Leaf Litter

Leaf Litter Talks with Bethanie Wilder

We get the chance to hear from Bethanie Walder, the Executive Director of Wildlands CPR, about her thoughts on roads and wildlife.

By Amy Nelson

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There are few people around the country who are as immersed in the field of road removal as Bethanie Walder. As an undergrad at Duke University in the late 80’s, Bethanie was an avid camper in the forests of North Carolina. Upon returning to a favorite hiking spot one year later to discover that numerous trails had been turned into roads, Bethanie became quite disillusioned about the role of the U.S. Forest Service and embarked on a personal research mission to find out more.

Assuming that the Forest Service simply protected our forests, she was surprised to learn about timber programs and road construction programs that seemed contrary to the goal of protecting forests. Eager to learn more about forestry and forestry issues, Bethanie enrolled in the Environmental Studies graduate program at the University of Montana. As she was completing her thesis on natural and human disturbance effects on forest ecosystems, Bethanie landed a job as co-director of Wildlands CPR – which, at that time, was called ROAD-RIP. The organization was founded in 1994 as a clearinghouse for research and information on road and off-road vehicle impacts to the environment. Today, Wildlands CPR maintains a 10,000 citation database on the ecological effects of roads and off-road vehicles and offers a multitude of guide books. Wildlands CPR has trained over 1,000 people around the country in these techniques and works closely with numerous land management agencies to advance more restorative and beneficial care of the land.

Leaf Litter recently had the opportunity to speak with Bethanie – just before she jaunted off to a rafting trip on the Lower Salmon River in Idaho – to get her thoughts on the subject of roads and their impact on the environment. Here’s some of what she had to say…

First let’s touch briefly on the differences between mitigation and restoration as it applies here.

Mitigation is, by definition, reducing or lessening an impact – not getting rid of it. Where as restoration – in my definition – is removing an impact so that you are restoring a habitat to a functioning capacity. There is a real link between restoration and mitigation and at some level restoration is just a stronger form of mitigation.

For example, if you want to reduce the impact of a highway on wildlife, there are a number of ways to do that. You can fence a highway to minimize road kill – but then you are imposing a wildlife barrier. You may have reduced road kill but you’ve increased habitat fragmentation. You can fence the road in combination with a wildlife overpass or underpass or some other type of crossing structure. This reduces road kill and allows for some level of connectivity, but even with these structures in place you are not restoring 100% connectivity to an area. You are restoring connectivity in a set number of places. That connectivity is critical, but you are only mitigating the habitat fragmentation you’re not restoring the area.

How do roads impact wildlife habitat?

The major impacts are habitat fragmentation, animal mortality (road kill), sedimentation that pollutes our waters, and the spread of non-native and invasive species – which is a significant problem along road right-of-ways.

From an aquatic perspective, roads completely change how water interacts with land. A perfect example of this is Route 41, which runs from Miami to Tampa, through the Florida Everglades. Route 41 functionally acts like a dam in the Everglades. You have all of this sheet (water) flow across the Everglades and it just hits the road and can’t get across.  As part of an Everglades restoration plan, there is a proposal to elevate an 11- mile section of Route 41 up above the Everglades.  Should this come to fruition, it would be such an amazing restoration opportunity that would result in 11 miles of virtually complete connectivity.

What types of crossings are being used to mitigate the impacts of roads on wildlife?

There are both terrestrial and aquatic crossing structures.


Underpasses – Large concrete structures or metal pipes or arches are used to create a tunnel under the road. In addition, regular culverts that are used to pass water under a road can be retrofitted with little ledges along the length of the culvert, above the water line, so small mammals can cross on the ledge.

Overpasses – or eco-ducts or wildlife bridges are constructed with dirt and vegetation to create contiguous habitat across the road. This type of bridge has been in use in Europe for many years and has been proven to be incredibly effective. They’ve also been used in Banff National Park (Canada). Researchers have found however that it takes time – sometimes several years – for wildlife to become acclimated to using these bridges.

Extended bridges – When you build a bridge across a river, for example, instead of finishing the bridge just at the water’s edge, you keep that bridge raised for another 5 yards to 100 yards or more so that there is a natural land embankment for wildlife to travel under that road. This kind of crossing is really fantastic because it is so natural and you are maintaining complete connectivity across that part of the wildlife habitat.

A good example of this is here in Montana on Highway 93 which is being re-constructed from Missoula to Polson. The highway is increasing from a two-lane to a three/four-lane highway in most areas. There will be 42 wildlife crossing structures – a combination of overpass and underpass bridges – installed along this 45-mile stretch.


