Solomon Islands is a South Pacific archipelago consisting of six major islands and a further 986 smaller islands, atolls and reefs. Around 84% of Solomon Islanders reside in rural villages and are dependent on subsistence-based agriculture and local fisheries [1
]. In recent times, commercial food supply chains have become increasingly important in the Solomon Islands due to a combination of rural to urban population drift [3
], population growth [5
], ongoing challenges associated with agricultural productivity [7
], and the impacts of adverse weather events [1
]. This trend is particularly acute in the capital Honiara, with only 32% of the urban population having access to a home garden [6
]. Most of the population that resides in Honiara, are now dependent on the municipal horticultural market and a network of smaller road-side markets to source their fresh fruits and vegetables.
Honiara’s horticultural markets not only provide important food security and human nutrition outcomes [9
], but create opportunities for local economic development and demonstrate a strong gender participation bias in favor of women market vendors [9
]. The income generated from these markets provides essential livelihood support for local squatter settlements in the “greater Honiara” region [3
] and are a primary source of income for many close proximity islands such as Savo Island [7
] and possibly Florida Island. This combination of socio-economic, pro-gender engagement and food security and nutrition benefits, has led to an increased focus by donors on market-based interventions in the Solomon Islands [12
The need to improve the operational efficiency and effectiveness of the Honiara municipal market have been widely recognized [2
]. The Honiara municipal market is constrained by overcrowding, poor sanitation and concerns about vendor safety [12
]. Most studies undertaken in support of the Honiara municipal markets have done so from a community resilience, gender and human security perspective [3
]. Its only recently that the underlying horticultural supply chains have been examined in any detail [7
], providing a wider understanding of farm demographics, transport logistics and vendor practice. What remains unclear, is how efficiently the Honiara markets and their associated supply chains operate in terms of postharvest horticultural loss. Unlike other South Pacific islands such as Fiji [17
] and Samoa [19
], there are no previous reported studies on postharvest market loss in any of the markets in the Solomon Islands. With generic poor postharvest handling, potentially high-levels of postharvest loss in Honiara markets could be undermining domestic food security.
This study reports on a preliminary assessment of postharvest horticultural market loss and associated supply chain logistics at the Honiara municipal market and five road-side markets on Guadalcanal Island. The inclusion of Honiara road-side markets in this study reflects an increasing recognition of their importance in the overall food distribution system in Solomon Islands [15
]. This study is part of an ongoing longitudinal assessment of postharvest horticultural loss in Honiara municipal market and road-side markets (Guadalcanal Island), Auki municipal market (Malaita Island) and the Gizo municipal market (Ghizo Island).
2. Materials and Methods
This study was undertaken at the Honiara municipal market and five road-side markets in the Honiara district, Guadalcanal Island and Solomon Islands (Figure 1
A,B). The location of the road-side markets assessed: Henderson, Fishing village, Lungga, King George VI and the White river, is shown in Figure 1
2.2. Survey Design and Ethics Approval
Vendor surveys were undertaken in November 2017 and March 2018. Markets were concurrently surveyed, and involved a series of enumerators from the Solomon Islands National University (SINU) to support this study. The selection of vendors to be surveyed was randomised, but excluded those vendors unable to identify where fruits and vegetables were grown (i.e., farm location) and therefore likely to be involved in inter-market trade, those vendors selling value-added or non-perishable products, and those vendors unwilling to participate in the survey. The survey design was based on semi-structured interview questions on harvesting and packaging practice, transport, market vendor practice, and postharvest loss. Enumerators received prior training in the survey methodology and ethics compliance.
A total of 198 vendors were assessed across all of the key Guadalcanal fruit and vegetable markets. This included 104 professional market vendors at the Honiara municipal market (42 vendors surveyed in November 2017 and an additional 62 vendors surveyed in March 2018). A further 94 road-side market vendors (occasional traders) were also surveyed (42 road-side vendors surveyed in November 2017 and 52 road-side vendors surveyed in March 2018). The survey was replicated across two sampling dates to partially account for potential differences in supply chain demographics and postharvest handling practice due to crop seasonality.
Surveys involved a short semi-structured interview lasting 5–10 min, commonly undertaken in the local language. All interviews were completed in compliance with the University of the Sunshine Coast Human Research Ethics Approval (A16814).
2.3. Data Collected
Postharvest market loss was determined using vendor recall, consistent with other recent Pacific market loss studies [18
]. This method excludes on-farm loss, does not include consumer waste nor does it account for potential re-use of market loss for non-human consumption (i.e., product used for animal feed). For the purposes of this study, postharvest loss is defined as a fresh horticultural product that was permanently removed from the chain due to being of an unsaleable quality and not provided to others with the intent of human consumption [20
]. Vendors were asked to quantify the level of postharvest loss of the main horticultural products on-display at their individual vendor stalls. This allowed for postharvest loss and handling practice to be further segregated and analysed according to crop type.
