SCUSA: integrated approaches and strategies to address the sanitation crisis in unsewered slum areas in African mega-cities

Africa, though reported to be the least urbanized continent, is recognized as one where the rate of urbanization is highest. The development and expansion of informal settlements in the suburbs of the cities is widespread, while they harbor the majority of the urban population. Slums are characterized by, among other things, poorly constructed houses, poor water supply and sanitary conditions, and lack or inadequate support services. Besides the spreading of diseases related to surface water (e.g., malaria), one of the main problems associated with sanitation and water in slum areas is related to the pollutant load entering and leaving the slum catchment, either as surface water or groundwater. This is polluting drinking water or causing eutrophication of surface water, due to the extremely high nitrogen and phosphorus fluxes discharging those slum catchments. The SCUSA research project aims at identifying the most sustainable sanitation solutions in urban slums, including the most important parameters determining and guaranteeing sustainability. Our approach is multidisciplinary, and should therefore yield answers with a financial, social, technical, and environmental view on the extremely complex field of sanitation in urban slums.     

Towards Measuring the Informal City: A Societal Metabolism Approach

The rapid growth of urban informal settlements, or slums, poses a particular challenge for balancing developmental and environmental goals. In South Africa, high levels of inequality, poverty, and unemployment contribute to widespread migration. The influx of migrant workers to cities, however, is rarely matched with adequate housing and infrastructure, resulting in the formation and growth of urban informal settlements. Despite the persistence of the slum phenomenon, very few studies provide an in‐depth understanding of the metabolic processes that link these spaces, and informal economies, to the broader urban environment and economy. This article therefore utilized a multiscale integrated assessment of the societal and ecosystem metabolism approach to examine human activity and land use in Enkanini, an urban informal settlement in Stellenbosch, South Africa. The results highlight a number of issues to be addressed through spatial, developmental, and local economic policy, such as the need for improved transport linkages. The time‐use results show that Enkanini is a net provider of labor to the surrounding area. Further, geographical mapping indicates Enkanini as a small, but vibrant, informal economy, while being grossly underserviced in terms of water, waste, and sanitation infrastructure. Key implications are discussed in terms of the theoretical, methodological, societal, and policy impact of the study, including the need for city observatories that conduct regular data collection and analysis.     

Sustainable sanitation technology options for urban slums

Poor sanitation in urban slums results in increased prevalence of diseases and pollution of the environment. Excreta, grey water and solid wastes are the major contributors to the pollution load into the slum environment and pose a risk to public health. The high rates of urbanization and population growth, poor accessibility and lack of legal status in urban slums make it difficult to improve their level of sanitation. New approaches may help to achieve the sanitation target of the Millennium Development Goal (MDG) 7; ensuring environmental sustainability. This paper reviews the characteristics of waste streams and the potential treatment processes and technologies that can be adopted and applied in urban slums in a sustainable way. Resource recovery oriented technologies minimise health risks and negative environmental impacts. In particular, there has been increasing recognition of the potential of anaerobic co-digestion for treatment of excreta and organic solid waste for energy recovery as an alternative to composting. Soil and sand filters have also been found suitable for removal of organic matter, pathogens, nutrients and micro-pollutants from grey water.     

Poverty,sanitation, and Leptospira transmission pathways in residents from four Brazilian slums

Residents of urban slums suffer from a high burden of zoonotic diseases due to individual, socioeconomic, and environmental factors. We conducted a cross-sectional sero-survey in four urban slums in Salvador, Brazil, to characterize how poverty and sanitation contribute to the transmission of rat-borne leptospirosis. Sero-prevalence in the 1,318 participants ranged between 10.0 and 13.3%. We found that contact with environmental sources of contamination, rather than presence of rat reservoirs, is what leads to higher risk for residents living in areas with inadequate sanitation. Further, poorer residents may be exposed away from the household, and ongoing governmental interventions were not associated with lower transmission risk. Residents at higher risk were aware of their vulnerability, and their efforts improved the physical environment near their household, but did not reduce their infection chances. This study highlights the importance of understanding the socioeconomic and environmental determinants of risk, which ought to guide intervention efforts.     

