A Critique of "A Comparative Study of Impacts to Mountain Bike Trails in Five Common Ecological Regions of the Southwestern U.S." (White et al 2006)

A Critique of "A Comparative Study of Impacts to Mountain Bike Trails
in Five Common Ecological Regions of the Southwestern U.S." (White et
al 2006)
Michael J. Vandeman

http://home.pacbell.net/mjvande

"If a journalist writes an erroneous article, you can send a letter to
the editor. If a businessman does not know what is going on, he will
probably lose money and his job as well. But, oddly enough, academics
can make mistakes, gross and manifest ones, time and again, and get
away with it. For they operate on the basis of peer review. Once the
overall community has been converted to a given position, they
regularly coopt members with the same views. And thus there is no one
to criticize them. Indeed, the critics are neatly kept out of the
academic establishment by those who are already in it." Jon Woronoff,
Japan as Anything But Number One, p.288

I am concerned about a trend I have noticed for advocates of mountain
biking to publish articles on mountain biking impacts that purport to
be scientific studies, but in fact are designed and intended to
promote mountain biking by minimizing its impacts and by drawing
conclusions that don't follow from their data. The White et al (2006)
study is a good example of this genre. The authors claim to show that
mountain biking impacts (specifically, erosion) are no worse than
those of hiking. However, in drawing this conclusion, they neglect to
state clearly the question (hypothesis) they are trying to answer,
rely on studies that are faulty, misinterpret other studies, make
subjective judgments where science requires statistics, and use a
research design that is not capable of supporting the conclusions they
draw. The danger is that people will quote such conclusions out of
context, as if they were really supported by the research, which they
are not.

I numbered my points to make it easier to coordinate their reply with
my comments. I would like the authors to respond to each point using
the same numbering scheme, so that I can see that they have addressed
every point.

1. Are the authors mountain bikers? They seem to be promoting mountain
biking -- trying to make it seem environmentally acceptable.

2. Why does the abstract and paper make comparisons between hiking and
mountain biking impacts? They apparently didn't collect any data that
would allow them to make such a comparison. In fact, the only way to
make such a comparison is with an experimental design, not a survey,
as they have done. It is logically impossible to draw any useful
conclusions from a design that includes measurements taken at only a
single point in time. The data (trail width and depth) provide no way
to distinguish between mountain biking impacts and the effects of
trail construction, trail maintenance, wind, rain, hiking, animals, or
any other factors.

3. The comparison of mountain biking vs. hiking impacts seems to rest
on three bits of information: Wilson and Seney (1994), Thurston and
Reader (2001), and a vague, non-statistical judgment about their
measurements being "similar" to those of hiking trails. The Wilson and
Seney study was discredited by Vandeman (2004), because they didn't
measure erosion accurately: they dripped water on the trail and
collected and weighed the solids carried into the collecting pan. This
only takes into account very fine particles able to be transported by
such "artificial rain"; it ignores all of the larger particles
dislodged by feet or tires. The Wilson and Seney study thus provides
no useful comparison between hiking and mountain biking impacts.

4. They also misrepresented Thurston and Reader's results. Actually,
Thurston and Reader found that after 500 passes, mountain biking had
greater impacts on plants than hiking. It doesn't take long to
accumulate 500 passes. Some trails will receive that amount of traffic
(250 visitors) in a day or two. So this study actually provides no
support for White et al's claim that hiking and mountain biking
impacts are "comparable" (whatever that means).

5. The authors provide no other quantitative, statistical comparison
between hiking and mountain biking impacts. The only way to do that
would be to do an experimental study, where all factors except hiking
vs. mountain biking are controlled (in other words, apply equal
amounts of hiking and mountain biking to identical trails and measure
the impacts using before-and-after measurements).

6. Their estimate of the number of mountain bikers ("21% of the
American public") seems grossly exaggerated. I think they need to find
a more reliable source for that information.

7. They make claims about the benefits of mountain biking. This seems
out of place in a scientific paper, especially since they provide no
evidence for any such (net) benefits. Such claims are usually biased
by tallying alleged positive benefits without subtracting the harm
caused by mountain biking (e.g. accidents, environmental damage,
wildlife impacts, and driving other trail users off of the trails).

8. They claim "management actions that limit access can be
controversial and raise issues of equity", but provide no evidence.
I'm not aware of any limited access or issues of equity. Since only
bicycles, not people, have ever been restricted, I don't see how they
can make such a claim. In fact, it is very unlikely that there are any
equity issues, since it was already determined by a federal court that
bikes may be banned from trails (see
http://home.pacbell.net/mjvande/mtb10).

9. I'm glad they mention "questionable studies". There are, indeed, a
lot of them! But I wonder why they included some of them in their
references, such as Wilson and Seney, and presented them without
comment, as if they were sound science (see Vandeman 2004). They also
misrepresented Thurston and Reader's results, as I explained above.

