Utility Rights-of-Way May Bee Friendly
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what’s buggin’ the bug guy?
Utility Rights-of-Way
May Bee Friendly
By Michael J. Raupp
Halictidae bees are among the most beautiful of all solitary bees.
In two recent publications, I have discussed how human by fragmenting large tracts of natural habitats. Habitat
intervention dramatically changes the character of eco- fragmentation is generally believed to be one of the most
logical communities, as natural areas are transformed serious threats to terrestrial biodiversity and may be espe-
into cities and suburbs as well as their respective buildings, cially disruptive to mammals requiring large undisturbed
roads, airports, waterways, gardens, and parks (Raupp et al. tracts of land for foraging and reproduction. Power lines
2010; Raupp et al. 2012). To supply energy to businesses, may also pose direct threats to particular animals, such as
homes, schools, and other elements of anthropogenic like raptors that can be electrocuted when they perch on
infrastructure, more than 300,000 kilometers (186,411 transmission towers (Wojcik and Buchmann 2012).
mi) of electrical corridors deliver power throughout the However, not all animals are affected negatively by
United States (Wojcik and Buchmann 2012). It is esti- utility corridors. Utility rights-of-way maintained as early
mated that utility rights-of-way cover five to eight mil- successional communities often house a great diversity of
lion acres (2.02–4.05 million hectares) of land in the plants and animals that thrive in habitats where forest
continental United States (Russell et al. 2005). Electrical edges meet fields and meadows (Wojcik and Buchmann
transmission corridors often transect natural, less managed 2012). One imperiled group of insects—social and soli-
habitats, thereby creating a juxtaposition of heavily managed tary bees—provide important ecosystem services, and
areas maintained in an early stage of succession adjacent these highly beneficial insects can flourish in properly
to natural/late-succession ones. This dramatic ecological managed utility corridors.
gradient where different biomes meet is called an ecotone. While most people are familiar with the iconic honey
Power-line corridors often engender negative opinions bee, few realize that some 20,000 other species of bees
because they impact communities of plants and animals have been described worldwide. In addition to providing
56 | Arborist•News | www.isa-arbor.com
more than 20 billion U.S. dollars in pollination services
annually to major crops, bees help make the world go
around by pollinating hundreds of species of native and
non-native trees, shrubs, and herbaceous plants in natu-
ral and managed landscapes. Without these vital pollina-
tors, the flowering plant world as we know it would cease
to exist, and eventually, so would our food supply.
So, what do bees need to survive
in a habitat?
The most essential needs for bees are floral resources—
nectar and pollen. Nectar is a carbohydrate-rich source
that fuels the activity of bees. Pollen is the source of pro-
tein and fat needed for the production of eggs. Pollen also
supports the growth and development of bee larvae. Bees Despite their tendency to damage structures, carpenter bees are important
native pollinators.
also need nesting sites. Many bees, including some of our
most important solitary bees—digger bees (Anthophorini),
plasterer bees (Colletidae), sweat bees (Halictidae), and compared to the grassland sites. Again, interesting results,
mining bees (Andrenidae)—nest in subterranean galleries but a question remains: Why were bees more abundant in
in the soil. Iconic, native bumble bees favor abandoned rights-of-way?
rodent burrows as nesting sites. Mowed grasslands provide floral resources for a rela-
Despite their well-deserved reputation as despoilers of tively short window of time. Grasses are primarily wind
decks and siding, carpenter bees are valuable native polli- pollinated and the most common flowers in the mowed
nators. Human dwellings are a recent contrivance in the meadows were provided by spring-blooming clover. By
evolutionary history of carpenter bees and their aborigi- contrast, the scrub vegetation in the rights-of-way had a
nal nesting resource was the deadwood of standing trees. diverse mix of trees, shrubs, and vines, including vibur-
Other pollinators use galleries in wood created by boring nums, greenbrier, wild grapes, huckleberry, he-huckleberry,
insects, such as beetles. Mason bees (Megachilidae) are blueberry, multiflora rose, American holly, American sil-
important pollinators of flowering trees early in spring. verberry, Japanese honeysuckle, sumac, and service berry.
