Ecosystem Services In Agroecosystems Research Articles

Trade-offs in the provisioning and stability of ecosystem services in agroecosystems.

Changes in land use generate trade-offs in the delivery of ecosystem services in agricultural landscapes. However, we know little about how the stability of ecosystem services responds to landscape composition, and what ecological mechanisms underlie these trade-offs. Here, we develop a model to investigate the dynamics of three ecosystem services in intensively managed agroecosystems, i.e., pollination-independent crop yield, crop pollination, and biodiversity. Our model reveals trade-offs and synergies imposed by landscape composition that affect not only the magnitude but also the stability of ecosystem service delivery. Trade-offs involving crop pollination are strongly affected by the degree to which crops depend on pollination and by their relative requirement for pollinator densities. We show conditions for crop production to increase with biodiversity and decreasing crop area, reconciling farmers' profitability and biodiversity conservation. Our results further suggest that, for pollination-dependent crops, management strategies that focus on maximizing yield will often overlook its stability. Given that agriculture has become more pollination-dependent over time, it is essential to understand the mechanisms driving these trade-offs to ensure food security.

Facing the gap: exploring research on local knowledge of insect-provided services in agroecosystems

ABSTRACTSustainable agroecosystems must be managed to support biodiversity conservation and food production, which occur at the interface of regional/national policy frameworks, and local knowledge and perspectives. This paper examines the current breadth of research examining farmer knowledge of beneficial insect activities that provide ecosystem services (or benefits) in agroecosystems. We identify patterns and gaps in the literature and opportunities for future research. We found 34 studies that explicitly focused on and documented local knowledge of how insect taxa provided ecosystem services in agroecosystems, the majority of which were immediately observable in farmers’ daily practice: pest control (n = 26), pollination (n = 4). We suggest that there is a need for greater investigation of local knowledge of the breadth of ecosystem services provided by insects and identify key research areas that are opportunities for investigation.

Legume Cover Crops and Tillage Impact Nitrogen Dynamics in Organic Corn Production

Core Ideas Reduced tillage of legume cover crops releases significant amount of N coupled with corn N uptake.Roller crimper termination of legumes releases nitrogen at similar total amounts to disking.Increased experimentation needed to improve corn population and yields in roller crimped stands. Cover cropping and reduced tillage are two management practices that increase ecosystem services in agroecosystems. However, their interactive effects on N dynamics and cash crop yield are underexplored. In this study, four different termination approaches, employing no‐till and tillage, and organic and conventional techniques were used with four winter annual leguminous cover crop species to investigate the combined effect on plant‐available nitrogen (PAN) and subsequent organic corn (Zea mays L.) yield. Termination treatments included roller‐crimping, flail‐mowing, disking, and herbicide application with cover crops of Austrian winter pea (Pisum sativum L. subs. arvense, AWP), hairy vetch (Vicia villosa var. AU Early Cover, HV), balansa clover [Trifolium michelianum Savi ssp. balansae (Boiss.) Ponert, BC] and crimson clover (Trifolium incarnatum var. Dixie, CC). Plant‐available N (NO3− and NH4+) was determined using biweekly soil inorganic N extractions and resin probes. Cover crop biomass, cover crop C/N ratio, and cover crop total N were measured prior to termination. Nitrogen was most available from AWP and HV across termination methods at 6 to 10 wk after termination. Disked HV contributed highest levels of N across all 16 cropping by termination combinations. Highest biomass N was found in HV (226 kg ha−1), followed by AWP (189 kg ha−1) and CC (181 kg ha−1). Corn yield ranged widely, from 0.23 Mg ha−1 in 0 N control to >9 Mg ha−1 in HV and AWP treatments. Cover crop species plays an important role in N dynamics, frequently influencing soil processes to a more significant degree than termination approach.

