|3.4. Designing to Accommodate Wildlife, Habitat
Connectivity, and Safe Crossings
Wildlife issues are on the rise for state DOTs. Wildlife related concerns include
habitat fragmentation and connectivity for wildlife, loss of habitat, increasing
numbers of threatened and endangered species, and secondary and cumulative impacts.
The federal Endangered Species Act prohibits harm to or take of any listed species
or adverse modification of designated critical habitat. Some of the existing regulations
can be reviewed at the Overview of the U.S.
Fish and Wildlife Service and recent developments at AASHTO's Center for
Environmental Excellence website. Other sites which provide regulatory information
include the USFWS' Digest of Federal Resource Laws of Interest to the U.S. Fish and Wildlife
Service , Executive Orders, FHWA's Summary of Environmental Legislation Affecting Transportation, December
1998 and the Center for Wildlife Law' Federal Wildlife and Related Laws Handbook, Statute Summaries
. Maintenance and construction staff are responsible for ensuring that no threatened
or endangered species within areas they are working are injured or destroyed or
their habitat impacted without proper permits. DOTs are implementing stewardship
practices specific to certain threatened and endangered species as well as practices
designed to benefit wider groups of species and ecosystems more proactively. This
sections specifically focuses on what DOTs are doing to improve habitat connectivity
and the ability of wildlife to safely cross roads.
State transportation agencies currently employ a mix of underpasses, bridge extensions,
culvert installations, and culvert modifications, and associated fencing and ecowalls
to facilitate wildlife movement. Effective wildlife fencing and crossing structures
can significantly reduce many harmful impacts of roads on wildlife populations,
though such measures can contribute to habitat fragmentation. More and more DOTs
are exploring wildlife passages and culvert retrofits as means to enhance wildlife
passage. In a few cases overpasses are being built. From a wildlife conservation
perspective, the impacts addressed by these stewardship measures include habitat
loss, habitat fragmentation, degradation of habitat quality, road avoidance zones,
increased human activities, direct mortality, reduced biodiversity, genetic isolation,
chemical contamination, changed hydrology for fisheries, reduced access to vital
habitat, disruption of processes important to animal life cycles, and disruption
of the food chain. Rigorous evaluation of the success of these measures has been
implemented more slowly as funding for such work after the conclusion of construction
is harder to find and frequently involves partnerships with others. In a 2002 survey
by the author, 17 of 50 state DOTs said they were beginning to systematically incorporate
wildlife crossings into roadway designs, but only a couple state DOTs had wildlife
crossing policies, and only two states reported they had prioritized barriers for
correction based on benefit evaluation. [N]
NCHRP 25-27, starting in 2004 and concluding in 2007, will investigate what guidelines
are currently used by DOTs to determine wildlife crossing dimensions or design,
the decision process, and any tools or aids that are used in that process. As of
early 2002, only five state DOTs reported providing some direction to designers
in this regard. In dissecting existing decision processes, NCHRP 25-27 will seek
to understand the various factors used to decide what type of crossing will be employed
as well as the extent to which long-term maintenance costs (annuities) of a highway
structure guide selection (e.g. steel arch culvert vs. precast concrete girders
with concrete deck). Ultimately the project will produce design guidance and a decision
support tool for DOTs, as well as measures of cost and effectiveness. [N]
|3.4.1 Identifying Locations
for Wildlife Crossings
< back to top >
The locations of wildlife crossings and/or problem areas are critical for effective
mitigation of the barrier effect caused by highways; however, few methodological
approaches to identify and prioritize these key areas have been explored. Researchers
from Madrid University found that 70 percent of collisions occurred on just 7.7
percent of the roads in the area they studied. [N]
Collisions tended to occur where animals found it easier to cross roads in the absence
of human habitation; fences or large, steep embankments deter animals from crossing
roads and funnel animals to easy crossing points. Habitat availability on either
side of the road is another factor in where animals choose to cross.
Only three state DOTs in the U.S. reported using modelling tools to identify habitat
linkages as of 2002, and only one state did so for a large number of species on
a statewide basis. [N]
Six states had embarked on or participated in statewide efforts to determine connectivity
needs as of early 2002. [N]
Several more have begun to do so over the past two years.
Planning for wildlife crossings can be very involved; however, much can be accomplished
using rapid assessment techniques, available information, and expert panels. The
Forest Service's national expert on wildlife crossings advocates a simple rapid
assessment approach that has proven effective in a variety of circumstances, is
fast, and affordable: [N]
- Select highways to be examined.
- Select species for analysis
- Use available, spatially specific information, especially that available digitally
in geographic information systems (GIS).
- Use a team of local biologists. Teams can often examine 100 miles/day.
DOTs, resource agencies, universities and non-governmental organizations such as
The Nature Conservancy, American Wildlands, and the Rocky Mountain Elk Foundation
have attempted to fill this gap by conducting workshops, often with DOT sponsorship.
Biologists, researchers, and regulatory specialists come together in a workshop
setting to make decisions on conservation and connectivity needs based on analysis
of best available environmental data. With recent requirements of all states to
identify priority conservation areas, new opportunities for interagency identification
and prioritization of wildlife crossing needs are emerging.
