No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Cocoa Production: Monocultures are Not the Solution to Climate Adaptation - - Response to Abdulai et al. 2017
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.
... 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). ...
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. ...
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. ...
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.
... Furthermore, fruit set and mature fruits increased in grafted cocoa trees by 31% (from 13.6 to 17.8 fruit set/tree) and by 37% (from 2.3 to 3.2 fruits/tree), in contrast to un-grafted trees. As fruit development improvements are achieved with minimum to intermediate labor effort in low and high canopy cover respectively, and to leverage the wellestablished shade tree benefits for biodiversity and climate resilience (Tscharntke et al., 2012;Wanger et al., 2018), we strongly recommend to perform hand pollination in plantations with shade under 40-50% canopy cover Steffan-Dewenter et al., 2007). ...
Agricultural diversification can enhance climate resilience, biodiversity conservation, and livelihood in global farming systems. Diverse agroforestry systems with cocoa have been shown to provide all these benefits, but the often-lower yields compared to monocultures limit agroforestry adoption by smallholder farmers. Cocoa yield is pollination-limited, and here, we quantified the effect of hand pollination in cocoa on fruit set, fruit abortion or cherelle wilt, pest and diseases, and number of mature fruits. Experiments were conducted in Bahia, Brazil, along a shade gradient from low [10-30%] to high [70-100%] canopy cover and with cocoa trees grafted with high-yielding varieties. We found on average 331% fruit set, and 300% mature fruit increase (i.e. ripe pods) per tree by enhancing pollination by hand as little as 10% of the flowers/tree, compared to the control (i.e. with only natural pollination). Fruit set, fruit losses, and mature fruit development linked to hand pollination was higher in low compared to highly shaded cocoa areas. We found 31% higher fruit set and 37% higher number of mature fruits in grafted than un-grafted trees. Further, when comparing efforts invested in hand pollination, minimum labor (~5 min/tree to pollinate 10-30% of the flowers/tree) led to a 871% fruit set and a 750% mature fruit increase under low canopy cover, and intermediate labor (~15 min/tree to pollinate 40-60% flowers/tree) to a 629% fruit set under high canopy cover. As ~5-15 min/tree hand pollination can substantially enhance fruit set and number of mature fruits in low as well as high shade management, we recommend performing hand pollination particularly in agroforests under 40-50% canopy cover to create win-win opportunities for high productivity and climate resilience. Future research should focus on the wide range of agroforestry, tree grafting and innovation strategies in all major production regions to capture the long-term variability of hand pollination as a basis to scale-up hand pollination for sustainable cocoa production globally.
... Furthermore, fruit set and mature fruits increased in grafted cocoa trees by 31% (from 13.6 to 17.8 fruit set/tree) and by 37% (from 2.3 to 3.2 fruits/tree), in contrast to un-grafted trees. As fruit development improvements are achieved with minimum to intermediate labor effort in low and high canopy cover respectively, and to leverage the wellestablished shade tree benefits for biodiversity and climate resilience (Tscharntke et al., 2012;Wanger et al., 2018), we strongly recommend to perform hand pollination in plantations with shade under 40-50% canopy cover Steffan-Dewenter et al., 2007). ...
... The cultivation of Theobroma cacao L (cocoa) is the third most important crop in the group of agricultural commodities, after coffee and sugarcane, worldwide, and represents an important source of economic income for the countries where it is grown (Wanger et al., 2018). Due to its biodiversity, Ecuador is suitable for the cultivation of Fino de Aroma cocoa, which is one of the most sought-after cocoa varieties by the main chocolatiers and chocolate manufacturers worldwide. ...
