Shading and agroforestry

Climate change impact

The changing climate of the coming decades is expected to alter the suitability of many current cocoa production sites. Increases in cocoa stress, mortality, and vulnerability along with lower growth, yields, and quality are the consequences of lower suitability. Production intensification efforts of the past decades led to the growing adoption of unshaded or low shade cultivation which increased the exposure of cocoa trees to unfavourable climatic developments. Cocoa trees in shaded farms experience less damage from floods, storms, heat stress, intensive rainfall, and pests. Moreover, as climate change increases the variability in yields and their quality, it becomes increasingly important for farmers to diversify their incomes.

Key points

Shade cover affects yields, but the relationship is likely not linear. Management characteristics are important.
Agroforestry provides many environmental benefits, including higher biodiversity, higher carbon stocks, and lower soil erosion.
Farmer’s livelihoods can be improved through agroforestry. Fruit trees production can be consumed or sold. Timber trees act as insurance or wealth storage.
Improved adaptation capacity through management of the cocoa microclimate is possible in agroforestry. Farmers can change their pruning practices, for example, to counter rising temperatures on the farm.
Several entities have made commitments to increase agroforestry/shaded production. As part of the Cocoa and Forests Initiative, for example, 33 manufacturers, suppliers, and retailers as well as the governments of Colombia, Côte d’Ivoire, and Ghana have signed up to restore forest land and produce zero-deforestation cocoa.

Description of practices

Shaded and agroforestry production systems are characterized by the canopy cover under which cocoa trees grow. During establishment, thinning of the forest canopy and eliminating some trees, helps preserve characteristics of the original forest but also has disadvantages: shade is not uniform, management is more difficult, and farming equipment may be restricted by tree arrangement (Asare, et al. 2017). Similarly, in fallow land farmers can plant shade trees alongside cocoa.

Cocoa agroforestry production systems vary in many aspects: shade tree species and age, canopy cover, canopy height, etc. Multistrata agroforestry systems, for example, have a microclimate defined by trees at different heights. Regarding shade tree species, cocoa-timber agroforestry systems are often recommended to fulfill ecosystem and livelihood objectives. Timber provides shade for cocoa and adds to farmer well-being through the use or sale of timber, or as a type of savings mechanism to be cut and sold when required (Somarriba et al. 2014). Other typical varieties used in agroforestry are fruit trees (banana, orange, peach palm, etc.). Successional agroforestry has been suggested to maximize biodiversity, diversify incomes, enhance soil fertility and provide other valuable ecosystem services. Successional agroforestry emphasizes the inclusion of a large diversity of vertical and horizontal crops associated with the local ecosystem (Milz, et al. 2011).

Shade tree management depends on the chosen system, but 30 to 50% is the CSC-recommended level of canopy cover. Canopy cover should be higher the warmer and drier the climate is. Shade tree species choice should be informed by leaf shedding pattern, deepness of roots to ensure no competition with cocoa tree roots, hosting of natural enemies of pests and diseases (or at least not hosting pests and diseases), and water tolerance, among others (Dohmen, et al. 2017).

State of the art

The relationschip between yields and shade is not-monocausal. In many cocoa zones light is not limiting yields, and a parabolic relationship between shade and yield can be found, where in low- to intermediate shade levels yields increase compared to full-sun systems. In the literature, also other relationships can be found, but it is generally agreed that shaded farms are more long-lived and that early positive results of full-sun systems could be reversed when the entire life span of the plantation is considered. Full-sun systems have higher short-term yields, but they are associated with the long-term loss of soil organic matter and nitrogen content, and lower environmental sustainability and food security (Tondoh, et al. 2015). Yield is limited in agroforestry by reduction in photosynthesis due to shade and competition for soil resources such as water (Carr and Lockwood, 2011). However, due to the diverse nature of shade tree species, the degree of soil water competition is hard to quantify (Mommer, 1999).

