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Baxter AJ, Verschuren D, Peterse F, Miralles DG, Martin-Jones CM, Maitituerdi A, Van der Meeren T, Van Daele M, Lane CS, Haug GH, Olago DO, Sinninghe Damsté JS. Reversed Holocene temperature-moisture relationship in the Horn of Africa. Nature 2023; 620:336-343. [PMID: 37558848 PMCID: PMC10412447 DOI: 10.1038/s41586-023-06272-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 05/25/2023] [Indexed: 08/11/2023]
Abstract
Anthropogenic climate change is predicted to severely impact the global hydrological cycle1, particularly in tropical regions where agriculture-based economies depend on monsoon rainfall2. In the Horn of Africa, more frequent drought conditions in recent decades3,4 contrast with climate models projecting precipitation to increase with rising temperature5. Here we use organic geochemical climate-proxy data from the sediment record of Lake Chala (Kenya and Tanzania) to probe the stability of the link between hydroclimate and temperature over approximately the past 75,000 years, hence encompassing a sufficiently wide range of temperatures to test the 'dry gets drier, wet gets wetter' paradigm6 of anthropogenic climate change in the time domain. We show that the positive relationship between effective moisture and temperature in easternmost Africa during the cooler last glacial period shifted to negative around the onset of the Holocene 11,700 years ago, when the atmospheric carbon dioxide concentration exceeded 250 parts per million and mean annual temperature approached modern-day values. Thus, at that time, the budget between monsoonal precipitation and continental evaporation7 crossed a tipping point such that the positive influence of temperature on evaporation became greater than its positive influence on precipitation. Our results imply that under continued anthropogenic warming, the Horn of Africa will probably experience further drying, and they highlight the need for improved simulation of both dynamic and thermodynamic processes in the tropical hydrological cycle.
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Affiliation(s)
- A J Baxter
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands.
| | - D Verschuren
- Department of Biology, Limnology Unit, Ghent University, Gent, Belgium
| | - F Peterse
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
| | - D G Miralles
- Department of Environment, Hydro-Climate Extremes Lab (H-CEL), Ghent University, Gent, Belgium
| | | | - A Maitituerdi
- Dr. Moses Strauss Department of Marine Geosciences, Leon H. Charney School of Marine Sciences, University of Haifa, Mount Carmel, Israel
| | - T Van der Meeren
- Department of Biology, Limnology Unit, Ghent University, Gent, Belgium
| | - M Van Daele
- Renard Centre of Marine Geology, Department of Geology, Ghent University, Gent, Belgium
| | - C S Lane
- Department of Geography, University of Cambridge, Cambridge, UK
| | - G H Haug
- Department of Climate Geochemistry, Max Planck Institute for Chemistry, Mainz, Germany
| | - D O Olago
- Institute for Climate Change and Adaptation, Department of Earth and Climate Science, University of Nairobi, Nairobi, Kenya
| | - J S Sinninghe Damsté
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, The Netherlands
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Amadi JA, Ong'amo GO, Olago DO, Oriaso SO, Nyamongo IK, Estambale BBA. Mapping potential Anopheles gambiae s.l. larval distribution using remotely sensed climatic and environmental variables in Baringo, Kenya. Med Vet Entomol 2018; 32:417-426. [PMID: 29926974 DOI: 10.1111/mve.12312] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 03/22/2018] [Accepted: 05/03/2018] [Indexed: 06/08/2023]
Abstract
Anopheles gambiae s.l. (Diptera: Culicidae) is responsible for the transmission of the devastating Plasmodium falciparum (Haemosporida: Plasmodiidae) strain of malaria in Africa. This study investigated the relationship between climate and environmental conditions and An. gambiae s.l. larvae abundance and modelled the larval distribution of this species in Baringo County, Kenya. Mosquito larvae were collected using a 350-mL dipper and a pipette once per month from December 2015 to December 2016. A random forest algorithm was used to generate vegetation cover classes. A negative binomial regression was used to model the association between remotely sensed climate (rainfall and temperature) and environmental (vegetation cover, vegetation health, topographic wetness and slope) factors and An. gambiae s.l. for December 2015. Anopheles gambiae s.l. was significantly more frequent in the riverine zone (P < 0.05, r = 0.59) compared with the lowland zone. Rainfall (b = 6.22, P < 0.001), slope (b = - 4.81, P = 0.012) and vegetation health (b = - 5.60, P = 0.038) significantly influenced the distribution of An. gambiae s.l. larvae. High An. gambiae s.l. abundance was associated with cropland and wetland environments. Effective malaria control will require zone-specific interventions such as a focused dry season vector control strategy in the riverine zone.
