Assessing the resilience of biodiversity-driven functions in agroecosystems under environmental change

From a local descriptive to a generic predictive model of cereal aphid regulation by predators

The temporal dynamics of insect populations in agroecosystems are influenced by numerous biotic and abiotic interactions, including trophic interactions in complex food webs. Predicting the regulation of herbivorous insect pests by arthropod predators and parasitoids would allow for rendering crop production less dependent on chemical pesticides. Curtsdotter et al. (2019) developed a food-web model simulating the influences of naturally occurring arthropod predators on aphid population dynamics in cereal crop fields. The use of an allometric hypothesis based on the relative body masses of the prey and various predator guilds reduced the number of estimated parameters to just five, albeit field-specific. Here, we extend this model and test its applicability and predictive capacity. We first parameterized the original model with a dataset with the dynamic arthropod community compositions in 54 fields in six regions in France. We then integrated three additional biological functions to the model: parasitism, aphid carrying capacity and suboptimal high temperatures that reduce aphid growth rates. We developed a multi-field calibration approach to estimate a single set of generic allometric parameters for a given group of fields, which would increase model generality needed for predictions. The original and revised models, when using field-specific parameterization, achieved quantitatively good fits to observed aphid population dynamics for 59% and 53% of the fields, respectively, with pseudo-R2 up to 0.99. But the multi-field calibration showed that increased model generality came at the cost of reduced model reliability (goodness-of-fit). Our study highlights the need to further improve our understanding of how body size and other traits affect trophic interactions in food webs. It also points up the need to acquire high-resolution data to use this type of modelling approach. We propose that a hypothesis-driven strategy of model improvement based on the integration of additional biological functions and additional functional traits beyond body size (e.g., predator space search or prey defences) into the food-web matrix can improve model reliability.

Functional redundancy of weed seed predation is reduced by intensified agriculture

Intensified agriculture, a driver of biodiversity loss, can diminish ecosystem functions and their stability. Biodiversity can increase functional redundancy and is expected to stabilize ecosystem functions. Few studies, however, have explored how agricultural intensity affects functional redundancy and its link with ecosystem function stability. Here, within a continental-wide study, we assess how functional redundancy of seed predation is affected by agricultural intensity and landscape simplification. By combining carabid abundances with molecular gut content data, functional redundancy of seed predation was quantified for 65 weed genera across 60 fields in four European countries. Across weed genera, functional redundancy was reduced with high field management intensity and simplified crop rotations. Moreover, functional redundancy increased the spatial stability of weed seed predation at the field scale. We found that ecosystem functions are vulnerable to disturbances in intensively managed agroecosystems, providing empirical evidence of the importance of biodiversity for stable ecosystem functions across space.

Economic costs of the invasive Yellow-legged hornet on honey bees

Biological invasions have ecological impacts worldwide with potential massive economic costs. Among other ecosystem services such as nitrogen cycle, carbon sequestration and primary production, invasive alien species are particularly known to impact pollination. By predating honey bees (Apis mellifera), the invasive Yellow-legged hornet (Vespa velutina nigrithorax) increases the mortality risk of European bee colonies; however, little is known about its economic costs. We developed an analytic process combining large-scale field data, niche modelling techniques and agent-based models to spatially assess the ecological and economic impacts of the Yellow-legged hornet on honey bees and beekeeping in France. In particular, we estimated (i) the hornet-related risk of bee colony mortality, (ii) the economic cost of colony loss for beekeepers and (iii) the economic impact of livestock replacement compared to honey revenues at regional and national scales. We estimated an overall density of 1.08 hornet nest/km2 in France, based on the field record of 1260 nests over a searched area of 28,348 km2. However, this predator density was heterogeneously spread out across the country as well as the distribution of managed honey bee colonies. Overall, this hornet-related risk of bee colony mortality could reach up to 29.2 % of the beekeepers' livestock at national scale each year in high predation scenario. This national cost could reach as much as € 30.8 million per year due to colony loss, which represents for beekeepers an economic impact of livestock replacement of 26.6 % of honey revenues. Our results suggest non-negligible ecological and economic impacts of the invasive Yellow-legged hornet on honey bees and beekeeping activities. Moreover, this study meets the urgent need for more numerous and accurate economic estimations, necessary to calculate the impact of biological invasions on biodiversity and human goods, with a view to enhance policies of biodiversity conservation.

What Are the Best Pollinator Candidates for Camelia oleifera: Do Not Forget Hoverflies and Flies

Camellia oleifera Abel. is an important woody oil plant, and its pollination success is essential for oil production. We conducted this study to select the best pollinator candidates for C. oleifera using principal component analysis and multi-attribute decision-making. Field observations of the flower-visiting characteristics of candidate pollinators were conducted at three sites. The insect species that visited flowers did not considerably differ between regions or time periods. However, the proportion of each species recorded did vary. We recorded eleven main candidates from two orders and six families at the three sites. The pollen amount carried by Apis mellifera was significantly higher than that of other insects. However, the visit frequency and body length of Apis mellifera were smaller than those of Vespa velutina. Statistical analysis showed that A. mellifera is the best candidate pollinator; Eristaliscerealis is a good candidate pollinator; Phytomia zonata, A. cerana, and V. velutina were ordinary candidate pollinators; and four fly species, Episyrphus balteatus, and Eristalinus arvorum were classified as inefficient candidate pollinators. Our study shows that flies and hoverflies play an important role in the pollination system. Given the global decline in bee populations, the role of flies should also be considered in C. oleifera seed production.