Retrofitting or Replacing Culverts – The U.S. Forest Service and many state agencies are upgrading culverts to install larger and better engineered culverts that are retrofitted for fish passage. Most older culverts were designed and constructed solely to pass water and not fish. When fish are trying to get upstream to their spawning grounds, if the existing culvert isn’t designed at the original stream bank level, it can create a waterfall at the edge of the culvert. For certain fish, these waterfalls are too significant of a barrier for them to pass through. Also, because culverts confine a whole stream into what is essentially a small tube, it dramatically increases the velocity of the water and that too can create a problem for the fish – even if the culvert is level with the stream bank bottom.

One technique being used is essentially squashing culverts – leaving the top like a regular culvert yet flattening out the bottom to create more of a natural gradient like a stream bottom. In some cases they are using half culverts to create less expensive bridges.  In these examples, the natural stream bottom is maintained to pass macroinvertabrates and fish – with no interruption whatsoever.

A good example of a successful culvert retrofit is one completed by the Clearwater National Forest in Idaho about two years ago. A stream in which they had not seen steelhead trout for about 50 years, had signs of the return of this species just one year after the retrofit.

It is very important to point out however, that there is not one sure fit solution for all circumstances. In some places culverts have actually prevented invasion of native fisheries from non-native fish. Culverts can block passage for both native fish and non-native fish.  There are some places where the land manager may determine that the risk to the native fishery is greater if you replace the culvert than if you leave it there. So, as you can see, connectivity is not always a straight forward thing.

How does wildlife know to use these crossings?

They don’t always use them. That’s why fencing is used to guide wildlife to the crossing structures. Scientists have found that animals learn where these crossing structures are and they use them more frequently. Over time, scientists and ecologists have made many improvements to wildlife fencing. “Escape ramps” have been created on the road side of the fence – for example a five-foot hill of dirt – which a deer could use to walk up and jump over the fence to the other side so that they can get out of the right-of-way. These seem to work better than “one-way” gates that an animal can push through in one direction but not in the other.

It’s also important to note that the dimensions of wildlife crossings influence how successful they are. Different wildlife species prefer different types of structures. For example, if you are trying to get deer or elk across a road, you’ll need a different sized structure than if you are trying to get smaller mammals across a road. Smaller, prey species prefer a really confined space because they don’t want to be out in the open. Where as ungulates – like deer and elk – prefer a really big open space because they want to be able to see around them.  So it may be necessary to use a wide variety of crossing structures along a stretch of road.

While crossing structures seem to work for nearly every type of animal, it can be expensive to retrofit old roads. For example, thousands of Common Toads in England have been killed by cars while trying to cross roads. During breeding season in late March or early April, Common Toads have a strong urge to return to their birth pond and are killed while crossing the road. Environmental organizations, like Froglife, have formed “toad patrols” – groups of volunteers who go out during breeding season and literally collect all the frogs in buckets and carry them across the road. Even in rural areas with very little road traffic, the mortality rate can be nearly 100%. For this reason they also advocate for amphibian tunnels to allow frogs to cross the roads on their own.

What can you tell us about wildlife detection systems?

This is an emerging field in wildlife mitigation – and it does not require the use of fencing, which may in fact contribute to habitat fragmentation. However wildlife detection systems may also be combined with fencing or other mitigation measures such as wildlife underpasses and overpasses. There are a number of different types of technologies being tested to determine which ones will be most effective in which situations.

Animal detection systems inform drivers that animals are present in the immediate vicinity, instead of relying on “deer crossing” signs that are posted all the time, regardless of the immediate presence of animals. Some systems being tested use a “break the beam” type technology that trigger lights to blink if an animal breaks an infrared, laser or microwave radio signal beam. There is also a system that relies on radio collared elk on the Olympic peninsula in the state of Washington. Since this resident herd of elk travels together, the dominant animals have been radio collared to activate blinking road signs when they are in the vicinity of the road. The Western Transportation Institute at Montana State University is conducting some of the research on this topic.

In our survey we asked readers about their use of mass transit as a means to mitigate transportation hazards to wildlife. But mass transit is clearly not a practical solution, or even available, for everyone. What are your thoughts on mass transit? 

If you’re living in an urban area good mass transportation options are a critical step, but major urban areas also tend to contain little viable wildlife habitat. But let’s look at mass transit from another perspective. There’s been a lot of discussion about electric cars, hybrid vehicles, hydrogen powered cars, etc. – but that individual form of transportation only necessitates more roads. It would be great if we could reduce air pollution by reducing the amount of gas we use, but it won’t reduce the congestion and road construction if our society continues to be based on individual modes of transportation.

