Article

Cocoa Production: Monocultures are Not the Solution to Climate Adaptation - - Response to Abdulai et al. 2017

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Abstract

Cocoa is a major trade commodity that is seeing increasing demand, but also climate-related yield declines1 . There has been an ongoing discussion whether both, the effective adaptation of plantations to climate change and a long term increase of cocoa yields, can only be achieved with shaded agroforestry or also with full-sun monocultures2 . Abdulai et al. 3 investigated the climate adaptation potential of full-sun cocoa monocultures and shaded agroforestry in Ghana West Africa. This article is protected by copyright. All rights reserved.

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... The biggest cocoa producing island Sulawesi in Indonesia will need strong climate adaptation strategies by 2050 (7). As yield declines also reduce the income of the 5 million cocoa farmers globally, small-scale producers either expand production into new, often forested areas or shift to alternative income sources to maintain their income (8). Stakeholders of the cocoa bean supply chain often advocate high-yielding monocultures to buffer climate-related yield declines and to avoid negative socioeconomic consequences for smallscale producers. ...
... In cocoa monocultures, shade trees have been removed and chemical inputs (i.e., pesticide and fertilizer) are used to maintain high yields and profits in the short-term (9). Monocultures, however, negatively affect biodiversity and critical ecosystem services such as soil fertility, biological pest control, and pollination (8), and overall climate resilience (8,10). By contrast, agroforestry systems maintain or restore a shade tree cover above 40% (11), create a high climate resilience, require less chemical inputs, maintain essential ecosystem services (12,13,14) and produce stable but lower yields than in monocultures (9,10,11,15). ...
... In cocoa monocultures, shade trees have been removed and chemical inputs (i.e., pesticide and fertilizer) are used to maintain high yields and profits in the short-term (9). Monocultures, however, negatively affect biodiversity and critical ecosystem services such as soil fertility, biological pest control, and pollination (8), and overall climate resilience (8,10). By contrast, agroforestry systems maintain or restore a shade tree cover above 40% (11), create a high climate resilience, require less chemical inputs, maintain essential ecosystem services (12,13,14) and produce stable but lower yields than in monocultures (9,10,11,15). ...
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Production of cocoa, the third largest trade commodity globally has experienced climate related yield stagnation since 2016, forcing farmers to expand production in forested habitats and to shift from nature friendly agroforestry systems to intensive monocultures. The goal for future large-scale cocoa production combines high yields with biodiversity friendly management into a climate adapted smart agroforestry system (SAS). As pollination limitation is a key driver of global production, we use data of more than 150,000 cocoa farms and results of hand pollination experiments to show that manually enhancing cocoa pollination (hereafter manual pollination) can produce SAS. Manual pollination can triple farm yields and double farmers annual profit in the major producer countries Ivory Coast, Ghana, and Indonesia, and can increase global cocoa supplies by up to 13%. We propose a win win scenario to mitigate negative long term price and socioeconomic effects, whereby manual pollination compensates only for yield losses resulting from climate and disease related decreases in production area and conversion of monocultures into agroforestry systems. Our results highlight that yields in biodiversity friendly and climate adapted SAS can be similar to yields currently only achieved in monocultures. Adoption of manual pollination could be achieved through wider implementation of ecocertification standards, carbon markets, and zero deforestation pledges.
... Conventional intensification strategies are dependent on agrochemical inputs and can help to boost cocoa productivity, these strategies will not be sufficient for stabilizing high yields. In contrast, ecological intensification, understood as increasing farmland productivity by enhancing ecosystem services such as pollination (Bommarco et al., 2013;Motzke et al., 2015) is a sustainable strategy for securing cocoa yields in the long term (Toledo-Hernández et al., 2017;Wanger et al., 2018); manually increasing the number of pollinated flowers by 13% can enhance cocoa yields by at least 51% at the farm level (Toledo-Hernández et al., 2020). ...