Exploring urban green packages as part of Nature-based Solutions for climate change adaptation measures in rapidly growing cities of the Global South

Given a lot of elusive information on the use and implementation of Nature-based Solutions (NbS) in the Global South, this review provides a synthesis of the evidence on the: - (1) distribution of urban green technologies in form of arboriculture and urban agriculture as a part of NbS packages for the sustainability of cities against population growth and impact of climate change; and (2) options of integrating and mainstreaming various NbS packages into city development policies, planning processes, and decision-making agendas. The sustainability of urban green as part of NbS packages and the usefulness for improvement of livelihoods is determined by the spatial (geographical location) and temporal (time of action) scales, and socio-ecological and institutional factors. Various NbS packages have shown the ability for use as climate change adaptation measures throughout the world. These functions include protection from soil erosion, protection from inland flooding, buffering natural resources against drier and more variable climates, protection from coastal hazards and sea-level rise, moderation of urban heatwaves and effects of heat island, and managing storm-water and flooding in urban areas. Furthermore, the benefits of urban agriculture and arboriculture include use as sources of food and generation of income; improve recreation and social interactions, and the sustainability of biodiversity. They also mitigate the impact of environmental pollution and climate change through reduction of gas emissions and act as carbon sinks. While the starting capital and lack of policy on urban agriculture and arboriculture in many countries, the importance of the industry is inevitably a useful agenda especially in the Global South due to vulnerability to the impact of climate change. This review also suggests the inclusion of all institutions, governments, and relevant stakeholders to emphasize gender sensitization at all levels of planning and decision-making in food production and adaptation measures to climate change.

Towards integrated pest and pollinator management in tropical crops

Biotic pollination and pest control are two critical insect-mediated ecosystem services that support crop production. Although management of both services is usually treated separately, the new paradigm of Integrated Pest and Pollinator Management (IPPM) suggests synergetic benefits by considering them together. We reviewed the management practices in two major tropical perennial crops: cocoa and coffee, to assess IPPM applications under the tropics. We found potential synergies and antagonisms among crop pest and pollination management, however, very few studies considered these interactions. Interestingly, we also found management practices focusing mainly on a single service mediated by insects although species can show multiple ecological functions as pests, natural enemies, or pollinators. The tropics represent a promising area for the implementation of IPPM and future research should address this concept to move towards a more sustainable agriculture.

Origin and expansion of the world's most widespread pinniped: range-wide population genomics of the harbour seal (Phoca vitulina)

The harbour seal (Phoca vitulina) is the most widely distributed pinniped, occupying a wide variety of habitats and climatic zones across the Northern Hemisphere. Intriguingly, the harbour seal is also one of the most philopatric seals, raising questions as to how it colonised virtually the whole of the Northern Hemisphere. To shed light on the origin, remarkable range expansion, population structure and genetic diversity of this species, we used genotyping-by-sequencing to analyse ~13,500 biallelic SNPs from 286 individuals sampled from 22 localities across the species' range. Our results point to a Northeast Pacific origin, colonisation of the North Atlantic via the Canadian Arctic, and subsequent stepping-stone range expansions across the North Atlantic from North America to Europe, accompanied by a successive loss of genetic diversity. Our analyses further revealed a deep divergence between modern North Pacific and North Atlantic harbour seals, with finer-scale genetic structure at regional and local scales consistent with strong philopatry. The study provides new insights into the harbour seal's remarkable ability to colonise and adapt to a wide range of habitats. Furthermore, it has implications for current harbour seal subspecies delineations and highlights the need for international and national red lists and management plans to ensure the protection of genetically and demographically isolated populations.

Landscape complexity promotes resilience of biological pest control to climate change

Increased climate variability as a result of anthropogenic climate change can threaten the functioning of ecosystem services. However, diverse responses to climate change among species (response diversity) can provide ecosystems with resilience to this growing threat. Measuring and managing response diversity and resilience to global change are key ecological challenges. Here, we develop a novel index of climate resilience of ecosystem services, exemplified by the thermal resilience of predator communities providing biological pest control. Field assays revealed substantial differences in the temperature-dependent activity of predator species and indices of thermal resilience varied among predator communities occupying different fields. Predator assemblages with higher thermal resilience provided more stable pest control in microcosms where the temperature was experimentally varied, confirming that the index of thermal resilience developed here is linked to predator function. Importantly, complex landscapes containing a high number of non-crop habitat patches were more likely to contain predator communities with high thermal resilience. Thus, the conservation and restoration of non-crop habitats in agricultural landscapes-practices known to strengthen natural pest suppression under current conditions-will also confer resilience in ecosystem service provisioning to climate change.

