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Ecosystem services (ES) provided by mobile organisms, such as pollinators or predators, can be crucial for agricultural production. The worldwide economic value of pollinating insects, for instance, is estimated at 153 Million Euro annually (Gallai et al. 2009). Whereas this figure is only an approximation, it strongly reflects the critical importance of considering these ecosystem services in agricultural decisions. Most fruit crops rely on insect pollination services to set a higher number of fruits of better quality (Klein et al. 2007), while effects of biocontrol agents are more case-specific (Simon et al. 2010). Fruit growers are often well aware of the importance of natural ES for crop production, but up to now prefer to substitute these ES by renting honeybee colonies or using insecticides (Garibaldi et al. 2009). Such management practices may not be sustainable, leading to production losses in years where honeybees are unavailable or when serious pests become resistant to pesticides (Wilson & Tisdell 2001, Kremen & Ostfield 2005). Using a variety of naturally occurring agents would both decrease the costs associated with high input management practices, as well as provide some insurance against ecosystem services losses due to variable environmental conditions within and across years (Bosch et al. 2006). For instance, an increased diversity of pollinators may provide higher or more stable pollination services because of species-specific differences in the pollination performance (Hoehn et al. 2008, Fründ et al. 2013), resulting in higher crop production (Garibaldi et al. 2013). Understanding the local and landscape characteristics and their interactions in driving biodiversity as well as the mechanisms of how biodiversity affects the provisioning of ES are pressing scientific goals.
Peter Hambäck, Alexandra-Maria Klein, Jordi Bosch, Ulrika Samnegård, Virginie Boreux, Anne-Kathrin Happe, Laura Roquer Beni, Karsten Mody, Daniel García, Marco Tasin, Marcos Miñarro The role of agri-environmental schemes for biodiversity, ecosystem services and disservices Agri-environmental schemes (AES) have been introduced by the European Common Agricultural Policy to “promote agricultural production compatible with nature conservation” (Primdahl et al. 2003). AES includes the creation and maintenance of small patches of semi-natural habitats at the boundaries of agricultural fields (e.g. hedgerows or flower strips), as well as organic farming practices, as a type of management limiting potential negative impacts of chemicals on the environment. While organic farming has been shown to benefit biodiversity and species abundance, including those of pollinators and predators (Bengtsson et al. 2005, Hole et al. 2005), the contribution of hedgerows and flower strips to biodiversity is less clear (Kleijn et al. 2001). Studies have demonstrated that crops with semi-natural hedgerows benefit from a higher abundance and diversity of pollinator or predator species (Haenke et al. 2009, Walton and Isaacs 2011), but assessments of AES at the European scale have yielded mixed results (Kleijn and Sutherland 2003, Kleijn et al 2006, Whittingham 2007). Especially for crops susceptible to pests and depending on pollination for production, it is crucial to establish (i) whether AES contribute more substantially to increasing the biodiversity of predators and pollinators, and (ii) if such AES might also facilitate pest access to crops, hence reducing the advantage of implementing agri-environmental schemes. Furthermore, it is crucial to understand how AES at the farm scale (organic/conventional farming) interact with adjacent farm scale AES (hedgerows and flower strips as providers of nesting and foraging resources for beneficial insects) and under which landscape conditions these schemes are most effective. Tscharntke et al. (2012) propose that AES are most effective in landscapes of intermediate complexity (% semi-natural habitat in the surrounding area of 10-30%). They argue that source populations of beneficial insects may not be available in cleared landscapes (< 10% of semi-natural habitat), while in complex landscapes (>30%) source populations are high and spill-over to intensified farms leading to optimal ES provisioning. We aim to disentangle the effectiveness of AES on pollination, pest infestation, pest control and fruit production implemented at the farm scale from the the adjacent-farm scale taking into account the landscape scale. Results will inform farmers about the landscape conditions in which specific AES are most effective and lead to net benefits for crop production and biodiversity. The implementation of AES and the landscape context may not only benefit crop production but also increase pests, providing negative effects to crops (Zhang et al. 2007, Martin et al. 2013). We therefore aim to distinguish between services and dis-services providers to model the trade-offs between the positive effects of pollinators/predators/parasitoids and the negative effects of pests on fruit production. Understanding the mechanisms of biodiversity-ecosystem services relationships Both the magnitude and the long-term persistence of ecosystem services are fundamentally affected by biodiversity of service providers in two main ways: (i) “Functional complementarity”: The species providing ecosystem services (e.g. pollinators, predators) have different quantitative and qualitative contributions. Species complementarity can occur due to specific preferences for hosts (Snyder et al. 2006) or parts of a fruit tree (Brittain et al. 2012), to temporal variation between species across time of the day or season (Stone et al. 1999), or to preferences for particular environmental conditions e.g. higher temperature or wind velocity (Vicens & Bosch 2000, Brittain et al. 2012). Recent studies also demonstrated synergistic effects of a more diverse pollinator assemblage (Brittain et al. 2013) and suggested an important role for pollinator species complementarity (Garibaldi et al. 2013). Similarly, different predator and parasitoid species control varying herbivore species, or perform different foraging strategies that synergistically suppress specific pest species (Snyder et al. 2006). Such complementary effects result in a direct positive effect of biodiversity on ecosystem functioning and services (Loreau et al. 2001). Functional complementarity may mechanistically explain why the seed set or fruit production increases with the diversity of pollinators. Mechanisms of functional complementarity are still poorly understood, both for biocontrol