Potential landscape-scale pollinator networks across Great Britain: structure, stability and influence of agricultural land cover

Understanding spatial variation in the structure and stability of plant-pollinator networks, and their relationship with anthropogenic drivers, is key to maintaining pollination services and mitigating declines. Constructing sufficient networks to examine patterns over large spatial scales remains challenging. Using biological records (citizen science), we constructed potential plant-pollinator networks at 10km resolution across Great Britain, comprising all potential interactions inferred from recorded floral visitation and species co-occurrence. We calculated network metrics (species richness, connectance, pollinator and plant generality) and adapted existing methods to assess robustness to sequences of simulated plant extinctions across multiple networks. We found positive relationships between agricultural land cover and both pollinator generality and robustness to extinctions under several extinction scenarios. Increased robustness was attributable to changes in plant community composition (fewer extinction-prone species) and network structure (increased pollinator generality). Thus, traits enabling persistence in highly agricultural landscapes can confer robustness to potential future perturbations on plant-pollinator networks

Plant connectivity underlies plant-pollinator-exploiter distributions in Ficus petiolaris and associated pollinating and non-pollinating fig wasps

Peer reviewedPostprin

A decline in pollinator dependent vegetable crop productivity in India indicates pollination limitation and consequent agro-economic crises.

Approximately 70% of the tropical crop species depend on pollinators for optimum yields (Roubik, 1995, Klein 2007). The economic value of such pollinated crops to India is $726 million and India is the world's second largest vegetable producer (Sidhu, 2005). This status has been underpinned by large-scale changes in land-use and pesticide dependency (Fazal, 2000; Shaw & Satish, 2007). A method (c.f. Aizen et al. 2008) that partitions crops into categories depending on their relative pollinator dependence (Index of pollinator dependence, DI) was applied to analysis of vegetable yields for India over 45 years (1963-2008) using FAO data. This has revealed that since 1993, relative yields of crop production has either flattened or declined, while pollinator non dependent crops show no similar decline. This pattern of yield limitation may be due to several factors, among which pollinator limitation would be a major factor (Kearns et al. 1998) and this risk is discussed. Pollinator decline will have serious socio-economic consequences for countries like India, which host a large population of small and marginal farms for whom falling yield level would be critical for subsistence (Kearns et al. 1998; Kremen et al., 2002; Klein et al., 2007; Potts et al., 2010). We show here for the first time any indication of pollination limitation in India, an emerging economy that is still predominantly agrarian. Detailed land use and ecological surveys are urgently required to assess the ecology of pollinating insects within and around agricultural systems in India

The macroeconomic cost of catastrophic pollinator declines

We develop a computable general equilibrium (CGE) approach to assess the macroeconomic impacts of productivity shocks due to catastrophic losses of pollination ecosystem services at global and regional scales. In most regions, producers of pollinator dependent crops end up benefiting because direct output losses are outweighed by increased prices, while non-agricultural sectors experience large adverse indirect impacts, resulting in overall losses whose magnitudes vary substantially. By comparison, partial equilibrium analyses tend to overstate the costs to agricultural producers, understate aggregate economy-wide losses, and overstate the impacts on consumers' welfare. Our results suggest an upper bound on global willingness to pay for agricultural pollination services of $127–$152 billion

A critical analysis of the potential for EU Common Agricultural Policy measures to support wild pollinators on farmland

1. Agricultural intensification and associated loss of high‐quality habitats are key drivers of insect pollinator declines. With the aim of decreasing the environmental impact of agriculture, the 2014 EU Common Agricultural Policy (CAP) defined a set of habitat and landscape features (Ecological Focus Areas: EFAs) farmers could select from as a requirement to receive basic farm payments. To inform the post‐2020 CAP, we performed a European‐scale evaluation to determine how different EFA options vary in their potential to support insect pollinators under standard and pollinator‐friendly management, as well as the extent of farmer uptake. 2. A structured Delphi elicitation process engaged 22 experts from 18 European countries to evaluate EFAs options. By considering life cycle requirements of key pollinating taxa (i.e. bumble bees, solitary bees and hoverflies), each option was evaluated for its potential to provide forage, bee nesting sites and hoverfly larval resources. 3. EFA options varied substantially in the resources they were perceived to provide and their effectiveness varied geographically and temporally. For example, field margins provide relatively good forage throughout the season in Southern and Eastern Europe but lacked early‐season forage in Northern and Western Europe. Under standard management, no single EFA option achieved high scores across resource categories and a scarcity of late season forage was perceived. 4. Experts identified substantial opportunities to improve habitat quality by adopting pollinator‐friendly management. Improving management alone was, however, unlikely to ensure that all pollinator resource requirements were met. Our analyses suggest that a combination of poor management, differences in the inherent pollinator habitat quality and uptake bias towards catch crops and nitrogen‐fixing crops severely limit the potential of EFAs to support pollinators in European agricultural landscapes. 5. Policy Implications. To conserve pollinators and help protect pollination services, our expert elicitation highlights the need to create a variety of interconnected, well‐managed habitats that complement each other in the resources they offer. To achieve this the Common Agricultural Policy post‐2020 should take a holistic view to implementation that integrates the different delivery vehicles aimed at protecting biodiversity (e.g. enhanced conditionality, eco‐schemes and agri‐environment and climate measures). To improve habitat quality we recommend an effective monitoring framework with target‐orientated indicators and to facilitate the spatial targeting of options collaboration between land managers should be incentivised