The objective of this study was to evaluate the behavior of mycorrhizae in national cocoa plantations (Theobroma cacao L.) with different production systems, through the relationship between soil physicochemical characteristics and the ecology of arbuscular mycorrhizae as bioindicators of soil quality. Sixty soil and root samples were taken from the cantons of Quevedo, Buena Fé, Valencia, La Maná, and Mocache, to recover and count arbuscular mycorrhizae that inhabit the cocoa rhizosphere. Descriptive statistical methods were used for the general representation of the results of the observations; inferential methods were used to determine if the study factor (fertilizer application) in the influence on the ecological parameters of mycorrhizae. In terms of arbuscular mycorrhizal fungi (AMF) species richness, the PERMANOVA test showed that there were no significant statistical differences in fungal genus richness between farms with fertilization (p: 0.9936). I
... 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. ...
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. ...
Climate models predict a possible increase in the frequency of strong climate events such as El Niño-Southern Oscillation (ENSO), which in parts of the tropics are the cause of exceptional droughts, these threaten global food production. Agroforestry systems are often suggested as promising diversification options to increase farmers' resilience to extreme climatic events. In the Northeastern state of Bahia, where most Brazilian cocoa is grown in wildlife-friendly agroforests, ENSOs cause severe droughts which negatively affect forest and agriculture. Cocoa (Theobroma cacao) is described as being sensitive to drought but there are no field-studies of the effect of ENSO-related drought on adult cocoa trees in the America's; there is one study of an experimentally-imposed drought in Indonesia which resulted in 10 to 46% yield loss. In our study, in randomly chosen farms in Bahia, Brazil, we measured the effect of the 2015–16 severe ENSO, which caused an unprecedented drought in cocoa agroforests. We show that drought caused high cocoa tree mortality (15%) and severely decreased cocoa yield (89%); the drought also increased infection rate of the chronic fungal disease witches' broom (Moniliophthora perniciosa). Ours findings showed that Brazilian cocoa agroforests are at risk and that increasing frequency of strong droughts are likely to cause decreased cocoa yields in the coming decades. Furthermore, because cocoa, like many crops, is grown somewhat beyond its climatic limits, it and other crops could be the 'canaries in the coalmine' warning of forthcoming major drought effects on semi-natural and natural vegetation.
Agroforestry is considered to be climate-smart; not only can it be profitable for smallholders, but also it represents a sustainable form of intensive agriculture that can help buffer the effects of extreme climate. However, its feasibility remains under dispute in semiarid regions, especially where there can be extreme droughts. We therefore investigated how intercropping with annual bioenergy crops, soybean (Glycine max) and canola (Brassica rapa), affects ecohydrology in young apple trees, and how the trees respond to droughts of varying degrees on the semiarid Loess Plateau of China. A monoculture orchard was used as a control, and the droughts were controlled by reducing natural precipitation by 15% (moderate drought) and 25% (severe drought). We found that, compared with the monoculture, the agroforestry system increased soil water storage (SWS) in the 80-280 cm by 5-8%, apple tree's daily water use (Q) by 76-118%, and transpiration per unit leaf area (TrL) by 33-71%; it also promoted tree growth. Both drought levels affected soil water availability and water use. Compared with agroforestry without an enforced drought, moderate drought conditions reduced SWS in the 80-180 cm by 11-15%, the Q value by 19-24%, and TrL value by 13-17%, and these apple trees still had higher Q and TrL levels than monoculture trees suffering no drought; and severe drought conditions caused the apple trees to absorb soil water from deeper soil layers, and reduced SWS in the 80-280 cm by 16-18%, Q by 50-60% and TrL by 12-38%. However, there were no significant difference in Q, TrL and aboveground growth parameters for trees between monoculture and severe drought treatments. These findings demonstrate that agroforestry has clear ecohydrological advantage to monoculture for young apple trees in semiarid regions.
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.