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Affiliation(s)
- J A Amadi
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
- Department of Plant Sciences, Kenyatta University, Nairobi, Kenya
| | - G O Ong'amo
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - D O Olago
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - S O Oriaso
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - I K Nyamongo
- Cooperative Development, Research and Innovation, Cooperative University of Kenya, Nairobi, Kenya
| | - B B A Estambale
- Division of Research Innovation and Outreach, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
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Amadi JA, Olago DO, Ong’amo GO, Oriaso SO, Nanyingi M, Nyamongo IK, Estambale BBA. Sensitivity of vegetation to climate variability and its implications for malaria risk in Baringo, Kenya. PLoS One 2018; 13:e0199357. [PMID: 29975780 PMCID: PMC6033402 DOI: 10.1371/journal.pone.0199357] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 06/06/2018] [Indexed: 11/24/2022] Open
Abstract
The global increase in vector borne diseases has been linked to climate change. Seasonal vegetation changes are known to influence disease vector population. However, the relationship is more theoretical than quantitatively defined. There is a growing demand for understanding and prediction of climate sensitive vector borne disease risks especially in regions where meteorological data are lacking. This study aimed at analyzing and quantitatively assessing the seasonal and year-to-year association between climatic factors (rainfall and temperature) and vegetation cover, and its implications for malaria risks in Baringo County, Kenya. Remotely sensed temperature, rainfall, and vegetation data for the period 2004–2015 were used. Poisson regression was used to model the association between malaria cases and climatic and environmental factors for the period 2009–2012, this being the period for which all datasets overlapped. A strong positive relationship was observed between the Normalized Difference Vegetation Index (NDVI) and monthly total precipitation. There was a strong negative relationship between NDVI and minimum temperature. The total monthly rainfall (between 94 -181mm), average monthly minimum temperatures (between 16–21°C) and mean monthly NDVI values lower than 0.35 were significantly associated with malaria incidence rates. Results suggests that a combination of climatic and vegetation greenness thresholds need to be met for malaria incidence to be significantly increased in the county. Planning for malaria control can therefore be enhanced by incorporating these factors in malaria risk mapping.
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Affiliation(s)
- Jacinter A. Amadi
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
- Department of Plant Sciences, Kenyatta University, Nairobi, Kenya
- * E-mail:
| | - Daniel O. Olago
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - George O. Ong’amo
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - Silas O. Oriaso
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - Mark Nanyingi
- Department of Public Health, Pharmacology and Toxicology, University of Nairobi, Nairobi, Kenya
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Isaac K. Nyamongo
- Cooperative Development, Research and Innovation, Cooperative University of Kenya, Nairobi, Kenya
| | - Benson B. A. Estambale
- Division of Research Innovation and Outreach, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
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Amadi JA, Olago DO, Ong'amo GO, Oriaso SO, Nyamongo IK, Estambale BBA. "We don't want our clothes to smell smoke": changing malaria control practices and opportunities for integrated community-based management in Baringo, Kenya. BMC Public Health 2018; 18:609. [PMID: 29743062 PMCID: PMC5944038 DOI: 10.1186/s12889-018-5513-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 04/26/2018] [Indexed: 11/30/2022] Open
Abstract
Background The decline in global malaria cases is attributed to intensified utilization of primary vector control interventions and artemisinin-based combination therapies (ACTs). These strategies are inadequate in many rural areas, thus adopting locally appropriate integrated malaria control strategies is imperative in these heterogeneous settings. This study aimed at investigating trends and local knowledge on malaria and to develop a framework for malaria control for communities in Baringo, Kenya. Methods Clinical malaria cases obtained from four health facilities in the riverine and lowland zones were used to analyse malaria trends for the 2005–2014 period. A mixed method approach integrating eight focus group discussions, 12 key informant interviews, 300 survey questionnaires and two stakeholders’ consultative forums were used to assess local knowledge on malaria risk and develop a framework for malaria reduction. Results Malaria cases increased significantly during the 2005–2014 period (tau = 0.352; p < 0.001) in the riverine zone. March, April, May, June and October showed significant increases compared to other months. Misconceptions about the cause and mode of malaria transmission existed. Gender-segregated outdoor occupation such as social drinking, farm activities, herding, and circumcision events increased the risk of mosquito bites. A positive relationship occurred between education level and opinion on exposure to malaria risk after dusk (χ2 = 2.70, p < 0.05). There was over-reliance on bed nets, yet only 68% (204/300) of respondents owned at least one net. Complementary malaria control measures were under-utilized, with 90% of respondents denying having used either sprays, repellents or burnt cow dung or plant leaves over the last one year before the study was conducted. Baraza, radios, and mobile phone messages were identified as effective media for malaria information exchange. Supplementary strategies identified included unblocking canals, clearing Prosopis bushes, and use of community volunteers and school clubs to promote social behaviour change. Conclusions The knowledge gap on malaria transmission should be addressed to minimize the impacts and enhance uptake of appropriate malaria management mechanisms. Implementing community-based framework can support significant reductions in malaria prevalence by minimizing both indoor and outdoor malaria transmissions.