Environmental Transmission of Typhoid Fever in an Urban Slum

BackgroundEnteric fever due to Salmonella Typhi (typhoid fever) occurs in urban areas with poor sanitation. While direct fecal-oral transmission is thought to be the predominant mode of transmission, recent evidence suggests that indirect environmental transmission may also contribute to disease spread.MethodsData from a population-based infectious disease surveillance system (28,000 individuals followed biweekly) were used to map the spatial pattern of typhoid fever in Kibera, an urban informal settlement in Nairobi Kenya, between 2010–2011. Spatial modeling was used to test whether variations in topography and accumulation of surface water explain the geographic patterns of risk.ResultsAmong children less than ten years of age, risk of typhoid fever was geographically heterogeneous across the study area (p = 0.016) and was positively associated with lower elevation, OR = 1.87, 95% CI (1.36–2.57), p <0.001. In contrast, the risk of typhoid fever did not vary geographically or with elevation among individuals less than 6b ten years of age.ConclusionsOur results provide evidence of indirect, environmental transmission of typhoid fever among children, a group with high exposure to fecal pathogens in the environment. Spatially targeting sanitation interventions may decrease enteric fever transmission.     

Dietary and toxicity exposure of emerging persistent organic pollutants to human health through consumption of cereal crops from Pakistan

There is a lack of scientific literature regarding the bioaccumulation, dietary, and toxicity exposure of emerging persistent organic pollutants through food crops. The current mini-review presents the dietary intake, spatial distribution pattern, and screening-levels risk assessment of persistent organic pollutants (POPs) in the cereal crops and environmental compartments from Punjab Province, Pakistan. Results of congener specific analysis were in accordance to the previously reported pattern of detected POPs across the globe. Spatial distribution was influenced by the industrial and urban fraction and trend of spatial distribution pattern was observed as follows: industrial/urban areas > industrial/peri-urban areas > agricultural/rural areas. Dietary intake of Organochlorine pesticides (OCPs) via consumption of cereal crops was observed higher and was in accordance to the previously reported levels while human health was at marginal risk to cancer. The results of dietary and toxicity exposure of detected POPs warrant auxiliary devotion in future, to this group of contaminants.     

Long-term adherence to antiretroviral treatment and program drop-out in a high-risk urban setting in sub-Saharan Africa: a prospective cohort study

Background

Seventy percent of urban populations in sub-Saharan Africa live in slums. Sustaining HIV patients in these high-risk and highly mobile settings is a major future challenge. This study seeks to assess program retention and to find determinants for low adherence to antiretroviral treatment (ART) and drop-out from an established HIV/ART program in Kibera, Nairobi, one of Africa''s largest informal urban settlements.

Methods and Findings

A prospective open cohort study of 800 patients was performed at the African Medical Research Foundation (AMREF) clinic in the Kibera slum. Adherence to ART and drop-out from the ART program were independent outcomes. Two different adherence measures were used: (1) “dose adherence” (the proportion of a prescribed dose taken over the past 4 days) and (2) “adherence index” (based on three adherence questions covering dosing, timing and special instructions). Drop-out from the program was calculated based on clinic appointment dates and number of prescribed doses, and a patient was defined as being lost to follow-up if over 90 days had expired since the last prescribed dose. More than one third of patients were non-adherent when all three aspects of adherence – dosing, timing and special instructions – were taken into account. Multivariate logistic regression revealed that not disclosing HIV status, having a low level of education, living below the poverty limit (US$ 2/day) and not having a treatment buddy were significant predictors for non-adherence. Additionally, one quarter of patients dropped out for more than 90 days after the last prescribed ART dose. Not having a treatment buddy was associated with increased risk for drop-out (hazard ratio 1.4, 95% CI = 1.0–1.9).

Conclusion

These findings point to the dilemma of trying to sustain a growing number of people on life-long ART in conditions where prevailing stigma, poverty and food shortages threatens the long-term success of HIV treatment.     

