Studies of MTB Trail Impact

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Studies of MTB Trail Impact

Postby tenbsmith » Fri Nov 21, 2008 12:33 pm

Schaarschmidt’s recent post mentioning “Marion (2006) Assessing and Understanding Trail Degradation: Results of Big South Fork Nataional River & Recreation Area” got me started on this.

That pdf is here:
http://www.parks.ca.gov/pages/1324/files/f10602%20marion&olive.pdf
Excerpt:
“Findings reported here related to type of use differences agree with those from other research studies. The lower weight and ground pressure of hikers and bikers creates less disturbance to vegetation and soils along trails, which have fewer problems with widening, erosion, and muddiness. Point sampling data reveals that bike trails are quite narrow at BSF with a mean width of 24 in, followed by hiking trails at 32 in. Horse trails are more than two times as wide (81 in) but ATV trails were widest at 104 in (Table 6). These differences in trail width were statistically significant.

Significant differences were also found in the extent of soil erosion associated with different types of use. Again, bike trails have the lowest CSA values (mean = 6 in2) followed by hiking trails with a mean CSA of 19 in2. However, a very substantial increase in erosion occurs on horse trails, with an average CSA of 150 in2, followed by another large and significant increase for ATV trails (mean CSA = 246) (Table 6). Mixed use trails (mean CSA = 144 in2) were similar in erosion levels to horse trails.

Results for tread muddiness were somewhat different (Table 6), though bike and hiking trails were again lowest (mean = 0). Muddiness across horse trail transects had a mean of 12%, with 3% for ATV trails, though these differences were also statistically significant (Table 6).”

These findings are all very positive about mountain biking. One limitation of the study is that type and level of use was assigned to each trail segment by a knowledgeable park ranger, which while reasonable and necessary given resources, is not as good as basing these assignments on systematically gathered data. One possible criticism of using this study to show that MTBing causes little erosion is that a relatively small proportion of trails were designated MTB and these trails were classified as low use; low use was confounded with MTB so that the favorable results of MTB may be attributable to their low use. Regardless of this, this study show that the real world impact of mountain biking at t some limitations

Other Citations of Interest

Assessing and Understanding Trail Degradation: Thurston, Eden and Reader, Richard L. 2001. Impacts of experimentally applied mountain biking and hiking on vegetation and soil of a deciduous forest. Environmental Management 27(3):397-409.
http://www.springerlink.com/content/5mdmme22vfhmptqf/fulltext.pdf
If the link doesn’t work for you, PM me and I’ll e-mail you a pdf.

Wilson, J.P. and Seney, J.P. 1994. Erosional Impact of Hikers, Horses, Motorcycles and Off-road Bicycles on Mountain Trails in Montana. Mountain Research and Development 14(1): 77-88.
This is not available online, if anyone can get an electronic copy I’d be interested.

Counter Point
One of the rules of rhetoric is to know the opposing point of view. Here’s an interesting counterpoint from the “hikers only” perspective:
http://home.pacbell.net/mjvande/marion
The best point made is that MTB riders tend to go further than hikers. If the erosion caused by a foot of MTB travel is the same as that caused by a foot of hiking, then the greater distances travelled by MTB riders will lead to greater erosion.

The notion that mountain bikers go further is likely true in terms of average distance per trip but, given the smaller number of mountain bikers than hikers, almost certainly untrue in terms of total number of miles travelled on trails in a given area by all users.

I also wonder if MTBers are more likely to avoid riding in wet conditions.
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Re: Studies of MTB Trail Impact

Postby kowen » Fri Nov 21, 2008 2:38 pm

In a related story, from Cycling News November 16 (and also posted on the IMBA website):
--------------------------------------------------------------------------------------
US Forest Service issues directive categorizing bicycles separately from motorized uses
Following a June internal memo differentiating mountain biking from motorized use, the US Forest Service issued fresh administrative directives including language clarifying bicycling as a non-motorized activity. The directives affect up to 130,000 miles of the agency's trails which are located all over the US.

