The role of ecological compensation areas in conservation biological control

Ecological compensation areas (ECAs), defined as all natural vegetation and non-crop plants within the rural landscape, are considered an important tool in multifunctional agriculture. In particular, ECAs are crucial in enhancing functional biodiversity for pest suppression and for the conservation of rare species. In my PhD thesis I focused on the role of ECAs on functional biodiversity, which is associated with the ecological services employed by the beneficial fauna. Within multifunctional agriculture, functional biodiversity is particularly aimed at establishing strategies for farmers to enhance ecosystem functioning for pest suppression and for conservation of insect diversity. I performed several case-studies about insect conservation within the rural landscape of the Po Valley in northern Italy. First, I carried out two case-studies at the farm-scale, which are presented in the first two sections of the thesis that address (i) the role of ECAs on generalist predators and (ii) the role of ECAs and flowering plants on parasitoids of leafminers. Then, in the last part of the thesis (section 3), I report a case of insect conservation at the landscape-scale, which involved the sampling of different insect bioindicators, like syrphids, carabids, butterflies and sawflies. The research described in the first two sections, resulted in the identification of many non-crop plants within ECAs that play an important role in the conservation of beneficial insects, including generalist predators and parasitoids. Knowledge about the role of non-crop plants on the multiplication, life cycle and population dynamics of these beneficial arthropods can be helpful to select weeds, trees and shrubs, in order to restore degraded agroecosystems. In the thesis I provide detailed lists of non-crop-plants and related beneficial insects that will assist in the implementation of management techniques of non-crop plants within ECAs. In the third section, I was able to demonstrate that each insect group displayed different biodiversity patterns in relation to the different landscape/micro-habitat categories. Bioindicators like syrphids and carabids were strongly affected by the landscape complexity, while butterflies were mainly influenced by the micro-habitat characteristics. I discuss the role of these insect groups as landscape/micro-habitat indicators and I provide faunistic list of species which may be helpful to compile regional lists for studies on insect conservation. Next, I discuss the importance of assigning a “functional meaning” to faunistic lists of insects in a landscape management approach. In order to develop this aspect, I used an expert system, called Syrph the Net, which is a tool that uses the so-called biodiversity maintenance function to explore elements of site quality and site management. In all the sections, I discuss the importance of sampling techniques for quantification of insect diversity. In conclusion, my thesis project demonstrates the importance of ECAs on insect conservation and biodiversity, and also provides information about management strategies for non-crop plants to improve conservation biological control and conservation of rare insect species.