Land-use activities, such as clearing tropical forests, practicing subsistence agriculture, and intensifying farmland production, are the most important drivers of biodiversity loss and the associated ecosystem services on the local- and landscape-scale [1
]. Although the rate of tropical forest loss is alarming, some agricultural systems offer a glimmer of hope. Systems using shade species offer greater potential for production, biodiversity conservation, and long-term environmental protection [3
]. Thus, agroforestry is proposed as one of the strategies for conserving natural resources in the tropics [4
]. The agroforestry practice provides a potentially valuable conservation tool that can be useful for reducing land-use pressure and enhancing income from rural livelihoods in tropical countries [5
]. Several examples across the tropics have shown that agroforests represent a substantial proportion of biodiversity of forest reserves [3
Cocoa is one of the most important crops in agroforests [8
]. Cocoa farming has played an important role in the conservation of lowland tropical forest landscapes in Latin America, Africa and Asia over the past centuries and continues to do so today [9
]. It helps to reduce land-use pressure through the availability of useful tree species and other non-timber forest products (NTFPs) and to improve rural livelihoods [10
]. Shade tree systems provide habitat diversity for plant and animal species that do not strictly depend on natural forest. They also connect otherwise disjunctive fragments of the remaining forest patches in the landscape [11
]. Cocoa agroforests systems with a mixture of diverse tree species provide more functions than other land-uses in forest landscapes. These functions include maintenance of carbon stocks, biodiversity conservation, and locally relevant ecosystem services, such as protection of the soil [12
] and better water management [13
]. The introduction of sustainable shade tree management can make cocoa agroforestry an important agent of reforestation [14
]. Shade tree management has positive effects on pest outbreaks that may hold the key to breaking cocoa production cycles and helping conserve valuable tropical biodiversity in agroforestry systems [15
Despite the benefits of agroforestry practices, cocoa agroforestry in natural habitats is an important driver of forest degradation and deforestation [14
]. Land-use planning is needed to reduce further deforestation for the expansion of cocoa land. Such planning can determine areas to preserve under forest cover for ecological reasons and also areas where cocoa might be planted [18
Introduced in Africa more than a century ago, cocoa production is a major contributor to the economies of many African countries [19
]. The continent supplies more than two-thirds of the world’s cocoa, the majority being produced by Côte d’Ivoire and Ghana [20
]. Full-sun systems are found mostly in the Lower Guinean forest systems of Liberia, Ghana, Côte d’Ivoire and Nigeria; the more complex systems are in the Congo Basin countries, mainly in Cameroon and the Democratic Republic of the Congo (DRC) [21
]. As cocoa production increases in DRC, the sector can learn a lot from its West African neighbours about mistakes to avoid and priorities to emphasize, including the importance of sustainable and climate-smart practices and good governance [22
]. In DRC, cocoa agroforests are frequently proposed in projects for REDD+ (reducing emissions from deforestation and forest degradation and the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks in developing countries). The Wildlife Conservation Society, for example, has adopted the idea of growing cocoa as a tool in forest conservation. In the Mambasa region, 1250 hectares (ha) of forest-cover cocoa has planted within the context of the national REDD+ program [23
In DRC, conflicts and political instability have deeply affected the agricultural sector. For example, there are insufficient data on initiatives in the cocoa sector [20
]. Cocoa is generally cultivated by small farmers, most often alongside other crops [22
]. However, the quantities produced are small in comparison to West Africa [24
]. On the other hand, in Tshopo province, cocoa has been promoted since the colonial era when it was planted under controlled forest cover from which cocoa pest species had been eliminated [23
]. However, cocoa cultivation has never been fully developed. Today, most farmers spontaneously plant cocoa in the region by sourcing from former plantations in response to market signals and rumors of market development in the east of DRC [25
]. With adequate assistance, cocoa can be produced sustainably without clearing new forest land and can help reduce household poverty [21
]. Further efforts are needed to rehabilitate existing cocoa farms to develop sustainable cocoa agroforestry [25
In cocoa agroforests, species richness and vegetation structure are key components of structural complexity and form the basis of biodiversity [26
]. Therefore, good knowledge is needed of the plants associated with cocoa trees in cocoa agroforests in DRC. However, no study on the contributions of cocoa agroforests to the conservation of floristic diversity has focused on DRC.
The choice of Tshopo province, more specifically the Bengamisa-Yangambi landscape, is based on its inclusion of the Yangambi Biosphere Reserve. The United Nations Educational, Scientific and Cultural Organization (UNESCO) declared Yangambi a biosphere reserve in 1977 [27
]. Thus, to preserve the important biodiversity of the Yangambi reserve, agroforestry systems in the Bengamisa-Yangambi forest landscape should be studied to understand their influence on the conservation of floristic diversity.
This study paid special attention to how distance from Kisangani (The main city in the landscape) and thus the related disturbance and land-use intensity have affected the floristic composition of cocoa agroforests in the forest landscape. The study is based on the hypothesis that native forest cover, disturbance, land-use intensity, and market access influenced floristic composition of cocoa agroforests. We thus recorded floristic composition of cocoa agroforest in four zones of 15 km each, defined along the main road, from Kisangani city to Yangambi forest reserve landscape, via Bengamisa village.
Cocoa trees introduced in the Yangambi-Bengamisa landscape have been associated with other plants in different cocoa agroforests that are part of the current landscape. Although farmers were advised not to keep some trees in the same field as cocoa plants, they have maintained/introduced plants over the last decades that have some function (edible, hosting caterpillars, medicinal, etc.). A multitude of cocoa farming systems could be classified into three main groups: Model F (agroforests in which companion plants (associated with cocoa trees) are dominated by forest species), Model FP (cocoa agroforests in which companion plants (associated with cocoa trees) are split equally between forest species and oil palms), and Model P (cocoa agroforests in which companion plants (associated with cocoa trees) are dominated by oil palms). Such models thus present different options for strengthening the livelihood of farmers, improving biodiversity conservation, and/or defining an appropriate climate change response in Tshopo province and other parts of DRC. Based on the findings of this study, the diversity of cocoa agroforest models offers a variety of options that can be used in the landscapes to search for balance between ecological conservation and farmers livelihoods.
The distance from the city (Kisangani) is a determining factor in the floristic composition (species diversity and plant density) of the cocoa agroforests. The area close to the city is marked by an abundance of oil palms and some edible species, such as avocados and African pear. Areas near the forests are more abundant to forest species for medicinal use.
The findings provide scientific evidence that can be useful in harnessing cocoa agroforest to improve the livelihoods of farmers, conserve biodiversity, and respond to climate change in the Bengamisa-Yangambi landscape and other forest landscapes of DRC.