Ontological Foundation of Ecosystem Services and the Human Dimension of Agroecosystems

The purpose of this contribution is to lay down a preparatory groundwork for an ontology of ecosystem services in the setting of agroecosystems viewed as social-ecological systems. This ontology aims at defining a set of representational primitives with which to model agroecosystems, through the prism of ecosystem service flows to and from agriculture. It helps delineate between biophysical structures, processes, functions, and ecosystem services. On the human side of agroecosystems, the ontology includes a conceptualization of the behaviors that govern the management of ecosystem services at different levels. It strengthens the existing analytic basis of multidisciplinary research on ecosystem services in agroecosystems by prompting modelers to stick to a homogeneous dynamic-system decomposition of the target agroecosystem. Most importantly, it provides the conceptual link between biophysical research on ecosystem services and equally important considerations on cognitive and social aspects involved in agricultural and landscape-level decisions that aim at implementing agroecological principles.

Predation by small mammalian carnivores in rural agro-ecosystems: An undervalued ecosystem service?

Africa is endowed with a diverse guild of small carnivores, which could benefit stakeholders by providing ecosystem services while fostering conservation tolerance for carnivores. To investigate the potential of small carnivores for the biological control of rodents within agro-ecosystems, we assessed both the ecological and social landscapes within two rural villages in the Vhembe Biosphere Reserve, South Africa. We employed a camera trapping survey underpinned by an occupancy modelling framework to distinguish between ecological and observation processes affecting small carnivore occupancy. We also used questionnaires to investigate perceptions of small carnivores and their role in pest control. We found the greatest diversity of small carnivores in land used for cropping in comparison to grazing or settlements. Probability of use by small carnivores was influenced negatively by the relative abundance of domestic dogs and positively by the relative abundance of livestock. Greater carnivore diversity and probability of use could be mediated through habitat heterogeneity, food abundance, or reduced competition from domestic carnivores. Village residents failed to appreciate the role of small carnivores in rodent control. Our results suggest that there is significant, although undervalued, potential for small carnivores to provide ecosystem services in agro-ecosystems.

Improving spatio-temporal benefit transfers for pest control by generalist predators in cotton in the southwestern US

ABSTRACTGiven rapid changes in agricultural practice, it is critical to understand how alterations in ecological, technological, and economic conditions over time and space impact ecosystem services in agroecosystems. Here, we present a benefit transfer approach to quantify cotton pest-control services provided by a generalist predator, the Mexican free-tailed bat (Tadarida brasiliensis mexicana), in the southwestern United States. We show that pest-control estimates derived using (1) a compound spatial–temporal model – which incorporates spatial and temporal variability in crop pest-control service values – are likely to exhibit less error than those derived using (2) a simple-spatial model (i.e., a model that extrapolates values derived for one area directly, without adjustment, to other areas) or (3) a simple-temporal model (i.e., a model that extrapolates data from a few points in time over longer time periods). Using our compound spatial–temporal approach, the annualized pest-control value was $12.2 million, in contrast to an estimate of $70.1 million (5.7 times greater), obtained from the simple-spatial approach. Using estimates from one year (simple-temporal approach) revealed large value differences (0.4 times smaller to 2 times greater). Finally, we present a detailed protocol for valuing pest-control services, which can be used to develop robust pest-control transfer functions for generalist predators in agroecosystems.EDITED BY Neville Crossman

High cover of hedgerows in the landscape supports multiple ecosystem services in Mediterranean cereal fields

Summary Field‐margin diversification through conservation and restoration of hedgerows is becoming a prominent intervention for promoting biodiversity and associated ecosystem services in intensive agricultural landscapes. However, how increasing cover of hedgerows in the landscape can affect ecosystem services has rarely been considered. Here, we assessed the effect of increased field‐margin complexity at the local scale and increasing cover of hedgerows in the landscape on the provision of pest control, weed control and potential pollination. Locally, three types of field margin were compared as follows: (i) standard grass margin, (ii) simple hedgerow and (iii) complex hedgerow, along two independent gradients of hedgerow cover and arable land cover in the landscape. We performed an exclusion experiment to measure biological control of cereal aphids and assessed natural enemy and pest abundance in the field. We sampled plant weed communities and performed a phytometer experiment to test the effects of pollinators on plant reproductive success. At the local scale, planting a new hedgerow or improving its structural complexity and vegetation diversity did not enhance the delivery of ecosystem services in the neighbouring field. However, high cover of hedgerows in the landscape enhanced aphid parasitism (from 12 to 18%) and potential pollination (visitation rate and seed set increased up to 70%) irrespective of local margin quality. The cover of arable land in the landscape reduced the abundance of plant‐dwelling predators and weed diversity, but did not affect the delivery of the investigated ecosystem services. Synthesis and applications. Our results highlight the key importance of the surrounding landscape context, rather than local factors, to the delivery of ecosystem services. This suggests a need for new policies that pay particular attention to the conservation of hedgerows at large scales for promoting multiple ecosystem services in agroecosystems. Specifically, hedgerows can serve to develop a network of ecological corridors that can facilitate the movement of beneficial organisms, such as pollinators and natural enemies in the agricultural matrix. Such interventions may be a ‘low cost–high benefit solution’, since farmers can create or conserve high‐quality habitats taking little or no land from crop production and without the need to change their crop management.

