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The Impacts of Mountain Biking on Wildlife and People -- A Review of the Literature

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Old May 27th 08, 01:57 AM posted to alt.mountain-bike,rec.bicycles.soc,rec.backcountry,ca.environment,sci.environment
Mike Vandeman
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Default The Impacts of Mountain Biking on Wildlife and People -- A Review of the Literature

The Impacts of Mountain Biking on Wildlife and People --
A Review of the Literature
Michael J. Vandeman, Ph.D.
July 3, 2004

"Every recreationist -- whether hiker, biker, horsepacker, or posey
sniffer -- should not begin by asking, 'What's best for ME?' but
rather 'What's best for the bears?'" Tom Butler

"Will we keep some parts of the American landscape natural and wild
and free -- or must every acre be easily accessible to people and
their toys? Mountain bikes' impacts on the land are large and
getting worse. The aggressive push of mountain bike organizations to
build ever-growing webs of trails poses serious problems of habitat
fragmentation, increased erosion, and wildlife conflicts.
As interest in extreme riding continues to grow, as trail
networks burgeon, and as new technology makes it possible for
ever-more mountain bicyclists to participate, even the most remote
wild landscapes may become trammeled -- and trampled -- by knobby
tires. The destruction of wilderness and the fragmentation of
habitats and ecosystems is death by a thousand cuts. Will introduction
of mountain bikes -- and their penetration farther into wilderness --
promote additional fragmentation and human conflicts with the natural
world? Yes." Brian O'Donnell and Michael Carroll

"Some things are obvious: mountain bikes do more damage to the land
than hikers. To think otherwise ignores the story told by the ground.
Although I have never ridden a mountain bike, I am very familiar with
their impacts. For the last seven years I have regularly run three to
six miles several times a week on a network of trails in the Sandia
Mountain foothills two blocks from my home. These trails receive use
from walkers, runners, and mountain bikers; they are closed to
motorized vehicles.
Because I'm clumsy, I keep my eyes on the trail in front of
me. I run or walk in all seasons, in all kinds of weather. I have
watched the growing erosion on these trails from mountain bike use.
The basic difference between feet and tires is that tire tracks are
continuous and foot tracks are discontinuous. Water finds that narrow,
continuous tire tracks are a rill in which to flow. Also, because many
mountain bikers are after thrills and speed, their tires cut into the
ground. Slamming on the brakes after zooming downhill, sliding around
sharp corners, and digging in to go uphill: I see the results of this
behavior weekly.
I regularly see mountain bikers cutting off cross-country,
even on steep slopes, for more of a challenge. They seem blind and
deaf to the damage they cause. Admittedly, backpackers and
horsepackers can cause damage to wilderness trails. But this is a poor
argument to suggest that we add another source of damage to those
trails." Dave Foreman

"Studies show that bike impacts are similar to those of other
non-motorized trail users." Jim Hasenauer (professor of rhetoric and
member of the board of directors of the International Mountain
Bicyclists Association)


I first became interested in the problem of mountain biking in
1994. I had been studying the impacts of the presence of humans on
wildlife, and had come to the conclusion that there needs to be
habitat that is entirely off-limits to humans, in order that wildlife
that is sensitive to the presence of humans can survive (see Vandeman,
2000). But what is the best way to minimize the presence of people?
Restricting human access is repugnant, and difficult and expensive to
accomplish. It occurred to me that the best way to reduce the presence
and impacts of humans is to restrict the technologies that they are
allowed to utilize in natu e.g. prohibit bicycles and other
vehicles (and perhaps even domesticated animals, when used as

Having been a transportation activist for eight years (working
on stopping highway construction), and having a favorable view of my
fellow bicyclists as environmentalists, I turned to them to help me
campaign to keep bicycles out of natural areas. Was I ever surprised!
I discovered that many bicyclists (e.g. many mountain bikers) aren't
environmentalists at all, but are simply people who like to bicycle --
in the case of mountain bikers, many of them just use nature, as a
kind of playground or outdoor gymnasium! (Of course, there are also
hikers, equestrians, and other recreationists who fall into this
category.) To my suggestion to keep bikes off of trails in order to
protect wildlife, they reacted with hostility! (There is a degree of
balkanization among activists, where some transportation activists
ignore the needs of wildlife, and some wildlife activists eschew bikes
and public transit.)