The yields of cocoa agroforestry systems are sustained over the long-term. Agroforestry systems are more resilient to climate change because farmers can regulate the microclimate of their plots through pruning and planting of shade trees. Shade trees protect cocoa plants from damaging winds and heat stress, among others (Carr and Lockwood, 2011). A meta-analysis on financial and biodiversity aspects of shaded vs. intensified cocoa and coffee production indicated that shaded production systems are more profitable and cost-efficient (Jezeer, et al. 2017). Moreover, agroforestry systems are better at conserving biodiversity than intensified production systems, especially when plant diversity and canopy complexity are considered (Jezeer, et al. 2017).

Tscharntke, et al (2011)

Johns (1999)

Asare, et al. (2014)

Schneider, et al. (2016)

Outlook

Growing demand and rising prices are likely to make full-sun production more attractive to farmers in the short-term (Lojka et al 2018). There is a lack of on-station trials considering different shade cover levels and age-yield profiles (Asare, et al. 2014) and studies working with long-term data on different production systems are rare, and the lack of systematic evidence on agroforestry leads to debates driven by ideology (Schneider, et al. 2017). Further research is required to ensure selected shade trees species do not increase incidence of pests and diseases (Smith-Dumont, et al. 2014). The choice of canopy cover is complex, the appropriate cover is dependent on the soil, present and future climate conditions, predominant pests and diseases, as well as farm-level financial decisions (Clough, et al. 2009). Action plans derived from commitments, such as the Cocoa and Forest Initiative, should consider the CSC as a tool for achieving their environmental, social, and productivity objectives.

Importance in terms of CSA

Productivity: Cocoa agroforestry systems lead to more stable and diversified incomes, a longer life-cycle, and greater climatic resiliency. Productive shade trees can significantly contribute to household incomes and consumption. At establishment, plantain, cocoyam, cassava, maize, etc. can serve as temporary shade for seedlings as well as increase food security of cocoa farming households (Aneani, et al. 2011). Even some forest species are useful as timber, medicine, or fuel (Asase, et al. 2010).

Adaptation: Shade trees not only protect cocoa seedlings from solar radiation during establishment, but also reduce the potential damage caused by flooding, strong winds, intensive rainfall, heat stress, etc. in mature farms. Microclimate regulation through pruning together with weather forecasts can help reduce short-term risks further.

Mitigation: Shade trees increase on-farm carbon stocks; the greater the number and size of shade trees the more carbon storage. Blaser, et al. (2018) find that low-to-intermediate shade (up to 30%) is optimal in terms of the trade-off between yields and ecosystems services.

blaser, et al (2018)

Complexity and link to other practices

The selection of adequate tree species and correct management of cocoa agroforestry systems is complex. On one hand, shade trees may reduce the requirements of fertilizer, pesticide, and herbicide inputs by increasing soil organic matter and creating a suitable space for natural enemies, thus lowering production costs and production losses. The roots of larger trees prevent soil erosion from intense rain and wind Leguminous shade trees increase additional carbon and nutrients in the soil and a reduction in soil degradation, leading to longer-term productivity (Dawoe et al. 2013). Furthermore, the remains of pruning can be used as a soil cover to reduce evapotranspiration during prolonged dry seasons and increase soil organic matter.

On the other hand, some shade tree species may contribute to pest and fungi by either being likely hosts or through the microclimate effect of increasing humidity (Tscharntke, et al. 2011) (Alfaro, et al. 2015). Despite higher levels of humidity, depending on the root depth and water tolerance of shade tree species water competition with cocoa may become a problem. Furthermore, intercropping with productive crops may generate additional changes in the landscape and its species with respect to native forests (Asase, et al. 2010). Price premiums for cocoa grown on agroforestry systems (as opposed to cocoa grown in monoculture systems), for carbon emissions reduction, and other environmental benefits such as forest connectivity and biodiversity preservation (Asare et al. 2014).

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Key studies

-Abdulai, I., Vaast, P., Hoffmann, M.P., Asare, R., Jassogne, L., Van Asten, P., Rötter, R.P. and Graefe, S., 2017. Cocoa agroforestry is less resilient to sub‐optimal and extreme climate than cocoa in full sun. Global change biology, 24(1), pp.273-286.

-Blaser, W.J., Oppong, J., Hart, S.P., Landolt, J., Yeboah, E. and Six, J., 2018. Climate-smart sustainable agriculture in low-to-intermediate shade agroforests. Nature Sustainability, 1(5), p.234.