ABSTRACT The physical and chemical properties of the soil, as a whole, condition the productive capacity of the plants. The research aimed to characterize the properties of the main cocoa soils in the province of El Oro (Ecuador), in the municipalities of El Guabo, Machala, San-ta Rosa and Pasaje. We selected 30 plots of cocoa types CCN51 (n = 18) and National (n = 12), from which soil samples from 0 cm to 30 cm were extracted to analyze various physical and chemical properties in the laboratory. The results showed no significant differences (P > 0.05) between the physical properties. The carbon levels, ranged from 1.58 % (El Guabo) to 2.06 % (Santa Rosa). In general, the nitrogen was low (0.16 % a 0.18 %). The values of: CE (0.13 13 dS/m to-0.21 dS/m), pH (6.46 to 7.72), CIC (23.4040 cmol/kg to-43.86 cmol/kg), potassium (0.310.31 cmol/kg to-1.86 cmol/kg) and calcium (19.99 cmol/kg to-37.73 cmol/kg) tended to be higher in Ma-chala soils (< 0.05) and lower in Pasaje soils. The soils of Santa Rosa had higher concentrations of copper (16.6 mg/k) (P < 0.05) than in the rest of the municipalities. Cocoa yield CCN51 (2 570.24 kg/ha/y to 4 158.34 kg/ha/y) was higher than National (324.00 kg/ha/y to 814.17 kg/ha/y). The soils of Machala presented higher nutritional values, associated with higher average yield for National variety cocoa , and a high yield for CCN51 variety.
With the objective of updating the criteria on agrarian sustainability of it is proposed the adaptation of a method from 3 labor frameworks for measuring agricultural systems sustainability. It was established a systematic review of the scientific information, with an assessment instrument (surveys) or type of sample (soil, water or biomass) to be taken from agricultural systems. The criteria are structured at the farm level, where the soil resource, water management, diversity of production, education and training are considered to be of higher incidence in the sustainability, producing indicators approved by a panel of experts whose contribution is validated with the coefficient alpha of Cronbach. Weight assignment to the indicators is contributed according to the scientific literature, it continues with the linear normalization of 0 to 1; In addition an analysis of main components is proposed to reduce indicators and to perform radial graphs for its examination by domains and criteria with the purpose of improving its qualification in the future.
Background and Aims
To increase yield, cacao is planted increasingly in unshaded monocultures, replacing a more traditional cultivation under shade. We investigated how shade tree cover and species diversity affect the root system and its dynamics.
Methods
In a replicated study in Sulawesi (Indonesia), we studied the fine and coarse root system down to 3 m soil depth in three modern and more traditional cacao cultivation systems: unshaded cacao monoculture (Cacao-mono), cacao under either the legume Gliricidia sepium (Cacao-Gliricidia), or a diverse (> 6 species) shade tree cover (Cacao-multi). We analysed the vertical distribution of fine, large and coarse roots as well as fine root production, turnover and morphology on the species level.
Results
Stand-level fine root biomass showed a doubling with increasing shade tree cover (from 206 to 432 g m⁻²), but a tendency for a decrease in cacao fine root biomass. The presence of Gliricidia roots seemed to shift the cacao fine roots to a more shallow distribution, while the presence of shade tree roots in the Cacao-multi systems caused a biomass reduction and relative downward shift of the cacao roots. The turnover of cacao fine roots was much higher in the Cacao-multi stands than in the other two cultivation systems, although stand-level root production remained unchanged across the three systems. According to the stable isotope signature, Gliricidia extracted water from deeper soil layers than cacao, while no soil water partitioning was observed in the Cacao-multi stands.
Conclusions
Our data suggest that the cacao trees altered their fine root distribution patterns in response to root competition. Both interspecific competition and root system segregation seem to play an important role in cacao agroforests with different shade tree cover.