In 1994 I attended a public hearing held by the East Bay
Municipal Utility (water) District to decide whether to allow bikes on
their watershed lands. Mountain bikers were there asking for bike
access, and the Sierra Club was there to retain the right to hike,
while keeping out the bicycles. I said that I had no interest in using
the watershed, but that I wanted to ensure that the wildlife are
protected -- hence, I asked that bikes not be allowed. Afterward, the
EBMUD Board of Directors took a field trip to Marin County, the
birthplace of mountain biking, to see the effects of mountain biking
there. While they were hiking along a narrow trail, a mountain biker
came racing by, swearing at them for not getting out of his way fast
enough. That helped them decide to ban bikes. Today bikes are still
restricted to paved roads, and EBMUD is still one of the public
agencies most protective of wildlife.

It is obvious that mountain biking is harmful to some wildlife
and people. No one, even mountain bikers, tries to deny that. Bikes
create V-shaped ruts in trails, throw dirt to the outside on turns,
crush small plants and animals on and under the trail, facilitate
increased levels of human access into wildlife habitat, and drive
other trail users (many of whom are seeking the tranquility and
primitiveness of natural surroundings) out of the parks. Because land
managers were starting to ban bikes from trails, the mountain bikers
decided to try to shift the battlefield to science, and try to
convince people that mountain biking is no more harmful than hiking.
But there are two problems with this approach: (1) it's not true, and
(2) it's irrelevant.

I will examine (1) in a moment. But first, let's look at
relevance: whether or not hiking (or All Terrain Vehicles or urban
sprawl or anything else) is harmful really has no bearing on whether
mountain biking is harmful: they are independent questions. Such a
comparison would only be relevant if one were committed to allowing
only one activity or the other, and wanted to know which is more
harmful. In reality, hiking is always allowed, and the question is
whether to add mountain biking as a permitted activity. In that case,
the only relevant question is: Is mountain biking harmful? Of course,
it is. However, since many people seem interested in the outcome of
the comparison, I will examine the research and try to answer it.

The mountain bikers' other line of research aims to prove that
mountain bikers are just like hikers, implying that they should have
the same privileges as hikers. (Of course, they already have the same
privileges! The exact same rules apply to both groups: both are
allowed to hike everywhere, and neither is allowed to bring a bike
where they aren't allowed.) Using surveys, they have tried to show
that mountain bikers are really environmentalists, lovers of nature,
and deep ecologists. Of course, surveys are notoriously unreliable:
statements of belief don't easily translate into behavior. I'm going
to ignore this research, since I am (and the wildlife are) more
interested in actual impacts, not intentions.

The International Mountain Biking Association (IMBA) has done
me the favor of collecting all the research they could find that
seemed favorable to mountain biking. Gary Sprung (2004) summarized it
in his carefully worded essay, "Natural Resource Impacts of Mountain
Biking". Gary says "the empirical studies thus far do not support the
notion that bikes cause more natural resource impact". I will show
that this is not true; in fact, those studies, if their data are
interpreted properly, show the exact opposite: that mountain biking
has much greater impact than hiking! Gary says that we should make
"make rational, non-arbitrary, less political decisions regarding
which groups are allowed on particular routes". This is disingenuous.
Mountain bikers (but not bikes) are already allowed on every trail.

Impacts on Soil (Erosion):

Gary says "No scientific studies show that mountain bikers
cause more wear to trails than other users". He cites Wilson and Seney
(1994) and claims that "hooves and feet erode more than wheels.
Wilson and Seney found no statistically significant difference between
measured bicycling and hiking effects". He quotes the study: "Horses
and hikers (hooves and feet) made more sediment available than wheels
(motorcycles and off-road bicycles) on prewetted trails" (p.74).

This study is frequently cited by mountain bikers as proof
that mountain biking doesn't cause more impact than hiking. But it has
a number of defects that call its conclusions into question. The
authors used a "rainfall simulator" to measure "sediment made
available" by the various treatments. They "[collected] surface runoff
and sediment yield produced by the simulated rainstorms at the
downslope end of each plot", which they claim "correlates with
erosion" (they don't say what the correlation coefficient is). This
doesn't seem like a good measure of erosion. For example, if a large
rock were dislodged, the very weak "simulated rainfall" wouldn't be
capable of transporting it into the collecting tray; only very fine
particles would be collected. In fact, they admit that the simulator's
"small size meant that the kinetic energy of the simulated rainfall
events was roughly one-third that of natural rainstorms". Another
reason to suspect that the measurements aren't valid is that "none of
the relationships between water runoff and soil texture, slope,
antecedent soil moisture, trail roughness, and soil resistance was
statistically significant".