"Mountain biking is incredibly popular in national forests, and we believe it's appropriate to clarify the distinction between mountain biking and motorized use. Better policies will foster improved partnerships and riding experiences," said IMBA Executive Director Mike Van Abel according to the IMBA website.

The actions come after several years of IMBA asking for further documentation on its mountain biking policies. While most national forests understand bicycling is a quiet, non-motorized activity, a few have implemented rules rendering bicycles akin to motorized travel. The new revisions to the Forest Service Handbook and Manual, which are the primary basis for control and management of agency programs, are a step toward standardizing mountain bike management at the field level.

"We're extremely pleased the Forest Service is taking these steps to formally recognize bicycling as low-impact and human-powered. Embedding this information in their employee handbooks will promote better understanding and practices in all 175 national forests and grasslands," said Van Abel.

The Forest service also updated its trail construction standards so that bicycling joins hiking as a potentially suitable use on all trail classes, from the most primitive of designated routes to more developed paths. Decision-making regarding bicycle access on specific trails will stay at a local level but the national-level change recognizes that the environmental impacts of bicycling are similar to hiking and less than other uses.

IMBA and the Forest Service have been formal partners since 1994 and on their third consecutive memorandum of understanding, which runs through 2010.
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Re: Studies of MTB Trail Impact

Postby mtnbikerider » Fri Nov 21, 2008 3:08 pm

Noting who the author of the letter is and his crusade against mountain biking, I wouldn't give much validity to anything he says. If erosion can be minimized to an acceptable level, than what difference does it make whether people are hiking or biking or how many miles they are going? If erosion on a trail cannot be maintained at an acceptable level, then why should why should any activity be allowed over another?
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Re: Studies of MTB Trail Impact

Postby LoneStar » Fri Nov 21, 2008 4:01 pm

Crusade is an understatement for that guy.
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Re: Studies of MTB Trail Impact

Postby tenbsmith » Fri Nov 21, 2008 5:08 pm

I’ve had debates with hikers about the relative impact of MTB and hiking, with hikers taking the stance that MTB has a more negative impact. I think this is a widely held belief, and it behooves us as MTBers to have a convincing argument against it. Citing specific, credible studies is part of a convincing argument.
Next time I get into this sort of discussion I'll say something about.
    A 2001 article in the scientific journal Environmental Management found that the physical impacts of mountain biking on vegetation and soil were no worse than those of hiking.
    A 2006 report by the National Parks Service found that MTB trails were narrower and less eroded than hiking, horsing, ATV, or mixed use trails.
    In 2008, the US Forest Service issued directives clarifying that bicycling as a non-motorized activity.

I agree that MJ Vande is on a crusade, but his point could be convincing if one didn’t have a well considered counter point ready to go.
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Re: Studies of MTB Trail Impact

Postby RedRocker » Fri Nov 21, 2008 5:17 pm

Ready for Fall!
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Re: Studies of MTB Trail Impact

Postby davidmuse » Fri Nov 21, 2008 5:18 pm

Here's a list of sources that were referenced in the Bull/Jake Assessment.


"Impacts of Experimentally Applied Mountain Biking and Hiking on
Vegetation and Soil of a Deciduous Forest" - Eden Thurston and Richard
Reader - University of Guelph Canada - 2001

"A Guide to the Impacts of Non-Motorized Trail Use" - Don Weir and Assoc - Alberta Canada

"Off Road Impacts of Mountain Bikes: A Review and Discussion, Science and Research - G.R. Cessford - Dept of Conservation Wellington New Zealand - 1995

"Erosional Impact of Hikers, Horses, Motorcycles and Off Road Bicycles
on Mountain Trails in Montana" - John Wilson and Joseph Seney - Mountain Research and Development - 1994


And my $0.02:

From what I've read, learned In the trail-building class and seen in the wild, for non-motorized access, trail placement and volume of traffic are the biggest factors in sustainability, well above the type of user.