NCHRP 25-27 will survey state transportation agencies to determine what information
is used to determine location and number of wildlife crossings on planned sections
of highway-improvement project, whether models are developed around political, project,
or ecological boundaries, and whether connectivity needs are assessed at the project
level, political/statewide level, or the level of ecoregions surpassing political
|3.4.2 Monitoring Wildlife Crossings
< back to top >
Performance evaluation of crossing structure depends upon adequate monitoring. Future
design benefits from such information as well. Most monitoring efforts to evaluate
wildlife crossings have been short-term and focused on discerning whether target
species are using the crossings. Monitoring programs have largely been aimed at
single-species or have been confined to certain taxonomic groups; consequently,
such programs may fail to recognize the requirements of other non-target species
and ecological processes. Further, studies have generally failed to address the
need for wildlife adaptation to environmental change. How well crossings ultimately
perform depends on how well they accommodate changes in wildlife species distributions,
abundance and behavioral profiles. Wildlife crossings are expensive measures, but
a large void exists in devising cost-effective designs based on ecological and engineering
criteria. Also, the current information base on wildlife crossing performance is
While nine of 50 state transportation had modified culverts for enhancement of connectivity
across roads as of 2002, only four of these monitored such crossings with feedback
to DOT designers and/or the state or federal wildlife agency. [N] Eight of 50 state DOTs
reported monitoring specially constructed wildlife underpasses, with feedback to
design and wildlife agencies. [N]
Though DOTs more commonly employed bridge extensions to facilitate wildlife passage,
usage by wildlife was much less frequently monitored than with other crossing technologies.
According to research by the Western Transportation Institute, evaluation of a wildlife
crossing structure installation may involve consideration of the following issues:
- Motorist safety and animal-vehicle collisions
- Ecological impacts of mortalities and the "barrier effect" due to
roads and traffic on individual animals, on a specific species, on populations of
animals, on ecological communities and biodiversity, or on ecosystem processes and
functional landscape integrity.
NCHRP 25-27 will add to this knowledge base by collecting details about types and
methods of wildlife crossing monitoring in use, how often monitoring occurs, and
the length of time for which it has occurred. The project will seek to detail the
ecological criteria currently used to judge whether wildlife crossings are functional
or effective, whether targets are established in advance, criteria are based on
single target species, observed frequency of use by target or multiple species,
population- or ecosystem-level data collection and analysis, or accident reduction.
|3.4.3 Wildlife Crossing Research,
Resources, and Techniques
< back to top >
This section reviews environmental stewardship practices and features that are being
incorporated in many transportation projects across the country, including the restoration
or preservation of habitat as mitigation and the addition of wildlife underpasses,
overpasses, bridge extensions, enlarged culverts, and fencing by many states dealing
with the realities of wildlife conservation and motorist safety. These practices
were initially presented in NCHRP Report 305 on Interaction Between Roadways and
Wildlife Ecology and are summarized herein. Habitat-related mitigation and conservation
measures are some of the most effective measures and are used to address the broader
ecological concerns associated with reductions in habitat and wildlife connectivity.
Model stewardship practices in this area will also be briefly reviewed.
Existing crossing techniques can also be view at the Wildlife Crossing Toolkit developed by the U.S. Forest Service.
Their website offers a searchable database of case histories from a wide variety
of locations, time periods and wildlife species where people have attempted to solve
issues resulting from wildlife/highway interactions. [N]
Research by the Western Transportation Institute found that the physical dimensions
of the underpasses had little effect on passage because animals in the Banff National
Park in Canada may have adapted to the 12-year old underpasses; however, structural
attributes were more important on newer structures. Furthermore, the level of human
activity in the vicinity was an important factor suggesting that mitigation strategies
need to be proactive at the site and landscape level to ensure that crossing structures
remain functional over time, including human use management. [N]
The Western Transportation Institute is developing a vehicle-animal collision "toolbox"
of countermeasures, which will provide detailed information to support application
choices and decisions, and performance measurement. [N]
The remainder of this section consists of summary excerpts from NCHRP Synthesis Report
305 on Interaction Between Roadways and Wildlife Ecology and practices adapted from
that discussion with regard to wildlife crossings, except where otherwise noted.
Fencing is a common practice used throughout the world to keep animals off
highways. Twenty-eight states report using fencing to protect wildlife. The most
frequent application is to keep deer off of roads. Deer are locally overabundant
in a number of states, and fencing has proven to be an effective way to keep deer
off the roads. Clevenger [N]
reported an 80 percent reduction in ungulate-vehicle collisions on the Trans-Canada
Highway in Banff National Park after fencing. [N]
- Design fencing applications for target species. Typical fencing
applications are rectangular mesh or chain link fence from 2.6 to 3.0 m (8.5-10
ft) high. Florida and some European countries use strands of barbed wire along the
top of the fence to discourage animals from climbing over the fence. Also used is
finer mesh wire of from 2 x 2 cm (0.78 in.) to 4 x 4 cm (1.57 in.) buried 20 to
40 cm (7.87-15.75 in.) with a height extending from the ground of from 0.5 to 1
m (1.64-3.28 ft).
- Keep local wildlife interactions in mind when designing fences.
For example, in California fencing application in areas with kit fox and coyotes
provide a gap under the fence just large enough for the kit fox to negotiate at
full run so that the latter can escape predators such as the coyote.
