maize and soya bean production, and large areas of relatively undisturbed miombo woodland and associated habitat types of high biodiversity value. Here, we present a new model designed to explore the potential for targeting agricultural expansion in ways that achieve quantitatively optimal trade-offs between competing economic and environmental objectives: total converted land area (the reciprocal of potential yield); carbon loss, biodiversity loss and transportation costs. To allow different interests to find potential compromises, users can apply varying weights to examine the effects of their subjective preferences on the spatial allocation of new cropland and its costs. We find that small compromises from the objective to convert the highest yielding areas permit large savings in transportation costs, and the carbon and biodiversity impacts resulting from savannah conversion. For example, transferring just 30% of weight from a yield-maximizing objective equally between carbon and biodiversity protection objectives would increase total cropland area by just 2.7%, but result in avoided costs of 27-47% for carbon, biodiversity and transportation. Compromise solutions tend to focus agricultural expansion along existing transportation corridors and in already disturbed areas. Used appropriately, this type of model could help countries find agricultural expansion alternatives and related infrastructure and land use policies that help achieve production targets while helping to conserve Africas rapidly transforming savannahs.This article is part of the themed issue Tropical grassy biomes: linking ecology, human use and conservation.
Comfort A.B.,Abt Associates |
Van Dijk J.H.,Macha Research Trust |
Thuma P.E.,Macha Research Trust |
Mharakurwa S.,Johns Hopkins Malaria Research Institute |
And 10 more authors.
American Journal of Tropical Medicine and Hygiene | Year: 2014
There is little evidence on the impact of malaria control on the health system, particularly at the facility level. Using retrospective, longitudinal facility-level and patient record data from two hospitals in Zambia, we report a pre-post comparison of hospital admissions and outpatient visits for malaria and estimated costs incurred for malaria admissions before and after malaria control scale-up. The results show a substantial reduction in inpatient admissions and outpatient visits for malaria at both hospitals after the scale-up, and malaria cases accounted for a smaller proportion of total hospital visits over time. Hospital spending on malaria admissions also decreased. In one hospital, malaria accounted for 11% of total hospital spending before large-scale malaria control compared with < 1% after malaria control. The findings demonstrate that facility-level resources are freed up as malaria is controlled, potentially making these resources available for other diseases and conditions. Copyright © 2014 by The American Society of Tropical Medicine and Hygiene.
Ando K.,Kyoto University |
Shinjo H.,Kyoto University |
Kuramitsu H.,Kyoto University |
Miura R.,Kyoto University |
And 2 more authors.
Agriculture, Ecosystems and Environment | Year: 2014
Recent shortened fallow in miombo woodland in southern Africa may affect the restoration process of soil organic carbon (SOC). This has not yet been clarified under controlled field experiments so the objective of this study was to evaluate the changes in SOC under different cropping periods followed by short fallow through changes in the composition and the amount of vegetation as input returned to soil. The treatments consisted of a cropping period for 1, 2, 3, 4, 5, 10 and 40 years, and a fallow period for 1, 2, 3 years after cropping for 1, 2, 3, 10 and 40 years. The SOC (<2000. μm), coarse organic matter C (COM-C, >2000. μm), particulate organic matter C (POM-C, 53-2000. μm), and the composition and the amount of plant materials returned to soil were measured. Results showed that SOC decreased significantly after 10-year cropping in response to a low amount of input. However, COM-C decreased after only 1-year cropping, and COM-C and POM-C decreased gradually during cropping for 2-5 years. The rapid changes of those labile fractions even with short cropping partially reflected the decrease in input and proportion of woody weeds that were decomposed slowly. Although the amount of input decreased after returning to fallow, SOC did not decrease because leaving plant litter on the soil surface retarded decomposition. Only in 2-year fallow after 3-year cropping, did POM-C recover to the level at the beginning of cropping. This was attributed to the large input from the growth of herbaceous plants which was accelerated due to the decreased competition with woody biomass which decreased with the increase in the previous cropping period. Therefore, 2-year fallow after 3-year cropping is a relatively sustainable management in terms of POM-C and SOC although woody biomass decreased compared to 1-year cropping. © 2014 Elsevier B.V.