Spatial patterns and determinants of wetland vegetation distribution in the Kumasi Metropolis,Ghana

The contribution of wetlands to livelihood in the forms of resources of direct consumptive uses, fishing and agriculture are of great importance to riparian communities in sub-Saharan Africa. It is unfortunate to note that these same areas are being degraded and converted to informal settlements through uncontrolled urbanisation. To improve urban environments and meet the various development targets, efforts are being made to rid sub-Saharan African cities of these informal wetland associated slums. The difficulty, however, lies in delineating wetland boundaries. This research is therefore aimed at determining the vegetation diversity of wetlands in Kumasi, Ghana and to identify and characterise the typical urban wetland and factors that influence the small scale heterogeneity in distribution of the wetland vegetation. Ten relatively large wetland sites associated with streams within the Kumasi Metropolis were selected for this study. Sampling in each site was done using 1 m² quadrats laid at 10 m intervals from the water channel. All plant species in each quadrat were identified. The soil and hydrologic conditions of each site were studied. A total of 112 species were identified in the 10 study sites. The study sites were found to be significantly different from each other in environmental conditions and species distribution. Species in these study sites could, however, be grouped into clusters according to the presence or absence of surface water. A wetland in Kumasi was found to be typified by high percentage organic carbon with Thelypteris palustris as the dominant species.     

Genetically modified and organic crops in developing countries: A review of options for food security

Since two decades ago, when the first GM crops were introduced, there have increasingly been hot debates on the applications of gene manipulation. Currently, the development of GM crop varieties has raised a wide range of new legal, ethical and economic questions in agriculture. There is a growing body of literature reflecting the socio-economic and environmental impacts of GM crops which aims to criticize their value for farming systems. While organic crops are promoted as environmentally-friendly products in developed countries, they have provoked great controversy in developing countries facing food security and a low agricultural productivity. Discussion has been especially vigorous when organic farming was introduced as an alternative method. There are in fact, a few tradeoffs in developing countries. On the one hand, farmers are encouraged to accept and implement GM crops because of their higher productivity, while on the other hand, organic farming is encouraged because of socio-economic and environmental considerations. A crucial question facing such countries is therefore, whether GM crops can co-exist with organic farming. This paper aims to review the main considerations and tradeoffs.     

Indigenous Cultural and Natural Resources Management and Mobility in Arnhem Land,Northern Australia

Many programmes formally engage Australian Indigenous people in land and sea management to provide environmental services. There are also many Indigenous people who ‘look after country’ without rewards or payment because of cultural obligations. We investigated how Indigenous peoples’ mobility in and around two communities (Maningrida and Ngukurr) is affected by their formal or informal engagement in cultural and natural resource management (CNRM). Understanding factors that influence peoples’ mobility is important if essential services are to be provided to communities efficiently. We found that those providing formal CNRM were significantly less likely to stay away from settlements than those ‘looking after their country’ without payment or reward. Paying Indigenous people to engage with markets for CNRM through carbon farming or payments for environmental services (PES) schemes may alter traditional activities and reduce mobility, particularly movements away from communities that extend the time spent overnight on country. This could have both environmental and social consequences that could be managed through greater opportunities for people to engage in formal CNRM while living away from communities and greater recognition of the centrality of culture to all Indigenous CNRM, formal or otherwise.     

Informal Urban Settlements and Cholera Risk in Dar es Salaam,Tanzania

Background

As a result of poor economic opportunities and an increasing shortage of affordable housing, much of the spatial growth in many of the world''s fastest-growing cities is a result of the expansion of informal settlements where residents live without security of tenure and with limited access to basic infrastructure. Although inadequate water and sanitation facilities, crowding and other poor living conditions can have a significant impact on the spread of infectious diseases, analyses relating these diseases to ongoing global urbanization, especially at the neighborhood and household level in informal settlements, have been infrequent. To begin to address this deficiency, we analyzed urban environmental data and the burden of cholera in Dar es Salaam, Tanzania.