- For reptiles and amphibians, bend the upper edge of the finer mesh at a
90-degree angle to provide a lip to prevent animals from climbing over
the fence. In Waterton Park, Canada, a temporary silt barrier type fence was used
to direct frogs into polyvinyl chloride (PVC) drop traps so that volunteers could
move them across the highway to a pond during the few-week-long migration period.
Europeans have used a PVC barrier with an angled lip to keep reptiles and amphibians
off the highways as well as a fabricated galvanized steel rail with a barrier lip
along the upper edge. Iowa DOT has placed finer mesh fence at the bottom of regular
fence to prevent smaller wildlife such as turtles, snakes and other small animals
from getting on the Eddyville Bypass and Highway 63 at the Bremer-Chicksaw county
line. This fencing approach has been commonly used in Europe to keep smaller animals
- Bury fine-meshed fencing at the bottom in use with pipe culverts for small
animal connectivity or in association with other ROW fences. This practice
has been successfully used under highways in Europe in culvert pipes with diameters
approximately 0.4 m to 2.0 m (1.31-6.56 ft). California used a unique fencing application
for desert tortoise approximately 6 km (3.7 mi) east of Kramer Junction on Highway
58 in San Bernardino County. A finer [1.27 cm (0.5 in.)] mesh section of wire fence,
approximately 50.8 cm (20 in.) in height, was installed along the bottom of a typical
1.22-m (4-ft) right-of-way fence. The finer mesh fence was buried approximately
15 cm (5.9 in.) to prevent animals from going under. This portion of the fence was
held in place using three strands of wire. The fencing application was done on an
approximately 35.42- km (22-mi) section of four-lane highway. The fencing angled
into the road at a series of culverts and bridges that were constructed for wildlife
- Fence installation decisions should account for the potential for wildlife
to be trapped between the fences should they find a way to enter the rights-of-way
under, over, or around the fence ends. Because fencing is not totally
exclusionary, Bissonette and Hammer studied two highway sites in Utah to compare
the use of one-way gates and earthen ramps. They found that earthen ramps were used
from 8 to 11 times more than one-way gates. Irrespective of the species, fencing
without provisions for movement across the road can cause disruption of connectivity
resulting in isolation of populations. This can be especially problematic for species
with low populations, where the possibility of extinction can result.
Properly designed culverts can enable wildlife to cross roadways by passing
under an intersecting roadway through a culvert. A culvert is a conduit covered
with embankment around the entire perimeter. It may or may not convey water. Small
conduits for amphibians are sometimes called tunnels. The following table is from
the U.S. Forest Service on-line Wildlife Crossing Toolkit . [N]
Table 8 : U.S. Forest Service Wildlife Crossing
Toolkit Guide to Culverts
Culvert has four sides, including bottom. Sometimes square or rectangular corrugated
metal pipe culverts without bottoms are called box culverts, but in this toolkit
they are referred to as bottomless culverts.
Box culverts may be arranged in a horizontal series of small culverts to form multiple
Culvert is continuous in circumference. The lower portion may or may not be buried.
Sometimes simply called pipe. European badger culverts are sometimes called
Slotted drain culverts are continuous except for a break
in the upper portion.
Corrugated metal pipe
Culvert is discontinuous in circumference with rounded or square top and natural
surface bottom. Also called open-bottom culvert.
Corrugated metal pipe
From Forest Service Wildlife Crossings Toolkit on-line at http://www.fs.fed.us/wildlifecrossings/
Modified Drainage Culverts
Drainage culverts can be modified to accommodate wildlife, a practice increasingly
implemented by state DOTs and for which the Netherlands is renowned. Small mammals
and amphibians are able to move through the culverts on shelves and floating docks
or through wildlife tunnels built parallel to the wet culvert. NCHRP Synthesis Report
305 identifies the following stewardship practices with regard to modified drainage
- Addition of a 0.46 m wide × 0.30 m high
(18 in. × 12 in.) elevated concrete
walkway can allow animals to move through a culvert even when water is present.
Such modified culverts were successfully tried on US-98 in Texas for bobcats.
- A central "sacrificial" culvert with other culverts placed on
both sides but at a higher elevation for drainage and connectivity can diminish
blockage by beavers, which attempt to block the lower culvert, and
the adjacent culverts at higher elevation remain open. Beaver-exclusion devices,
including fencing, perforated pipe, or a combination of the two have been successfully
used throughout the United States to reduce impounding of water behind road fills
and for wetland mitigation and habitat preservation.
Colorado DOT has addressed a number of safety issues with beaver damage to roadways
by using a modified culvert such as that described above. Safety issues have included
potential to damage to the roadbed from water saturation, loss of flood capacity
that otherwise would have been provided in the area flooded by the beaver dams,
potential for heaving of the road way from frost or ice, and concern for motorist
safety should they skid into the deeper water caused by the beaver dams. CDOT also
wanted to cooperate with residents of nearby neighborhoods who desired the beavers
to remain. To allow beavers to remain, CDOT perforated the beaver dams with pipes
long enough to defeat the beavers natural inclination to plug holes in their dams.
The pipes were inserted at a level that would allow the beavers to have a pond but
not at such a level that the water continued to be a serious threat to the highway.