Frogs taste nice when there are few mice: Do dietary shifts in barn owls result from rapid farming intensification?

Biodiversity ecosystem services in agroecosystems are negatively affected by farmland homogenisation due to intensive agriculture. The Pampas, an important worldwide region producing commodity crops, have been greatly homogenised with the expansion no-tillage and herbicide-tolerant transgenic soybeans since the 1990s. Here, we tested the hypothesis of that dietary changes in barn owls will be associated with the loss of semi-natural habitats derived from farming intensification. We characterised the dietary habits of western barn owls by analysing their pellets between two sampling periods (2004–2005 and 2010–2012). We also assessed the habitat loss due to cropping intensification through fencerow removal and pasture conversion to annual crops during the same period. We observed that barn owls shifted from eating mostly rodents in the first sampling period to eating a higher proportion of anurans in the second sampling period. Between sampling, rodent proportion in pellets decreased from 80% to 61.6%, while anuran proportion increased from 20% to 37.7%. A rapid farming intensification occurred on the farm between both sampling periods. Pastures were ploughed to grow annual crops. Thus, the annually cropped area increased by 60% from 2004 to 2012, while the area with pastures was reduced in about 80%. During the same period, nearly two-thirds of fences on the farm were removed to enlarge the cropped area. Our findings suggest that dietary habits of barn owls may shift to consume more anurans when rodent availability declines in association with the loss of semi-natural habitats, which resulted from rapid farming intensification on the studied farm. We suggest monitoring the population size and diet of barn owls for evaluating environmental changes produced in agroecosystems by farming intensification, as well as the adaptive responses of different rodent and anuran species to such changes.

Quantifying the impacts of ecological restoration on biodiversity and ecosystem services in agroecosystems: A global meta-analysis

Landscape transformation due to agriculture affects more than 40% of the planet’s land area and is the most important driver of losses of biodiversity and ecosystem services (ES) worldwide. Ecological restoration may significantly reduce these losses, but its effectiveness has not been systematically assessed in agroecosystems at the global level. We quantitatively meta-analyzed the results of 54 studies of how restoration actions reflecting the two contrasting strategies of land sparing and land sharing affect levels of biodiversity and ES in a wide variety of agroecosystems in 20 countries. Restoration increased overall biodiversity of all organism types by an average of 68%. It also increased the supply of many ES, in particular the levels of supporting ES by an average of 42% and levels of regulating ES by an average of 120% relative to levels in the pre-restoration agroecosystem. In fact, restored agroecosystems showed levels of biodiversity and supporting and regulating ES similar to those of reference ecosystems. Recovery levels did not correlate with the time since the last restoration action. Comparison of land sparing and land sharing as restoration strategies showed that while both were associated with similar biodiversity recovery, land sparing led to higher median ES response ratios. Passive and active restoration actions did not differ significantly in the levels of biodiversity or ES recovery. Biodiversity recovery positively correlated with ES recovery. We conclude that ecological restoration of agroecosystems is generally effective and can be recommended as a way to enhance biodiversity and supply of supporting and regulating ES in agricultural landscapes. Whether a land sharing or land sparing strategy is preferable remains an open question, and might be case dependent. Moreover, it is unclear whether crop production on restored land can meet future food production needs.

