Vincent de Leijster

14 Chapter 1 Figure 1-1, the number of pollinators is an indicator of the ecosystem service provider, flower visitation rates is an indication of pollination, and the number of flowers that turn into fruit gives the fruit set. Each of these indicators provides information about the ecosystem service ‘pollination’. Many studies focus on changes in the supply of a single ecosystem service, but more recently multiple ecosystem services have been studied simultaneously in the same system (Lee & Lautenbach, 2016). Studying multiple ecosystem services improves our understanding of how ecosystem services interrelate (Bennett et al., 2009). If two ecosystem services show a similar response to a driver, i.e. their supplies both increase or both decrease, the two form an ecosystem services bundle (Bennett et al., 2009). Alternatively, a driver may improve one ecosystem service but negatively affect another, and then a trade-off emerges between the ecosystem services (Bennett et al., 2009). Assessing multiple ecosystem services provides a more comprehensive image of a system’s impact (Lee & Lautenbach, 2016). In agricultural systems, trade-offs are observed widely on different spatial scales. For example, Schulte et al. (2017) describe prairie strips that were planted experimentally in corn-soybean croplands in a water catchment area in the US. The authors found that the strips improved erosion control, biodiversity and water retention; however, soybean and corn yields were reduced (Schulte et al., 2017). A similar trade-off between provisioning services and regulating and supporting services was found on a global scale (IPBES, 2019) as well as on a regional scale in Canada (Raudsepp-Hearne et al., 2010). To optimize most ecosystem services, various agroecosystems are proposed (Foley et al., 2005). In El Salvador, for example, it was found that the accumulated ecosystem service supply was 25% higher in maize-bean agroforestry farms than in organic and conventional maize-bean inter-croplands, although no trade-offs were found between regulating and provisioning services, as the agroforestry farms also produced tree products to contribute to more diverse provisioning (Kearney et al., 2017). Trade-off or synergy relationships may vary with land management, geographical regions, climates, and other biotic or abiotic conditions (Fremier et al., 2013); in other words, they may vary across time and space (Bennett et al., 2009; Willemen, 2020). The supply of most ecosystem services is declining (IPBES, 2019); therefore, there is an urgent need to find new land management approaches that restores it. By changing land management, we can expect changes both in the supply of ecosystem services and in their interactions. This response may be fast, slow or absent, and the development of the ecosystem service supply over time is referred to as a trajectory. The term ‘trajectory’ stems from ecological trajectories and refers to pathways of ecological conditions over time, such as degradation, adaptation or restoration, in response to changes in land management or environmental conditions (Gann et al., 2019). Ecosystem-service trajectories often follow