Wire cages were placed over the ends of the pipes to prevent the beavers from clogging
the pipes. [N]
NCHRP Synthesis Report 305 reports a number of states are using culverts in
different applications for a variety of species. Florida, Montana, New Hampshire,
Texas, and Wisconsin are using culverts for reptiles and amphibians. Nebraska and
South Dakota are using them for turtles. [N]
Culverts with dual drainage and wildlife crossing purposes have proven successful
in accommodating both terrestrial and aquatic organisms depending on water levels
in the area of the culverts. When placed at the proper elevation, they can serve
both types of organisms. Drainage culverts are typically used where highway causeways
or fill sections transverse wetlands with fluctuating water levels such as wet prairies
and marsh. They are also used on intermittent streams and floodplain areas that
may inundate during wet periods. Aquatic species such amphibians and fish use them
when they are wet and terrestrial species including reptiles and small mammals use
them when they are dry.
Pictures of Florida DOT drainage/wildlife culverts, Massachusetts amphibian tunnels,
Dutch structures, and wildlife using the culverts mentioned above, as well as other
projects around the world can be seen at FHWA's wildlife crossings website; however, Evink notes that
few states have researched the effectiveness of these structures. [N]
Nevertheless, it is known that
Stream Culverts and Bridges
- Culverts should be sized for use by multiple species, wherever possible.
Like drainage culverts in upland areas, oversized culverts can be designed
and placed at the proper elevation over waterways to provide passage for a large
number of aquatic and terrestrial species. [N]
Wildlife Underpass Bridges and Dry Culverts
- Use the natural stream bottom rather than a concrete or metal bottom.
- Provide shallow water or even dry edges along the stream edge in the culvert
or bridge to allow the greatest number of species to move through.
- Allow extra height for larger mammals, such as deer, bear, and other species
that ordinarily follow riparian corridors for movement and pass safely under roads.
A wide variety of designs are possible depending on the site-specific construction
environment - concrete box culverts, and round, oval, and elliptical pipe culverts.
- Provide cover as well as substrate on the inside of the culvert, similar
to that of the exposed stream, to expand utility of the culvert. Proper
sizing of the culvert depends on site-specific considerations and hydraulics, but
including the natural streambed and as much adjacent upland as possible proves most
Upland culverts are one of the most frequently used structures for wildlife
crossings and have proven successful for accommodating a wide variety of species.
Pipe culverts and box culverts have proven effective for small animals. California
is using culverts for San Joaquin kit fox. Illinois, Kansas, Montana, New Hampshire,
New Jersey, Oregon, Texas, Utah, and Virginia are using culverts for other small
mammals. Arkansas, Colorado, New Jersey, Wyoming, Utah, Michigan, Washington, and
Kansas report using larger culverts for deer and other wildlife. [N]
- A range of culvert sizes, from 1.22 m × 1.22 m
(4 ft × 4 ft) in Arkansas up
to 2.44 m × 7.32 m (8 ft ×
24 ft) in Florida and from 1.5 to 10 m (4.92 - 32.81
ft) in New South Wales, Australia, have been
successfully used for various species of terrestrial mammals and reptiles.
- Use frequently placed culverts [150 - 300 m (492.13 - 984.25
ft)] of varying size in close proximity to shrub or tree cover.
Clevenger and Waltho found that for a variety of culvert sizes for small and medium-sized
mammals, passage was positively correlated with traffic density, road width, road
clearance, and culvert length. They also found that all species with the exception
of coyotes and shrews preferred small culverts with low openness ratios. There appeared
to be some evidence of predation at crossings so the thought was that the smaller
culverts provided comfort to the prey species. Weasels and shrews preferred culverts
with nearby cover. The researchers felt that drainage culverts could be used to
mitigate the harmful effects of high-speed roads. [N]
Wildlife underpasses are bridges and/or large culverts over dry land and sometimes
land and water, constructed expressly to facilitate wildlife movement in important
corridor areas. The length and height of these large culverts or bridges varies
with the wildlife expected to use them. Twenty-three states report using underpasses
for wildlife. The Western Transportation Institute is cataloging existing uses of
and research on underpasses and culverts to provide further guidance to DOTs on
stewardship practice in this area. [N]
Extended Bridges and Existing Structures
One of the most successful and cost-effective means of providing for wildlife
movement down riparian corridors is the extended bridge. Twenty-four states report
using extended bridges for wildlife movement and wetland protection. [N]
- Provide adequate area for both water movement with associated organisms
and dry habitat for terrestrial species movement.
- Consider the characteristics of the area when trying to determine the appropriate
length of the bridge. In cases where there is an important corridor
for movement of rare or protected wildlife species, bridging the entire floodplain
may be necessary. At the other end of the spectrum, where the floodplain is being
used by habitat-limited species, a combination of smaller structures and fences
may be possible.
- When choosing a combination of bridge and fill, consider what reptile and
amphibian species will likely move up the fill slope onto the road.
Standard fencing will not stop this movement so that very expensive barrier walls
and associated guard rails may be necessary to prevent significant kills of these
species during periods of the year when they are moving around in large groups.
- Consider the cost of mitigation for wetland takings by opting for a fill
section. By the time the costs of shorter bridges or culverts, fill
acquisition, barrier walls for reptiles and amphibians, guardrails, and fencing
are factored in, along with the cost of wetland mitigation, the cost of a more substantial
bridge, preferred for habitat connectivity, may already have been approached.