Developing European conservation and mitigation tools for pollination services: approaches of the STEP (Status and Trends of European Pollinators) project

Pollinating insects form a key component of European biodiversity, and provide a vital ecosystem service to crops and wild plants. There is growing evidence of declines in both wild and domesticated pollinators, and parallel declines in plants relying upon them. The STEP project (Status and Trends of European Pollinators, 2010-2015, www.stepproject.net) is documenting critical elements in the nature and extent of these declines, examining key functional traits associated with pollination deficits, and developing a Red List for some European pollinator groups. Together these activities are laying the groundwork for future pollinator monitoring programmes. STEP is also assessing the relative importance of potential drivers of pollinator declines, including climate change, habitat loss and fragmentation, agrochemicals, pathogens, alien species, light pollution, and their interactions. We are measuring the ecological and economic impacts of declining pollinator services and floral resources, including effects on wild plant populations, crop production and human nutrition. STEP is reviewing existing and potential mitigation options, and providing novel tests of their effectiveness across Europe. Our work is building upon existing and newly developed datasets and models, complemented by spatially-replicated campaigns of field research to fill gaps in current knowledge. Findings are being integrated into a policy-relevant framework to create evidence-based decision support tools. STEP is establishing communication links to a wide range of stakeholders across Europe and beyond, including policy makers, beekeepers, farmers, academics and the general public. Taken together, the STEP research programme aims to improve our understanding of the nature, causes, consequences and potential mitigation of declines in pollination services at local, national, continental and global scales

Investigations into stability in the fig/ fig-wasp mutualism

Fig trees (Ficus, Moraceae) and their pollinating wasps (Chalcidoidea, Agaonidae) are involved in an obligate mutualism where each partner relies on the other in order to reproduce: the pollinating fig wasps are a fig tree’s only pollen disperser whilst the fig trees provide the wasps with places in which to lay their eggs. Mutualistic interactions are, however, ultimately genetically selfish and as such, are often rife with conflict. Fig trees are either monoecious, where wasps and seeds develop together within fig fruit (syconia), or dioecious, where wasps and seeds develop separately. In interactions between monoecious fig trees and their pollinating wasps, there are conflicts of interest over the relative allocation of fig flowers to wasp and seed development. Although fig trees reap the rewards associated with wasp and seed production (through pollen and seed dispersal respectively), pollinators only benefit directly from flowers that nurture the development of wasp larvae, and increase their fitness by attempting to oviposit in as many ovules as possible. If successful, this oviposition strategy would eventually destroy the mutualism; however, the interaction has lasted for over 60 million years suggesting that mechanisms must be in place to limit wasp oviposition. This thesis addresses a number of factors to elucidate how stability may be achieved in monoecious fig systems. Possible mechanisms include: 1) a parasitoidcentred short ovipositor hypothesis in Ficus rubiginosa, which suggests that a subset of flowers are out of reach to parasitoid ovipositors making these ovules the preferred choice for ovipositing pollinators and allowing seeds to develop in less preferred ovules; 2) the presence of third-party mutualists such as non-pollinating fig wasps (F. burkei) and patrolling green tree ants on the fig surface (F. racemosa) that limit pollinator and parasitoid oviposition respectively; and 3) selection on fig morphology which constrains the size (and therefore fecundity) of the associated pollinators. I discuss the lack of evidence for a single unifying theory for mutualism stability and suggest that a more likely scenario is the presence of separate, and perhaps multiple, stabilising strategies in different fig/ fig-wasp partnerships

Preventing a Risk/Risk Trade-off: An Analysis of the Measures Necessary to Increase U.S. Pollinator Numbers

This Note will proceed in four parts. Part II will discuss the importance of pollinators and the possible reasons for their declining numbers. Part III will delve into the current and proposed actions to increase pollinator populations that are taking place in the United States. Part IV will then discuss the generally desired and widely accepted solution: a ban on neonicotinoids. This Part will introduce the implementation and results of a neonicotinoid ban in the European Union, and the risk/risk trade-off presented by a neonicotinoid ban. Finally, Part V will compile the solutions discussed in Parts III and IV, and present possible legal and administrative solutions that can be put in place to protect bees, modeled after the legal actions that have successfully increased monarch butterfly populations while avoiding the issues the European Union faced with its neonicotinoid ban. Part V will conclude that banning neonicotinoids is not the save-all solution to pollinator decline, and propose that focusing on a multiplicity of avenues—both legal and administrative—that tackle the many reasons why pollinator populations are in decline is more likely to increase pollinator numbers than focusing on one single facto