Ecosystem function and service quantification and valuation in a conventional winter wheat production system with DAISY model in Denmark

With inevitable link between ecosystem function (EF), ecosystem services (ES) and agricultural productivity, there is a need for quantification and valuation of EF and ES in agro-ecosystems. Management practices have significant effects on soil organic matter (SOM), affecting productivity, EF and ES provision. The objective was to quantify two EF: soil water storage and nitrogen mineralization and three ES: food and fodder production and carbon sequestration, in a conventional winter wheat production system at 2.6% SOM compared to 50% lower (1.3%) and 50% higher (3.9%) SOM in Denmark by DAISY model. At 2.6% SOM, the food and fodder production was 6.49 and 6.86tha−1year−1 respectively whereas carbon sequestration and soil water storage was 9.73tha−1year−1 and 684mmha−1year−1 respectively and nitrogen mineralisation was 83.58kgha−1year−1. At 2.6% SOM, the two EF and three ES values were US$ 177 and US$ 2542ha−1year−1 respectively equivalent to US$ 96 and US$1370 millionyear−1 respectively in Denmark. The EF and ES quantities and values were positively correlated with SOM content. Hence, the quantification and valuation of EF and ES provides an empirical tool for optimising the EF and ES provision for agricultural productivity.

Ants as indicators of soil-based ecosystem services in agroecosystems of the Colombian Llanos

Ants represent a widespread and functionally diverse taxonomic group that are both sensitive to land management and serve as important regulators of key soil processes. Building upon this idea, we sought to understand the impacts of agricultural management on ant communities in the Orinoco River Basin of eastern Colombia and to identify species that could be used as indicators of soil-based ecosystem services. Ants were collected and identified from the soil and litter layer within 75 fields (nine TSBF sub-samples along a transect in each field) divided among five common agricultural land uses in the region: 1) annual crops (maize, soy and rice), 2) rubber plantations, 3) oil palm plantations, 4) improved pastures (based on Brachiaria spp.), and 5) semi-natural savannas. As expected, land management was found to greatly influence ant communities. Improved pastures showed the highest species richness (6.9 species per transect) and semi-natural savanna the greatest abundance of ants (145 individuals per transect). Within each of these fields a suite of soil and agroecosystem characteristics were measured and combined into synthetic indicators of five soil-based ecosystem services: 1) nutrient provision, 2) water storage and regulation, 3) maintenance of soil structure, 4) climate regulation services and 5) soil biodiversity and biological activity. Ant species were then associated with these synthetic indicators using the IndVal method to identify indicator species for each of the five consolidated ecosystem services measured. In total, 14 indicator species were identified and found to be significantly associated with either the high or low provision of each of the five services. The development of such bioindicators offers a rapid and relatively inexpensive tool to facilitate land management and policy decisions in this biologically diverse and rapidly changing region of Colombia.

Epigeal arthropod communities in intensively farmed landscapes: Effects of land use mosaics, neighbourhood heterogeneity, and field position

Trophic guilds of epigeal arthropods regulating insect pest populations may be affected by factors acting across spatial scales. Although the influence of landscape factors associated with farming effects on arthropod assemblages has received increasing attention in the last decades, most research was carried out in fine-grain landscapes by comparing conventional and organic cropping systems. Here, we aimed at identifying the role of fencerows and crop heterogeneity in defining arthropod diversity in intensively farmed, coarse-grain landscapes. Hence, we developed a multi-scale heterogeneity approach based on fitting linear-mixed models to elucidate the effects of three spatial scales (local, neighbouring crop types, and landscape) on arthropod diversity. Mixed models were fitted to arthropod data obtained by pitfall trap samplings in 22 field pairs. Field position was a major determinant of arthropod species diversity at local scale, due to the contrasting disturbance regimes of fencerows and adjoining field edges. Fence density at landscape scale contributed to retain diverse arthropod assemblages in farmland mosaics by supplying habitats and refuges. In addition, extended fence network may function as corridors for dispersal, increasing connectivity between dissimilar habitats. Fence habitats, as well as their density in the landscapes, enhance both richness and abundance of beneficial arthropods. Our findings indicate that the overall arthropod diversity was benefited by landscape complexity, being the presence and density of fencerows key landscape attributes. Contrasting disturbance regimes at different field positions emerged as a major driver modulating arthropod species diversity in intensively managed farmland mosaics. Non-cropped habitats associated with fencerows and field margins play key ecological functions that are of vital importance for providing ecosystem services in agro-ecosystems. Complex landscapes may help to conserve overall plant diversity in agro-ecosystems, as well as the spillover of arthropod species from fencerows towards crop fields. Even in heavily intensified landscapes, where crop diversity is the main source of heterogeneity, promoting measures intended for both restoring and managing fencerow and non-cropped habitats through landscape planning will contribute to maintain arthropod richness (almost 70% of total richness) across the entire landscape.

