Photo : Près de 95% des productions éthiopiennes de café n’utilisent pas de pesticides selon la Banque mondiale. (Michael Tewelde /Xinhua. AFP)
Coffee, machete and biodiversity
Early night; this working day will once again hang on my coffee pot. Where would I be without this beverage, in a less globalised world? My daily life depends on a multitude of other imported products, but it is probably coffee that would be the most difficult to give up. Debates about local supply chains carefully avoid questioning the import of teas, coffees and chocolates, which are always available in our organic shops in their multi-certified forms. In the tropical world, the trade in these products is essential to the survival of small producers, who would be plunged into poverty if international transport was to slow down.
But what are the links between coffee growing and biodiversity? Beyene Zewdie and his colleagues from Addis Ababa and Stockholm Universities studied this essential question in the Ethiopian highlands, the multi-millennial source of the energising potion. Coffee trees grow there naturally under the forest canopy, between 1000 and 2000 metres above sea level. Villagers harvest their berries and the primary forests also provide firewood, honey and spices. In the shade, coffee yields are low and farmers often thin the canopy to provide sunny clearings. In some areas, the forest almost completely disappears in favour of coffee plantations. This intensification is strongly encouraged by development programmes and the World Bank.
Three years during the rainy season, when plant identification is best, the researchers visited 60 coffee-growing plots, dividing their efforts between those located in the forest and others that were more or less deforested. They expected to find fewer woody species (trees and shrubs) where coffee trees produce the most fruit in full sunlight, but were surprised by the strong impact of even minor agricultural practices on biodiversity: As soon as farmers prune the primary forest to favour coffee trees, half of the woody species disappear, and it can be assumed that this disadvantages resident animals in these landscapes. Subsequently, even if coffee cultivation is intensified, the number of wild woody species present in the plantations remains stable.
According to the authors, these results argue for a strict separation of areas dedicated to coffee cultivation from those left untouched. These latter areas favour regional biodiversity and natural genetic resources of coffee trees. Around them, coffee plantations dotted with large trees remain ecologically much richer than our western monocultures, and they form buffer zones between the villagers’ livestock and the large predators that roam the forest.
Olivier Dangles, a tropical ecologist at IRD, emphasises the interest of these results in a little-studied region, but puts their significance into perspective: “As the authors acknowledge, it is perfectly logical to observe a strong loss of diversity in wild woody plants as soon as a few coffee plants are introduced. What I find more surprising, however, is that satisfactory levels of biodiversity can be maintained with high coffee yields. It would be interesting to understand what kind of management is carried out in these systems, in order to apply it more widely.”
 Zewdie, B., Tack, A. J., Ayalew, B., Wondafrash, M., Nemomissa, S., & Hylander, K. Plant biodiversity declines with increasing coffee yield in Ethiopia’s coffee agroforests. Journal of Applied Ecology (in press).