Petrol exhaust pollution impairs honey bee learning and memory

Air pollution modifies colonisation factors in beneficial symbiont Snodgrassella and disrupts the bumblebee gut microbiome

Particulate air pollutants, a major air pollution component, are detrimental to human health and a significant risk to wildlife and ecosystems globally. Here we report the effects of particulate pollutant black carbon on the beneficial gut microbiome of important global insect pollinator, the buff-tailed bumblebee (Bombus terrestris). Our data shows that exposure to black carbon particulates alters biofilm structure, gene expression and initial adhesion of beneficial bee gut coloniser, Snodgrassella alvi. Exposure of adult Bombus terrestris to non-toxic black carbon particulates significantly increased viable bacteria on MRS agar and 16S absolute abundance of beneficial bacteria Bombilactobacillus in Post-treated bumblebees compared to Pre-treated, demonstrating disruption of the bumblebee gut microbiome. These findings show that black carbon exposure has direct, measurable effects on bees' beneficial commensal bacteria and microbiome. Together these data highlight that black carbon, a single type of particulate pollution, is an underexplored risk to insect pollinator health.

Like a moth to a flame: the effect of megafires on pollinators and pollination systems

Fire is a natural part of many ecosystems; however, as a consequence of climate change, unusually large 'megafires' are expected to increase in occurrence. Given their large spatial extent, the impacts of megafire on biodiversity and ecosystem functioning could differ substantially from the impacts of typically sized fires, even in fire-adapted ecosystems. In this review, we investigate the potential impacts of megafires on pollination systems. The extensive spatial extent of megafires can lead to large amounts of habitat being exposed to high-severity fires, which may increase insect mortality, especially for taxa that cannot take refuge in underground nests or other refuges. In the most extreme cases, megafires may result in the local - or global - extinction of plant and pollinator species, which, in turn, can trigger co-extinctions and lessen the resilience of pollination networks. In addition, smoke can exacerbate initial mortality by interfering with insect sensory systems, decreasing foraging behaviours, and negatively impacting insect health and immunity. Worryingly, smoke can impact pollination systems thousands of kilometres away from the fire. The negative effects of megafires may be exacerbated by inter-connected nonlinear feedback loops such as extinction cascades, colony collapse and Allee effects, which may make the response of pollination systems to fires harder to predict. Since megafires will almost certainly become a feature of our future, understanding how interconnected stressors will impact pollinators and pollination systems is key to safeguarding global pollination systems.

Interspecific interactions disrupted by roads

Roads have pervasive impacts on wildlife, including habitat loss and fragmentation, road mortality, habitat pollution and increased human use of habitats surrounding them. However, the effects of roads on interspecific interactions are less understood. Here we provide a synthesis of the existing literature on how species interactions may be disrupted by roads, identify knowledge gaps, and suggest avenues for future research and conservation management. We conducted a systematic search using the Web of Science database for each species interaction (predation, competition, mutualism, parasitism, commensalism and amensalism). These searches yielded 2144 articles, of which 195 were relevant to our topic. Most of these studies focused on predation (50%) or competition (24%), and less frequently on mutualism (17%) or, parasitism (9%). We found no studies on commensalism or amensalism. Studies were biased towards mammals from high-income countries, with most conducted in the USA (34%) or Canada (18%). Our literature review identified several patterns. First, roads disrupt predator-prey relationships, usually with negative impacts on prey populations. Second, new disturbed habitats created in road corridors often benefit more competitive species, such as invasive species, although some native or endangered species can also thrive there. Third, roads degrade mutualistic interactions like seed dispersal and pollination. Fourth, roads can increase parasitism rates, although the intensity of the alteration is species specific. To reduce the negative impacts of roads on interspecific interactions, we suggest the following management actions: (i) verges should be as wide and heterogenous as possible, as this increases microhabitat diversity, thus enhancing ecosystem services like pollination and seed dispersal; (ii) combining different mowing regimes can increase the complexity of the habitat corridor, enabling it to act as a habitat for more species; (iii) the use of de-icing salts should be gradually reduced and replaced with less harmful products or maintenance practices; (iv) wildlife passes should be implemented in groups to reduce animal concentrations inside them; (v) periodic removal of carcasses from the road to reduce the use of this resource by wildlife; and (vi) implementation of traffic-calming schemes could enhance interspecific interactions like pollination and avoid disruption of predator-prey relationships.