The authors also ignored the relative distances that various
trail users typically travel (for example, bikers generally travel
several times as far as hikers, multiplying their impacts accordingly)
and the additional impacts due to the mountain bike bringing new
people to the trails that otherwise would not have been there (the
same omission is true of all other studies, except Wisdom et al
(2004)). They do say "Trail use in the last ten years has seen a
dramatic increase in off-road bicycles" (p.86), but they don't
incorporate this fact into their comparison. In addition, there is no
recognition of different styles of riding and their effect on erosion.
We don't know if the mountain bikers rode in representative fashion,
or, more likely, rode more gently, with less skidding, acceleration,
braking, and turning. There was also no recognition that soil
displaced sideways (rather than downhill) also constitutes erosion
damage. It seems likely that they underestimated the true impacts of
mountain biking. I don't think that these results are reliable. (Note
that the study was partially funded by IMBA.)

Gary next cited Chiu ) and Kriwoken
), claiming that there was "no significant
difference between hiking and biking trail wear". It is apparent he
and the authors misstated the implications of the study. If we assume,
as they claim, that bikers and hikers have the same impact per mile
(which is what they measured), then it follows that mountain bikers
have several times the impact of hikers, since they generally travel
several times as far. (I haven't found any published statistics, but I
have informally collected 72 mountain bikers' ride announcements,
which advertise rides of a minimum of 8 miles, an average of 27 miles,
and a maximum of 112 miles.)

Besides ignoring distance travelled, there were a number of
other defects in the study. The biking that was compared with hiking
was apparently not typical mountain biking. It was apparently slower
than normal and included no skidding. Bikers who skidded (a normal
occurrence) were not compared with hikers. Their erosion impacts were
much greater than those of any hikers (judging from the study's graph
labelled "Figure 3"). Bikers' impacts under wet conditions were also
greater than those of the hikers, which probably would have been
statistically significant, if the numbers (of data points) had been
greater. One useful result was that the bikers tended to create a
V-shaped groove, whereas the hikers' impact was spread more evenly
across the trail. They admit that this "could act as a water channel
and increase erosion" (p.356). They also surveyed trail users: "34% of
riders listed excitement/risk as a main reason for visiting [the
park]. This, combined with the 57% of 'other users' who visit for
relaxation, sets up a potential for goal interference, in that a rider
aiming for an exciting/risky experience has the potential to interfere
with a walker aiming to have a relaxing experience." (p.357) This
would also tend to indicate that many bikers travel faster than those
in this study, since they are seeking "excitement" and "risk".

Impacts on Plants:

Gary says "No scientific studies indicate that bicycling
causes more degradation of plants than hiking. Trails are places
primarily devoid of vegetation, so for trail use in the center of
existing paths, impacts to vegetation are not a concern." However this
is a concern for plants that try to establish themselves in the trail,
and for roots that cross the trail and end up being killed or damaged.

He cites Thurston and Reader (2001), claiming that "hiking and
bicycling trample vegetation at equal rates the impacts of biking
and hiking measured here were not significantly different". Actually,
that is not true. Although overall impacts weren't significantly
different, "soil exposure [was] greater on biking 500 pass lanes than
hiking 500 pass lanes" (p.404). In other words, after 500 passes,
mountain biking began to show significantly greater impacts. Thus
their conclusion, "the impacts of biking and hiking measured here were
not significantly different" (p.405) is unwarranted.

The authors said "Bikers traveled at a moderate speed, usually
allowing bicycles to roll down lanes without pedaling where the slope
would allow." Thus it would appear that the mountain biking that they
measured is not representative: it was unusually slow and didn't
include much opportunity for braking, accelerating, or turning, where
greater impacts would be expected to occur.

The authors also said "Some hikers feel that bikers should be
excluded from existing trails" (p.397). Of course, this is not true.
Hikers are only asking that bikes be excluded, not bikers. On page 407
they admit the "possibility that mountain bikers simply contribute
further to the overuse of trails". In other words, allowing bikes on
trails allows trail use to increase over what it would be if bikes
weren't allowed. This is probably true, and deserves to be recognized
and researched.

They found that "One year following treatments, neither
vegetation loss nor species loss was significantly greater on treated
lanes than on control lanes" (p.406). They conclude that the
recreation impacts are "short-term", and experience "rapid recovery".
This is unjustified. Killing plants and destroying seeds modifies the
gene pool, and introduces human-caused loss of genetic diversity, and
evolution. Dead plants and lost genetic diversity do not "recover"
(see Vandeman, 2001).

