Agroforestry systems come in a wide variety of shapes and forms in Africa. These systems all include woody perennials combined with agricultural crops and/or livestock. Trees or shrubs in the landscape or on farms are either solitary, in lines or woodlots and in a random array in the forest before agriculture changed them.

Different compositions

Several agroforestry practices can be relevant for different agroecological zones, and many systems with a range of different compositions can fulfil essentially the same functions for livelihoods and landscapes. There is thus no single classification scheme that can be universally applied. What differentiates agroforestry from other land uses is the deliberate inclusion of woody perennials on farms, which usually leads to significant economic and/or ecological interactions between woody and non-woody system components. In most documented cases of successful agroforestry establishment, tree-based systems are more productive, more sustainable and more attuned to people’s cultural or material needs than treeless alternatives.

Yet agroforestry is not being adopted everywhere, and better insights are needed into the productive and environmental performance of agroforestry systems, socio-cultural and political prerequisites for their establishment, and the trade-offs farmers face in choosing between land use practices. These site factors are likely to vary at fine spatial and possibly temporal scales, making the development of
robust targeting tools for agroforestry intervention a key priority in agroforestry research.

The different types of agroforestry systems in different places depend on the environmental, climatic, economic or socio-cultural role they play. Some prominent examples that illustrate the diversity of agroforestry include the parkland systems of the Sahel, multistorey home gardens on Mt Kilimanjaro in Tanzania, cocoa systems in Côte d’Ivoire, and rotational woodlots in Kenya.

The lush green of the Sahelian acacia savanna during the rainy summer season in Mali. Note the large baobab among the acacias. (Source: https://en.wikipedia.org/wiki/Sahel#/media/File:Sahel_forest_near_Kayes_Mali.jpg)

Agrobiodiversity by means of agroforestry systems

Biodiversity, also in agriculture, is crucial to agricultural production and food security, but also to enhance ecosystem services, including biological pest control, pollination and nutrient recycling. Important components of biodiversity in agricultural landscapes are compositional heterogeneity, that refers to the number and proportions of different land usage or cover types, and configurational heterogeneity, which refers to the spatial arrangement of those land usage or cover types. On large farms in developed countries, intensification has led to simplified landscape structures dominated by annual crops. Smallholder farmers in developing countries manage a diversity of crops, animals, trees and natural resources, thereby creating complex and diverse agricultural landscapes that often include natural and semi-natural lands.

Biodiversity within agricultural landscapes enhance farm productivity through the provision of ecosystem services (water retention, soil erosion control), but can also directly contribute to better food security and income. Integrated tree-crop-livestock systems on smallholder farms increase diversity of nutritious food products, such as the conservation of wild vegetables that are rich in nutrients and can complement staple food crops. Sale of tree products, including fruits, fodder and fuelwood, can contribute to the household income, especially for poor families.

Sahel parkland

The Sahel spans 5 900 km from the Atlantic Ocean in the west to the Red Sea in the east, in a belt several hundred to a thousand kilometres wide.

It covers an area of 3 053 200 square kilometres. It represents a climatic and ecological transition zone with hot semi-desert and steppe conditions, bordering the more humid Sudanian savannas to the south and the dry Sahara Desert to the north. The ecoregion is also called the Sahelian Acacia savanna after its most prominent and drought-tolerant genus of tree.

Agroforestry systems are a good example of diverse agricultural landscapes. The parkland in the Sahel is a good example of such a system where farmers have preserved indigenous trees for centuries and introduced exotic trees for the ecological, economic and cultural benefits they provide.

This has resulted in diverse agricultural landscapes where trees play a direct and important role in nutrition, as they produce fruits, nuts and leaves that humans can consume.

Food trees in parklands include the shea tree (Vitellaria paradoxa), which provides nut butter and oil, the baobab (Adansonia digitata) leaves, and the jujube (Ziziphus mauritania) fruit pulp that are additional sources of carbohydrates and proteins in the diets of the local population.

Besides contributing to food security, these agricultural landscapes also drive many processes occurring in agricultural systems. These include natural pest control, such as the control of the millet head miner moth (Heliocheilus albipunctell) by natural enemies, crop pollination by the abundance of bees supported by the trees, and enriching the soil underneath nitrogen-fixing trees.
The spatial composition of landscape elements also enhances crop yield. For example, a density of ten trees/ha is considered optimal to support crop productivity in Faidherbia albida parklands, since these trees allow light to reach the crops under the canopy.