Cocoa agroforestry is perceived as potential adaptation strategy to sub-optimal or adverse environmental conditions such as drought. We tested this strategy over wet, dry and extremely dry periods comparing cocoa in full sun with agroforestry systems: shaded by (i) a leguminous tree species, Albizia ferruginea and (ii) Antiaris toxicaria, the most common shade tree species in the region. We monitored micro-climate, sap flux density, throughfall and soil water content from November 2014 to March 2016 at the forest-savannah transition zone of Ghana with climate and drought events during the study period serving as proxy for projected future climatic conditions in marginal cocoa cultivation areas of West Africa. Combined transpiration of cocoa and shade trees was significantly higher than cocoa in full sun during wet and dry periods. During wet period, transpiration rate of cocoa plants shaded by A. ferruginea was significantly lower than cocoa under A. toxicaria and full sun. During the extreme drought of 2015/16, all cocoa plants under A. ferruginea died. Cocoa plants under A. toxicaria suffered 77% mortality and massive stress with significantly reduced sap flux density of 115 gcm⁻²d⁻¹ whereas cocoa in full sun maintained higher sap flux density of 170 gcm⁻²d⁻¹. Moreover, cocoa sap flux recovery after the extreme drought was significantly higher in full sun (163 gcm⁻²d⁻¹) than under A. toxicaria (37 g cm⁻² d⁻¹). Soil water content in full sun was higher than in shaded systems suggesting that cocoa mortality in the shaded systems was linked to strong competition for soil water. The present results have major implications for cocoa cultivation under climate change. Promoting shade cocoa agroforestry as drought resilient system especially under climate change needs to be carefully reconsidered as shade tree species such as the recommended leguminous A. ferruginea constitute major risk to cocoa functioning under extended severe drought.
Forest-driven water and energy cycles are poorly integrated into regional, national, continental and global decision-making on climate change adaptation, mitigation, land use and water management. This constrains humanity's ability to protect our planet's climate and life-sustaining functions. The substantial body of research we review reveals that forest, water and energy interactions provide the foundations for carbon storage, for cooling terrestrial surfaces and for distributing water resources. Forests and trees must be recognized as prime regulators within the water, energy and carbon cycles. If these functions are ignored, planners will be unable to assess, adapt to or mitigate the impacts of changing land cover and climate. Our call to action targets a reversal of paradigms, from a carbon-centric model to one that treats the hydrologic and climate-cooling effects of trees and forests as the first order of priority. For reasons of sustainability, carbon storage must remain a secondary, though valuable, by-product. The effects of tree cover on climate at local, regional and continental scales offer benefits that demand wider recognition. The forest-and tree-centered research insights we review and analyze provide a knowledge-base for improving plans, policies and actions. Our understanding of how trees and forests influence water, energy Adaptation Sustainability and carbon cycles has important implications, both for the structure of planning, management and governance institutions, as well as for how trees and forests might be used to improve sustainability, adaptation and mitigation efforts.
The negative effects of climate change on cocoa production are often enhanced through agricultural intensification, while research institutions and enterprises try to minimize yield gaps with production strategies mitigating climate risk. Ecological intensification is such a production strategy, whereby yield increase is promoted through reduced agrochemical inputs and increased regulating ecosystem services such as pollination. However, we still know little about cocoa pollination ecology and services, although they appear to be key to understand yield functions. Here, we provide an extensive literature review on cocoa pollination focusing on three main aspects: non-plant (external) and plant regulated (internal) factors affecting pollination, pollinator agents, and ecological intensification management for enhancing pollination success and yield. Pollination services by many arthropod groups such as ants, bees, and parasitic wasps, and not only ceratopogonids, may be a way to increase cocoa productivity and secure smallholders income, but their role is unknown. Several environmental and socioeconomic factors can blur potential pollination benefits. Current knowledge gaps preclude our understanding of how to (i) identify the major pollinator species, (ii) disentangle the direct or indirect role of ants in pollination, (iii) design effective habitat improvements for pollination (by litter and shade management), and (iv) quantify the yield gaps due to pollination limitation. Optimizing cocoa pollination alone appears to be a powerful ecological tool to increase the yield of smallholders, but experimental research is required to validate these results in a realistic setting. In general, industry, governments and smallholders need to develop more joined efforts to ecological production strategies. In particular, farm-base management innovations based on robust scientific evidence must be designed to meet the increasing demand for chocolate and to mitigate cocoa yield gaps. This review suggests that diversified systems and associated ecosystem services, such as pollination, can help to achieve such goals.