Viaducts are a potential solution for the entire spectrum of species moving through
an area, as these long bridges can leave wetlands, rivers, and variable topography
and geology below largely intact. Typically, this approach is most cost-effective
where there is topographic relief, such as in mountainous areas, is sufficient to
make bridging necessary for a significant span of a waterway, canyon, or valley;
use of spanned lands by wildlife is typically a secondary benefit. [N]
Design of viaducts for wildlife connectivity and habitat enhancement is increasing,
especially in Europe.
Although wildlife overpasses are largely a European phenomenon, Florida, Hawaii,
New Jersey, and Utah reported overpasses being used by wildlife and the Montana
Department of Transportation and the Connecticut DOT are installing wildlife overpasses
on Highway 93 and Route 6, respectively. The New Jersey overpasses, among the first
in the United States, were completed in 1985 at a cost of $12 million. The overpasses
were designed to provide connectivity across I-78 (a six-lane highway) at an approximately
2-mile stretch that crossed the Watchung Reservation in Union County. Specifically,
one was constructed solely for wildlife use (especially deer). Another one was constructed
for shared wildlife and vehicular use; however, it has since been closed to traffic.
A third overpass was constructed as a shared use between wildlife, vehicular traffic,
and a bridle path for horses. The Utah overpass was constructed principally for
deer. The Florida overpass on I-75 in Marion County just north of County Road 484
is a multi-use overpass designed to accommodate a recreational and equestrian trail,
as well as for wildlife use. Two overpasses were built over the Trans-Canada Highway
in Banff National Park and are being used by a variety of wildlife. [N]
Other Structural and Non-Structural Measures for Wildlife
- Allow the widest width possible. Wildlife overpasses can vary
in width from 3.4 m (11.15 ft) to 870 m (2,853.6 ft). Wider passages are more effective
at allowing animals to cross and animal behavior on wider structures is more normal
than on narrower ones.
- Establish or preserve suitable habitat at and leading to the overpasses.
Where this has been accomplished, it has been found that the overpasses were effective
for a wide variety of animals including invertebrates.
Signage and deer reflectors are common approaches to informing motorists when
they are entering an area where the danger of wildlife collision is high, though
the effectiveness of these methods has not been demonstrated. However, a few methods
have been documented to work: [N]
- Use a series of solar-powered, battery-operated, motion sensors to determine
animal presence and trigger low-voltage, LED-illuminated warning signs that reduce
the posted speed limit to 40 km/h (25mi/h) and alert motorists to the
presence of approaching wildlife. This method has been successfully used in Switzerland,
though the location on the road was also adjacent to a large wildlife overpass over
a major nearby freeway.
- Install vertical pipes perpendicular to bridge railings to keep bird flight
patterns above the elevation of traffic. Florida reported installing
PVC pipe approximately 3 m (9.84 ft) in height perpendicular to the railing on the
San Sebastian Bridge. The poles were spaced approximately 3.7 m (12 ft) and kept
birds hovering over the bridge from dropping down into traffic crossing the bridge,
reducing bird kills.
|3.4.4 State DOT Initiatives
to Address Wildlife Habitat Connectivity Needs in Planning and Design
< back to top >
|Maine DOT Initiatives to Limit
Disruption of Habitat and Transportation Related Wildlife Mortality
Maine DOT chairs a multi-agency task force looking into how to prevent collisions
between vehicles and animals, predominantly moose and deer. This task force, initiated
in 1999, comprises members from Maine Department of Inland Fisheries and Wildlife,
Maine Secretary of State, Maine Turnpike Authority and Maine Department of Public
A focused, statewide campaign begun in 2001 to make the public aware that moose and
deer crashes are likely to happen on any road in Maine and providing tips for drivers
to avoid or lessen the severity of these crashes. This public information campaign
was expanded in April 2004 to include a new brochure with safe driving tips distributed
statewide to all towns, libraries, schools, state parks, tourism centers, and other
distribution points. News media alerts are distributed to all radio and TV stations,
and to newspapers throughout the state each spring, in time to alert the traveling
public that May and June are the most dangerous months of the year for moose/vehicle
collisions. In 2004, Maine DOT's efforts were publicized by statewide media outlets
and picked up by other news outlets including the Washington Post and Chicago Tribune.
Public outreach also includes a module on large animal collisions that continues
to be part of driver education programs throughout the state. In addition, the task
force produced a safety video in 2001 and distributed the video to all driver educators
Maine is increasing the number of available moose hunting permits in areas with severe/high
crash locations. Maine DOT is supplementing these efforts by examining and testing
measures to prevent collisions by either warning motorists or warning/excluding
animals from roadsides. Some of these measures include alternative striping, reflectors,
signs (with and without additional warning lights), and fencing. The Department
is also looking at increased roadside clearing widths, to make moose visible from
greater distances, allowing drivers more time to react and therefore prevent or
lessen consequences of collisions. Roadside vegetation management practices, such
as the composition of seed mixes and preventing sprouting of roadside woody plants,
are also being examined to eliminate choice food sources close to highways. Maine
DOT is investigating habitat conditions, especially at historically high crash locations,
to better predict likely cross locations and to choose and install appropriate prevention
measures in the most effective locations.
On the planning end, Maine DOT has initiated meetings and invited representatives
from resource agencies to join them in speaking with officials from New Brunswick
and Quebec who are facing the same issues with wildlife and the traveling public.