-Jezeer, R.E., Verweij, P.A., Santos, M.J. and Boot, R.G., 2017. Shaded Coffee and Cocoa–Double Dividend for Biodiversity and Small-scale Farmers. Ecological Economics, 140, pp.136-145.

-Schneider, M., Andres, C., Trujillo, G., Alcon, F., Amurrio, P., Perez, E., … & Milz, J. (2017). Cocoa and total system yields of organic and conventional agroforestry vs. monoculture systems in a long-term field trial in Bolivia. Experimental Agriculture, 53(3), 351-374.

-Schroth, G., Jeusset, A., da Silva Gomes, A., Florence, C.T., Coelho, N.A.P., Faria, D. and Läderach, P., 2016. Climate friendliness of cocoa agroforests is compatible with productivity increase. Mitigation and adaptation strategies for global change, 21(1), pp.67-80.

-Tscharntke, T., Clough, Y., Bhagwat, S.A., Buchori, D., Faust, H., Hertel, D., Hölscher, D., Juhrbandt, J., Kessler, M., Perfecto, I. and Scherber, C., 2011. Multifunctional shade‐tree management in tropical agroforestry landscapes–a review. Journal of Applied Ecology, 48(3), pp.619-629.

– Vaast, P. and Somarriba, E., 2014. Trade-offs between crop intensification and ecosystem services: the role of agroforestry in cocoa cultivation. Agroforestry systems, 88(6), pp.947-956.

Study cases

Case study 1: Bolivia

Agroecosystem resilience and farmers’ perceptions of climate change impacts on cocoa farms in Alto Beni, Bolivia – Jacobi et al. 2013

Background

This study reviews the results of a field trial carried out in Alto Beni, Bolivia to determine the outcomes of monoculture and agroforestry systems (4m x 4m intercropping with plantain) under conventional and organic input use. Full-sun cocoa production is has higher short-term yields, however, it is also likely to have decreasing yields much earlier and it lacks the food security benefits of agroforestry systems. It is crucial to understand the long-term yield development of both production systems.

Relation to CSA

Agroforestry systems provide ecosystem services not available in full-sun cultivations. Full-sun plantations are more sensitive to agrochemical inputs. A large gap is found between the conventional and organic production yields under full-sun, suggesting that access to fertilizers and pesticides is an important factor driving the decision-making process when establishing a cocoa farm. Even though cocoa yields were on average 86% higher in full-sun systems than in agroforestry systems during the establishment phase, the total yields of the system are greater in agroforestry systems by 135%. These results support the food security and stability attributes from which farmers can benefit when adopting agroforestry systems. These can be especially important under increasing cocoa price volatility and changing climate. Agroforestry system yields were less reliant on the use of agrochemical inputs, whereas organic monoculture produced 47% less than with conventional input use. Further trials in different contexts should be carried out to prove whether results are replicable and can be used to inform farmers in other regions

Case study 2: Bolivia

Cocoa and total system yields of organic and conventional agroforestry vs monocultures systems in a long-term field trial in Bolivia. – Schneider et al. 2017

Background

Relation to CSA

Case study 3: Ghana

Cocoa agroforestry is less resilient to sub-optimal and extreme climate than cocoa in full-sun – Abdulai et al. 2017

Background

This study reviews the results of an experiment on a ten-year-old cocoa plantation in Ghana. Three production systems were compared, two with different shading species (A.taxicaria and A.ferruginea), and one under full-sun. The study period was of one and a half years. Three main variables were studied: daily tree water use rate, daily sap flux density, and daily transpiration rate. The hypothesis of the study was that shade trees would improve resilience to dry and extremely dry periods. These climatic events are expected to become more common in West Africa and other parts of the world where cocoa is grown.

Relation to CSA

It is important that the recommended methods for adaptation are informed by field and research station trials. In this case, the common CSC recommendation of planting shade trees to improve resilience was put into question by the results. Findings could not confirm the initial hypothesis that shade trees increased the resiliency of cocoa under conditions of drought and heat. Although shade trees contributed positively to microclimate moderation during dry and extremely dry periods, and transpiration in shade plots was lower, the full-sun cultivated cocoa plants sustained transpiration and sap flux during drought periods, suggesting greater resilience. Furthermore, there was competition in the soil water as both shade and cocoa tree roots were located at the same depth. It should be noted, however, that this study does not mention any other CSC recommended practice for agroforestry systems. For instance, when dry periods are expected in the future, pruning and thinning should be carried out to increase throughfall and preventative irrigation systems should be considered.