Mukuka J.,University of Kiel |
Mukuka J.,Zambia Agricultural Research Institute |
Strauch O.,University of Kiel |
Hoppe C.,University of Kiel |
Ehlers R.-U.,University of Kiel
BioControl | Year: 2010
Genetic selection can be a powerful tool to increase beneficial traits in biological control agents. In this study the heat and desiccation tolerance of the entomopathogenic nematode Heterorhabditis bacteriophora Poinar (Rhabditidomorpha: Strongyloidea) were significantly increased by cross breeding tolerant parental strains and successive genetic selection. These strains originated from a prior screening among 60 strains for increased stress tolerance. During genetic selection, the selection pressure was constantly increased and only the most tolerant 10% of the nematode populations were propagated for further selection steps. Assessment of tolerance and selection for both traits was performed with and without prior adaptation to the stress conditions. Eleven selection steps were performed to increase heat tolerance. A final overall increase in mean heat tolerance of 5.5°C was achieved when nematodes had been adapted to heat stress. For non-adapted tolerance an increase of 3.0°C from 40.1°C to 43.1°C was recorded. For comparison, a commercial strain had a mean tolerated temperature after adaptation of 38.2°C and of 36.5°C without adaptation. For assessment of the desiccation tolerance the mean tolerated water activity (aw-value) of a population was measured. Cross-breeding most tolerant strains reduced the aw-value from 0.67 to 0.65 after adaptation and from 0.9 to 0.7 without prior adaptation. The following six selection steps could not increase the tolerance whether nematodes had been adapted to stress or not. In comparison, the commercial strain tolerated a mean aw-value of 0.985 after adaptation and 0.951 without adaptation. Further investigation will have to assess trait stability and possible trade-off effects. This study is a first important step on the road towards domestication of the entomopathogenic nematode H. bacteriophora. © 2010 International Organization for Biological Control (IOBC).
Mukuka J.,University of Kiel |
Mukuka J.,Zambia Agricultural Research Institute |
Strauch O.,University of Kiel |
Hoppe C.,University of Kiel |
Ehlers R.-U.,University of Kiel
Journal of Pest Science | Year: 2010
Entomopathogenic nematodes of the genus Heterorhabditis are a suitable alternative to chemical insecticides because of their high control effect against insects in cryptic environments and their environmental safety. The availability of H. bacteriophora hybrid strains with increased tolerance to environmental extremes could be a driving force for a more widespread use of nematode-based plant protection products. However, increase in heat and desiccation tolerance of hybrid strains could compromise their fitness regarding virulence, host penetration and reproductive capacity. The fitness of heat and desiccation tolerant hybrid strains was compared to the commercial strain EN 01. Only the heat tolerant strains were superior or similar in fitness to strain EN 01. The strains with increased desiccation tolerance were usually less fit, a possible result of a trade-off effect of selection for desiccation tolerance. Hybrid strains selected for enhanced tolerance after an adaptation to stress were generally better in fitness ranking compared to those for which adaptation prior to stress exposure was excluded. This might be a result of pleitropy. Host penetration and virulence was not correlated. The commercial strain had the highest reproduction per mean number of nematodes penetrating the host insect, which is a result of automatic selection of inbred lines with high reproduction potential during the commercial production process in liquid culture. © 2010 Springer-Verlag.
PubMed | French Natural History Museum, EPHE Paris, National Institute for Space Research and Zambia Agricultural Research Institute
Type: Journal Article | Journal: Proceedings of the National Academy of Sciences of the United States of America | Year: 2016
Erickson [Erickson CL (2000) Nature 408 (6809):190-193] interpreted features in seasonal floodplains in Bolivias Beni savannas as vestiges of pre-European earthen fish weirs, postulating that they supported a productive, sustainable fishery that warranted cooperation in the construction and maintenance of perennial structures. His inferences were bold, because no close ethnographic analogues were known. A similar present-day Zambian fishery, documented here, appears strikingly convergent. The Zambian fishery supports Ericksons key inferences about the pre-European fishery: It allows sustained high harvest levels; weir construction and operation require cooperation; and weirs are inherited across generations. However, our comparison suggests that the pre-European system may not have entailed intensive management, as Erickson postulated. The Zambian fisherys sustainability is based on exploiting an assemblage dominated by species with life histories combining high fecundity, multiple reproductive cycles, and seasonal use of floodplains. As water rises, adults migrate from permanent watercourses into floodplains, through gaps in weirs, to feed and spawn. Juveniles grow and then migrate back to dry-season refuges as water falls. At that moment fishermen set traps in the gaps, harvesting large numbers of fish, mostly juveniles. In nature, most juveniles die during the first dry season, so that their harvest just before migration has limited impact on future populations, facilitating sustainability and the adoption of a fishery based on inherited perennial structures. South American floodplain fishes with similar life histories were the likely targets of the pre-European fishery. Convergence in floodplain fish strategies in these two regions in turn drove convergence in cultural niche construction.