Methodology/Principal Findings

Cholera incidence was examined in relation to the percentage of a ward''s residents who were informal, the percentage of a ward''s informal residents without an improved water source, the percentage of a ward''s informal residents without improved sanitation, distance to the nearest cholera treatment facility, population density, median asset index score in informal areas, and presence or absence of major roads. We found that cholera incidence was most closely associated with informal housing, population density, and the income level of informal residents. Using data available in this study, our model would suggest nearly a one percent increase in cholera incidence for every percentage point increase in informal residents, approximately a two percent increase in cholera incidence for every increase in population density of 1000 people per km² in Dar es Salaam in 2006, and close to a fifty percent decrease in cholera incidence in wards where informal residents had minimally improved income levels, as measured by ownership of a radio or CD player on average, in comparison to wards where informal residents did not own any items about which they were asked. In this study, the range of access to improved sanitation and improved water sources was quite narrow at the ward level, limiting our ability to discern relationships between these variables and cholera incidence. Analysis at the individual household level for these variables would be of interest.

Conclusions/Significance

Our results suggest that ongoing global urbanization coupled with urban poverty will be associated with increased risks for certain infectious diseases, such as cholera, underscoring the need for improved infrastructure and planning as the world''s urban population continues to expand.     

Adaptive Strategies of Highlands-Origin Migrant Settlers in Port Moresby, Papua New Guinea

This study examined adaptive strategies of Huli-speaking migrants from the Tari Basin in the Southern Highlands Province to Port Moresby, the capital of Papua New Guinea. An interview survey of all migrant dwellers in two Huli communities, and time allocation and food consumption studies in their three primary settlements revealed that the subject households relied for their livelihood on a variety of activities in the informal sector (e.g., vending, small-scale retailing, moneylending, and chicken rearing) and jobs in the formal sector (e.g., driver, public servant, security guard, and storekeeper). Unexpectedly, the average income of households that exclusively depended oninformal sector jobs was equivalent to, or higher than, that of households which included an employee in the formal sector. In addition, the average working hours were shorter in the former. Large interhousehold variation characterized the sample. The residential environment and composition of each household influenced economic strategies, which in turn determined the income, labor hours, and labor efficiency. However, food and nutrient intakes did not vary widely because leveling mechanisms among households, which are social norms in their homeland, still function in the urban settlements. The roles of settlements in Port Moresby are also discussed in relation to urban problems and rural-urban connections.     

Hepatitis B,Hepatitis C and HIV-1 Coinfection in Two Informal Urban Settlements in Nairobi,Kenya

Background

HIV-1 and Hepatitis B and C viruses coinfection is common in Sub-Saharan Africa due to similar routes of transmission and high levels of poverty. Most studies on HIV-1 and Hepatitis B and C viruses have occurred in hospital settings and blood transfusion units. Data on Hepatitis B and C viruses and HIV-1 coinfection in informal urban settlements in Kenya are scanty, yet they could partly explain the disproportionately high morbidity and mortality associated with HIV-1 infections in these slums.

Objectives

The objective of this study was to determine the prevalence of HIV and Hepatitis B and C dual infection in urban slums in Nairobi.

Methods

Blood samples were collected from residents of Viwandani and Korogocho between 2006 and 2007. A structured questionnaire was used to obtain socio-demographic data from participants. Samples were screened for Hepatitis B surface antigen (HBsAg), anti-HCV and anti-HIV-1. Statistical analysis was done using STATA.

Results

Samples were successfully collected from 418 (32%) men and 890 (68%) females. The HIV-1, HBV and HCV prevalence was 20.4%, 13.3% and 0.76% respectively at the time of the study. Of the 268 (20.4%) HIV-1 positive participants, 56 (4.26%) had HBV while 6 (0.46%) had HCV. Of the 1041 HIV-1 negative participants, 117 (8.9%) had HBV while 4 (0.31%) had HCV. Only two people (0.15%) were co-infected with all the three viruses together.

Discussion

The odds of getting hepatitis infection were higher in HIV-1 participants (for HBV OR 2.08,p<0.005 and for HCV OR 5.93, p<0.005). HIV prevalence rates were similar in both informal settlements. HIV infection was highest in age group 35-39 years and among the divorced/separated or widowed. Prevalence of all viruses was highest in those who did not have any formal education.