There are a couple of really good books on this topic. One book, written by one of the founders of Wildlands CPR, Katie Alvord, is called “Divorce Your Car: Ending the Love Affair with the Automobile” — it deals with these larger issues of the effects of an individual car culture on the environment as a whole. Another great book on this subject is by James Howard Kunstler called “The Geography of Nowhere: The Rise And Decline of America’s Man-Made Landscape” and it’s about how our society at the turn of the century shifted very deliberately from a mass transit based society to an individual car culture. Who was behind that change? The auto industry of course. This shift greatly reduced our country’s investment in mass transit, while concurrently increasing our investment in road and highway construction.

One brilliant solution for people who live in cities is car sharing, which originated in Switzerland in the late 80’s. There are more than a dozen such programs in the U.S. where individuals pay a small fee to have access to a fleet of cars that are shared by a large number of people. It’s a great way to save money on car ownership and do something good for the environment at the same time.

Which states are most pro-active in addressing road removal and mitigating road impacts on wildlife?

Two that stand out are Montana and Florida. Within the last couple of years, Montana has really taken a lead in this field. Case in point — the example I gave earlier with Highway 93 which is being done through a memorandum of agreement between Montana Department of Transportation (MDT), the Salish Kootenai Indian Tribe, and the Federal Highways Administration.  And in Florida, the DOT built culverts under I-75 for panther crossings.

We are starting to see more and more states getting interested in wildlife crossings – though in some instances they may be more concerned about road kill than habitat connectivity. Highway departments tend to be more interested in safety, human mortality and costs. Road kill is very expensive in terms of human lives and insurance costs. So there are different motivations in different places for addressing the issue of wildlife crossings.

What is being done in other countries to mitigate the effects of large roads or highways on wildlife?

This field it is in its infancy in the U.S., but it is at least in its adolescence, if not young adulthood, in many other countries. The Netherlands is certainly a leader in this area. I had attended a conference in Belgium and the thing that amazed me the most was the work being done by some of the eastern European countries like Slovenia and Bulgaria which are relatively poor countries. Some of these countries have incredible habitat and they’re spending money on crossing structures to maintain habitat connectivity across highways to a much greater extent than in the U.S. The people giving the presentations at the conference were the Transportation Ministers talking about why they do crossing structures vs. the researchers and conservationists here in the states who are making the case for crossing structures in this country. In other countries it is an integral part of how they do their transportation planning. And it is only just becoming a part of our transportation planning in the U.S.

One forum that provides a great opportunity to learn from shared research and information is the International Conference on Ecology and Transportation (ICOET). This conference is held every other year and it is THE conference at which road mitigation is discussed.

You spoke about Wildlands CPR’s work on road removal in U.S. forests. Why is this so important?

The Forest Service has more than $10 billion in road maintenance backlogs that needs to be carried out in order to prevent further erosion, sedimentation, and landslides. The road system costs more money than taxpayers can afford to maintain. Removing roads makes more sense economically and ecologically.

We have no qualms about the roads that are needed to move people but presently there is an unsustainable level of roads in the national forests. There are 380,000 miles of official forest service roads. If you add in city, county, state and federal roads – like a U.S. highway – plus the roads that are not on any map – you actually end up with more than 500,000 miles of roads on forest service lands. This is many, many times the size of the U.S. highway system.

So there is a need both to mitigate the roads that the Forest Service needs to keep and to remove the roads that they don’t need anymore. And what the Forest Service has found is that 80% of the use of the roads on national forest lands occurs on 20% of the roads – that’s only about 60,000-70,000 miles that are really needed to meet most forest transportation needs.

What are the motivations for road removal in more urban areas?

It really comes down to safety and money. The city of Seattle is spending $6 million over the next 20 years to remove roads to protect their municipal watershed. The alternative – the building of a water filtration system – would cost $120 million plus ongoing maintenance costs. By removing 10 miles of dirt roads in forested areas each year, they remove the main source of sediment into their municipal watershed. So by spending money to remove roads, they are saving money. They are keeping their water clean; they are putting people to work in high skilled, high wage jobs, and saving the taxpayers money.

What else can Leaf Litter readers do to educate themselves on this issue?

They can contact their state DOTs to find out what work is underway or being proposed. In a number of states there are transportation centers affiliated with local Universities that are conducting research and offering educational programs in this field.

They can also visit Wildlands CPR and learn about both the impacts of roads and the different ways that mitigation and restoration address those impacts. I also invite your readers to become members of Wildlands CPR.

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