These meetings have helped Maine DOT understanding issues in a regional context,
learn from the experience of experts in those fields, and further develop Maine
DOT strategies that will benefit the traveling public while responsibly addressing
wildlife issues related to transportation. Maine DOT is also actively participating
in a "Beginning With Habitat" initiative for Habitat and Transportation
with Maine Audubon, The Nature Conservancy, Maine State Planning Office, Maine Department
of Environmental Protection, Maine Department of Conservation, and Maine Department
of Inland Fisheries and Wildlife. The group is looking into comprehensive awareness
and protection measures for all types of wildlife and identifying transportation
related actions to benefit habitat statewide. Maine DOT is also developing a process
to screen future projects for valuable wildlife habitat and has funded research
into developing crossing measures for smaller animals, amphibians and other species.
Maine DOT develops mitigation for projects specifically looking for opportunities
to protect, improve or restore significant wildlife/fisheries corridors and habitats.
Recently, as part of a cooperative assessment of the Sunday River watershed, a restoration
plan was developed providing a number of projects that could be implemented by various
partners. Maine DOT will construct a tributary restoration project during 2005 in
the lower Sunday River watershed. Other agencies and groups are organizing to implement
additional projects from the watershed plan.
Caltrans Interchange Removal and Partnership to
Identify and Address Habitat Connectivity Needs
Due to the rising importance of the wildlife connectivity issue and implications
for future construction, Caltrans participated in a statewide symposium/workshop
with scientists, activists, and planners from resource agencies and conservation
organizations to identify "Missing Linkages" in fall 2000. The meeting
report identifies 232 critical habitat linkages in the state, 59 percent of which
are threatened. Connectivity areas identified in the report ranged from narrow choke
points, like the Coal Canyon underpass, later removed by Caltrans, to long stretches
of rivers and broad swaths of redwood forest. More than half of the linkages were
deemed to be high priorities because of development threats and good opportunities
The interchange Caltrans decided to remove was located where two intersecting state
highways divided several protected natural areas, including greater diversity of
vegetation types than any other area of comparable size in the United States . By
closing the ramps, removing the pavement and lighting, rearranging fencing, and
restricting access, Caltrans created a wildlife crossing with substantial height,
width, ample natural lighting, and openness. In addition, Caltrans worked with State
Parks to find funding to purchase approximately 685 additional acres of conservation
lands adjacent to the freeway and interchange, ultimately linking the Tecate Cypress
Reserve, the Cleveland National Forest and the Irvine Company's Gypsum Canyon Preserve
and lowering development pressure in the area.
Caltrans determined that the site has great mitigation value for transportation impacts,
but no agreements exist with other resource agencies to obtain credits at this point.
Instead, Caltrans still considers the site an excellent example of leadership and
interagency cooperation, which "indirectly facilitates other transportation
efforts." Wildlife passage features were incorporated into current and future
state highway improvements nearby, benefiting both federally listed species and
non-federally listed species with large habitat ranges.
Caltrans plans to utilize the products of the state's collaborative "Missing
Linkages" project to assess viable communities, habitats, and wildlife movement
corridors throughout the state. This resource will be used to help environmental
impacts wherever possible, and as a guide for addressing habitat and wildlife connectivity
needs when the state implements conservation measures. Generation of the statewide
conservation and connectivity maps is providing the foundation for interagency buy-in,
acknowledgement, and utilization of a common set of environmental priorities. The
mapped priorities are expected to streamline interagency coordination and negotiation
on a project-by-project basis, reduce conflict, and facilitate achievement of mutual
stewardship objectives among Caltrans, FHWA, federal and state resource and regulatory
agencies, non-profit conservation organizations, and environmental advocates. The
Nature Conservancy (TNC) is now assisting Caltrans in comparing the 20-year transportation
plan to priority conservation areas, to minimize potential impacts and to identify
opportunities where Caltrans mitigation projects could achieve the greatest environmental
benefit and make a tangible contribution to achievement of interagency, public and
private conservation objectives.
Florida DOT Partnership to Determine and Prioritize
Connectivity Needs and Contribute to "Green Infrastructure"
The State of Florida issued a report in 1994 that identified the state's highest
priority wildlife habitat, which is the basis for a successful current state-funded
effort to protect priority habitat conservation areas. The Florida Game and Fresh
Water Fish Commission completed a land cover map of Florida's 34 million acres and
performed modeling to identify the long-term habitat needs of many focal species
on public and private lands. Florida DOT helped support the development of the extensive
wildlife occurrence and habitat geographic information system database, which is
used in roadway alignment analysis and impact assessment. The database includes:
1) a statewide vegetation map with 22 land cover classes; 2) habitat maps for over
150 individual wildlife species, constructed by modeling habitat requirements, radio-telemetry
range data, museum records, and other surveys, and 3) statewide maps of strategic
habitat conservation areas, defined as lands which have a high priority for protection
and acquisition, but are not in public ownership.
Because significant efficiencies and ecological gains can be made by coordinating
wildlife crossing installation with statewide efforts to map conservation areas
and large scale linkage needs, FDOT and the Florida Game and Fresh Water Fish Department
developed a decision-based geographic information system (GIS) computer model for
FDOT road improvement projects associated with road mortality of wildlife and other
environmental impacts. This system is integrated with other state environmental
initiatives such as the greenways and CARL (Conservation and Recreation Lands) programs.
An interactive CD-ROM allows the user to perform multiple scenarios and develop
their own priorities, and contains all necessary data and information to perform
analyses. The computer model program enables FDOT to appropriately schedule future
projects according to critical environmental and transportation improvement needs.
