[Pollinator] roads and pollinators

[Chip Taylor]

Some of you interested in the issue raised by Lucy Jordon may find 
the comments of Jennifer Hopwood to be of interest.


From: Hopwood, Jennifer L
Sent: Thu 8/31/2006 1:10 PM
To: lucy_jordan at fws.gov
Subject: roads and pollinators

Hi Lucy,
I wanted to clarify a few things about my study on pollinators and 
roadsides (the recent abstract in question) and to respond to your 
most recent posting on the pollinator website by sharing with you 
what I know.  Firstly, my study sites were roadsides that had been 
restored to native prairie vegetation by the Kansas Department of 
Transportation in hopes to prevent erosion, reduce maintenance costs 
(these roadsides are mowed much less frequently and are not broadly 
sprayed with herbicides), and to look nice.  Several Midwestern 
states, including Iowa and Minnesota, have restored sections of 
roadsides in hopes to find ways to better manage the roadside 
vegetation by allowing native vegetation to reestablish.  So the 
roadsides I studied were not restored specifically restored with 
animals in mind, and are not currently managed specifically with 
wildlife in mind since this is not the primary objective of the DOT 
(positive influences of restorations on wildlife are just side 
benefits).

The overall objective of my study was to determine how the management 
of roadsides might affect wild bee communities.  As you know from my 
abstract, I sampled bees from roadside restorations as well as 
roadsides that had not been restored, and found significant 
differences.  I found that the floral community, as well the 
availability of nesting substrate for ground-nesting bees, had 
significant influences on bee abundance and richness.  In addition to 
these factors, I also looked at how the width of the roadside, the 
slope and topography of the roadside, and the amount of traffic of 
the adjoining road affected bee diversity, but found no correlations 
(this was not mentioned in my abstract).  I did not make direct 
counts of bees killed by cars driving alongside my roadside 
restorations, and so cannot offer as much information about whether 
these restorations are more deadly than weedy roadsides as to be 
conclusive, but my results do suggest that heavy traffic/road 
size made no difference to bees in my study.

While I know of no studies that have looked directly at 
source-sink dynamics for insects along roadsides, I did want to share 
with you what I do know, in case it is of some use to you.  I think 
you might find the publication, "Environmental Concerns in 
Rights-of-Way Management" to be informative.  It contains several 
articles about butterflies and habitat restoration, as well as an 
article about the effect of right-of-way management on birds.  I 
think you might also find the book, "Road Ecology" to be of interest. 
The authors mention multiple studies which suggest that roadside 
habitat is beneficial for wildlife, including birds.   

In addition, a 1992 study investigating butterfly use of roadsides in 
the UK found that wide and busy roads were not a barrier to the 
movement, and concluded that roads should not be considered a barrier 
to gene flow for any of the species they found.  In this study only 
7% of individuals from open populations were killed by vehicles, and 
these researchers considered the mortalities to be insignificant when 
compared with natural factors.  A 2001 study conducted along roadside 
restorations in Iowa found butterflies were significantly less likely 
to cross the road when in a restored roadside than a grassy or weedy 
roadside, suggesting that roadside restorations have the potential to 
act as better corridors than weedy or grassy roadsides. 

I agree that it would be extremely beneficial to look at source-sink 
dynamics of bees and other pollinators in restored roadsides, however 
difficult these dynamics might be to demonstrate.  However, I also 
think that roadside restorations should be encouraged, not only from 
a roadside management perspective (to save costs, to reduce noxious 
weeds, etc), but also because research suggests roadsides offer 
pollinators foraging and nesting opportunities that may be scarce 
elsewhere.  Please let me know if you have any questions about my 
study.
Thanks very much,
Jennifer Hopwood


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