Transport distance from the farm (village) to the market was determined using Google Earth Pro™ Distance Calculator based on the most probable road transport route. Where the location of the village could not be directly identified, transport distance was calculated by cross referencing the map location given by the vendor with the nearest village. Village locations were further validated in discussions with the enumerators. For inter-island supply chains, transport distance was based on the most likely direct ferry route. For the intra-island transport supply chains that involved a combination of boat and road transport, such as those from southern Guadalcanal, transport distance was calculated based on a boat transport route from the farm to the nearest village with continuous road access to Honiara, and the most probable road transport route thereafter.
Product was identified as either fruits, vegetables, or fruits and vegetables, based on generic (non-botanical) crop classification (i.e., tomato and similar crops were classified as vegetables). Semi-processed, processed and non-horticultural commodities were excluded from this study.
2.4. Statistical Analysis
Data analysis was undertaken using one-way analysis of variance (ANOVA). Analysis of market vendor survey loss was undertaken using ANOVA followed by the Tukey–Kramer multiple comparison test (with consideration for uneven vendor numbers between markets). The relationship between market loss and transport distance was determined using a linear regression analysis.
Horticultural postharvest loss in the Honiara municipal market was 7.9 to 9.5%. In comparison, postharvest loss in the Honiara road-side markets tended to be lower (2.6 to 7.0%) but more variable. This level of loss was consistent with other South Pacific municipal markets, with Reference [19
] reporting a 6.2% loss in the central municipal market in Samoa. Most municipal market vendors in Honiara experienced some level of postharvest loss, whereas road-side market vendor loss tended to be less common. Based on mean postharvest market loss and the incidence of individual vendor loss, Honiara’s road-side market system appears to be more effective in minimising postharvest loss, compared to the municipal market.
The potential contributors to postharvest market loss in Guadalcanal markets and reasons for reduced loss in the road-side markets are likely to be multifaceted. Diverse market participation (commercial-scale farmers through to semi-subsistence farm surplus), poor road infrastructure, the lack of a cool chain, limited or poor packaging, and inadequate market storage facilities needs to balance against potential supply chain practices that seek to mitigate or lessen potentially elevated postharvest loss. While the contributors to generic postharvest loss in horticultural markets have been widely reported [19
], the inclusion of possible vendor or farmer strategies to reduce this loss are often overlooked.
Intuitively, it would be logical to assume that transport distance would have a significant effect on the level of postharvest loss seen in the market, consistent with the findings in other postharvest supply chain studies [24
]. While inter-island supply chains appear to have higher levels of postharvest loss compared to intra-island chains, we found that postharvest loss was poorly correlated to transport distance. Farms with very high levels of postharvest loss (>30% loss) tend to be located within 50 km of the markets, most supply chains with a transport distance of greater than 100 km have less than 10% loss, and loss associated with very remote intra-island supply routes was similarly less than 10%. These observations would suggest that the distance horticultural produce needs to travel from the farm to market is not a good indicator of potential market postharvest loss in Guadalcanal.
The type of crops sourced from inter-island and remote intra-island farms and their associated supply chain practice may provide some insight into the disconnect between transport distance and postharvest loss. Most inter-island supply chains included in this study were dominated by semi-perishable crops such as watermelon, pineapple and citrus. Such crops are often considered to be more tolerant of challenging transport logistics and potentially prolonged market storage. In the more remote Malaita to Guadalcanal inter-island supply chains, the product was sourced from two fruit production centers, watermelons from Buma and pineapples from Bina. These chains involved commercial-scale farms with relatively predictable transport logistics, with resultant postharvest loss being relatively low (<5%). Georgeou et al. [11
] reported that the most commonly traded crops from Savo and Nggela Islands into the Honiara markets were fruits, nuts and root crops. In remote intra-island chains, such as products sourced from Mbalo on the far south-eastern part of Guadalcanal and Tangarare on the far south eastern part of Guadalcanal, there was a similar dominance of semi-perishable crops such as watermelon and citrus. While this might simply reflect local agronomic production conditions favouring certain crops, it is also possible that there is deliberate strategy by farmers supplying the Honiara market to avoid highly perishable cash crops if the associated transport logistic is likely to incur high-levels of postharvest loss.
Vegetable supply chains still represented a significant portion of the overall inter-island trade into Honiara. A recent study of the Savo to Honiara market supply chains [16
] reported not only semi-perishable crops but also highly perishable leafy vegetables being traded. Savo farmers indicated high levels of postharvest loss due to in-transit damage and delays in accessing transport [16
], even though Savo Island is only about 35 km from Honiara. The presence of inter-island trade of perishable vegetable crops in spite of high-levels of postharvest loss is interesting. Georgeou et al. [16
] reported that much of the trade from Savo Island into the Honiara municipal market was due to opportunistic market participation due to surplus local production [16
]. Faced with possibly few alternative local market opportunities on Savo Island, potentially high postharvest loss does not appear to disincentivise market participation.