... In the landscape and farm-level approach we observed that a higher canopy cover and cocoa flower abundance was positively correlated with Diptera abundance. This can be associated to the microclimate given by shade trees (Young, 1986;Tscharntke et al., 2011), as their canopy reduces light intensity, increases humidity, and buffers farm temperatures (Wanger et al., 2018). Dead leaves and branches of shade trees contribute to enrich the soil organic substrates which are presumably important for securing flower visitor habitats and enhancing their populations (Kaufmann, 1975;Young, 1986;Tscharntke et al., 2011;Toledo-Hernández et al., 2017: Arnold et al., 2018. ...
Article
Cocoa (Theobroma cacao L.), a major commodity globally, depends on insects for pollination. However, the cocoa pollinator identity is largely unknown and there are important knowledge gaps regarding landscape and farm-level management driving pollinators. Here we analyzed flower visitation with two approaches to quantify how landscape and farm-level factors affect potential pollinators (flower visitors) of cocoa in Central Sulawesi, Indonesia. In the first approach (landscape and farm-level) we selected 18 farms and focused on the relative importance of distance to forest (m), potential-pollinator habitats surrounding the farm (i.e. secondary forests and cocoa agroforests [%]), canopy cover (%), leaf-litter amount (kg/m²), and cocoa flower abundance for flower visitors. In the second approach (experimental farm management) we manipulated leaf-litter in 24 farms, because high leaf-litter is suggested to enhance flower visitors. We found that ants and Diptera were the most common flower visitors, and although previous studies suggest ceratopogonids as main cocoa pollinators, none were captured in this study. In the landscape and farm-level approach, potential-pollinator habitats surrounding the farm, and increased canopy cover enhanced ant and Diptera abundance, whereas distance to forest had no effect. In the experimental farm management approach, potential-pollinator habitats surrounding the farm rather than leaf-litter manipulation increased Diptera and ant abundance. In summary conservation of forests and agroforests surrounding the farm, maintaining canopy cover and minimum leaf-litter enhance cocoa flower visitors. Thus, farms with shade trees embedded in a biodiversity-friendly landscape are important for conservation of potential pollinators and pollination services and, thereby, promotion of sustainable cocoa.
... On the other hand, higher overall water demand in certain agroforestry species combinations (vs. monoculture) may increase negative effects on cocoa physiology and survival when water is limited (Abdulai et al. (2018), but see Norgrove (2018) and Wanger et al. (2018)). To discriminate among different outcomes, however, it is challenging to systematically measure and predict biophysical processes on agroforestry systems due to their inherent structural and functional diversity. ...
... However, in another study in Ghana, mortality of mature cocoa during a drought was shown to be higher in agroforestry than in monoculture (Abdulai et al., 2018). In that study, soil texture (sandy loam and loams) was not controlled across the different shade tree treatments (Abdulai et al., 2018;Wanger et al., 2018). Our study shows that overall soil texture is important in driving variation in cocoa root traits but also can directly affect soil moisture availability, in turn regulating leaf traits such as SLA in cocoa when in agroforestry. ...
Article
The diversification of agroecosystems with shade trees has a complex role in climate change adaptation. Multiple interactions among shade tree composition, heterogeneous soil conditions, and resulting microclimate modifications makes reproducible evaluations of agroforestry as a climate change adaptation practice challenging. In this study we systematically investigate soil water and nutrient acquisition strategies in cocoa (Theobroma cacao) along a climatic and diversity gradient in Ghana, West Africa. We adopted a functional trait-based approach to comparatively examine cocoa root strategies in monoculture or in agroforestry with a single species of shade tree (Terminalia ivorensis) across two precipitation regimes (optimal and suboptimal dry), and in contrasting edaphic conditions (sandy and loam). Variance decomposition indicated that shade trees explained 20 % of the variability in absorptive root trait covariation in cocoa. However, shade tree effects on trait expression were not systematic and depended on climatic and edaphic conditions. Notably, effects of shade trees were amplified on fine-textured soils, with significantly higher conservative trait values of cocoa absorptive roots when in agroforestry within a suboptimal precipitation regime. Transport root traits (root tissue density, diameter) associated with water and solute transport strongly varied among contrasting climate and edaphic conditions. Structural equation models indicated that soil texture played a critical role in regulating transport root trait expression. In agroforestry, clay content improved soil moisture levels, and, in suboptimal climate, fine root growth rates were positively affected by specific leaf area while being significantly controlled by soil texture. Results describe the importance of soil texture in controlling the effect of shade trees on cocoa cultivated in suboptimal precipitation regimes. Thus, agroforestry success as a climate change adaptation strategy in cocoa systems requires detailed assessments of crop strategies in different climatic conditions, as well as identification of soil-mediated filters on crop function.
