Kenya – « Central Province » 

Central Province is the main coffee producing region in Kenya. It is located north of Nairobi and is bordered to the north by Mount Kenya, to the west by the Aberdare range and to the south-east by the Machakos hills. Coffee is grown there on the hillsides of these reliefs between 1,400 and 2,000 m.a.s.l., in very varied agroforestry systems of the enclosure type and on small farms of under one hectare (more than 300,000 today). Kenyan coffee has a good international reputation for its aroma and mild acidity.

Since the last coffee price crisis (98/04), and due to strong population pressure and increasing urbanization in the region, the areas planted to coffee and coffee production are in decline. Recent work undertaken in this region (CAFNET project, CIRAD/ICRAF/CRF/Mugama Coffee Farmer Union partnership) shows that the incomes derived from associated trees (timber, firewood, fruit trees) are often higher than those derived from coffee, which nonetheless remains vital for the survival of the farm.

The trees associated with coffee trees are mainly exotic species (Grevillea robusta and Eucalyptus spp) planted around the edges of plots, which greatly contribute to the households’ wood requirements, but they do not fulfil the ecosystem functions expected of an agroforestry combination. In Kenya, one of the main challenges is to re-introduce tree diversity within coffee plots and on farms. Some recent surveys on farmer knowledge show that there exists a wide range of native species that could play that role, notably in terms of improving the microclimate, soil fertility, the water cycle and nutrient recycling, and for reducing parasite pressure on coffee trees.

In East Africa, and more particularly in Kenya, the research work undertaken in recent years by the national institutions has primarily focused on optimizing coffee productivity in intensified monocultures or in low-diversity systems; shade was discouraged by the extension services in Kenyan coffee plantations until recent times. Consequently, little research has been carried out on the functioning of complex coffee agroforestry systems. By identifying the multiple functions of these complex agroforestry systems, if will be possible to offer farmers improvements in their agroforestry practices which will lead to greater resilience in relation to severe climatic variations, increase the currently low coffee yields, and diversify their sources of income, whilst increasing the ecosystem services that these complex systems can provide.

Tanzania – South Tanzania: Rungwe climosequence

The Rungwe topo-climosequence, which is located in southern Tanzania and has a unimodal rainfall pattern, contains one of the country’s main coffee growing zones and is crucial for the 300,000 inhabitants who live there. This coffee zone is located between ~900 and ~1500 m.a.s.l., at a lower elevation than the Kenyan Aberdares, but with similar temperature conditions. It is interwoven into a succession of forest hydro- and agrosystems typical of the hydroclimatic and socio-economic gradient of the volcanic highlands of East Africa, whose poles are the afromontane forest at Hagenia and Maesa at high altitude (P>2,000 mm) and (for the southern tropical region) the Zambezian woodlands at Uapaca, Brachystegia and Julbernardia in the lower zone (P<1,500 mm, 4-month dry season).

Coffee-banana-maize (CBM) agroforestry systems have made a decisive contribution to the structuring of the landscape since the 1960s and occupy a key position as regards the water balance and soil erosion (mollic to humic cambisols and andosols) at the lower limit of the regional aquifer replenishment zone. Like the Kenyan Aberdares, some constraints that are both climatic (warming of more than 1°C and 30% drop in annual rainfall over a period of twenty years), demographic and socio-economic (market instabilities and recent coffee crisis, abandonment of fallow, deforestation and increase in farm density) considerably affect the resilience of the associated resources, including wood, soil and water. This impact is particularly obvious in the lower part of the coffee zone, with the recent shift from the coffee/plantain combination to maize, cocoa and rice.

Unlike the Aberdares, where the incorporation of Grevillea and Eucalytus in small farm management seems systematic, the Rungwe coffee zone is characterized by a relatively low tree density. The native species (e.g. Maesa and Ficus at altitude, Bridelia, Millicia, Treculia, Toona in the lower zone) are still very present alongside fruit trees (Persea, Mangifera, Psidium, to which Phoenix Uapaca and Citrus are added in the low zone) and some other exotic species (Rothmania, Pterocarpus, Pinus and Eucalyptus, Neem tree in the lower zone).

Given the linchpin position of the coffee zone in the toposequence and the current and future mobility of this zone, the impacts of agroforestry practices (notably the introduction of trees) and of hydroclimatic change on yields and on the water and biogeochemical balances, need to be better understood on a toposequence scale (upscaling) in order to identify adaptation strategies relevant to the economic and ecological challenges of the region. In the higher zone, these challenges concern the gradual encroachment of CBM in the tea growing zones and afromontane forest. In the lower zone, they concern the abandonment of CBM for cocoa and rice monocultures supported by major investments (irrigation) and expenditure (in water).