Roadside Revegetation

INTRODUCTION
Photo: USFS Chris Jensen
Photo: USFS Lynda Moore
Photo: BPA Justin Moffett
Photo: USFS Lynda Moore
Figure 1-8 | Vegetated linear
corridors as habitat for
pollinators and other wildlife
Linear corridors such as irrigation canals
(top), utility rights-of-way (second from
top), roadways (second from bottom),
and river ways and riparian areas (bottom),
present opportunities to reconnect
fragmented pollinator habitats.
With at least 17 million acres of roadsides in the United States, roadside vegetation can serve
as much needed habitat for pollinators, offering food, breeding, or nesting opportunities
and connectivity that can aid pollinator dispersal (Hopwood and others 2015). Roadsides can
support a diversity of generalist pollinators, including bumble bees, honey bees, butterflies,
and hummingbirds as well as rare or federally listed species. Roadsides sustain plants that
are sources of pollen and nectar for adult pollinators as well as host plants for the caterpillars
of butterflies and moths. The availability of floral resources influences the abundance and
diversity of butterflies and bees found on roadsides (Saarinen and others 2005; Hopwood
2008), and pollinators on roadsides benefit in particular from native plants (Ries and others
2001; Hopwood 2008). Roadsides also can provide pollinators with shelter, sites for nesting or
egg-laying, and overwintering habitat. Pollinators have complex life cycles, with different needs
at different stages of their lives. Roadsides can provide resources for a portion of the life cycle
of some species, while providing resources needed for the entire life cycle of other species.
Evidence also suggests that the linear shape and connectivity of roadsides may help pollinators
to move through landscapes in search of food or in pursuit of new habitat (Ries and others
2001; Dirid and Cryan 1991). Roadsides extend through all landscapes and can be particularly
important sources of habitat for pollinators in highly altered landscapes such as intensely
managed agricultural lands (Figure 1-8).
Not all roadsides are equally beneficial to pollinators. Roadsides that are intensively mown,
blanket-sprayed with herbicides, or planted with introduced grasses support far fewer
species of pollinators and smaller population densities than roadsides managed for native
plants (Smallidge and Leopold 1997; Johst and others 2006; Reis and others 2001). Roadside
vegetation management influences how pollinators use roadsides, and even influences the
number of pollinators killed by vehicles. For example, butterfly vehicle mortality rates increase
with more frequent mowing and decrease with high plant diversity in roadside vegetation
(Skorka and others 2013) (Figure 1-9).
Roadsides play an important role in the conservation of declining wild pollinators and
in supporting the health of managed pollinators. Throughout the revegetation process,
practitioners and designers can enhance roadsides to benefit pollinators.
1.5.4 GOAL-ORIENTED, CONTEXT-SENSITIVE, AND INTEGRATED
The overall approach in every aspect of this report is goal-oriented, context-sensitive, and
integrated (Clark and others 2001). The goals of establishing and protecting native plant
communities are considered along with transportation goals, including safety, efficiency, and
cost-effectiveness for the life of the road. This is not an idealistic approach; while recognizing
that resources are limited and conditions are degraded, the approach is technically and
economically feasible while still enabling the integration of roads with ecological processes.
Sensitivity and appropriateness to the local context are essential parts of successful revegetation.
This report is intended to facilitate the process of developing locally appropriate,
context-sensitive prescriptions on a project-by-project basis, integrating top-down and
ground-up information to meet the specific challenges at hand. For this reason, the report
does not provide cookbook-type “recipes” or specific prescriptions. For example, no “onesize-fits-all”
seed mix exists for roadside revegetation. The process and tools needed to arrive
at context-sensitive solutions are not difficult to apply; by following the steps outlined in this
report, practitioners will be able to generate the information they need.
The approach integrates multiple disciplines from both private and public sector partners in
a comprehensive process for effective revegetation with native plants. The report was written
with inputs from specialists in soil science, genetics, landscape architecture, entomology,
botany, ecology, plant pathology, environmental management, and engineering, and is based
on experiences in revegetating a range of diverse projects, and the principles and methods
used are broadly applicable nationwide.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat 10