Native species, such as the blue orchard mason bee, and This array of flowering plants provided a long-lasting
exotic species, such as the hornfaced mason bee, nest in smorgasbord of different nectars and pollens on which
vacated galleries of wood-boring insects or in hollow the bees could dine (Russell et al. 2005).
canes and reeds. Another interesting finding was the greater number
and abundance of cavity-nesting bees in the utility rights-
What is it about rights-of-way that of-way. About 25 percent more species of cavity-nesters
and 30 percent more individual cavity-nesting bees were
makes them bee friendly? found in the utility rights-of-way (Russell et al. 2005). As
In an important study conducted at a wildlife preserve
previously mentioned, many species of solitary bees require
in central Maryland, U.S., scientists compared the com-
vacated galleries and cavities in wood to construct their
munities of bees found in transmission rights-of-way to
those found in nearby fields that were regularly mowed. A
vegetation management plan was created with the wildlife
preserve and the two major utility companies that owned
the overhead transmission lines. These rights-of-way were
maintained without regular mowing and without regular
applications of non-selective herbicides. Instead, herbi-
cides were administered as basal sprays to tall-growing trees
every four to five years, other trees were removed, and
shrubs taller than three meters (9.84 ft) were topped. This
resulted in rights-of-way described as scrub vegetation.
A comparison of the bee communities in the rights-of-
way with bees in nearby fields (mowed annually or bi-
annually) revealed several interesting results. Utility
rights-of-way were home to approximately 25 percent
more species of bees than were mowed fields. Of special
significance was the fact that rare species of bees were Honey bees assist in pollinating many important crops like apples, cherries,
more than twice as likely to be found in the rights-of-way and almonds.
u
JUNE 2014 | 57
Utility Rights-of-Way May Bee Friendly (continued)
nests and raise brood. Apparently, scrub vegetation found
beneath transmission lines provided these critical resources.
In addition to plant biodiversity, scrub vegetation pro-
vided structural diversity not found in nearby grassland.
Scientists have discovered that structural complexity
plays an important role in conserving beneficial insects in
landscapes (Raupp et al. 2010; Raupp et al. 2012). Oth-
ers suggeste that the early succession status of rights-of-
way may provide homes for ground-dwelling rodents.
Once abandoned, these dens are highly suitable sites for Plasterer bees provision their nests (in soil) with pollen from
colonies of bumble bees (Wojcik and Buchmann 2012). spring flowers.
In addition, service roads beneath or adjacent to trans-
mission lines may expose bare ground and provide sunny Russell, K.N., H. Ikerd, and S. Droege. 2005. The poten-
nesting sites for ground-nesting bees not found beneath tial conservation value of unmowed powerline strips
the dense forest canopy (Wojcik and Buchmann 2012). for native bees. BiologicalConservation 124:133–148.
In a time when bees are threatened by loss and degra- Shrewsbury, P.M., and M.J. Raupp. 2006. Do top-down
dation of habitat, the applications of pesticides, and the or bottom-up forces determine Stephanitis pyrioides
arrival of exotic parasites and diseases, creating habitat for abundance in urban landscapes? Ecological Applications
our industrious pollinators is a banner idea. Utility rights- 16:262–272.
of-way may be an underutilized resource for maintaining Wojcik, V.A., and S. Buchmann. 2012. A review of pol-
these highly beneficial insects. linator conservation and management on infrastructure
Additional Reading supporting rights-of-way. Journal of Pollination Ecology
Raupp, M.J., P.M. Shrewsbury, and D.H. Herms. 2010. Cholula Special Issue 7(3):16–26.
Ecology of herbivorous arthropods in urban landscapes. For more information on the bees mentioned in this
Annual Review of Entomology 55:19–38. article, go online:
Raupp, M.J., P.M. Shrewsbury, and D. H. Herms. 2012.
• Bumble bees: http://bugoftheweek.com/blog/2013/
Disasters by design: Outbreaks along urban gradients.
7/8/be-careful-with-bumble-bees-ibombusi-spp
In: P. Barbosa, D. Letourneau, and A. Agrawal (Eds.).
Insect outbreaks revisited. Wiley-Blackwell, Oxford, • Plaster bees: http://bugoftheweek.com/blog/2013/
UK. 27 pp. 1/28/spring-beauties-plasterer-bees-and-yellow-
faced-bees-icolletidaei
• Mason bees: http://bugoftheweek.com/blog/
2014/4/14/welcome-mason-bees-iosmiai-spp
• Carpenter bees: http://bugoftheweek.com/blog/
2013/1/24/carpenter-bees-ixylocopa-virginicaimissing-
video
• Honey bees: http://bugoftheweek.com/blog/2014/
2/3/zombie-bees-iapis-melliferai-and-their-
tormentors-the-humpbacked-fly-iapocephalus-
borealisi
Michael J. Raupp is a professor and
extension specialist at the University of
Maryland (College Park, Maryland).
He has published articles, presentations,
and books, and he frequently appears
on major television and radio networks.
His book Managing Insect and Mite
Pests of Woody Landscape Plants is an authoritative guide
for arborists and landscapers, and his most recent book, 26
Things that Bug Me, introduces youngsters to the wonders
of insects. Visit his website (www.bugoftheweek.com).
More than 40 species of bumble bees are found in North America. Photos courtesy of the author.
58 | Arborist•News | www.isa-arbor.com
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