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



 
 
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Old November 3rd 11, 05:04 PM posted to alt.mountain-bike,rec.bicycles.soc,rec.backcountry,ca.environment,sci.environment
Mike Vandeman[_4_]
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Default The Impacts of Mountain Biking on Wildlife and People -- A Review ofthe 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)

Introduction:

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
vehicles).

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".

Another problem with the study is that the hikers and mountain bikers
used trails that were significantly different, prior to the
experiment!: "The results from Part A of Table 4 suggest that the
trails used for the five treatment types were not similar in terms of
their sediment yield behavior prior to the treatments. Trail plots
used for hikers were statistically different from one of the other
groups (off-road bicycles) at the .05 level" (p.84). This makes it
even less likely that the hiker-mountain biker comparison is valid.

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 measuring.

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
bikers.

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 biking.

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
question.

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.

Summary:

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.

References:

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

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, http://www.mountainbike.co.nz/politi...acts/index.htm..

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.

Holzer, K. , 2008-07-10 "Bike Paths and New Ponds: Amphibian
Restoration in the Pacific Northwest" Paper presented at the annual
meeting of the International Congress for Conservation Biology,
Convention Center, Chattanooga, TN. 2010-06-06 from
http://www.allacademic.com/meta/p244181_index.html

Lathrop, Jason, "Ecological impacts of mountain biking: a critical
literature review". 2003, http://www.wildlandscpr.org/resource...kingreport.htm.

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,
pp.573-82.

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, http://www.imba.com/resources/scienc...t_summary.html.

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
http://mjvande.nfshost.com/india3.htm.

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,
http://mjvande.nfshost.com/sustain.htm.

Vandeman, Michael J. ), 2008. The Impacts of
Mountain Biking on Amphibians and Reptiles. In Urban Herpetology. J.
C. Mitchell, R. E. Jung Brown, and B. Bartholomew, editors. Society
for the Study of Amphibians and Reptiles, Herpetological Conservation
3:155-156; expanded version also available at http://mjvande.nfshost.com/herp.htm.

Vandeman, Michael J. ) http://mjvande.nfshost.com/white..htm
and http://mjvande.nfshost.com/marion.htm.

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.
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Old November 4th 11, 07:24 PM posted to alt.mountain-bike,rec.bicycles.soc,rec.backcountry,ca.environment,sci.environment
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Default The Impacts of Mountain Biking on Wildlife and People -- A Reviewof the Literature

On Nov 3, 12:04*pm, Mike Vandeman wrote:
The Impacts of Mountain Biking on Wildlife and People --
A Review of the Literature
Michael J. Vandeman, Ph.D.
July 3, 2004


Means nothing now that you're a criminal.

 




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