Ecological and social drivers of coffee pollination in Santander, Colombia
Introduction
Landscapes that are dominated by agriculture are subject to changes resulting from the choice of cropping and from land-use patterns. These changes affect pollinator biodiversity and the provision of pollination services (Kleijn et al., 2011). Market forces and agricultural policy are often the driving factors behind an expansion of crops that were previously only grown over limited areas, and can bring about the introduction of novel crops into the landscape (Haughton et al., 2009).
The integration of pollination management into agricultural practice is essential since pollination by insects can increase the yield of 75% of global crops (Klein et al., 2007). Looking specifically at coffee production, studies have found that pollinators have a positive impact on the Coffea arabica L. yield of between 10 and 40% (Klein et al., 2007), despite the fact that the plant has a high degree of self-fertility (Klein et al., 2003a). A wide range of studies have been reviewed (Ngo et al., 2011) to investigate the effect of insects on coffee pollination. They have found that bees are widely recognised for their important role in pollination, especially the highly eusocial tribe Meliponini and the Africanized honey bee. The roles of other insects such as vespid wasps and syrphid flies have not been explored in detail, although species from these groups have been observed visiting coffee flowers.
Several studies have analysed the landscape contexts of coffee farms and have documented increases in bee species richness, visitation frequency, fruit set or berry weight when coffee crops are located in sites close to forest fragments (e.g. De Marco and Coelho, 2004, Klein et al., 2003a, Ricketts, 2004, Roubik, 2002a, Roubik, 2002b). Other studies in Mexico (Vergara and Badano, 2009) found that the greatest richness of pollinator species and the greatest fruit production were found on more structurally and floristically complex shaded coffee agro-ecosystems. Similarly, it has been stated (Jha and Vandermeer, 2010) that the most important factors predicting bee abundance were related to the diversity of vegetation within the agroforestry system. However, the impact of particular management practices (irrigation, liming, and shading) on pollination services to Coffea canephora production were assessed in India (Boreux et al., 2013), where it was found that managing irrigation to produce asynchronous flowering was a more effective tool for securing good pollination than maintaining high shade tree densities as pollinator habitat. Together these studies demonstrate the variety of factors affecting coffee pollinators and that they vary with farm type and location.
Thomas and Kevan (2012) reviewed evidence of the economic impact of pollination services in coffee plantation mosaic habitats and made several relevant policy recommendations. One key finding was that the value of pollination services is influenced directly by the amount of intact forest within 400 m of coffee trees, and that the average pollination value is reduced from US$100/ha to US$74/ha over that distance (Olschewski et al., 2006). They concluded, therefore, that at the global scale, policies such as direct subsidies for forest conservation would positively affect yields.
Further, empirical studies have recently shown the efficacy of pollinators as biocontrol agent vectoring (BVT) against populations of coffee borer, a disease that severely reduces crop yields (Vergara et al., 2014). Special dispensers can be placed at the exit/entrance of hives of managed pollinators (e.g. some honeybees and bumblebees). The dispensers contain specially formulated, naturally-occurring biological control agents that bees carry from their hives to the flowers they visit.
Thus, the two ecosystem services of insect pollination and crop protection combine to improve yields, and it is possible that their promotion at farm level could encourage the adoption of certified management schemes, i.e. practices that encourage farmers to grow coffee crops and manage farms sustainably.
Olschewski et al. (2006) also noted that economic incentives would improve production and advocated policies to support higher prices for certified coffee. Similarly, governmental and trade organizations involved in the import and export of coffee could also potentially influence policies and practices by promoting insect pollination in the process of coffee certification (Thomas and Kevan, 2012).
In addition to the ecological and economic factors noted above, an understanding of the social factors that influence farmers’ decisions at the local level is essential since these decisions affect farm management, which ultimately determines pollination services and crop yields (Plieninger et al., 2013). Most research of Arabica coffee has separately analysed either ecological or economic variables and often failed to take into account social factors and their combined effects on coffee pollination systems. If coffee production is to be sustainably managed, then it is important to understand the farm context and what factors drive pollinator biodiversity and pollination services at both the local farm level and on the wider landscape scale, and how these factors interact. The farm scale perspective is particularly important in Colombia and Latin America where smallholder coffee production is predominant, and the adoption of any given agricultural management practice primarily relies on the land owner’s decisions.
Focusing on the predominant pollinator groups in the study area, our research aims to quantify the response of pollinators to both farm management (organic vs. conventional) and distance to the nearest forest. Having established these environmental conditions, this study has also attempted to identify the various economic and social factors that influence farmers’ decisions regarding management methods. It is hoped that an improved understanding of these factors will allow farmers, in the future, to improve pollination rates, benefiting coffee fruit set and therefore their own livelihoods. We focused on the following questions: (1) What are the effects of both farm management and the surrounding landscape on pollinators and pollination delivery? (2) What is the economic value of pollination services provided by stingless and honeybees? (3) What social drivers affect the provision of pollination services through their influence on both ecological and economic factors?
Section snippets
Study sites
The study was undertaken in the Santander area, a mountainous region where a high proportion of Colombian specialty coffees are produced. The field work was carried out on 12 farms in Ocamonte, a town located in the south of the region (N6°22′945″, W73°07′552″, at elevations ranging from 1577 m to 1919 m). A balanced two factor design was developed to test the effects of proximity to forest, farm management type, and their interaction. Twelve farms of different smallholders were selected based on
Pollinator community and contribution of open pollination to coffee fruit production
Across all sites, bees were the predominant group observed, representing 92% of individual pollinators. Other insects accounted for just 8%, included wasps (Hymenoptera), flies (Diptera), butterflies and moths (Lepidoptera), and beetles (Coleoptera). Honeybees comprised 59% of the bees and stingless bees were found to be 40%; bumblebees, carpenter bees and small solitary bees constituted less than 2%.
Comparisons from the pollination experiments (using bagged branches alongside braches left open
Discussion
As discussed above, this study found that open pollination contributes an increased fruit set of 10.5 ± 2.0% to coffee fruit production, which is consistent with Klein et al. (2003a) who recorded a 12.3% increase in initial fruit set. Similarly, it is comparable to the 17.1% reported by Roubik (2002a). Our findings are also consistent with previous studies in which social bees (i.e. stingless and honeybees) were found to be the primary pollinators of coffee (Bos et al., 2007, Ricketts, 2004,
Conclusions
In summary, our results suggest that open pollination contributes an increased final fruit set of 10.5 ± 2.0%. The most important factors enhancing wild bee and insect pollinators in coffee agro-ecosystems is the proximity to forest in combination with local management methods, organic or conventional. Both schemes of management promote pollinators with a statistically significant effect on the composition of pollinator community (richness of stingless bees), whereas conventional management
Acknowledgements
We are grateful to coffee growers of Ocamonte (APCO), Federación Nacional de Cafeteros de Colombia and their Comités Cafeteros in Charalá, Socorro and San Gil, for orientations, farm access and collaboration. L.B.M. expresses her deepest gratitude to her family for their immense support and help, and to CAER and the University of Reading for an outstanding research-oriented environment, and also to Colfuturo for significant funding. We are also grateful for the highly-constructive comments of
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