... unutilized at the time of drought-induced tree mortality (Norgrove 2018;Wanger et al. 2018). In terms of type II evidence, the initial experiments suggested this had not been the 'right tree for the right place', rather than a generic test of whether shaded cocoa systems can contribute to climate resilience. ...
Article
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Agroforestry (AF)-based adaptation to global climate change can consist of (1) reversal of negative trends in diverse tree cover as generic portfolio risk management strategy; (2) targeted, strategic, shift in resource capture (e.g. light, water) to adjust to changing conditions (e.g. lower or more variable rainfall, higher temperatures); (3) vegetation-based influences on rainfall patterns; or (4) adaptive, tactical, management of tree-crop interactions based on weather forecasts for the (next) growing season. Forty years ago, a tree physiological research tradition in aboveground and belowground resource capture was established with questions and methods on climate-tree-soil-crop interactions in space and time that are still relevant for today’s challenges. After summarising early research contributions, we review recent literature to assess current levels of uncertainty in climate adaptation assessments in and through AF. Quantification of microclimate within and around tree canopies showed a gap between standard climate station data (designed to avoid tree influences) and the actual climate in which crop and tree meristems or livestock operates in real-world AF. Where global scenario modelling of ‘macroclimate’ change in mean annual rainfall and temperature extrapolates from climate station conditions in past decades, it ignores microclimate effects of trees. There still is a shortage of long-term phenology records to analyse tree biological responses across a wide range of species to climate variability, especially where flowering and pollination matter. Physiological understanding can complement farmer knowledge and help guide policy decisions that allow AF solutions to emerge and tree germplasm to be adjusted for the growing conditions expected over the lifetime of a tree.
... There seems to be only one other on-farm study of the effect of 2015/16 ENSO drought on cocoa trees, done in Ghana [43].The authors concluded that full-sun plantations were more resilient to drought than agroforests by comparing mortality, transpiration rates and soil water content in cocoa trees under only three specific shading regimes (full sun cocoa, cocoa-Albizia ferruginea and cocoa-Antiaris toxicaria) in only one farm. The generality of this conclusion have been questioned by [44,45] who pointed out that 1) these two cocoa-shade tree associations were not representative of an agroforest and 2) the sub-optimal climate of the region (based on a single site) was not representative of climate conditions where cocoa is usually grown. Thus, our study is the first recording the effect of a natural severe drought on shaded cocoa in complex agroforestry systems based on data from several cocoa farms. ...
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Agroforestry is widely promoted as a potential solution to address multiple UN Sustainable Development Goals, including Zero Hunger, Responsible Consumption and Production, Climate Action, and Life on Land. Nonetheless, agroforests in the tropics often result from direct forest conversions, displacing rapidly vanishing and highly biodiverse forests with large carbon stocks, causing undesirable trade-offs. Scientists thus debate whether the promotion of agroforestry in tropical landscapes is a sensible policy. So far, this debate typically fails to consider land-use history, that is, whether an agroforest is derived from forest or from open land. Indeed, 57% of papers which we systematically reviewed did not describe the land-use history of focal agroforestry systems. We further find that forest-derived agroforestry supports higher biodiversity than open-land-derived agroforestry but essentially represents a degradation of forest, whereas open-land-derived agroforestry rehabilitates formerly forested open land. Based on a conceptual framework, we recommend to (a) promote agroforestry on suitable open land, (b) maintain tree cover in existing forest-derived agroforests, and (c) conserve remaining forests. Land-use history should be incorporated into land-use policy to avoid incentivizing forest degradation and to harness the potential of agroforestry for ecosystem services and biodiversity.