However, the greatest defect of the study and its
interpretation is that is that it doesn't consider the distance that
bikers travel. Even if we accepted their conclusions that impacts per
mile are the same, it would follow that mountain bikers have several
times the impact of hikers, since they are easily able to, and do,
travel several times as far as hikers. Try walking 25 or 50 or 100
miles in a day!

Impacts on Animals:

Gary cites Taylor and Knight (1993), claiming that "hiking and
biking cause [the] same impact to large mammals on Utah island".
First, as noted by Wisdom et al (2004), this study lacked a control
group, and hence can't infer causation. Second, the authors made the
same mistake that all other researchers made: they ignored the
different distances that hikers and bikers travel. I also wonder how
realistic it was to have all recreationists continue past the animals
without stopping to look at them. (All of those researchers also
failed to implement blind measurement and analysis: the researchers
were aware, as they were measuring, which treatment they were testing.
Only Wisdom et al were able to carry out their measurements
(electronically) without any people even being present.)

This is a very informative paper. The authors "examined the
responses of bison , mule deer , and pronghorn antelope to hikers
and mountain bikers by comparing alert distance, flight distance,
and distance moved" (p.951). They noted, significantly, that "Outdoor
recreation has the potential to disturb wildlife, resulting in
energetic costs, impacts to animals' behavior and fitness, and
avoidance of otherwise suitable habitat. outdoor recreation is the
second leading cause for the decline of federally threatened and
endangered species on public lands" (p.951). They also noted that
"Mountain biking in particular is one of the fastest-growing outdoor
activities, with 43.3 million persons participating at least once in
2000" (p.952). However, they didn't draw on this fact when they
concluded "We found no biological justification for managing mountain
biking any differently than hiking" (p.961).

The authors also surveyed the recreationists, and found that
they "failed to perceive that they were having as great an effect on
wildlife as our biological data indicated. Most recreationists felt
that it was acceptable to approach wildlife at a much closer distance
(mean acceptable distance to approach = 59.0 m) than wildlife in our
experimental trials would typically allow a human to approach (mean
flight distance of all species = 150.6 m). Of all visitors surveyed,
46%, 53%, and 54%, respectively, felt that bison, deer, and pronghorn
were being negatively affected by recreation on Antelope Island.
Visitors expressed little support for allowing only one type of
recreational use on island trails, having fewer trails on the island,
for requiring visitors to watch an educational video about the effects
of recreation on wildlife, and for allowing recreation only on the
north (developed) end of the island" (p.957). (Gary Sprung omitted
this information from his summary.)

They noted that the wildlife might habituate to the presence
of humans, but that exactly the opposite happened with the pronghorn:
they "in fact used areas that were significantly farther from trails
than they had prior to the start of recreational use on the island"
(p.961). They also noted: "Because flushing from recreational activity
may come at the cost of energy needed for normal survival, growth, and
reproduction , and because it may cause animals to avoid otherwise
suitable habitat , it is important that recreationists understand
that their activities can flush wildlife and may make suitable habitat
unavailable" (p.961). I think that the wealth of such information
provided by the authors makes this paper especially valuable.

They concluded "Our results indicate that there is little
difference in wildlife response to hikers vs. mountain bikers"
(p.957). I was present when Ms. Taylor presented her findings at the
Society for Conservation Biology meeting at the University of Kent, in
Canterbury, England, in July, 2002. I pointed out to her that she
wasn't justified in concluding, as she did, that "hiking and mountain
biking have the same impacts", since she only measured impacts per
incident. Since bikers are able, and typically do, travel several
times as far as hikers, a more proper conclusion would be that bikers
have several times as much impact on wildlife as hikers. That is why I
am so disappointed to find her later concluding in this 2003 paper,
"We found no biological justification for managing mountain biking any
differently than hiking" (p.961). If mountain bikers can travel even
twice as far as hikers, and disturb twice as many animals, I would
think that that is biologically significant! It isn't much help that
she goes on to admit that "because bikers travel faster than hikers,
they may cover more ground in a given time period than hikers, thus
having the opportunity to disturb more wildlife per unit time"
(p.961). She has still drawn an unjustified conclusion, and it is
certain to be frequently quoted (out of context) by mountain bikers,
as they try to lobby for more trail access.