In 2000, the Florida Department of Transportation DOT initiated a cooperative effort
with the Florida Fish & Game Commission to prioritize and begin to address black
bear roadkill problem areas on a statewide basis, to focus and direct investments
in habitat conservation and connectivity improvements, and to streamline project
approvals. Bear roadkill data were re-analyzed to rank road segments by the percent
of total statewide roadkills and percentage of kills in the past ten years. This
ranking was then combined with habitat information, including percent of road buffer
encompassed by conservation lands and strategic habitat conservation areas. The
ranking is providing guidance in siting wildlife underpasses on a statewide basis.
Fifteen black bear roadkill problem areas were identified, comprising 40 percent
of the total transportation-related bear mortality in the state. The core habitat
systems surrounding these problem areas also provide important habitat for many
species of mammals, amphibians and reptiles. At least as important as the priority
crossing and connectivity needs, the analysis revealed that land management and
conservation are critical in enhancing the black bear's potential for long-term
survival in Florida. The results were shared with the state's Conservation and Recreational
Lands program to help justify the purchase of a 22,260-acre tract associated with
the Aucilla River Project in the Big Bend area of north Florida, a top three conservation
priority as a result of the study.
As part of Florida's DOT's updated environmental policy, approved in February 2002,
FDOT committed to cooperate in the state's Greenways Program of land acquisition
and management through identification and prioritization of important habitat connections.
The objective of the statewide greenways program is to establish an ecological network
of green infrastructure to reduce wildlife mortality and restore connectivity to
the landscape by restoring natural processes as they originally occurred across
the landscape (e.g., wildlife movement and migration, flood, and fire). Where alternative
mitigation strategies permit, FDOT will support land acquisition activities to help
achieve this ecological infrastructure, and will utilize methods to preserve, enhance,
and protect trees and other vegetation as valuable natural resources consistent
with ecosystem management principles. So far, over one million acres have been preserved
through this program, which has garnered the support of a diverse array of citizens,
land managers, and state policy-makers.
New Hampshire DOT's Pilot Project for Identifying
Habitat Connectivity and Wildlife Crossing Needs
The New Hampshire Department of Transportation (NHDOT) is engaged in a pilot project
effort with the New Hampshire Audubon Society, the New Hampshire Fish & Game
Department, and others to develop a methodology for predicting wildlife movement
in the state. The effort is an outcome of a discussion on how NHDOT and these partners
could cooperatively address wildlife and transportation issues. The partners hope
to develop a geographic information system (GIS) layer of important wildlife habitat
areas and locations of frequent wildlife crossings to be used as a planning and
design tool for future projects.
The pilot effort focuses on Route 4, one of the state's major east-west routes. When
sections of Route 101 were widened to four lanes, NHDOT extended bridges to improve
habitat linkages. NHDOT is now interested in further increasing the level of connectivity.
To this end, NHDOT has contacted Fish & Game Conservation Officers, local road
agents, conservation commission members, and NHDOT maintenance patrol foremen to
collect anecdotal evidence of crossings and road kills and record that information
in a database. In the future, roadkill data will be collected by maintenance staff.
Concurrently, the New Hampshire Audubon Society is reviewing mapping of the corridor
to identify prospective habitat units, for purposes of predicting where wildlife
crossings are likely to occur. The partners will pool efforts to see how well the
field data correlates with the mapping predictions. The goal is to develop a predictive
model that can be used elsewhere in the State.
To further improve habitat linkages, NHDOT is also supporting efforts to develop
an inventory of contiguous habitat areas, to be taken into consideration when siting
new alignments, bridge extensions, and crossing locations. The New Hampshire Fish
& Game Department has decided that investing in habitat preservation in key
areas can be a higher priority than adding or enhancing crossing structures. The
New Hampshire Ecological Reserve Project, a partnership between The Nature Conservancy
and the University of New Hampshire, is working with the New Hampshire Department
of Environmental Services and the Fish & Game Department to develop criteria
for the identification of priority conservation parcels. This will generate information
that NHDOT can use in planning and project development, and will also guide state
investment through the New Hampshire Land and Community Heritage Investment Program.
Maryland SHA's Net Gain Wetland Mitigation Policy
& Contribution to Regional Restoration/Connectivity Goals
The Maryland State Highway Administration (SHA) has made a commitment to mitigate
for historical impacts to wetlands from transportation projects, with an overall
"net gain" wetland mitigation policy. The MDSHA is working with local
jurisdictions and watershed groups around the state to realize watershed goals and
restore stream segments, and contribute to the state's green infrastructure at the
Maryland has two million acres of ecologically significant land that has not been
developed, of which almost three-quarters are unprotected. The state designated
the GreenPrint program to preserve the state's remaining natural resources and to
create an extensive, intertwined network of conservation lands. The purpose of the
program is threefold:
- Identify, using the most up-to-date computer mapping techniques, the most important
unprotected natural lands in the state;
- Link, or connect, these lands through a system of corridors or connectors; and
- Save those lands through targeted acquisitions and easements.
GreenPrint databases and watershed plans are available to Maryland State Highways'
planning, environmental, and design staff to reference in avoiding, minimizing,
and mitigating for unavoidable impacts from transportation. The State Highway Administration
is currently undertaking internal discussions to maximize use of this resource.
