Vincent de Leijster

152 Chapter 7 carbon and plant diversity in almond orchards, and between above-ground carbon and butterfly diversity and epiphyte richness in coffee plantations. This further supports the findings of other studies about the synergistic relationship between these two services (Girardello et al., 2019; Steur et al., 2020). In the coffee case study, we also found a positive relationship between above-ground carbon stock and erosion control. Although we did not study erosion control in almond plantations, it has often been demonstrated that vegetation cover improves above-ground carbon and reduces erosion risk (Almagro et al., 2016; Maetens et al., 2012a). We also found a trade-off between main crop yield and regulating and supporting ecosystem services in both case studies, which was similar to what was found in other studies (Kearney et al., 2017; Raudsepp-Hearne et al., 2010; Schulte et al., 2017). However, not all interactions among ecosystem services were found to be consistent over time (Table 5-2 in Chapter 5). The development of ecosystem service trade-offs and bundles is being studied increasingly often, and authors generally conclude that these vary across time (Renard et al., 2015; Rodríguez et al., 2006; Sutherland et al., 2016); still, more information from a wider range of geographical locations and land-use systems is needed to better predict the development of ecosystem service interactions (Willemen, 2020). The strongest trade-offs were found between provisioning ecosystem services and regulating and supporting ecosystem services. However, this finding would not hold if a larger diversity of products were produced, as we have seen in the coffee case studies, where timber and other fruit compensated for the trade-off relationship between the productivity of the main crop versus the provision of regulating and supporting ecosystem services. Crop diversification may therefore be an important farming strategy that can optimize both environmental and economic outcomes. However, in the answer to RQ3 (Section 7.2) I showed that crop diversification does not always provide enough benefits and that differences in market prices also play a role. The effectiveness of crop diversification may be dependent on the ecological relationships that emerge: competition, mutualism, or commensalism. We need a better understanding of these relationships in an agricultural context, and we need to understand which crops can be combined as they do not compete for resources but have commensal relationships in which they use different resources. Furthermore, in the almond case study we demonstrated that different agroecological practices provided a specific set of ecosystem services. A more recent study in the same almond landscape demonstrated that combining vegetation cover with organic amendments results in higher ecosystem service provisioning than applying the two separately (Luján Soto et al., 2021). This suggests that combining multiple practices and following a more holistic approach may improve a wider set of ecosystem services. Science and the agricultural sector are at the beginning of the road towards finding a land