Background: Issues of food security and nutrition have wide reaching implications for people and their environments, particularly in low and middle-income countries. One proposed solution is urban agriculture, which has been widely upheld as a solution to the food-crisis facing increasingly metropolitan populations. It is believed to provide the urban poor with food and a source of potential income, whilst improving the urban environment and reducing pressure on finite farmland. Although it faded from many development agendas in the 1990's, urban agriculture has seen a resurgence since a peak in global food prices in the late 2000's. There are, however, potential disadvantages to this increasing drive for urban agriculture including associated urban health risks and implications for the environment. The usage of waste-water, for example, may contaminate produced food and intensive irrigation might lead to the spread of malaria and water borne diseases, as well as threatening already limited water supplies. Soil erosion and the intensive use of fertilizers and pesticides might also present health risks to urban populations and damage the environment. Despite the potential benefits and harms of urban agriculture, the evidence-base is not well understood. Given the current policy drive to promote urban agriculture, there is an urgent need to understand its effects on urban populations and their environments.

Background Urban Agriculture is considered to contribute to improved food security among the income poor in urban contexts across developing countries. Much literature exists on the topic assuming a positive relationship. The aim of this review was to collect and analyse available evidence on the impact of urban agriculture in low and middle-income countries. Methods We employed systematic review methods to identify all relevant and reliable research on UA’s impact on food security and nutrition. Only impact evaluations that set out to measure the effectiveness of UA interventions on food security, as compared to the effects of not engaging in UA, qualified for inclusion. Studies had to have a comparison group and at least two data points. Results Systematic searches resulted in 8142 hits, and screening of abstracts resulted in 198 full texts identified. No studies met the review’s inclusion criteria. Therefore, the review found no available evidence that supports or refutes the suggestion that urban agriculture positively impacts on individual or household food security in low and middle-income countries. The largest proportion of studies at full text stage was excluded based on study design, as they were not impact evaluations, i.e. they did not have a comparison group and at least data points. Two observations were made: Firstly, searches yielded a range of studies that consider associations between UA and certain aspects of food security. Secondly, there is a large pool of cross-sectional studies on UA’s potential to contribute to increased food security, particularly from west and east Africa. Conclusions The research currently available does not allow for any conclusions to be made on whether or not urban agriculture initiatives contribute to food security. The fact that impact evaluations are absent from the current evidence-base calls for increased efforts to measure the impact of urban agriculture on food security in low and middle-income countries through rigorous impact evaluations. With regard to systematic review methodology, this review alludes to the value of compiling a systematic map prior to engaging in a full systematic review.

A new technology or innovation (see Table 2 below) Other An example of an evaluation of this kind of intervention is Anyango et al. (2010), who evaluated a five-year project in Kenya aimed at improving the income and food security of smallholder farmers through a number of training interventions, including introducing new cultivars to the farmers and training them through farmer field schools, as well as providing training on marketing skills, amongst other things. Ashraf et al. (2008), on the other hand, evaluated agricultural interventions that worked with pre-existing farmer self-help groups and provided farmers with information and short orientation-sessions about switching to export crops and offered in-kind loans and facilitated transactions with exporters.

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Many poor people living in Africa depend on their small farms for survival. There has been a lot of interest in trying to reduce poverty in the region by supporting these farmers to produce more and make a profit from their farms. Such interventions include training farmers and introducing them to new farming techniques and products, such as new crop types or fertilisers. Although a substantial amount of money has been invested in these approaches by governments and international donors, the effects of these interventions on food security and economic outcomes are unclear. This review examines the effectiveness of training, innovation and new technology interventions on the economic outcomes and food security of smallholder farmers in Africa. Interest has grown in interventions to support smallholder farmers because such interventions have the potential to improve both household income and food security. This review confirms providing smallholders with new biological or chemical inputs, particularly orange‐fleshed sweet potato, can lead to improved income and nutrition status. More high‐quality studies are needed to assess other types of training, innovation, and new technology interventions. Research is also needed to assess whether such interventions have sustainable, long‐term effects and whether they may cause harm to farmers or their communities. Plain Language Summary BACKGROUNDMany poor people living in Africa depend on their small farms for survival. There has been a lot of interest in trying to reduce poverty in the region by supporting these farmers to produce more and make a profit from their farms. This has included providing training programmes for farmers and introducing new products and farming techniques, such as fertilizers or new types of crops. Although a substantial amount of money has been invested in these approaches by governments and international donors, the effects of these interventions on food security and economic outcomes are unclear. We therefore set out to systematically review the available evidence. APPROACHWe searched thoroughly in major academic databases related to agricultural development (e.g. CAB abstracts, EbscoHost), as well as in the grey literature for all relevant research about the effects of training or the introduction of new approaches on smallholder farmers in Africa. We took steps to ensure we only selected the research that was relevant to our question and where we had confidence in the results. We synthesised the results of included studies using meta–analysis, although some sub–groups of studies could not be combined due to heterogeneity of outcome measures and lack of consistent reporting of statistical information. FINDINGSOut of the many thousands of research studies available on farming in Africa, we identified 19 relevant studies. Our analysis does not provide a coherent picture of the effects of training, innovation and new technology interventions on smallholder farmers' livelihoods. The conducted meta–analyses are based on very limited samples of rigor...