On the other hand, the nitrogen-fixing Ana tree or African locust bean (Parkia biglobosa), the beans of which are fermented to produce nététou, a traditional spicey condiment, compete with the crops for water, light and nutrients, thereby decreasing the crop yield of millet cultivated beneath the canopy. These trade-offs can be minimised by a mix of tree species with contrasting functional diversity. In parklands, the trees’ effects on food security are tightly linked to agricultural landscape composition and configuration.

The sun sets over a baobab forest in Africa. (Source: Pixabay)

Characteristics of agroforestry systems

Multiple characteristics are needed to explain the major distinctive attributes of the diversity of agroforestry systems.

Geographical location refers to particular ecologies, such as lowland humid or sub-humid tropics.
Physiognomy, or appearance, refers to parklands, such as Faidherbia and Shea butter parks in West Africa.
Physiognomy also refers to mosaic veld with different plant species, with multi-storeyed home gardens that makes use of long-term fallows, that refers to farmland left without sowing for one or more vegetative cycles.
Compositional or structural characteristics refers to simultaneous or consequential combination of trees, crops and livestock.
Practices refers to management systems and livelihood strategies, including trees and pasture in rangelands (sylvopastoral) and agriculture (agrosilvopastoral).

Different agroforestry systems include the following:

•Lowland humid or sub-humid tropics
•Parkland: Faidherbia and Shea butter parks in the Sahel, West Africa
•Mosaic veld with multi-storeyed home gardens and long-term fallows
•Compositional, structural, and simultaneous or sequential combination of trees, crop, animals, including silvopastoral and agrosilvopastoral
•Socio-economic scale of production and level of technology, input and management, which refers to low input, high input agroforestry
•Functional erosion control and provision for building soil fertility with wind breaks, shelterbelts, erosion control and soil conservation, scattered nitrogen fixing trees, and boundary planting.

In the next issue, we take a closer look at the Sahelian Parklands.

Source references

Ayanlaija, S.A., Sanwo, J.O. (1991) Management of soil organic matter in the farming systems of the low land humid tropics of West Africa: a review. Science Direct. https://doi.org/10.1016/0933-3630(91)90006-9. https://www.sciencedirect.com/science/article/abs/pii/0933363091900069

Boffa, J.M. (West African agroforestry parklands: keys to conservation and sustainable management (2000) Unasylva 200, Vol. 51.
https://forest-genetic-resources-training-guide.bioversityinternational.org/fileadmin/bioversityDocs/Training/FGR_TG/additional_materials/Boffa_2000.pdf

Leroux , L., Faye, N.F., Jahel, C., Falconnier, G.N., Diouf, A.A., Nda, B., Tiaw, I., Senghor, Y, Kanfany, G., Balde, A., Dieye, M., Sirdey, N., Alob o loison, S., Corbeels, M., Baudron, F., Bouquet, E. (2022) Exploring the agricultural landscape diversity-food security nexus: an analysis in two contrasted parklands of Central Senegal. Science Direct
https://doi.org/10.1016/j.agsy.2021.103312
https://www.sciencedirect.com/science/article/abs/pii/S0308521X21002651

Mbow, C., Van Noordwijk, M., Luedeling, E., Neufeldt, H., Minang, P.A., Wowero, G. (2013) Agroforestry solutions to address food security and climate change challenges in Africa. https://doi.org/10.1016/j.cosust.2013.10.014 https://www.sciencedirect.com/science/article/pii/S1877343513001449#bib0075

Sheth, K. (2017) windbreaks and shelterbelts: Wind Erosion Control In Farming World Atlas Economics
https://www.worldatlas.com/articles/windbreaks-and-shelterbelts-wind-erosion-control-in-farming.html

Sharma, R., Mina, U. & Kumar, B.M. (2022) Homegarden agroforestry systems in achievement of Sustainable Development Goals. A review. Agron. Sustain. Dev. 42, 44 (2022). https://doi.org/10.1007/s13593-022-00781-9
https://link.springer.com/article/10.1007/s13593-022-00781-9#citeas

Russo, R.O. (2022) Agroforestry: An Approach for Sustainability and Climate Mitigation. Intechopen.com
DOI: 10.5772/intechopen.105406. https://www.intechopen.com/chapters/82465