Flow and stability of natural pest control services depend on complexity and crop rotation at the landscape scale

Summary Increasing landscape complexity can enhance biodiversity and ecosystem services in agroecosystems. However, policies based on conversion of arable land into semi‐natural habitats to increase landscape complexity and ecosystem services can be difficult to implement. Although it appears to be a promising management option, nothing is known about the effect of increasing landscape diversity through crop rotations on the delivery of ecosystem services. In this study, we examined how landscape complexity and crop rotation intensity in the landscape at different spatial scales affect the flow and the stability of natural pest control services in barley fields using manipulative cage experiments. Exclusion experiments revealed that natural enemies can have a strong impact on aphid population growth and that the delivery of pest control services is strongly dependent on the landscape context. We found that the overall level of pest control increased with landscape complexity and that this effect was independent of crop rotation intensity. In addition, the within‐field stability in pest control services increased with crop rotation intensity in the landscape, although stability in parasitism rates decreased. Multiple spatial scales analyses showed that the mean level of natural pest control was best predicted by landscape complexity at the 0·5‐km and the 1‐km spatial scales. The stability in overall pest control decreased with proportion of ley at the 2·5‐km and the 3‐km spatial scales. Synthesis and applications. Our study disentangled, for the first time, the relative effects of landscape complexity and crop rotation intensity on the delivery of an ecosystem service. We show that combined management of semi‐natural habitat and crop rotation can stabilize and enhance natural pest control in agricultural landscapes. Our findings have important implications in terms of management options to maintain and enhance ecosystem services in agroecosystems. They suggest that conservation of heterogeneous landscapes, characterized by a higher proportion of semi‐natural habitats such as pastures and relatively small fields, is essential for maintaining and enhancing effective biological control in agroecosystems.

Short‐term responses of native bees to livestock and implications for managing ecosystem services in grasslands

Rangelands are significant providers of ecosystem services in agroecosystems world‐wide. Yet few studies have investigated how different intensities of livestock grazing impact one important provider of these ecosystem services—native bees. We conducted the first large‐scale manipulative study on the effect of a gradient of livestock grazing intensities on native bees in 16 40‐ha pastures in the Pacific Northwest Bunchgrass Prairie. Each pasture was exposed to one of four cattle stocking rates for two years and grazing intensity was quantified by measuring utilization. We measured soil and vegetation characteristics related to floral and nesting resources as well as several metrics of the bee community. Increased grazing intensity significantly reduced vegetation structure, soil stability, and herbaceous litter and significantly increased soil compaction and bare ground. Native bees responded with changes in abundance, richness, diversity, and community composition. Responses varied with taxa and time of season. Bumble bees were sensitive to grazing intensity early in the season, showing reduced abundance, diversity, and/or richness with increased intensity, potentially because of altered foraging behavior. In contrast, sweat bees appeared unaffected by grazing. These results show that native bee taxa vary in their sensitivity to livestock grazing practices and suggest that grazing may potentially be a useful tool for managing pollination services in mosaic agroecosystems that include rangelands.