10. On p.24 they mention "visitor-related factors", but omitted
impacts on other trail users. I think that that is one of the major
impacts of mountain biking. I'm aware of many parks where mountain
bikers have driven other trail users off the trails and out of the
parks.

11. On p.26 they claim that "the magnitude of ecological impacts
attributed to mountain biking appear to be comparable to those of
hiking". "Comparable" is vague or meaningless as a scientific term.
The Earth is comparable to the Sun (they can be compared). I think
that they also misrepresent the implications of those studies (see
Vandeman 2004).

12. On p.29 they mention "user-created" trails. Why use a euphemism,
in a scientific paper? Those trails were built illegally. The authors
only add to the impression that their paper is deliberately slanted.

13. They make a good point on p.36 about trail users having to leave
the trail to allow mountain bikers to pass. This is a good reason to
ban bikes from trails: they lead inevitably to trail widening. But the
authors don't suggest banning bikes as an option, even though it is a
very common management tool. This adds to the impression of bias.

14. On p.37 they claim that "the width and depth" of their trails is
"similar" (not a scientific term, since it is so vague) to that of
Marion & Leung, although their trails averaged 32" wide (median 26")
and his median trail width was 17", so theirs was 50% greater. Why be
scientifically precise in some contexts, but totally vague when they
want to advocate for mountain biking? It is scientifically meaningless
to compare trails in different areas, since the differences or
similarities could be caused by many irrelevant factors, such as
differences in soil type, kind and amount of use, management policies,
etc.

15. Also on p.37 they claim that "The findings from our study thus
reinforce results from previous research that certain impacts to
mountain bike trails, especially width, are comparable or less than
hiking ... trails". On the contrary, they presented zero data on the
width of hiking trails. In fact, they gave evidence (see # 13 above)
that mountain biking tends to widen hiking trails, by forcing hikers
and equestrians off the trail.

16. They also say "average width in our study was similar to lower use
mountain bike trails in Australia ... which [were] from 17 in. to 26
in." "Similar" is not a scientific term. It would appear, on the
contrary, that their trails were much wider than those ones. But as I
mentioned earlier, it is meaningless to compare trails in different
areas. There is no way to determine the cause of any differences or
lack of differences.

17. They claim on p.37 that "mountain biking is likely a sustainable
activity on properly managed trails". What does that mean? They have
just documented erosion and trail widening. Those effects are not
"sustainable"; they constitute environmental damage, in addition to
that of other trail users. They go on to mention several other
negative effects of mountain biking (wildlife impacts and spread of
exotic species) that also contradict the idea that mountain biking is
"sustainable". It would appear that they are bending over backwards to
conclude that mountain biking is acceptable.

18. I fail to see the value of "the introduction of CERs" (Common
Ecological Regions). It seems to have no relevance to policy or
management, unless we are going to prohibit mountain biking in desert
areas where trails can't be clearly delimited. But we already know
that trail widening is harmful: it represents habitat destruction.

In summary, I was bothered most by the authors' unquestioning
acceptance at face value of (or even misrepresenting) some rather
questionable studies, and their drawing conclusions not warranted by
their data. If they really want to do science, and not just promote
mountain biking, I think they should adhere better to what the data
tell us.

Actually, it's much easier than trying to slant results. Permit me to
tell a little story. I was in graduate school at UCLA, was trying to
write a literature-review paper, and was having a terrible time
writing it -- until I realized that I was trying to make the results
come out the way I wanted them to. When I decided to "just tell it
like it was" and let the cards fall as they might, the paper almost
wrote itself. It became easy.

Mountain biking is such a contentious issue that there is a great
temptation to slant the results to support one's preferred management
policy. The result is a lot of questionable studies that don't really
further science and don't really help provide sound scientific
management of our precious remaining wildlife habitat. I suggest that
they first find out what kind of answers are needed (especially by
land managers), and then design research specifically to answer those
questions, instead of first collecting data, and then trying to see
how they can force it to yield the conclusions that they desire.

References:

Thurston, E. and R. J. Reader. 2001. Impacts of experimentally applied
mountain biking and hiking on vegetation and soil of a deciduous
forest. Environmental Management 27:397-409.

Vandeman, M. J. 2004. The Impacts of Mountain Biking on Wildlife and
People -- A Review of the Literature. Available at
http://home.pacbell.net/mjvande/scb7.

White, D. D., M. T. Waskey, G. P. Brodehl, and P. E. Foti. 2006. A
Comparative Study of Impacts to Mountain Bike Trails in Five Common
Ecological Regions of the Southwestern U.S. Journal of Park and
Recreation Administration, 24:2, 21-41.

Wilson, J. P. and J. Seney. 1994. Erosional impact of hikers, horses,
motorcycles, and off-road bicycles on mountain trails in Montana.
Mountain Research and Development. 14:77-88.

--
I am working on creating wildlife habitat that is off-limits to
humans ("pure habitat"). Want to help? (I spent the previous 8
years fighting auto dependence and road construction.)

Please don't put a cell phone next to any part of your body that you are fond of!

http://home.pacbell.net/mjvande