When intra-island vendor loss was analysed in terms of where produce was grown, we found that there was a cohort of villages in the western and southern parts of the main horticultural production (which is located in eastern Guadalcanal) which were consistently associated with atypically high levels of postharvest loss. This result might reflect the type of crops grown in these locations, with Reference [11
] reporting that most of the perishable leafy vegetables sold in the Honiara municipal market were sourced from farms located in north-eastern Guadalcanal. An alternative or additional possibility is a lack of reliable commercial transport options in these villages, or generic poor harvesting and handling practice. Further studies are required to better understand on-farm postharvest practice and supply chain logistics within these villages. Spatial mapping of high-loss postharvest chains has not been previously reported in the South Pacific, and provides useful information in terms of helping to better target possible future technical farmer assistance and supply chain remediation.
Supply chain modes of transport associated with Honiara’s markets reflect the diversity of agronomic production systems, from the commercial-scale through to semi-subsistent trade farm surplus. The most common form of transport was open trucks, consistent with the findings reported by Reference [11
]. Nearly all of the supply chains sourcing products from eastern Guadalcanal were dependant on trucks, possibly reflecting the volume of trade, poor road conditions and some level of local transport coordination. In Samoa and Vanuatu, where there is a relatively well maintained road-network and small production volumes, public buses, minivans and private vehicles are more commonly used [19
]. While the mode of transport is interesting, the specific postharvest transport conditions need to be better understood. How crops are loaded and the load configuration within the truck, the volume being transported, other possible items being co-transported can also have a significant influence on postharvest loss. More work is required to better understand transport logistics especially between eastern Guadalcanal and the Honiara markets as a possible contributor to postharvest loss.
A range of packing types were used by farmers, the most common of which was 40 kg of woven sacks. Given the large diversity of crops and packaging options, only a superficial assessment of the implication of packaging type on loss could be undertaken. As anticipated, very large agricultural sacks (>100 kg) used transport traditional leafy vegetables incurred significantly high levels of postharvest loss compared to smaller sizes of the same packaging type. Most heavy produce (such as pineapples, watermelon) were transported loose (no packaging). In the case of pineapples, the product was often tied into bundles of up to 40 fruit and carried using wooden poles. Plastic crates were rarely observed. Plastic buckets and steel trays were used for crops prone to damage during transport (such as tomato and papaya). The packing options used by farmers and vendors is thought to simply reflect the type of packaging readily available, with Reference [23
] noting that vendors in Malaita Island were aware of the adverse implication of poor packaging.
Comparatively low postharvest loss (4 to 5%) associated with a commonly used form of packaging (i.e., woven sacks ≤40 kg) would suggest that while packing is far from ideal, for most farmers packing had little effect on resultant postharvest loss. However, damage associated with poor packaging can be latent and, therefore, not immediately evident when product arrivals at the market. Georgeou et al. [11
] reported that product in the Honiara municipal market is commonly sold with ½ to 1 day or arriving at the market. It is possible that the potential full implications of poor packaging may be somewhat negated due to rapid market-throughput.
How efficiently the market-to-consumer food system operates directly influences postharvest supply chain loss. Noting high tropical ambient conditions, prolonged market storage has been reported to significantly elevate postharvest loss in other Pacific horticultural markets [19
]. The observation by Reference [11
], that most vendors in the Honiara municipal market sell their produce within ½ to 1 day is therefore significant. Honiara’s road-side markets are likely to experience even more rapid product throughput due to fewer vendors and smaller volumes of product being sold, reducing vendor competition, and road-side markets located close to the resident’s areas increasing potential consumer accessibility. In comparison, a product traded through the municipal market in Samoa is often stored for 2 to 3 days before it can be sold [19
]. In Samoa, the benefits of comparatively good on-farm postharvest handling practice and shorter transport distances are being undermined by prolonged market storage [19
]. In the Honiara markets, rapid market throughput of a perishable product is thought to be an important factor in avoiding potentially higher-levels of postharvest loss due to poor on-farm and transport practice. Fast on-selling by vendors in the Honiara municipal market is not the result of a better designed market infrastructure. Instead, high market vendor fees, over-crowding, poor market storage conditions, and significant concerns over vendor safety and hygiene create tangible incentives for Honiara vendors to sell their produce as quickly as possible. Further studies are required to better understand road-side market trading practices and whether this further contributes to slightly lower postharvest loss in these markets. The implications of current vendor practice on postharvest loss at the consumer-end of the value chain also warrants further investigation.
One variable that needs to be considered when interpreting market survey data in this study is the potential for inter-market trade (particularly between the Honiara municipal market and the various road-side markets). Georgeou et al. [11
] reported that approximately 30% of consumers at the Honiara market were on-selling products in other markets. In this study, we sought to exclude vendors who had sourced products from other markets from the survey, however, 2.6% of market vendors surveyed were unable to identify the farm location where the product was sourced. However, given that Reference [11
] further highlighted ongoing tension between farmer vendors and re-sellers, suggesting that re-sellers may not self-identify when surveyed, we cannot exclude the possibility of some level of data error based on vendors providing deliberately inaccurate survey responses.