A note on case studies 1, 2, and 3

There is an apparent contradiction between the studies carried out in Bolivia by Jacobi, et al. 2013, and Schneider, et al. 2017, in Bolivia and the study by Abdulai, et al. 2017 in Ghana. It should be borne in mind that CSC practices are not a fixed set of specific rules. In fact, implementation of the recommendation of adopting agroforestry as the main production system still requires localized input into which species are preferable for planting alongside cocoa and what the actual design of the agroforestry system should be. The study by Abdulai, et al. 2017 is a cautionary tale that not all agroforestry production system designs will lead to greater resilience and higher yields. Shade trees should not draw water at the same soil depth as cocoa to prevent water competition, which was a major contributor to the lack of resilience in the Ghanaian agroforest study. Moreover, as has been pointed out elsewhere, different authors dichotomize agroforestry and full-sun according to varying levels of shade cover or number of shade trees per hectare complicating the task of making comparisons between studies. The combination of local knowledge of suitable shade tree species and recommendations from scientific research is likely to result in improved outcomes from switching to agroforestry cultivation.

Case study 4: Brazil

Climate friendliness of cocoa agroforests is compatible with productivity increase – Schroth, et al. 2016.

Background

Using data gathered in Southern Bahia, Brazil, the authors take a look at the trade-off that confronts the increasing demand for sustainably produced cocoa in importing countries and the growing adoption of intensification in producing countries. To assess this relationship, they interviewed farmers at 26 different cocoa farms and recorded field inventories including information on management and production practices, carbon stocks and carbon footprints, shade cover, etc.

Relation to CSA

This article supports the CSC approach to cocoa farming by providing evidence as to the compatibility between the pillars of increasing productivity and mitigation of greenhouse gases. The authors’ findings suggest that the highest yields in the region are compatible with higher shade covers and consequently higher carbon stocks in large trees. The excessive use of fertilizer was associated with relatively high emissions often without proportionately increasing yields (possibly due to abundant shade or poor maintenance of cocoa trees). Low-shade production systems had on average little more than half the carbon stocks found in traditional shaded systems. Farm shade levels ranged from 20 to 90% and an optimal relationship with yields was estimated at 55% shade cover. A conclusion that could be drawn from the research into cocoa plots in Southern Bahia is that intensification efforts do not always lead to higher yields, and they come at the cost of higher greenhouse gas emissions and lower carbon stocks. In terms of carbon stocks, larger trees are the most relevant, as thinning and pruning affects the carbon stocks of smaller trees more significantly. Most importantly, this article recognizes the compatibility between production and mitigation objectives in agroforestry production systems.

Case study 5: Ghana

Influences of shading and fertilization on on-farm yields of cocoa in Ghana – Asare, et al. 2017)

Background

Complex agroforest systems are found in most cocoa farms in Ghana. In this collaboration between the International Institute of Tropical Agriculture in Ghana, the Nature Conservation Research Centre, a Danish University, and a Ghanaian University. 24 farms from four different districts were identified and studied. Researchers looked at canopy cover in relation with soil nutrients, peak plot temperatures, and yields. The study does not consider other effects shade tree species may have on cocoa trees and yields.

Relation to CSA

When advocating for agroforestry production it is important to consider all farming aspects which are affected. Because the trees in this study were deciduous, the dry season yields were similar between agroforestry and low-shade systems. However, in some locations yields during the main crop season were higher under low-shade. In other locations, canopy cover had positive effects on yields. What this demonstrates is that there is no clear direction in the effect of shade cover on yields, therefore the recommendations of shade tree removal may be misguided in a substantial amount of cases. Although no significantly large differences in soil nutrients were found, the authors highlight the need for soil nutrient analysis to enhance input efficiency by applying nutrient targeted fertilizers.