What is the impact of infrastructural investments in roads, electricity and irrigation on agricultural productivity? (systematic review)
Infrastructural services including roads, electricity, telecommunications and irrigation, are all considered to be of major importance in stimulating agricultural investment and growth. However, their existence is still very limited in most rural areas of many developing countries. Whilst there exist much information in the scientific and grey literature on the issues relating to infrastructural impacts on agricultural development, there is no recent, objective, and independent review of the available evidence. The research question for this systematic review was therefore to assess “What is the impact of infrastructural investments in roads, electricity and irrigation on agricultural productivity?” This systematic review summarises the research objectives, approaches and methods, including the search criteria, data sources, search and extraction strategies, data synthesis, analysis and interpretation. The systematic review principally focussed on four main areas (i) road infrastructure (incorporating road networks and transport vehicles) and its impact on farmer access to agricultural markets; (ii) rural electricity supplies (consumption and expenditure) and its impact on agricultural productivity (irrigation, storage, cooling/refrigeration), product price, labour wages and rural GDP; (iii) telecommunications (telephones and internet) and its impact on crop prices, response to market demands, feed and fertilizer supply and costs, and (iv) irrigation infrastructure (incorporating water storage capacity per unit area, access to water and expansion of irrigated areas) and its impact on crop diversity, crop productivity (yield), crop prices, labour costs, rural consumption and returns of irrigation investment to the rural community and poverty reduction. Following definition of suitable search terms and study inclusion/exclusion criteria, a detailed search of available evidence was completed using a range of scientific bibliographic sources and internet websites. In total, 934 articles were identified, and then screened by title and abstract to provide a final listing of 155 articles and reports. These were imported into Refworks and analysed. Data were presented on the basis of a narrative synthesis but supported by quantitative analysis, based on an aggregation of reported observations and using simple impact assessment classification (positive impact, neutral impact and negative impact). An attempt was made to undertake some meta-analysis based on 307 observations, but this was not possible given the wide range of units reported in the literature, even within a particular impact indicator, and the impact of various ‘effect modifiers’. A narrative synthesis by infrastructural impact was therefore completed first, with evidence aggregated by country, where possible. Tables summarising the reported effects on agricultural productivity were produced for a range of productivity/output indicators. Next, a quantitative analysis using the 307 ‘observations’ was completed. From the evidence, it was apparent that a wide range of indicators had been used to assess the impact of investment in rural infrastructure on agricultural productivity. These were categorised into 9 main classes (i) agricultural productivity (measures of crop yield and output per unit area), (ii) consumption (measures of rural consumption and expenditure), (iii) GDP (measures of changes in total or rural GDP), (iv) income (measures of rural income, crop revenues and gross margins), (v) inputs (measures prices, demand, use and supply of agricultural inputs including seeds, fertilisers, fuel, labour and high yielding varieties (HYVs)), (vi) labour (measures of rural employment and wages), (vii) poverty (measures of the number of people in poverty, (viii) prices (measures of process of agricultural outputs) and (ix) production (measures of the quantity of production of crops and livestock). For road infrastructure, most evidence (37% observations) related to this investment, with the majority of reported impacts on agricultural productivity being positive, particularly in relation to GDP gains and poverty reduction. For electricity infrastructure, there was limited evidence (16% observations) but again positive, especially for poverty reduction. For telecommunication infrastructure, there was very limited evidence (6% observations) but the majority were positive. The impacts for this area are most likely to be mixed in with other forms of infrastructural investment. Finally, for irrigation infrastructure, a third of all evidence related to this aspect, with the majority of impacts on agricultural productivity being positive, especially in relation to income and poverty reduction. The SR also identified some important gaps in knowledge on the direct impacts of investment in electricity and telecommunications infrastructure on agricultural productivity, and a number of methodological limitations due to ‘effect modifiers’. This may not be surprising given that these types of investment are difficult to examine in isolation. Finally, the review has generated significant new aggregated data on infrastructural impacts on agricultural productivity which should be of broad international relevance to those engaged in assessments of agricultural and rural development.
rural; infrastructure; roads, transport; electricity; irrigation; agriculture; productivity; crop; yield
As in all systematic reviews, one of the most important aspects is formulating the primary question, which itself is inevitably a compromise between taking a holistic approach, involving a large number of variables and relevant studies, and a reductionist approach that limits the review’s relevance, utility, and value. It is proposed that this systematic review principally focuses on three main areas:
- Rural road infrastructure (incorporating road networks and transport vehicles) and its impact on farmer access to agricultural markets. In this context, the whole transport network is critical – feeder road projects are often linked into poorly maintained and degraded secondary/primary roads and their agricultural impact can diminish as a result;
- Electricity (supply) and its impact on agricultural crop storage, processing, cooling / refrigeration;
- Irrigation infrastructure (water storage, access to water, irrigation distribution and application equipment) and its impact on the crop diversity, yield, quality and resilience to drought.