I also wonder about the accuracy of their measurements of
distance. Distance is notoriously difficult to measure accurately,
especially when animals and recreationists may be hidden from view
("Due to the inherent errors in triangulating in the steep canyon
country, only ground visual locations were used in the analysis"
p.577). Bias may also have been introduced by the fact that
researchers knew, as they were measuring, which treatment they were

Sprung next cited Papouchis et al (2001), claiming that
"Hikers have [the] greatest impact on bighorn sheep [in Canyonlands
National Park] because the hikers were more likely to be in
unpredictable locations and often directly approached [the] sheep".
Actually, this is an artifact of the experimental design, and not a
result of research: the researchers, for some reason, told the hikers
(who were research assistants) to approach the sheep! So the study
actually compared apples and oranges: bikers who stay on a road, vs.
hikers who approach bighorn sheep! Nothing useful can be concluded
from such a study, except that people who approach bighorn sheep
disturb them. Of course, there is nothing to prevent mountain bikers
from getting off their bikes and doing the same thing. It's
unfortunate that the opportunity was lost to gain more valuable
knowledge. I wrote the authors, asking why they had done this, but I
got no reply. It would appear that the intention was to exonerate
mountain biking (this also applies to most of the other studies).

It is interesting that "when bighorn sheep did respond to
human activity, they noticed vehicles and mountain bikers, on average,
from twice the distance they noticed hikers" (p.577). This would seem
to imply that, were hikers to remain on the trail where the mountain
bikers were, they might have equal or lower impacts than the mountain

It is also unfortunate that there was no control group, so
that they could determine the effect of the presence of roads, with
and without people on them. They did note that "avoidance of the road
corridor by some animals represented 15% less use of potential
suitable habitat in the high-[visitor-]use area over the
low-[visitor-]use area. human presence in bighorn sheep habitat may
cause sheep to vacate suitable habitat" (p.573). This argues for
eliminating all recreation in the area, especially since the absence
of water forces recreationists to bring motor vehicles carrying water
and other supplies: "mountain bikers frequently use the 161-km White
Rim trail, a 4-wheel-drive road. Caravans of mountain bikers
accompanied by support vehicles are common. Day use along the Shafer
and White Rim trails exceeded 17,500 vehicles during the study period,
1993-1994. This use was concentrated from March to October, with peak
use of 134 vehicles/day in May" (p.575).

The authors conclude "Contrary to our original expectations
and the concerns of park managers, the increase in numbers of mountain
bikers visiting the park does not appear to be a serious threat to
desert bighorn sheep, probably because mountain bikers are restricted
to predictable situations such as the currently designated road
corridors" (p.580). For several reasons, this conclusion is not
justified: (1) as they reported, all recreationists drive the sheep
away from parts of their habitat, causing loss of energy as well as
habitat; (2) permitting bikes causes the total number of visitors to
increase significantly; (3) bikes can't travel alone -- they require
motorized support vehicles, further increasing impacts (e.g. worsening
air quality); (4) there is nothing to prevent mountain bikers from
getting off their bikes and approaching the wildlife; if hikers do
that, so will mountain bikers; there is no reason to exonerate
mountain bikers.

They note, significantly, "However, these results should not
be extrapolated to other public lands where mountain bikers are not
confined to designated trails and may surprise sheep in novel
situations" (p.580). Gary Sprung didn't mention this, thus encouraging
inappropriate use of this study's already-questionable results.

I would like, however, to commend the authors for stating "we
recommend that park managers manage levels of backcountry activity at
low levels" (p.580). The best policy would be to ban all vehicles,
including bicycles (as well as animals used as vehicles). That would
reduce human impacts, without directly restricting who could go there
(perhaps occasional exceptions could be made for the disabled).

Gary next cited Gander and Ingold (1997), claiming that
"hikers, joggers & mountain bikers [are] all the same to chamois". But
again, this is not an accurate representation of the results: "They
fled over longer distances in jogging and mountain biking experiments
carried out late in the morning" (p.109). Also, "the three
activities carried out on the ground could have long-term consequences
as they prevent the animals from using areas near trails. Thus,
depending on the density of trails and the intensity of recreational
activities in a certain area, animals may lose a large part of their
habitat" (p.109).

The authors conclude "Our results show that specific
restrictions on mountainbiking above the timberline are not justified
from the point of view of chamois" (p.109). Once again (is there a
pattern here?), this conclusion is not justified. It ignores the fact
that mountain bikers are able to travel several times as far as
hikers, and thus negatively impact several times as much wildlife. It
also ignores the fact that bicycles enable a large increase in numbers
of human visitors (note that this places the blame on the bicycle, not
the bicyclists -- my argument doesn't depend on there being any
difference between hikers and mountain bikers). And, of course,
wherever the number of visitors increases, there is pressure to build
more trails, destroying even more habitat. Once again, it would appear
that this study was undertaken with the intent of excusing mountain

