How to increase the joint provision of ecosystem services by agricultural systems. Evidence from coffee-based agroforestry systems

CONTEXT: Agricultural systems can provide ecosystem services (ES) beneficial for both the sustainability of farms and the quality of life for humans. Agriculture is regularly criticized for focusing technical management of cropping systems more on production services than on support or regulation services. To achieve the agroecological intensification of cropping systems, a joint provision of multiple ES is required. OBJECTIVE: Our aim was to (i) understand the determinants of the provision of ES and (ii) analyze the relationships between these services in order to (iii) identify agroecological intensification pathways. We focused our study on four ES, which are (1) coffee production, (2) water quality preservation, (3) carbon sequestration and (4) biodiversity conservation, provided by coffee agroforestry systems in a small region in Nicaragua. METHODS: A two-phase sampling scheme was implemented to measure and elucidate the provision of these services. First, we selected a large sample (82 coffee plots) to gain insight into and quantify the four ES. Secondly, we extracted a sub-sample (27 plots) showing variability in the provision of the four ES, to closely examine the determinants of the service most useful to farmers, coffee production. RESULTS AND CONCLUSION: The results showed that carbon sequestration (in average 36 t.ha−1.yr−1) was not correlated with coffee yield (in average 1127 kg.ha−1.yr−1) and depended more on the presence of a few big trees in farm plots (Ø > 0.9 m) than on tree density. Yield increased with tree biodiversity up to a threshold (Shindex = 1.5), after which it clearly declined. The use of the most harmful pesticides to human health at higher doses than recommended did not lead to the highest yields. The most important determinants of coffee production were soil nitrogen content, soil pH, solar radiation, disease and weed incidence. Although reducing the shade tree density increased coffee production, this reduction was not necessarily related to a decrease in shade tree biodiversity and carbon sequestration, or an increase in water contamination potential. A few farmers actually achieved such high joint ES provision, in particular by selecting adequate shade trees grown at moderate densities. SIGNIFICANCE: The novelty of this article lies on an original method that consists in analyzing the ES provided by cropping systems in order to identify management strategies that are effective in providing a higher combined level of ES than those currently provided. We emphasize the importance of linking agricultural practices to the ES delivered, in order to gain an in-depth understanding of which technical levers are positively correlated with the determinants of the expected services.