Coffee productivity, ecosystem services provision and adaptation to climate change: How useful can a model be?

Due to the lack of a simulation model, predictions of climate change (CC) impact on coffee do not include CO2 fertilization; they include only changes in temperature and rainfall patterns. It is hypothesized that temperature, rainfall and CO2 will have interacting effects on coffee productivity in agroforestry systems and on the environmental services they provide to society. The aim of this presentation is to include CO2 fertilization in the predictions of CC impacts using CAF2007, a coffee simulation model developed during the EU--funded CASCA project by Van Oijen et al. The model considers, for shaded and sunlit coffee plants separately, how carbon and nitrogen content, leaf area and phenology change over time. Simulations were done for three locations at contrasted altitudes in Chiapas, Mexico. The model calculated a very significant CO2 fertilization effect on coffee bean production. Production, as calculated by the model, increased with altitude, irrespective of the climate considered. When CO2 fertilization was not considered, temperature increase and modification of rainfall pattern reduced bean production. This reduction was worse at higher than at lower altitudes. When CO2 fertilization was included, the model calculated a positive effect of CC on bean production, and this effect was higher at intermediate altitude. Simulations were made to show the possible use of CAF2007 to test shade management effects on coffee production and on environmental services provision. Management modified all performances, and these effects were modified by CC. The CAF2007 model has not been thoroughly validated so far; the results have to be considered with care, and used for discussion more than predictions of the future of coffee productivity. The model is being validated in 2009. Nevertheless, fertilization is a well known effect, and these results showed that it must be taken into account to determine possible impacts of CC on coffee. (Texte intégral