Gary next cites a study of bald eagles by Robin Spahr (1990).
"Spahr found that walkers caused the highest frequency of eagle
flushing". However, this study is difficult to interpret. Eagles don't
congregate in large numbers, like sheep, so it is hard to ensure that
all treatments are equally balanced: it is hard to imagine that the
conditions under different treatments (or even within treatments) were
equal. Also, the bikers were apparently instructed to ride by without
looking at the eagles, whereas some of the walkers were told to look
and point at the eagles (the paper is vague on this point). In other
words, the study was comparing apples with oranges. Thus, I don't know
if this was really a controlled study. Spahr also found that
"bicyclists caused eagles to flush at [the] greatest distances", which
would tend to indicate that bicyclists have greater impacts. Distances
are also notoriously difficult to measure accurately. We are given no
information about the "rangefinder", in order to judge its accuracy.
At best, these are mixed results. And, once again, the greater
distances that bikers travel are ignored, as well as the greater
visitor numbers that the bicycle enables. Therefore, the study cannot
be said to support any conclusion about how hiking compares with
mountain biking, and certainly not Gary's statement: "Hikers have
greater impact on eagles than cyclists". To Spahr's credit, she did
not attempt to generalize beyond her data.

Gary concludes "Mountain biking, like other recreation
activities, does impact the environment. On this point, there is
little argument. But a body of empirical, scientific studies now
indicates [sic] that mountain biking is no more damaging than other
forms of recreation, including hiking [Gary's emphasis]. Thus,
managers who prohibit bicycle use (while allowing hiking or equestrian
use) based on impacts to trails, soils, wildlife, or vegetation are
acting without sound, scientific backing." Au contraire, as I have
indicated, the very studies that Gary and IMBA cite as support for
mountain biking actually show that mountain biking does much more harm
to the environment than hiking! Gary goes on to fault "the wisdom of
prohibiting [sic] particular user groups". However, as I explained
earlier, mountain bikers are not prohibited from using any trails.
Bicycles are occasionally prohibited. Mountain bikers are merely
required to follow the same rules as everyone else, and walk.

At the bottom of the same web page is the notice: "IMBA wishes
to obtain and incorporate into future revisions of this document any
new or additional empirical science regarding the impacts of mountain
biking. IMBA welcomes input [my emphasis]. To offer information,
please contact the author at ". On April 25 I emailed
Gary (and Pete Webber,
) the Wisdom et al study, which
demonstrates that mountain bikers have a greater impact on elk than
hikers. Not only hasn't this new research been incorporated into his
paper, but I haven't even received a reply. It would appear that IMBA
isn't really interested in achieving a scientific answer to this

In 2003, Jason Lathrop wrote an excellent "critical literature
review" on the ecological impacts of mountain biking, raising some
questions found nowhere else. He quotes the BLM: "An estimated 13.5
million mountain bicyclists visit public lands each year to enjoy the
variety of trails. What was once a low use activity that was easy to
manage has become more complex". He criticizes all of the studies for
not using realistic representations of mountain biking. For example,
on Thurston and Reader, he says "this study's treatment passes at best
loosely approximate the forces exerted by actual mountain biking. On
real trails, riders possess widely varying levels of skill, resulting
in variant speeds, turning, and braking. This study does not address
these variables." Lathrop also makes the excellent point that "Direct
mortality [of animals] is virtually unstudied. I could find no
references to it in the literature. Anecdotal evidence suggests,
however, that small mammals are vulnerable to impact and are not
uncommonly killed."

And: "Taylor (2001) concluded that short-term behavioral
changes do not vary between bicyclists and hikers on a per-encounter
basis. However, because bicyclists are capable of and, in most areas,
typically do travel much farther than hikers, it is reasonable to
conclude that they will create a somewhat higher total number of
encounters and flushings."

Cessford (1995) did an oft-quoted review (which I am including
only because it is so widely cited) that, like all others,
uncritically accepts Wilson and Seney (1994) as proof that mountain
biking impacts are no worse than those of hikers. His paper is mostly
speculation, based on few actual research findings. He disparages
negative information about mountain biking by such devices as claiming
that problems are caused by a minority of mountain bikers, exhibiting
"poor riding habits", that accidents involving hikers and bikers are
"rare", that hikers' dislike for being around bikes in the woods, and
feelings that bikes cause greater environmental harm than hiking, are
mere "perceptions". He blames hikers for "misperceiving" mountain
bikers, claiming that "the two groups are more similar than is
generally perceived. The bicyclists are basically hikers who are
using mountain bikes to gain quicker access to the wilderness
boundary". He speculates, without any evidence, that "the degree of
conflict with mountain biking may diminish over time as other users
become more familiar with bike-encounters and riders themselves". A
more likely interpretation is that hikers who dislike being around
bikes simply stop using trails that are open to bikes, thereby
lessening the conflict!