A global meta-analysis reveals contrasting impacts of air, light, and noise pollution on pollination

In the face of biodiversity decline, understanding the impact of anthropogenic disturbances on ecosystem functions is critical for mitigation. Elevated levels of pollution are a major threat to biodiversity, yet there is no synthesis of their impact on many of the major ecosystem functions, including pollination. This ecosystem function is both particularly vulnerable as it depends on the fine-tuned interaction between plants and pollinators and hugely important as it underpins the flora of most habitats as well as food production. Here, we untangle the impact of air, light, and noise pollution on the pollination system by systematically evaluating and synthesizing the published evidence via a meta-analysis. We identified 58 peer-reviewed articles from three databases. Mixed-effects meta-regression models indicated that air pollution negatively impacts pollination. However, there was no effect of light pollution, despite previous studies that concentrated solely on pollinators suggesting a negative impact. Evidence for noise pollution was extremely limited. Unless action is taken to tackle air pollution, the capacity to support well-functioning diverse pollination systems will be compromised, with negative consequences for habitat conservation and food security.

A Monitoring System for Carbon Dioxide in Honeybee Hives: An Indicator of Colony Health

Non-dispersive infra-red (NDIR) detectors have become the dominant method for measuring atmospheric CO₂, which is thought to be an important gas for honeybee colony health. In this work we describe a microcontroller-based system used to collect data from Senserion SCD41 NDIR sensors placed in the crown boards and queen excluders of honeybee colonies. The same sensors also provide relative humidity and temperature data. Several months of data have been recorded from four different hives. The mass change measurements, from hive scales, when foragers leave the hive were compared with the data from the gas sensors. Our data suggest that it is possible to estimate the colony size from the change in measured CO₂, however no such link with the humidity is observed. Data are presented showing the CO₂ decreasing over many weeks as a colony dies.

Can biodiverse streetscapes mitigate the effects of noise and air pollution on human wellbeing?

Most of the global population are urban, with inhabitants exposed to raised levels of pollution. Pollutants negatively impact human wellbeing, and can alter the structure and diversity of ecosystems. Contrastingly, urban biodiversity can positively contribute to human wellbeing. We know little, however, about whether the negative impacts of pollution on wellbeing could be lessened for householders living on more biodiverse streets, as the complex interlinkages between pollution, biodiversity and wellbeing have rarely been examined. Here, we used structural equation modelling to simultaneously test whether biodiversity (actual and perceived) mediates the relationship between traffic-related pollution (noise, dB; nitrogen dioxide, NO₂) or air pollution (PM_2.5) and wellbeing (mental wellbeing, happiness). In summer 2019, we conducted questionnaires and biodiversity surveys, and collected noise and air pollution data, from households (n = 282) across the streetscapes of Leeds, UK. Biodiversity (actual or perceived) showed no mediating effects. However, increased flowering plant richness was positively associated with mental wellbeing. Traffic-related pollution negatively affected pollinator and flowering plant richness, but not wellbeing. This could be because householders are not exposed to high levels of noise or NO₂ because they do not maintain front gardens on noisier streets. There was no measurable effect of air pollution on biodiversity or wellbeing. These findings shed light on the complex mechanisms through which biodiversity could improve human wellbeing. Enhancing the diversity of plant species in streetscapes would have a positive effect on wellbeing, further emphasising the important role that biodiverse urban streetscapes play in improving the liveability of cities.

Odor-Pollution From Fungicides Disrupts Learning and Recognition of a Common Floral Scent in Bumblebees (Bombus impatiens)

Background and Aims

Bumblebees provide vital pollination services to both natural and agricultural ecosystems. Consequently their declines in species-diversity and population size over the last five decades is alarming. Direct contributors to these declines include pesticides, habitat loss, and disease. However, given that colony fitness is linked to foraging success, successful conservation requires mitigation of any anthropogenic practices that negatively impact foraging. Previous work has shown that agrochemical odor-pollution, including that of fungicides, can modulate bumblebee foraging behavior. This study investigates how odor pollution from three common fungicides (Safer® Brand Garden Fungicide II, Scotts® Lawn Fungus Control, and Reliant® Systemic Fungicide) affects Bombus impatiens’ floral-odor learning and recognition using an associative learning paradigm.