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Affiliation(s)
- Jacinter A Amadi
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya. .,Department of Plant Sciences, Kenyatta University, Nairobi, Kenya.
| | - Daniel O Olago
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - George O Ong'amo
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - Silas O Oriaso
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - Isaac K Nyamongo
- Cooperative Development, Research and Innovation, The Cooperative University of Kenya, Nairobi, Kenya
| | - Benson B A Estambale
- Division of Research Innovation and Outreach, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
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Ochieng AO, Nanyingi M, Kipruto E, Ondiba IM, Amimo FA, Oludhe C, Olago DO, Nyamongo IK, Estambale BBA. Ecological niche modelling of Rift Valley fever virus vectors in Baringo, Kenya. Infect Ecol Epidemiol 2016; 6:32322. [PMID: 27863533 PMCID: PMC5116061 DOI: 10.3402/iee.v6.32322] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 10/19/2016] [Accepted: 10/20/2016] [Indexed: 11/14/2022] Open
Abstract
Background Rift Valley fever (RVF) is a vector-borne zoonotic disease that has an impact on human health and animal productivity. Here, we explore the use of vector presence modelling to predict the distribution of RVF vector species under climate change scenario to demonstrate the potential for geographic spread of Rift Valley fever virus (RVFV). Objectives To evaluate the effect of climate change on RVF vector distribution in Baringo County, Kenya, with an aim of developing a risk map for spatial prediction of RVF outbreaks. Methodology The study used data on vector presence and ecological niche modelling (MaxEnt) algorithm to predict the effect of climatic change on habitat suitability and the spatial distribution of RVF vectors in Baringo County. Data on species occurrence were obtained from longitudinal sampling of adult mosquitoes and larvae in the study area. We used present (2000) and future (2050) Bioclim climate databases to model the vector distribution. Results Model results predicted potential suitable areas with high success rates for Culex quinquefasciatus, Culex univitattus, Mansonia africana, and Mansonia uniformis. Under the present climatic conditions, the lowlands were found to be highly suitable for all the species. Future climatic conditions indicate an increase in the spatial distribution of Cx. quinquefasciatus and M. africana. Model performance was statistically significant. Conclusion Soil types, precipitation in the driest quarter, precipitation seasonality, and isothermality showed the highest predictive potential for the four species.
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Affiliation(s)
- Alfred O Ochieng
- Department of Biological Sciences, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | - Mark Nanyingi
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.,Department of Public Health, Pharmacology and Toxicology, University of Nairobi, Nairobi, Kenya;
| | - Edwin Kipruto
- Division of Research Innovation and Outreach, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | - Isabella M Ondiba
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - Fred A Amimo
- School of Health Sciences, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | | | - Daniel O Olago
- Department of Geology, University of Nairobi, Nairobi, Kenya
| | - Isaac K Nyamongo
- Institute of Anthropology, Gender and African Studies, University of Nairobi, Nairobi, Kenya
| | - Benson B A Estambale
- Division of Research Innovation and Outreach, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
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Olaka LA, Wilke FDH, Olago DO, Odada EO, Mulch A, Musolff A. Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study. Sci Total Environ 2016; 545-546:641-53. [PMID: 26775113 DOI: 10.1016/j.scitotenv.2015.11.161] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 11/27/2015] [Accepted: 11/28/2015] [Indexed: 05/10/2023]
Abstract
Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02-75 mg/L. 73% exceed the health limit (1.5mg/L) in both dry and wet seasons. F(-) concentrations in rivers are lower (0.2-9.2mg/L) than groundwater (0.09 to 43.6 mg/L) while saline lake waters have the highest concentrations (0.27-75 mg/L). The higher values are confined to elevations below 2000 masl. Oxygen (δ(18)O) and hydrogen (δD) isotopic values range from -6.2 to +5.8‰ and -31.3 to +33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750-6000 ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (<1000 ppm). Thus, geochemical F(-) enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management in Naivasha as well as similar active rift setting environments.