Finally, in 2004, Wisdom et al did a very well controlled
study comparing the impacts of ATV riders, mountain bikers, and hikers
on elk and mule deer. They say we have an "urgent need for timely
management information to address the rapid growth in off-road
recreation. Mountain biking [is] increasing rapidly".
Recreationists were allowed to stop for less than a minute to look at
the animals. All measurements were made electronically, using an
Automated Telemetry System and GPS, allowing control measurements to
be made "blind", with no humans present! "Use of the automated
telemetry system to track animal movements, combined with the use of
GPS units to track human movements, provided real-time, unbiased
estimates of the distances between each ungulate and group of humans
[the recreationists were in pairs]". He pointed out that direct
measurements, a la Taylor and Knight, tend to be biased, because some
animals can't be observed. The area was entirely fenced, allowing
researchers to completely control human access.

They found: "Movement rates of elk were substantially higher
during all four off-road activities as compared to periods of no human
activity. For the morning pass, movement rates of elk were highest
during ATV activity, second-highest during mountain bike riding, and
lowest during hiking and horseback riding. Peak movement rates of
elk during the morning pass were highest for ATV riding (21
yards/minute), followed by mountain bike riding (17 yards/minute) and
horseback riding and hiking (both about 15 yards/minute). By
contrast, peak movement rates of elk during the control periods did
not exceed 9 yards/minute during daylight hours of 0800-1500, the
comparable period of each day when off-road treatments were
implemented. Interestingly, movement rates of elk were also higher
than control periods at times encompassing sunrise and sunset for the
days in which an off-road activity occurred, even though humans were
not present at these times of the day. These higher movement rates
near sunrise and sunset suggest that elk were displaced from preferred
security and foraging areas as a result of flight behavior during the
daytime off-road activities. In particular, movement rates of elk at
or near sunrise and sunset were higher during the 5-day treatments of
mountain bike and ATV activity".

"Higher probabilities of flight response occurred during ATV
and mountain bike activity, in contrast to lower probabilities
observed during hiking and horseback riding. Probability of a flight
response declined most rapidly during hiking, with little effect when
hikers were beyond 550 yards from an elk. By contrast, higher
probabilities of elk flight continued beyond 820 yards from horseback
riders, and 1,640 yards from mountain bike and ATV riders. In contrast
to elk, mule deer showed less change in movement rates during the four
off-road activities compared to the control periods". (Perhaps they
seek cover, rather than running away.)

"The energetic costs associated with these treatments deserve
further analysis to assess potential effects on elk survival. For
example, if the additional energy required to flee from an off-road
activity reduces the percent body fat below 9 percent as animals enter
the winter period, the probability of surviving the winter is
extremely low. Animal energy budgets also may be adversely affected by
the loss of foraging opportunities while responding to off-road
activities, both from increased movements, and from displacement from
foraging habitat. Our results from 2002 also show clear differences
in elk responses to the four off-road activities. Elk reactions were
more pronounced during ATV and mountain bike riding, and less so
during horseback riding and hiking. Both movement rates and
probabilities of flight responses were higher for ATV and mountain
bike riding than for horseback riding and hiking."

It is also instructive to note that only one pair of ATV users
were needed to cover the 20-mile study area, but two pairs of mountain
bikers and three pairs of hikers were needed, to cover the distance in
the time allotted, underscoring the different relative distances that
the three groups are capable of covering.


Mountain bikers have turned to scientific research to try to
make mountain biking seem less harmful, and in particular, to studies
comparing it with hiking. Although they have interpreted this data as
indicating that mountain biking impacts are no greater than those of
hiking, a more careful look at these studies leads to the conclusion
that mountain biking impacts are actually several times greater than
those of hikers.

Some of the important characteristics of mountain biking that
have been ignored a speed; distance traveled; the increase in
number of visitors that bikes allow; increased trail-building, with
its attendant habitat destruction; the displacement of soil (other
than downhill); the killing of roots and soil organisms and
ecosystems; most effects on wildlife; manner of riding (skidding,
braking, acceleration, turning, and representativeness); tire tread;
and noise (bikes are relatively quiet, but a rattling chain may be
perceived as "alien" to natural surroundings).