Ecosystem services and Australian agricultural enterprises

The role of ecosystem services in agro-ecosystems is often poorly understood by those in agricultural production. Yet food production, itself an ecosystem service, is critical to the survival of humanity and dominates much of the world's terrestrial and marine environments. There is a need to address the under-estimation of ecosystem services in farmland and develop concepts, policies and methods to evaluate them. In this paper, we develop a conceptual framework and consult with agro-industry experts to identify the impacts of different agricultural practices on ecosystem services. We also identify the ecosystem services crucial to the long term functioning of agroecosystems in Australia. Our results demonstrate that the regulating ecosystem services are the most relevant to all of the agriculture sectors we examined. Most concern is the recognised impact that the agricultural sector has had on ecosystem services provision. Results from our survey indicate that the agricultural sector in Australia negatively impacts on all regulating and supporting ecosystem services, despite the importance of these services in the process of agricultural production. We conclude with various policy arguments for better and more explicit recognition of ecosystem services in the management of agroecosystems.

Assessment of soil organic carbon and total nitrogen under conservation management practices in the Central Claypan Region, Missouri, USA

Conservation management practices including upland vegetative filter strips (VFS) and no-till cultivation have the potential to enhance soil carbon sequestration and other ecosystem services in agroecosystems. A modified two-factor analysis of variance (ANOVA) with subsamples was used to compare SOC and TN on a concentration, soil volume and soil mass basis in claypan soils planted to different conservation management practices and as a function of landscape position. The three conservation management practices (no-till cultivation, grass VFS and agroforestry VFS) and four landscape positions (summit, shoulder, backslope and footslope) investigated were compared 10 years after VFS establishment in a no-till system planted to maize ( Zea mays. L.)–soybean ( Glycine max (L.) Merr.) rotation. Two soil depth increments (0–5 cm and 5–13 cm) were modeled separately to test for treatment effects. In the surface layer, mean SOC concentration was significantly greater in the VFS soils compared to no-till. On a soil volume or mass basis, no significant differences in SOC stocks were found among treatment means. Concentration and mass based TN values were significantly greater in the grass VFS relative to no-till in the surface layer. A rapid slaking stability test, developed to separate particulate, adsorbed and occluded organic carbon (PAO-C) and nitrogen (PAO-N), showed that VFS soils had significantly greater mean PAO-C and PAO-N concentrations, soil volume and soil mass based stocks than no-till. In addition, comparison of SOC:TN and PAO-C:PAO-N ratios suggest reduced decomposition and mineralization of SOC in the PAO fraction. No significant treatment effects were detected in total or PAO soil fractions in the subsurface layer or among landscape position in either depth increment. Study results emphasize the need to compare soil carbon and nitrogen stocks on a soil volume and/or soil mass basis using bulk density measurements. Additionally, the rapid PAO separation technique was found to be a good indicator of early changes in SOC and TN in the systems studied. Overall, this research indicates that grass VFS may sequester TN more rapidly than agroforestry VFS and that a greater proportion of SOC and TN may be stabilized in VFS soils compared to no-till.

The role of ecological models in linking ecological risk assessment to ecosystem services in agroecosystems

Agricultural practices are essential for sustaining the human population, but at the same time they can directly disrupt ecosystem functioning. Ecological risk assessment (ERA) aims to estimate possible adverse effects of human activities on ecosystems and their parts. Current ERA practices, however, incorporate very little ecology and base the risk estimates on the results of standard tests with several standard species. The main obstacles for a more ecologically relevant ERA are the lack of clear protection goals and the inherent complexity of ecosystems that is hard to approach empirically. In this paper, we argue that the ecosystem services framework offers an opportunity to define clear and ecologically relevant protection goals. At the same time, ecological models provide the tools to address ecological complexity to the degree needed to link measurement endpoints and ecosystem services, and to quantify service provision and possible adverse effects from human activities. We focus on the ecosystem services relevant for agroecosystem functioning, including pollination, biocontrol and eutrophication effects and present modeling studies relevant for quantification of each of the services. The challenges of the ecosystem services approach are discussed as well as the limitations of ecological models in the context of ERA. A broad, multi-stakeholder dialog is necessary to aid the definition of protection goals in terms of services delivered by ecosystems and their parts. The need to capture spatio-temporal dynamics and possible interactions among service providers pose challenges for ecological models as a basis for decision making. However, we argue that both fields are advancing quickly and can prove very valuable in achieving more ecologically relevant ERA.

