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Road verges can provide valuable habitats for insect pollinators such as bees, butterflies & beetles. 
But does pollution from roads/traffic make verges less good for pollinators?
Our new paper tackles this question: https://doi.org/10.1111/1365-2664.13844
A thread (1/n)
But does pollution from roads/traffic make verges less good for pollinators?
Our new paper tackles this question: https://doi.org/10.1111/1365-2664.13844
A thread (1/n)
It is well established that road verges can provide important flower-rich habitats for pollinators, especially in agricultural landscapes.
See our recent review in https://doi.org/10.1016/j.biocon.2020.108687
See our recent review in https://doi.org/10.1016/j.biocon.2020.108687
But our previous work found 
pollinators in verges along road edges compared to further into verges, and pollinators in verges along busier roads.
See https://doi.org/10.1111/1365-2664.13470
@JAppliedEcology
pollinators in verges along road edges compared to further into verges, and pollinators in verges along busier roads.See https://doi.org/10.1111/1365-2664.13470
@JAppliedEcology
We wondered - is this something to do with pollution? Roads produce noise, exhaust emissions, light, metals and many other types of pollution.
Some of these can extend very far. See:
https://doi.org/10.1016/j.scitotenv.2021.145589
But pollution is generally greatest at the road edge.
Some of these can extend very far. See:
https://doi.org/10.1016/j.scitotenv.2021.145589
But pollution is generally greatest at the road edge.
Our question: Is pollution making road verges less good for pollinators?
To address this, we surveyed pollinators+flowers & measured pollution in verges.
We then used experiments away from roads to test impacts of simulated pollution on pollinator activity and foraging.
To address this, we surveyed pollinators+flowers & measured pollution in verges.
We then used experiments away from roads to test impacts of simulated pollution on pollinator activity and foraging.
We focused on four widespread and little studied forms of pollution: noise, turbulence, dust and metals.
A quick overview of some of the slightly wacky methods that we used...
A quick overview of some of the slightly wacky methods that we used...
Measuring turbulence (windy conditions when vehicles pass by) was tricky...
...so we created a 'pollinator swing-ometer': a deceased pollinator attached to a piece of cotton hanging from a stick. We measured how much it swung when a car went past. Yes, i know...
...so we created a 'pollinator swing-ometer': a deceased pollinator attached to a piece of cotton hanging from a stick. We measured how much it swung when a car went past. Yes, i know...
Measuring roadside dust... sellotape on a stick (obviously).
To measure the impact of traffic noise on pollinators, we played recorded traffic noise to pollinators in wildflower patches...
To measure the impacts of turbulence, we used blower fans programmed to turn on/off periodically (at a frequency representing a busy or a typical road).
Not a perfect imitation, but reflects intermittent windy disturbance from traffic & provided similar swingometer measurements.
Not a perfect imitation, but reflects intermittent windy disturbance from traffic & provided similar swingometer measurements.
For dust, we placed plants out in road verges for 4 days to allow them to accumulate dust.
We also sprinkled some plants with dust collected from roadsides with a dustpan and brush...
We also sprinkled some plants with dust collected from roadsides with a dustpan and brush...
For metals, we used bee feeders, laced with different concentrations of metals (Cd, Cu, Pb, Sb, Zn) representing those measured in roadsides.
So, what did we find?
First, pollinators in road verges were exposed to noise, turbulence, dust and metal pollution.
These decreased with distance from the road edge but, with the exception of turbulence, extended more than 8 m into verges.
These decreased with distance from the road edge but, with the exception of turbulence, extended more than 8 m into verges.
Second, we found fewer pollinators in verges closer to the road edge - particularly within the first 2 m from the road (55% lower than 7-9 m) where pollution is greatest.
This was despite a similar density and species richness of flowers.
This was despite a similar density and species richness of flowers.
Third, experiments simulating roadside noise and dust found no effect on pollinator activity/foraging...
BUT simulated turbulence deterred pollinators - reducing visit duration by up to 54%.
BUT simulated turbulence deterred pollinators - reducing visit duration by up to 54%.
Also, honeybees and wasps avoided concentrations of metals that were frequently found within 2 m of road edges (with up to 75% fewer visits).
This is probably a good thing because there is some evidence that these concentrations can have (sub)lethal effects.
This is probably a good thing because there is some evidence that these concentrations can have (sub)lethal effects.
Unfortunately we didn't manage to get other pollinator taxa to visit feeders (e.g. bumblebees, flies, beetles, butterflies), or find a better alternative method. So more work to be done here.
So what does this all mean?
The findings suggest that verge management enhancements should prioritise areas more than 2 m from the road edge, and along roads with less traffic.
< 2 m from roads might still be good for pollinators, but just used less. BUT...
The findings suggest that verge management enhancements should prioritise areas more than 2 m from the road edge, and along roads with less traffic.
< 2 m from roads might still be good for pollinators, but just used less. BUT...
This was very much a broad initial assessment.
We really need more research to test if there are longer-term (sub)lethal impacts on pollinators. E.g. of pollution levels found < 2 m from roads.
Plenty more to do, with exciting work underway by the wonderful @ClaireWallace95
We really need more research to test if there are longer-term (sub)lethal impacts on pollinators. E.g. of pollution levels found < 2 m from roads.
Plenty more to do, with exciting work underway by the wonderful @ClaireWallace95
My guess is that lethal impacts are likely to be minor for most adult pollinators because they only spend a % of their time in road verges.
To me, pollution seems a greater worry for less mobile pollinators + eggs/larvae in verges, which are exposed for longer periods.
To me, pollution seems a greater worry for less mobile pollinators + eggs/larvae in verges, which are exposed for longer periods.
Thanks to Juliet Osborne, @KevinJGaston @JMBecologist @KarenHEGeochem @CarmenFalagan , Dave Cruse, @ClaireWallace95 @LynnDicks & many others for their help with this work.
Please do check out the paper for more info: https://doi.org/10.1111/1365-2664.13844
@UniofExeterESI @JAppliedEcology
Please do check out the paper for more info: https://doi.org/10.1111/1365-2664.13844
@UniofExeterESI @JAppliedEcology