In addition, measuring techniques need to be described in more
detail, "blind" measurements should be considered (where the measurers
don't know what treatment they are measuring), controls need to be
added, and "intangibles" (e.g. loss of feelings of safety and loss of
the primitive feel of natural settings) need to be taken more
seriously. The direct killing of small animals deserves attention.

On the other hand, why do we need research to prove what is
obvious? We don't need any research to know that we shouldn't step in
front of a speeding truck. Or mountain bike.


Butler, Tom, "Mountain biking in wilderness: What bears want -- a
wilderness view". Wild Earth, Vol.13, No.1, 2003, p.4,

Cessford, Gordon R. ), "Off-road impacts of
mountain bikes -- a review and discussion". Science & Research Series
No.92, Department of Conservation, P. O. Box 10-420, Wellington, New
Zealand, 1995,

Chiu, Luke ) and Lorne Kriwoken
), "Managing Recreational Mountain Biking in
Wellington Park, Tasmania, Australia". Annals of Leisure Research,
Vol.6, No.4, 2003, pp.339-361.

Foreman, Dave, "A modest proposal". Wild Earth, Vol.13, No.1, 2003,
pp.34-5, http://www.wildlandsproject.org.

Gander, Hans and Paul Ingold, "Reactions of male alpine chamois
Rupicapra r. rupicapra to hikers, joggers and mountainbikers".
Biological Conservation, Vol.79, 1997, pp.107-9.

Goeft, Ute and Jackie Alder, "Sustainable mountain biking: a case
study from the southwest of Western Australia". Journal of Sustainable
Tourism, Vol.9, No.3, 2001, pp.193-211.

Hasenauer, Jim ), "A niche for bicycles". Wild Earth,
Vol.13, No.1, 2003, pp.21-22, http://www.wildlandsproject.org.

Lathrop, Jason, "Ecological impacts of mountain biking: a critical
literature review". 2003,

McCoy, Michael and Mary Alice Stoner, "Mountain bike trails:
Techniques for design, construction and maintenance". Bikecentennial,
P. O. Box 8308, Missoula, MT 59807, 1992.

O'Donnell, Brian and Michael Carroll, "Don't tread here". Wild Earth,
Vol.13, No.1, 2003, pp.31-33, http://www.wildlandsproject.org.

Papouchis, Christopher M. ), Francis J. Singer,
and William B. Sloan, "Responses of desert bighorn sheep to increased
human recreation". Journal of Wildlife Management, Vol.65, No.3, 2001,

Spahr, Robin, "Factors affecting the distribution of bald eagles and
effects of human activity on bald eagles wintering along the Boise
River". A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Science of Raptor Biology, Boise State
University, March, 1990.

Sprung, Gary ), "Natural resource impacts of mountain
biking -- a summary of scientific studies that compare mountain biking
to other forms of trail travel", 2004,

Taylor, Audrey ) and Richard L. Knight
) "Wildlife responses to recreation and
associated visitor perceptions". Ecological Applications, Vol.13,
No.4, 2003, pp.951-63.

Thurston, Eden and Richard J. Reader ), "Impacts
of experimentally applied mountain biking and hiking on vegetation and
soil of a deciduous forest". Environmental Management, Vol.27, No.3,
2001, pp.397-409.

Vandeman, Michael J. ), 1998. Wildlife Need
Habitat Off-Limits to Humans! in Personal, Societal, and Ecological
Values of Wilderness: Sixth World Wilderness Congress: Proceedings on
Research, Management, and Allocation: A. E. Watson, G. H. Aplet, J. C.
Hendee, eds. Fort Collins, CO: U.S. Dept. of Agriculture, Forest
Service, Rocky Mountain Research Station; also available at

Vandeman, Michael J. ), "The Myth of the
Sustainable Lifestyle". Presented at the Society for Conservation
Biology meeting, University of Hawaii, Hilo, Hawaii, July 30, 2001,

Wilson, John P. ) and Joseph Seney, "Erosional impact
of hikers, horses, motorcycles, and off-road bicycles on mountain
trails in Montana". Mountain Research and Development, Vol.14, No.1,
1994, pp.77-88.

Wisdom, M. J. ), Alan A. Ager ), H.
K. Preisler ), N. J. Cimon ), and
B. K. Johnson ), "Effects of off-road recreation on
mule deer and elk". Transactions of the North American Wildlife and
Natural Resources Conference 69, 2004, pp.531-550.
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!

Old May 27th 08, 03:21 AM posted to alt.mountain-bike,rec.bicycles.soc,rec.backcountry,ca.environment,sci.environment
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On May 26, 8:57*pm, Mike Vandeman wrote:
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I just bought a new bike, I did my share.

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