MDSHA is contributing to watershed restoration and regional habitat connectivity
through 23 separate stream restoration projects across the state, with funding matched
by local project sponsors. MDSHA has plans to restore approximately nine miles of
streams and install a number of stormwater retrofits to improve water quality and
stream habitat over the next three years.
VTrans Habitat Connectivity Training
The Vermont Agency of Transportation (VTrans) began offering Habitat Connectivity
Training in 2002, which has been very popular. The training is offered to VTrans
staff to help them understand the importance of habitat and consider it while doing
their work as transportation professionals. In particular, the training fosters
an awareness of habitat and encourages a lively dialog about how transportation
can fit into the landscape while still considering habitat and connectivity and
incorporating that into the planning and design of projects. Solutions that are
discussed range from big-picture land use discussions to the details of engineering
a bridge or culvert to allow wildlife passage to the merits of including warning
signs to alert drivers of wildlife hazards and many things in between. Engineers,
planners, environmental specialists, biologists, maintenance staff, landscape designers,
project managers, have joined bridge and roadway designers in the training program.
Consultants and DOT staff from neighboring states have also attended. Much of the
discussion engages transportation professionals in discussions about the challenges
they face when planning, designing, constructing, and maintaining a transportation
VTrans Habitat Linkage Area Assessment
In a collaborative effort with the Vermont Department of Fish and Wildlife, VTrans
has sponsored development of a GIS habitat database, called the Habitat Linkage
Area Assessment. This tool will be used for making decisions for addressing habitat
connectivity on VTrans projects and also help the two agencies identify priority
areas for consideration for habitat connectivity investments. The project utilizes
landscape features as its base and is augmented by years of existing data collected
on wildlife crossing areas, recorded road kill locations, anecdotal reports of crossing
areas, land ownership, conservation lands, and other data layers. The database identifies
areas that range from high priority to low priority in terms of habitat linkage
areas and relationship to the Vermont transportation infrastructure.
The Habitat Linkage Area Assessment efforts rests upon VTrans' Operations and Maintenance
Division, which collaborated with the Environmental Section and the Vermont Department
of Fish and Wildlife in developing a method for collecting roadkill information
from District Maintenance Crews. The method utilizes an existing database called
MATS that the Maintenance and Operation Division was already using to manage their
resources. An existing but unused field was modified, with the guidance of VT DF&W,
as a field for recording roadkill data. The Maintenance field crews keep a log in
their trucks. When they identify a road kill that is included as a target species
in the database they record it (species, location/mile marker, date, and route).
These road kill data sheets are collected on a monthly basis and then entered into
the database. This information is shared with the VT DF&W and is included as
a field in the Habitat Linkage Assessment described above.
|3.4.5 Maintenance and Management
of Created, Modified, or Restored Habitat
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Most state DOTs try to find a land management agency to provide maintenance for mitigation/conservation
habitats. A few have sought to perform mitigation (modification or restoration)
on public lands that are already being managed by a resource agency. While some
federal resource agencies encourage this approach, others disallow it. Universities,
conservation groups, resource agencies, and even private groups where consistent
with the objectives of the mitigation have become involved in maintenance of habitat
by taking possession or easement of land from the state DOTs. Few transportation
departments are maintaining habitat except for wetland mitigation sites, though
creative conservation partnerships have been developed in a number of states through
in lieu fee arrangements. Texas, Tennessee, Kentucky, North Carolina, and Florida
are among the DOTs allowed to provide funding instead of mitigation. Habitat management
is frequently the responsibility of the agency or partnering organization holding
title to the land or conservation easement.
In most cases, when a state uses a habitat strategy as a conservation or mitigation
measure, the maintenance plans for these habitats contain a monitoring requirement.
These requirements vary in length and design, but states are often required to maintain
sites to varying performance levels (such as a percent survival of desired species
and exotic/invasives free) for some period of time (commonly 3 to 5 years). Specific
management plans including funding can also be a requirement. Such a monitoring
program is designed to:
- Specify recommended mitigation and ensure that it is included in the final design
- Monitor the implementation of the mitigation through design, construction, and
- Resolve issues that are contingent on the outcome of design as it progresses
to more detailed stages.
- Report on progress toward implementation of mitigation measures to responsible
Biologists from resource and conservation agencies associated with CDOT's Shortgrass
Prairie Initiative crafted recommended Baseline/Annual Reporting Requirements that
would provide an effective yet practicable framework for adaptive management and
annual reporting: [N]
- Type of plant communities/habitats present:
- Size/extent of each present plant community or habitat group.
- Description of plant communities present and estimated percent cover.
- General condition of each plant community/habitat type (estimated percent weed
cover, estimated weed sp. relative abundance, estimated percent bare ground, etc.).
- Juxtaposition of communities/habitats.
- Brief description of land use on-site and in surrounding areas documented in
initial baseline. Report changes over the past year.
- Recommendations for management of parcel (i.e., grazing, controlled burns, plantings,
etc.) to achieve conservation goals.
- Success of recommendations from previous year and suggested modifications.
- Observations on wildlife diversity, activity, and general trends. i.e. field
notes. Surveys and quantitative data are not required.
- Photo points at established permanent locations according to protocols to be
developed in the management plan. The on-site managers and regulatory oversight
agreed that new aerial photos would be acquired as they become available.
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|Continue to Section 3.5»