and pollination services. (ii) “Functional redundancy”: Several species can overlap in their particular contribution to ES and thus replace each other in their functional performance. The “insurance hypothesis” (Loreau et al. 2001) suggests that if some species become unreliable (e.g. due to population declines following unfavourable weather conditions), functionally redundant species may compensate for the loss of other species over time. The prerequisite of such compensatory effects is that responses to stress and environmental changes differ between functionally ‘redundant’ species, as described by the concept of response diversity (Elmqvist et al. 2003). Consequently, more species-rich systems with functional redundancy and response diversity may be more resilient against perturbations, variable environmental conditions and global change. It is crucial to understand the extent of functional complementarity/redundancy to unravel the Biodiversity-Ecosystem Services relationship. Functional complementarity between species leads to a positive contribution of biodiversity to ES, but also represents a higher sensitivity of ES to disturbances that affect single species, whereas redundancy represents a buffer against such perturbations. In multispecies communities with complex interactions, the degree of complementarity/redundancy and specialisation/generalisation can be analysed with recently developed network metrics (Blüthgen et al. 2007). Such network analyses provide powerful tools to predict consequences of biodiversity loss for the functional resistance of communities against environmental change. Understanding the role of biodiversity in the provision of ecosystem services is even more critical in the current context of climate change, since global warming can potentially lead to a separation between the species currently delivering the ecosystem services and the crop species (Donnelly et al. 2011). Biodiversity may play a key role in buffering the negative consequences of climate change for ES and the resulting crop production. For instance, variable responses to climatic conditions (response diversity) among species might represent a potential buffer against climate change. Such a stabilizing role of biodiversity is expected for pollinators (Hegland et al. 2009) as well as biocontrol agents (Mody et al. 2011) and represents a major hypothesis of this proposal. The importance of species traits in changing climatic conditions The response diversity and the functional role of animals in agro-ecosystems are closely linked to species- or group-specific traits, which can be classified as response traits and as functional or effect traits (Larsen et al. 2005, Flynn et al. 2009). Response traits describe the species’ properties in relation to environmental conditions and determine the species’ tolerance to disturbances and changes in the abiotic and biotic environment (Larsen et al. 2005). Functional traits are defined as phenotypic characteristics that contribute to ecosystem processes (Flynn et al. 2009). Traits that are relevant for the functional role of organisms and for their responses to environmental change can be any measurable aspect of the organisms and may include physiological, morphological and behavioral characteristics. Both species functionality and response to disturbance may depend simultaneously on the same set of traits (e.g. big-bodied bees are more efficient pollinators but more prone to extinction under habitat loss than small-bodied ones; Larsen et al. 2005). Thus, assessing the relationships of effect and response traits is mandatory to predict the collapse of ecosystem services under the biodiversity decays imposed by anthropogenic change (Suding et al. 2008). At large, the traits of the members of animal communities can be summarized (i) as the communities’ response diversity, which captures the diversity of species-specific responses to environmental variability within a functionally redundant group (Elmqvist et al. 2003, Laliberté et al. 2010), and (ii) as the communities’ functional diversity, which describes the heterogeneity of ecosystem functions performed by species in a community (Hillebrand & Matthiessen 2009). In the proposed project we carry out an extensive literature review to obtain information on species-specific traits for pollinator, pests and predators/parasitoids. The data will be complemented by measuring morphological traits of pollinators, main pests and their predators/parasitoids and by measuring physiological traits of a subset of species to relate them to the morphological traits. The comprehensive list of traits will then be used to predict the occurrence of main pollinators, pest and predators in different climate scenarios. Such predictions on species occurrences will also be linked to the effectiveness of AES. Proposed model farming systems: Apple orchards Apple, Malus x domestica, is grown throughout the world and is the most important fruit crop in terms of production in Europe (Leonhardt et al. 2013). Across Europe, the economic gain of pollination services is higher for apples than for any other crop grown in Europe (Leonhardt et al. 2013). The main apple varieties need insects, mainly bees, to transfer the pollen between compatible varieties (Delaplane & Mayer 2000, Garratt et al. 2014) besides being susceptible to a large number of pests such as aphids or moth larvae (Jenser et al. 1999, Simon et al. 2010), controlled by a diverse array of arthropods and vertebrates (Cross et al., 1999, Miliczky & Horton 2005, Mols & Visser 2007, Luck et al. 2012). We selected apples as the model crop system for our proposed pan-European project because of (i) the economic importance of apple production across Europe and the globe, (ii) the sensibility of the apple crop to the loss of pollinators and natural enemies, and (iii) the different AESs being implemented in apple orchards in Europe. Objectives The overarching goal of our project is to understand how European AES (farm scale: organic vs. conventional farming, adjacent-farm scale: flowering strips/ hedgerows) affect biodiversity and ecosystem services (pollination, predation/parasitism) and disservices (pest levels) in different landscape context and how this relates to net fruit production in different climates across Europe. These results will be combined with species-specific traits susceptible to climate change to predict changes in response and functional diversity on ecosystem services with changing climates. The project is divided into five work packages (WP) with each project partner being responsible for one WP. |
| ← EU-BiodivErsa-Project |