Rubber tree mono-cultural plantations are expanding. Also, there is an increasing search for 'green' rubber production. Rubber tree cultivation in stands with admixed, spontaneously established native trees, referred to as jungle rubber, has a long tradition on Sumatra. For rubber tree monocultures on mainland Asia, concerns have been raised because of potentially very high tree transpiration rates. The objectives of our study were to analyze tree water use rates and tree soil water uptake depths in mono-cultural and jungle rubber stands with a focus on the role of tree diameter. Sap flux measurements suggest similar water use rates for rubber trees in the two cultivation systems. Stand-level transpiration in jungle rubber was 27% higher than in rubber monocultures, which was related to higher stand densities in jungle rubber stands. A water stable isotope (d 18 O and dD) approach suggests different soil water uptake depths for the rubber trees in the two cultivation systems. In a relatively dry period, the main tree water uptake in the monoculture was relatively close to the soil surface, whereas rubber trees in jungle rubber stands mainly took up water from deeper soil strata; here the native trees had their main uptake depth relatively close to the soil surface. This pattern indicates plasticity in rubber tree water uptake and points to competitive displacement. Across rubber trees in both cultivation systems and also among the native trees, there was a clear relationship between tree diameter and soil water uptake depth: bigger trees tended to take up soil water closer to the soil surface. Diameter and density regulation by thinning of big native trees thus appears as a potential management option for influencing water uptake in jungle rubber stands in favor of rubber trees.
Ecological intensification of agriculture (EI) aims to conserve and promote biodiversity and the sustainable use of associated ecosystem services to support resource-efficient production. In many cases EI requires fundamental changes in farm and landscape management as well as the organizations and institutions that support agriculture. Ecologists can facilitate EI by engaging with stakeholders and, in the process, by generating "actionable knowledge" (that is, knowledge that specifically supports stakeholder decision making and consequent actions). Using three case studies as examples, we propose four principles whereby science can improve the delivery of actionable knowledge for EI: (1) biodiversity conservation helps to ensure the delivery of ecosystem services, (2) management of ecosystem services benefits from a landscape-scale approach, (3) ecosystem service trade-offs and synergies need to be articulated, and (4) EI is associated with complex social dynamics involving farmers, governments, researchers, and related institutions. These principles have the potential to enhance adoption of EI, but institutional and policy challenges remain.
Ghana and Côte d’Ivoire are the world’s leading cocoa (Thebroma cacao) producing countries; together they produce 53 % of the world’s cocoa. Cocoa contributes 7.5 % of the Gross Domestic Product (GDP) of Côte d’Ivoire and 3.4 % of that of Ghana and is an important cash crop for the rural population in the forest zones of these countries. If progressive climate change affected the climatic suitability for cocoa in West Africa, this would have implications for global cocoa output as well as the national economies and farmer livelihoods, with potential repercussions for forests and natural habitat as cocoa growing regions expand, shrink or shift. The objective of this paper is to present future climate scenarios for the main cocoa growing regions of Ghana and Côte d’Ivoire and to predict their impact on the relative suitability of these regions for growing cocoa. These analyses are intended to support the respective countries and supply chain actors in developing strategies for reducing the vulnerability of the cocoa sector to climate change. Based on the current distribution of cocoa growing areas and climate change predictions from 19 Global Circulation Models, we predict changes in relative climatic suitability for cocoa for 2050 using an adapted MAXENT model. According to the model, some current cocoa producing areas will become unsuitable (Lagunes and Sud-Comoe in Côte d’Ivoire) requiring crop change, while other areas will require adaptations in agronomic management, and in yet others the climatic suitability for growing cocoa will increase (Kwahu Plateu in Ghana and southwestern Côte d’Ivoire). We recommend the development of site-specific strategies to reduce the vulnerability of cocoa farmers and the sector to future climate change.
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.
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.