Biodiversity plays a key role in ecological processes and the delivery of ecosystem services and its importance has been widely recognized (MA, 2005). However, many uncertainties over the effect of biodiversity decline on the provisioning of ecosystem services remain (Balvanera et al., 2014; Schroter et al., 2014). Furthermore, an important challenge remains in the quantification of the economic consequences of the loss of biodiversity (De Meester et al., 2011). The aim of this paper is twofold and consists of (i) contributing to the quantification of the link between the loss of species and the provisioning of the ecosystem service biological pest control and (ii) quantifying the market value losses which can be attributed to the loss of those species. An integral part of agricultural intensification at the plot level is the deliberate reduction of biodiversity (Bianchi et al., 2013; Swift et al., 2004). Biodiversity provides however a wide variety of ecological services and disservices in agro-ecosystems (Tschjarntke et al., 2005, De Meester et al., 2011, Kragt et al., 2014). The control of pests by their natural enemies represents an important ecosystem service that maintains the stability of agro-ecosystems and has the potential to mitigate pest control costs both to private producers and to society (Zhang and Swinton, 2006). In this research, the indirect use value of the presence of natural enemies for the biological pest control of pear psylla (Cacopsylla pyri) is analyzed for two pear orchard agro-ecosystems in Belgium, being: (i) organic production and (ii) Integrated Pest Management (IPM). In a first part, a dynamic predator-prey model is built in which the functional role of natural predators in suppressing the outbreak of pear psylla is simulated for the reference scenario (organic production) and the alternative scenario (IPM). The model describes predator-prey dynamics between the pest insect pear psylla (Cacopsylla pyri) and three of its main natural enemies Anthocoris nemoralis, Allothrombidium ...