Methods

The effects of fungicide-odor pollution were tested in three ways: (1) background pollution during floral-odor learning; (2) background pollution during floral-odor recognition; and (3) point (localized) pollution during floral-odor recognition. Electroantennogram (EAG) recordings from B. impatiens confirmed the salience of all odor-stimuli and examined impacts of background fungicide-odor on antennal responses to floral-odor. To better understand how fungicide-odor structure related to behavioral data, scents were sampled (Solid Phase Microextraction) and analyzed using gas chromatography–mass spectrometry. Odors were then characterized using the Compounds Without Borders (CWB) vectorization method.

Conclusion

All fungicides tested disrupted floral-odor learning and recognition for at least one concentration tested, and Scotts® was universally disruptive at all tested concentrations. All fungicides induced EAG responses, indicating they provide perceivable odor stimuli. Interestingly, two of three tested fungicides (Scotts® and Reliant®) inhibit antennal responses to Monarda fistulosa odor. Odor characterization supports previous findings that sulfurous scents could be disruptive to odor-driven foraging behaviors. Inability for foraging bumblebees to associate to rewarding floral odors in the presence of fungicidal odor pollution could have negative large-scale implications for colony health and reproductive fitness.

Repeated short-term exposure to diesel exhaust reduces honey bee colony fitness

Production of insect-pollinated crops is often reliant on honey bee (Apis mellifera) pollination services. Colonies can be managed and moved to meet the demands of modern intensified monoculture farming systems. Increased colony mortalities have been observed, which are thought be caused by interacting factors including exposure to pesticides, parasites, viruses, agricultural intensification, and changes in global and regional climate. However, whilst common tropospheric air pollutants (e.g. NO_x, particulate matter etc) are known to cause a range of negative effects on human health, there is little evidence of their impact on the health of A. mellifera. This study investigates the effects of exposure to diesel exhaust on A. mellifera, both at the level of individual foragers and on the whole colony. We exposed a series of colonies to diesel exhaust fumes for 2 h a day over the course of three weeks and contrasted their performance to a series of paired control colonies located at the same field site. We investigated markers of neuronal health in the brains of individual foragers and measured the prevalence of common viruses. Electronic counters monitored daily colony activity patterns and pollen samples from returning foragers were analysed to investigate plant species richness and diversity. The amounts of honey, brood and pollen in each colony were measured regularly. We demonstrated an upregulation of the synapse protein Neurexin 1 in forager brains repeatedly exposed to diesel exhaust. Furthermore, we found that colonies exposed to diesel exhaust lost colony weight after the exposure period until the end of the summer season, whereas control colonies gained weight towards the end of the season. Further investigations are required, but we hypothesise that such effects on both individual foragers and whole colony fitness parameters could ultimately contribute to winter losses of honey bee colonies, particularly in the presence of additional stressors.

Opportunities and threats for pollinator conservation in global towns and cities

Urban expansion is considered to be one of the main threats to global biodiversity yet some pollinator groups, particularly bees, can do well in urban areas. Recent studies indicate that both local and landscape-level drivers can influence urban pollinator communities, with local floral resources and the amount of impervious cover in the landscape affecting pollinator abundance, richness and community composition. Urban intensification, chemicals, climate change and increased honey bee colony densities all negatively affect urban pollinators. Maintaining good areas of habitat for pollinators, such as those found in allotments (community gardens) and domestic gardens, and improving management approaches in urban greenspace and highly urbanised areas (e.g. by increasing floral resources and nesting sites) will benefit pollinator conservation. Opportunities for pollinator conservation exist via multiple stakeholders including policymakers, urban residents, urban planners and landscape architects.

Acute exposure to urban air pollution impairs olfactory learning and memory in honeybees

While the ecological effects of pesticides have been well studied in honeybees, it is unclear to what extent other anthropogenic contaminants such as air pollution may also negatively affect bee cognition and behaviour. To answer this question, we assessed the impacts of acute exposure to four ecologically relevant concentrations of a common urban air pollutant-diesel generated air pollution on honeybee odour learning and memory using a conditioned proboscis extension response assay. The proportion of bees that successfully learnt odours following direct air pollution exposure was significantly lower in bees exposed to low, medium and high air pollutant concentrations, than in bees exposed to current ambient levels. Furthermore, short- and long-term odour memory was significantly impaired in bees exposed to low medium and high air pollutant concentrations than in bees exposed to current ambient levels. These results demonstrate a clear and direct cognitive cost of air pollution. Given learning and memory play significant roles in foraging, we suggest air pollution will have increasing negative impacts on the ecosystem services bees provide and may add to the current threats such as pesticides, mites and disease affecting colony fitness.