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Affiliation(s)
- Lydia A Olaka
- Department of Geology, University of Nairobi, P.O Box 30197, Nairobi, Kenya.
| | | | - Daniel O Olago
- Department of Geology, University of Nairobi, P.O Box 30197, Nairobi, Kenya
| | - Eric O Odada
- Department of Geology, University of Nairobi, P.O Box 30197, Nairobi, Kenya
| | - Andreas Mulch
- Senckenberg Biodiversity and Climate Research Centre, Senckenberganlage 25, 60325 Frankfurt, Germany; Institut für Geowissenschaften, Goethe Universität Frankfurt, Altenhöferallee 1, 60438 Frankfurt, Germany
| | - Andreas Musolff
- UFZ-Helmholtz-Centre for Environmental Research, Department of Hydrogeology, Permoserstr. 15, 04318 Leipzig, Germany
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Abstract
This paper assesses the vulnerability of schools to floods in the Nyando River catchment (3,600 km(2)) in western Kenya and identifies measures needed to reduce this vulnerability. It surveys 130 schools in the lower reaches, where flooding is a recurrent phenomenon. Of the primary schools assessed, 40% were vulnerable, 48% were marginally vulnerable and 12% were not vulnerable. Of the secondary schools, 8% were vulnerable, 73% were marginally vulnerable and 19% were not vulnerable. Vulnerability to floods is due to a lack of funds, poor building standards, local topography, soil types and inadequate drainage. The Constituencies Development Fund (CDF), established in 2003, provides financial support to cover school construction and reconstruction costs; CDF Committees are expected to adopt school building standards. In an effort to promote safe and resilient construction and retrofitting to withstand floods, this paper presents vulnerability reduction strategies and recommendations for incorporating minimum standards in the on-going Primary School Infrastructure Programme Design.
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Affiliation(s)
- Samuel O Ochola
- Department of Environmental Studies and Community Development, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya.
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Odada EO, Olago DO, Kulindwa K, Ntiba M, Wandiga S. Mitigation of environmental problems in Lake Victoria, East Africa: causal chain and policy options analyses. Ambio 2004; 33:13-23. [PMID: 15083646 DOI: 10.1579/0044-7447-33.1.13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Lake Victoria is an international waterbody that offers the riparian communities a large number of extremely important environmental services. Over the past three decades or so, the lake has come under increasing and considerable pressure from a variety of interlinked human activities such as overfishing, species introductions, industrial pollution, eutrophication, and sedimentation. In this paper we examine the root causes for overfishing and pollution in Lake Victoria and give possible policy options that can help remediate or mitigate the environmental degradation.
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Affiliation(s)
- Eric O Odada
- Pan-African START Secretariat (PASS), Department of Geology, University of Nairobi, P. O. Box 30197, Nairobi, Kenya.
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Street-Perrott FA, Huang Y, Perrott RA, Eglinton G, Barker P, Khelifa LB, Harkness DD, Olago DO. Impact of lower atmospheric carbon dioxide on tropical mountain ecosystems. Science 1997; 278:1422-6. [PMID: 9367947 DOI: 10.1126/science.278.5342.1422] [Citation(s) in RCA: 282] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Carbon-isotope values of bulk organic matter from high-altitude lakes on Mount Kenya and Mount Elgon, East Africa, were 10 to 14 per mil higher during glacial times than they are today. Compound-specific isotope analyses of leaf waxes and algal biomarkers show that organisms possessing CO2-concentrating mechanisms, including C4 grasses and freshwater algae, were primarily responsible for this large increase. Carbon limitation due to lower ambient CO2 partial pressures had a significant impact on the distribution of forest on the tropical mountains, in addition to climate. Hence, tree line elevation should not be used to infer palaeotemperatures.
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Affiliation(s)
- FA Street-Perrott
- F. A. Street-Perrott and R. A. Perrott are in the Tropical Palaeoenvironments Research Group, Department of Geography, University of Wales Swansea, Swansea SA2 8PP, UK. Y. Huang and G. Eglinton are at the Biogeochemistry Research C
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