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1. Agricultural intensification reduces ecological resilience of land-use systems, whereas paradoxically, environmental change and climate extremes require a higher response capacity than ever. Adaptation strategies to environmental change include maintenance of shade trees in tropical agroforestry, but conversion of shaded to unshaded systems is common practice to increase short-term yield. 2. In this paper, we review the short-term and long-term ecological benefits of shade trees in coffee Coffea arabica, C. canephora and cacao Theobroma cacao agroforestry and emphasize the poorly understood, multifunctional role of shade trees for farmers and conservation alike. 3. Both coffee and cacao are tropical understorey plants. Shade trees in agroforestry enhance functional biodiversity, carbon sequestration, soil fertility, drought resistance as well as weed and biological pest control. However, shade is needed for young cacao trees only and is less important in older cacao plantations. This changing response to shade regime with cacao plantation age often results in a transient role for shade and associated biodiversity in agroforestry. 4. Abandonment of old, unshaded cacao in favour of planting young cacao in new, thinned forest sites can be named ‘short-term cacao boom-and-bust cycle’, which counteracts tropical forest conservation. In a ‘long-term cacao boom-and-bust cycle’, cacao boom can be followed by cacao bust due to unmanageable pest and pathogen levels (e.g. in Brazil and Malaysia). Higher pest densities can result from physiological stress in unshaded cacao and from the larger cacao area planted. Risk-averse farmers avoid long-term vulnerability of their agroforestry systems by keeping shade as an insurance against insect pest outbreaks, whereas yield-maximizing farmers reduce shade and aim at short-term monetary benefits. 5. Synthesis and applications. Sustainable agroforestry management needs to conserve or create a diverse layer of multi-purpose shade trees that can be pruned rather than removed when crops mature. Incentives from payment-for-ecosystem services and certification schemes encourage farmers to keep high to medium shade tree cover. Reducing pesticide spraying protects functional agrobiodiversity such as antagonists of pests and diseases, pollinating midges determining cacao yields and pollinating bees enhancing coffee yield. In a landscape perspective, natural forest alongside agroforestry allows noncrop-crop spillover of a diversity of functionally important organisms. Knowledge transfer between farmers, agronomists and ecologists in a participatory approach helps to encourage a shade management regime that balances economic and ecological needs and provides a ‘diversified food-and-cash crop’ livelihood strategy.
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Agroforestry systems may play a critical role in reducing the vulnerability of farmers' livelihood to droughts as tree-based systems provide several mechanisms that can mitigate the impacts from extreme weather events. Here, we use a replicated throughfall reduction experiment to study the drought response of a cacao/Gliricidia stand over a 13-month period. Soil water content was successfully reduced down to a soil depth of at least 2.5 m. Contrary to our expectations we measured only relatively small nonsignificant changes in cacao (−11%) and Gliricidia (−12%) sap flux densities, cacao leaf litterfall (+8%), Gliricidia leaf litterfall (−2%), soil carbon dioxide efflux (−14%), and cacao yield (−10%) during roof closure. However, cacao bean yield in roof plots was substantially lower (−45%) compared with control plots during the main harvest following the period when soil water content was lowest. This indicates that cacao bean yield was more sensitive to drought than other ecosystem functions. We found evidence in this agroforest that there is complementary use of soil water resources through vertical partitioning of water uptake between cacao and Gliricidia. This, in combination with acclimation may have helped cacao trees to cope with the induced drought. Cacao agroforests may thus play an important role as a drought-tolerant land use in those (sub-) tropical regions where the frequency and severity of droughts is projected to increase.