Diversity and invasion within a predator community: impacts on herbivore suppression

Summary 1. Management strategies to enhance ecosystem services in agroecosystems often seek to increase predator biodiversity. Invaders commonly dominate predator communities in agricultural landscapes, however, and the impacts of exotic predators on native predators and ecosystem services are largely unknown. Exotic predators may complement native predator diversity and enhance herbivore suppression, or they may disrupt herbivore suppression through predator interference. 2. We examined the impacts of a dominant exotic predator within the diverse predator community of a California vineyard. Interactions between the exotic wandering spider Cheiracanthium mildei, its closest native ecological homologue (the wandering spider Anyphaena pacifica) and a native spider displaying a different hunting mode (the cobweb‐weaving spider Theridion melanurum) were tested in a manipulative field experiment, with the grape leafhopper Erythroneura elegantula acting as a shared herbivore prey source. 3. We found that the exotic wandering spider suppressed both grape leafhoppers and other unmanipulated leafhopper species that were present in cages. Native spiders had little or no impacts on leafhopper suppression. Thus, C. mildei appears to drive predatory impacts in this system, although evidence also indicated that it is limited by intraspecific interactions. The superior predatory ability displayed by this spider may be shared by other invasive predators that dominate agroecosystems. 4. Despite its effects on leafhoppers, C. mildei negatively impacted a range of spider species, including A. pacifica, T. melanurum, and other unmanipulated native spiders. These impacts are likely to have been mediated through intraguild predation. The wandering hunting mode of C. mildei may have facilitated its role as an intraguild predator. 5. Synthesis and applications. Our results highlight the sometimes conflicting aims of biological control and conservation. Here, a dominant invasive predator increased ecosystem services but also caused declines in numbers of native predators. As disturbed conditions in agroecosystems are likely to put invasive predators at an adaptive advantage, efforts to conserve biodiversity in agricultural landscapes should focus on shifting the outcomes of species interactions to favour native species.

A novel method for assessing risks to pollinators from plant protection products using honeybees as a model species

Pollination is one of the most important ecosystem services in agroecosystems and supports food production. Pollinators are potentially at risk being exposed to pesticides and the main route of exposure is direct contact, in some cases ingestion, of contaminated materials such as pollen, nectar, flowers and foliage. To date there are no suitable methods for predicting pesticide exposure for pollinators, therefore official procedures to assess pesticide risk are based on a Hazard Quotient. Here we develop a procedure to assess exposure and risk for pollinators based on the foraging behaviour of honeybees (Apis mellifera) and using this species as indicator representative of pollinating insects. The method was applied in 13 European field sites with different climatic, landscape and land use characteristics. The level of risk during the crop growing season was evaluated as a function of the active ingredients used and application regime. Risk levels were primarily determined by the agronomic practices employed (i.e. crop type, pest control method, pesticide use), and there was a clear temporal partitioning of risks through time. Generally the risk was higher in sites cultivated with permanent crops, such as vineyard and olive, than in annual crops, such as cereals and oil seed rape. The greatest level of risk is generally found at the beginning of the growing season for annual crops and later in June-July for permanent crops.

Seed predation increases with ground beetle diversity in a Wisconsin (USA) potato agroecosystem

Agri-environmental schemes (AES) are hypothesized to enhance biodiversity and ecosystem services in agroecosystems. We investigated how non-crop habitats in one AES influence seed-eating ground beetles (Coleoptera: Carabidae) and post-dispersal weed seed predation, an ecosystem service provided by these beetles. We found that the abundance of beetles was higher in the non-crop habitats than within the crop fields. Species diversity (measured by Simpson's D), however, was greater in crop fields than in non-crop habitats. In addition, beetle assemblages were distinct between the crop and non-crop habitats possibly due to differences in the frequency and intensity of disturbance between crop and non-crop habitats. Seed predation by small predators (mainly ground beetles) was greater in the non-crop habitat than within the potato field. Moreover, we found a positive association between seed predation and beetle diversity both within the crop and in the non-crop habitat which provides evidence of a relationship between biodiversity and ecosystem services. Yet, differences in species assemblages suggest that species identity also affects rates of seed predation.