M
Mike Vandeman
Guest
On 26 Sep 2004 11:29:30 GMT, [email protected]ospam (Stephen Baker) wrote:
..MV blathers:
..
..>Name a more destructive activity allowed in parks, liar.
..
..Ummm..... Horse riding (equestrianism for you snobs) Certainly more
..destructive per rider.
Not true. See:
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 nature: 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".
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 ([email protected]) and Kriwoken
([email protected]), claiming that there was "no significant difference
between hiking and biking trail wear". I wasn't able to acquire this study, but
it is apparent from Gary's description of it that he (and perhaps the authors)
misstated the conclusions. 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.)
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).
..MV blathers:
..
..>Name a more destructive activity allowed in parks, liar.
..
..Ummm..... Horse riding (equestrianism for you snobs) Certainly more
..destructive per rider.
Not true. See:
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 nature: 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".
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 ([email protected]) and Kriwoken
([email protected]), claiming that there was "no significant difference
between hiking and biking trail wear". I wasn't able to acquire this study, but
it is apparent from Gary's description of it that he (and perhaps the authors)
misstated the conclusions. 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.)
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).