Naturally occurring trails tend to form in places that are the most scenic or easiest to navigate, but the least sustainable; along ridges, along creeks and up fall lines.

A purpose-built trail can typically withstand whatever traffic it was designed for and lots of it, indefinitely. However, purpose-built trails are a recent invention and are often bench-cut into side-slopes where a trail would not likely form naturally. The formal study of trail wear has also only been going on for about 30 years, and it takes a long time to collect and evaluate data. Trail maintenance is also a developing science.

It seems that trail users who crusade against other trail users are typically unaware of the science, rely totally on anecdotal evidence and typically confuse the impact of wear factors. In my experience, typically "when bikes came in here the trails went to hell" really means "this used to be my favorite hiking trail because only I and a few others knew about it, but now 30 bikes a day ride here, and by the way every trail in the system goes straight up or down a fall line". The volume of traffic and trail placement are the actual problems. It is true that if bikes hadn't been allowed on the trails, there would have been no problem, but it's a function of the increased volume of traffic, not the type. If it became a popular hiking trail system, the same damage would have occurred. For anecdotal evidence of that, just hike the AT in the Blue Ridge WMA. Note the sheer number of reroutes and note how long stretches would be considered eroded to the point of impassibility by most bikers.

There also seems to be a great deal of exaggeration about trail conditions. The ones making the claims appear to be betting that no one will bother to go out and check it out for themselves, but direct inspection often reveals a very different picture.

That said, there are specific unique wear patterns for each trail user that are pretty bad; bikers skid, horses tear up steep slopes, hikers cross-cut switchbacks, backpackers camp along creeks, anglers create run-off channels. All highly damaging behaviors. However, it's rare that the problems caused by these behaviors can't be mitigated if remedied early enough.
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Re: Studies of MTB Trail Impact

Postby davidmuse » Fri Nov 21, 2008 8:48 pm

Here's an interesting one, also has a gazillion references to other studies, books, papers, etc. at the end of it.

Cessford, G.R. 2002. Perception and Reality of Conflict: Walkers and Mountain Bikes on the Queen Charlotte Track in New Zealand.

http://www.google.com/url?sa=t&source=web&ct=res&cd=5&url=http%3A%2F%2Fwww.mountainbike.co.nz%2Fpolitics%2Fdoc%2Fconflict%2Fperception_and_reality_of_conflict.doc&ei=DjEnSZXBBoPktgeh_8zwAg&usg=AFQjCNGipalSTe51UXxRstDiV6g8NoLsKA&sig2=UFlEPE6MEKckn6143YSSaQ
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Re: Studies of MTB Trail Impact

Postby rdhood » Wed Nov 26, 2008 1:39 pm

davidmuse wrote:A purpose-built trail can typically withstand whatever traffic it was designed for and lots of it, indefinitely. However, purpose-built trails are a recent invention and are often bench-cut into side-slopes where a trail would not likely form naturally. The formal study of trail wear has also only been going on for about 30 years, and it takes a long time to collect and evaluate data. Trail maintenance is also a developing science.

It seems that trail users who crusade against other trail users are typically unaware of the science, rely totally on anecdotal evidence and typically confuse the impact of wear factors. In my experience, typically "when bikes came in here the trails went to hell" really means "this used to be my favorite hiking trail because only I and a few others knew about it, but now 30 bikes a day ride here, ". =


Bingo.
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Re: Studies of MTB Trail Impact

Postby Andy » Thu Nov 27, 2008 11:59 pm

If you have ridden enough then you know, as a cyclist and an observer, that bikes cause less impact than hikers. It is good to see an official report to back that up. I think the narrowness of the trail is one of the biggest factors in low impact, although the trails I ride on tend to be more narrow on average than what was reported.
The worst abuse I have hear of from a hiker/anti-bike advocate was when someone used the definition of a trail against cyclist. They said that cycling causes "soil compaction and debris removal". An elected official might cringe at the idea of our forest trails being compacted or the debris being removed from the trail; they just don't care enough about any of this to realize that a trail is just that.
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