Conclusion

The HIV prevalence in these informal settlements suggests a higher rate than what is observed nationally. The prevalence rates of HBV are significantly higher in the HIV-1 positive and negative populations. HCV as well as triple HIV-1, HBV and HCV coinfection are uncommon in Korogocho and Viwandani. This clearly indicates the need for HIV-1 control programmes and hepatitis B virus vaccination to be promoted through public awareness as preventive strategy.     

Population-based incidence of typhoid fever in an urban informal settlement and a rural area in Kenya: implications for typhoid vaccine use in Africa

Background

High rates of typhoid fever in children in urban settings in Asia have led to focus on childhood immunization in Asian cities, but not in Africa, where data, mostly from rural areas, have shown low disease incidence. We set out to compare incidence of typhoid fever in a densely populated urban slum and a rural community in Kenya, hypothesizing higher rates in the urban area, given crowding and suboptimal access to safe water, sanitation and hygiene.

Methods

During 2007-9, we conducted population-based surveillance in Kibera, an urban informal settlement in Nairobi, and in Lwak, a rural area in western Kenya. Participants had free access to study clinics; field workers visited their homes biweekly to collect information about acute illnesses. In clinic, blood cultures were processed from patients with fever or pneumonia. Crude and adjusted incidence rates were calculated.

Results

In the urban site, the overall crude incidence of Salmonella enterica serovar Typhi (S. Typhi) bacteremia was 247 cases per 100,000 person-years of observation (pyo) with highest rates in children 5–9 years old (596 per 100,000 pyo) and 2–4 years old (521 per 100,000 pyo). Crude overall incidence in Lwak was 29 cases per 100,000 pyo with low rates in children 2–4 and 5–9 years old (28 and 18 cases per 100,000 pyo, respectively). Adjusted incidence rates were highest in 2–4 year old urban children (2,243 per 100,000 pyo) which were >15-fold higher than rates in the rural site for the same age group. Nearly 75% of S. Typhi isolates were multi-drug resistant.

Conclusions

This systematic urban slum and rural comparison showed dramatically higher typhoid incidence among urban children <10 years old with rates similar to those from Asian urban slums. The findings have potential policy implications for use of typhoid vaccines in increasingly urban Africa.     

Urbanization and its implications for food and farming

This paper discusses the influences on food and farming of an increasingly urbanized world and a declining ratio of food producers to food consumers. Urbanization has been underpinned by the rapid growth in the world economy and in the proportion of gross world product and of workers in industrial and service enterprises. Globally, agriculture has met the demands from this rapidly growing urban population, including food that is more energy-, land-, water- and greenhouse gas emission-intensive. But hundreds of millions of urban dwellers suffer under-nutrition. So the key issues with regard to agriculture and urbanization are whether the growing and changing demands for agricultural products from growing urban populations can be sustained while at the same time underpinning agricultural prosperity and reducing rural and urban poverty. To this are added the need to reduce greenhouse gas emissions and to build resilience in agriculture and urban development to climate change impacts. The paper gives particular attention to low- and middle-income nations since these have more than three-quarters of the world''s urban population and most of its largest cities and these include nations where issues of food security are most pressing.     

森林凋落物对林地微生境的影响

评述了凋落物改变林地微生境的效应.凋落物减弱了林地地表及表层土壤(2mm厚)中的光照,改变了光谱特性,降低了PPFD和Pfr,缩小了日温差,提高了土壤湿度和肥力,增加了毒素和土壤动物的活动等,但凋落物改变生境的效应强度与凋落物组成、厚度、分解状态和周围生境(如植被、气候、地形和地貌等特性)等有关.在自然森林生态系统中,凋落物对林地微生境的效应因凋落物、植被、气候、地形和地貌的多样化变得更为复杂,而凋落物对植被天然更新的影响也因其对生境改变效应的复杂性而具有多样性和综合性.最后,对凋落物改变生境效应的复杂性和有关研究进行了展望.     

