11Bees are subject to numerous pressures in the modern world. The abundance and diversity of 12 flowers has declined, bees are chronically exposed to cocktails of agrochemicals, and they are 13 simultaneously exposed to novel parasites accidentally spread by humans. Climate change is 14 likely to exacerbate these problems in the future. Stressors do not act in isolation; for example 15 pesticide exposure can impair both detoxification mechanisms and immune responses, 16 rendering bees more susceptible to parasites. It seems certain that chronic exposure to 17 multiple, interacting stressors is driving honey bee colony losses and declines of wild 18pollinators, but such interactions are not addressed by current regulatory procedures and 19 studying these interactions experimentally poses a major challenge. In the meantime, taking 20 steps to reduce stress on bees would seem prudent; incorporating flower-rich habitat into 21 farmland, reducing pesticide use through adopting more sustainable farming methods, and 22

(2016) Widespread contamination of wildflower and beecollected pollen with complex mixtures of neonicotinoids and fungicides commonly applied to crops. Environment International, This version is available from Sussex Research Online: http://sro.sussex.ac.uk/59217/ This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the URL above for details on accessing the published version. Copyright and reuse:Sussex Research Online is a digital repository of the research output of the University.Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available.Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Widespread contamination of wildflower and bee-collected pollen1 with complex mixtures of neonicotinoids and fungicides. There is considerable and ongoing debate as to the harm inflicted on bees by exposure to 16 agricultural pesticides. In part, the lack of consensus reflects a shortage of information on field-17 realistic levels of exposure. Here, we quantify concentrations of neonicotinoid insecticides and 18 fungicides in the pollen of oilseed rape, and in pollen of wildflowers growing near arable fields. We 19 then compare this to concentrations of these pesticides found in pollen collected by honey bees and 20 in pollen and adult bees sampled from bumblebee colonies placed on arable farms. We also 21 compared this with levels found in bumblebee colonies placed in urban areas. Pollen of oilseed rape 22 was heavily contaminated with a broad range of pesticides, as was the pollen of wildflowers growing 23 nearby. Consequently, pollen collected by both bee species also contained a wide range of 24 pesticides, notably including the fungicides carbendazim, boscalid, flusilazole, metconazole, 25 tebuconazole and trifloxystrobin and the neonicotinoids thiamethoxam, thiacloprid and 26 imidacloprid. In bumblebees, fungicides carbendazim, boscalid, tebuconazole, flusilazole and 27 metconazole were present at concentrations up to 73 nanogram/gram (ng/g). Pesticide 28 concentrations in pollen collected by honeybees tended to be lower than those in pollen collected 29 by bumblebees. It is notable that pollen collected by bumblebees in rural areas contained high levels 30 of the neonicotinoids thiamethoxam (mean 18 ng/g) and thiacloprid (mean 2.9 ng/g), along with a 31 range ...

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World‐wide declines in pollinators, including bumblebees, are attributed to a multitude of stressors such as habitat loss, resource availability, emerging viruses and parasites, exposure to pesticides, and climate change, operating at various spatial and temporal scales. Disentangling individual and interacting effects of these stressors, and understanding their impact at the individual, colony and population level are a challenge for systems ecology. Empirical testing of all combinations and contexts is not feasible. A mechanistic multilevel systems model (individual‐colony‐population‐community) is required to explore resilience mechanisms of populations and communities under stress.We present a model which can simulate the growth, behaviour and survival of six UK bumblebee species living in any mapped landscape. Bumble‐BEEHAVE simulates, in an agent‐based approach, the colony development of bumblebees in a realistic landscape to study how multiple stressors affect bee numbers and population dynamics. We provide extensive documentation, including sensitivity analysis and validation, based on data from literature. The model is freely available, has flexible settings and includes a user manual to ensure it can be used by researchers, farmers, policy‐makers, NGOs or other interested parties.Model outcomes compare well with empirical data for individual foraging behaviour, colony growth and reproduction, and estimated nest densities.Simulating the impact of reproductive depression caused by pesticide exposure shows that the complex feedback mechanisms captured in this model predict higher colony resilience to stress than suggested by a previous, simpler model. Synthesis and applications. The Bumble‐BEEHAVE model represents a significant step towards predicting bumblebee population dynamics in a spatially explicit way. It enables researchers to understand the individual and interacting effects of the multiple stressors affecting bumblebee survival and the feedback mechanisms that may buffer a colony against environmental stress, or indeed lead to spiralling colony collapse. The model can be used to aid the design of field experiments, for risk assessments, to inform conservation and farming decisions and for assigning bespoke management recommendations at a landscape scale.

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