A comprehensive approach for agroecosystem services and disservices valuation

The use of the ecosystem services approach for ecosystem management, including the valuation of ecosystem services, has grown in recent decades. Although a common framework is used, each ecosystem has its own characteristics. The agroecosystem, for example, is an anthropised ecosystem where ecosystem service flows are highly interrelated with the environment, positively or negatively. Therefore, agroecosystem services are usually accompanied by disservices. The valuation of agroecosystem services and disservices requires adaptation of existing ecosystem services paradigms to accommodate the innate agroecosystem idiosyncrasies. To this end, in this study, a comprehensive approach for valuation of agroecosystem services and disservices was proposed and validated in a semi-arid western Mediterranean agricultural area through stakeholder assessment, using a choice experiment. The results suggest that all categories of services (provisioning, regulating, and cultural) should be taken into account when valuing agroecosystem services and disservices. In particular, food provision (a provisioning service), water (a provisioning disservice), local climate regulation and biodiversity (regulating services), waste treatment and water purification (regulating disservices), and recreation and tourism (cultural services) are relevant for this purpose. Their relative importance in agroecosystems valuation reached 70% for agroecosystem services and 30% for disservices. Specifically, biodiversity (38%) emerged as the most relevant agroecosystem service to be valued, followed by recreation and tourism (20%), local climate regulation (7%), and food provision (5%). Among the agroecosystem disservices, water and waste treatment (15%), and water purification (15%) together contributed to 30% of the total importance. Agroecosystems should be valued considering their multifunctional character and the integration of agroecosystem services and disservices.

Grassland-to-crop conversion in agricultural landscapes has lasting impact on the trait diversity of bees

CONTEXT

Global pollinator decline has motivated much research to understand the underlying mechanisms. Among the multiple pressures threatening pollinators, habitat loss has been suggested as a key-contributing factor. While habitat destruction is often associated with immediate negative impacts, pollinators can also exhibit delayed responses over time.

OBJECTIVES

We used a trait-based approach to investigate how past and current land use at both local and landscape levels impact plant and wild bee communities in grasslands through a functional lens.

METHODS

We measured flower and bee morphological traits that mediate plant-bee trophic linkage in 66 grasslands. Using an extensive database of 20 years of land-use records, we tested the legacy effects of the landscape-level conversion of grassland to crop on flower and bee trait diversity.

RESULTS

Land-use history was a strong driver of flower and bee trait diversity in grasslands. Particularly, bee trait diversity was lower in landscapes where much of the land was converted from grassland to crop long ago. Bee trait diversity was also strongly driven by plant trait diversity computed with flower traits. However, this relationship was not observed in landscapes with a long history of grassland-to-crop conversion. The effects of land-use history on bee communities were as strong as those of current land use, such as grassland or mass-flowering crop cover in the landscape.

CONCLUSIONS

Habitat loss that occurred long ago in agricultural landscapes alters the relationship between plants and bees over time. The retention of permanent grassland sanctuaries within intensive agricultural landscapes can offset bee decline.

Ecological pest control fortifies agricultural growth in Asia-Pacific economies

The Green Revolution is credited with alleviating famine, mitigating poverty and driving aggregate economic growth since the 1960s. In Asia, high-input technology packages secured a tripling of rice output, with germplasm improvements providing benefits beyond US$4.3 billion yr^-1. Here, we unveil the magnitude and macro-economic relevance of parallel nature-based contributions to productivity growth in non-rice crops over the period 1918-2018 (across 23 different Asia-Pacific geopolitical entities). We empirically demonstrate how biological control resolved invasive pest threats in multiple agricultural commodities, ensuring annually accruing (on-farm) benefits of US$14.6-19.5 billion yr^-1. Scientifically guided biological control of 43 exotic invertebrate pests permitted 73-100% yield-loss recovery in critical food, feed and fibre crops including banana, breadfruit, cassava and coconut. Biological control thereby promoted rural growth and prosperity even in marginal, poorly endowed, non-rice environments. By placing agro-ecological innovations on equal footing with input-intensive measures, our work provides lessons for future efforts to mitigate invasive species, restore ecological resilience and sustainably raise output of global agrifood systems.

The interplay of landscape composition and configuration: new pathways to manage functional biodiversity and agroecosystem services across Europe

Managing agricultural landscapes to support biodiversity and ecosystem services is a key aim of a sustainable agriculture. However, how the spatial arrangement of crop fields and other habitats in landscapes impacts arthropods and their functions is poorly known. Synthesising data from 49 studies (1515 landscapes) across Europe, we examined effects of landscape composition (% habitats) and configuration (edge density) on arthropods in fields and their margins, pest control, pollination and yields. Configuration effects interacted with the proportions of crop and non-crop habitats, and species' dietary, dispersal and overwintering traits led to contrasting responses to landscape variables. Overall, however, in landscapes with high edge density, 70% of pollinator and 44% of natural enemy species reached highest abundances and pollination and pest control improved 1.7- and 1.4-fold respectively. Arable-dominated landscapes with high edge densities achieved high yields. This suggests that enhancing edge density in European agroecosystems can promote functional biodiversity and yield-enhancing ecosystem services.