跨国土地利用及其生态影响

在全球食物价格不断上涨,粮食安全已经威胁到经济安全的环境下,跨国农用地投资成为国际浪潮。跨国农用地投资推动着各国的土地资源向全球化资源转变,对土地的跨国利用成为全球土地资源优化配置的必然。在对跨国土地利用的背景及现状进行阐述的基础上,指出"代理性农业耕作"方式对区域生态环境可能造成的影响。同时,新型农业科技与跨国土地利用的结合,也在推动着农业经济发展的同时,改变着传统的土地利用模式,进而改变着区域生态环境。最后,指出需要对跨国土地利用做出理性分析并建立相关的国际规则,从而维护可持续粮食安全及生态安全。     

Diffusing Risk and Building Resilience through Innovation: Reciprocal Exchange Relationships,Livelihood Vulnerability and Food Security amongst Smallholder Farmers in Papua New Guinea

This paper examines how oil palm migrant farmers in Papua New Guinea are responding to shortages of land for food gardening. Despite rapid population growth and planting nearly all of their land to oil palm, virtually all families continue to grow sufficient food for their families. The paper outlines the diverse range of adaptive strategies that households have employed to maintain food security, involving both intensification and innovation in farming systems. While gains from intensification have been significant and built resilience, they have been incremental, whereas innovation has been transformative and led to large gains in resilience. The adoption of more flexible land access arrangements on state leasehold land that ‘revive’ and adapt indigenous systems of land sharing and exchange that operated through kinship networks on customary land are innovative; they have increased the supply of land for food gardening thereby reducing risk for individual households and the broader smallholder community. The paper highlights the value of understanding farmer-driven innovations and the role of indigenous institutions and cultural values in sustaining and enhancing household food security.     

Neo- and archaeophytes respond more strongly than natives to socio-economic mobility and disturbance patterns along an urban–rural gradient

Aims To clarify the distribution and abundance of natives, archaeophytes and neophytes in settlements along an urban–rural gradient we investigated the importance of site‐related and socio‐economic factors within settlements in determining the abundance and species richness of these three groups of plant species. Location The Wetterau region north of Frankfurt/Main, Hesse, Germany. Methods The occurrence and abundance of plant species were recorded in 2003 along transects in 66 settlements in a region north of Frankfurt/Main (Germany). The transect routes had been established in an earlier study in 1974–81. We used ordinations to analyse species composition, fitting 10 independent variables to explain the main gradient in species composition. Additionally, socio‐economic styles (derived from interviews of 1359 households) were fitted, to analyse the influence of these on plant communities. Finally, we analysed species richness by calculating independent contributions of the variables using hierarchical partitioning. Results Many species of neophytes have expanded their range since the 1974–81 survey, but this was not associated with a general decline of archaeophytes and natives. The main variation of species composition was along a rural to urban gradient, associated with site conditions and with socio‐economic factors that vary from settlements dominated by households rooted in the local community to settlements characterized by a mobile new middle class. For neophytes, variables describing the connection to Frankfurt (distance or connectivity) were most important in predicting species richness. For archaeophytes, the data showed a positive relationship between species richness and increasing herbicide application. Main conclusions These results suggest that the occurrence of neophytes within settlements along the urban–rural gradient is triggered by dispersal, related to human mobility patterns. In contrast, the occurrence of archaeophytes in settlements is determined by disturbance‐related factors that predominantly depend on traditional gardening practices and weed control practices associated with farming.     

The evolution of plant cultivation by ants

Outside humans, true agriculture was previously thought to be restricted to social insects farming fungus. However, obligate farming of plants by ants was recently discovered in Fiji, prompting a re-examination of plant cultivation by ants. Here, we generate a database of plant cultivation by ants, identify three main types, and show that these interactions evolved primarily for shelter rather than food. We find that plant cultivation evolved at least 65 times independently for crops (~200 plant species), and 15 times in farmer lineages (~37 ant taxa) in the Neotropics and Asia/Australasia. Because of their high evolutionary replication, and variation in partner dependence, these systems are powerful models to unveil the steps in the evolution and ecology of insect agriculture.