Outside Voice

Here is my Outside Voice blog on TheInterTwine.org .

You can also find NWTA's case for MTBs in Natural Areas. [LINK]

Mountain Bikes don't belong in Natural Areas

Lost in thought, in a Natural Area...

Mountain Bikes are an intrusion on wildlife habitats, and they disturb the peace and quiet local natural areas offer to humans who visit them.

What are 'Natural Areas'? They aren't just any old pieces of undeveloped land in some 'natural' state. By Natural Area, we refer to an officially designated area, set aside for posterity by some collective action of people. Various natural areas are defined technically and legally by state, local, and federal agencies. Examples are Research Natural Area, Wilderness Area, State Natural Area, Wildlife Refuge, Wilderness Study Area, and so on. The Intertwine is home to quite a few such Natural Areas.

To more fully answer the question of whether Mountain Bikes belong in Natural Areas, we can think critically about several aspects.

  • What kind of land is required to support mountain biking?
  • Is the sport consistent with the conservation values typically ascribed to Natural Areas?
  • Is it reasonable to expect that mountain biking experiences can be provided near everyone's home?
  • What are the impacts on nature?


Mountain Biking, by definition requires the elevation drop provided by hillsides. Portland hills are mostly covered with houses and streets, with streams under-grounded. The steepest hillsides have been left undeveloped, carved by natural streams. A few of those hillsides have been protected against development. The question for many is whether these native hillsides should be carved up by downhill runs for wheels.

Ranunculus Repens - Creeping Buttercup

Two images associated with mountain biking come to mind. One is a biker or bikers treading slowly along a verdant level trail, seemingly at the same rate as a hiker. One can compare square inches of contact of two tires on the trail with the area of treads on a pair of boots, and so on. The weight of a mountain bike is a slight addition. This is a very appealing image shown to the public. In some contexts, such as a ride along a river or on a desert trail, this would be an honest image of that off-road experience. A better name might be trail bike used for bike camping, where bikes can extend the range of a hiker, assuming good trail conditions. Even so, a biker might go off trail into the grass of a fragile meadow or over cryptobiotic crust, forever scarring that desert skin.

The other image is of a mountain bike literally flying down hill, wheels off the ground, throwing dirt off to the side while skidding around corners, bouncing over rocks and roots, splashing through a stream, and so on. Examining the trail, one might find skid marks made by an unskilled biker who was afraid to go with the flow, dirt formed into jumps and banks, and gouges where the bike comes back to earth. A trail crew makes repairs from one day to the next.

The first image might be considered consistent with conservation values, but the second clearly does not, just based on the flying machinery.

Many natural areas allow passive recreation. Passive recreation includes walking, hiking and birding in small groups. Active recreation includes running, cycling, groups such as the Hash House Harriers, and so on. The thumps, whooshes, whoops and screams of two mountain bikers flying downhill are signatures of active recreation. There's nothing wrong with active recreation, it just doesn't belong in a natural area.

We are often shown a family of little kids biking along a wooded trail or road. It would be great if these experiences were available close to home, for everyone. There are such urban trails, but this can't be expected realistically in an urban area without projects such as the Green Loop, shown recently during Portland Design Week. The Green Loop would be a purpose-built environment, not a wooded trail. It may even be possible to develop mountain biking experiences in the city using parts of the urban landscape. But, a lovely family outing can't be used to justify an expensive downhill sport in a natural area.

Mountain Bikes may have no significant impact on the volume of water flowing out of a natural area, but there is an impact on water quality when bikers run amuck. Wear and tear on trails is of less concern, since trails can be engineered (literally) to handle wear, and even water runoff. Noise and rapid movement, however, cannot be avoided. Higher momentum generates unnatural sounds that stress fauna.

A popular, accessible site will attract a large number of mountain bikers. While group size and time of group rides might be limited, individuals would ride all the time. Could their total numbers be limited by permits? Doubtful. Mountain Bikers even ride at night with fancy lights.

Mountain bike trail builders have a propensity to dig and move dirt to build new trails. A warren of trails often arises to make use of unused slopes.

There are additional aspects to consider.

The Fight for Access

Some mountain bikers believe that their sport is not an intrusion, and that they are being discriminated against. They sometimes argue that they are an excluded class of users. But bikes have no right to go everywhere that people go. This has been decided by a U.S. District Court in the Northern District of California.

Surveys showing how many people enjoy off-road cycling include the use of Springwater Corridor, the Banks-Vernonia Trail, and other such trails in the region. These stats can't be used to justify single-track mountain bike trails. Single-track trails are about the width of a mountain bike, as opposed to these wider commuter paths.

A trail going through a natural area as part of a transportation link could be nice for a few, but what about volume? Many cyclists would enjoy a quiet ride through nature on the way to work. Would ten morning riders be disruptive? What if 25 commuted through a natural area? It depends where the path runs, of course, but I hope you get my point. It sounds wonderful when one does it, but when 100 do it, we have the Tragedy of the Commons.

How might such a passage through a Natural Area be justified for connectivity purposes?

Taxes & Levys

Many tax payers are mountain bike owners. So? Many are also gun owners, dog owners, and so on.

A voter-approved Metro levy funding natural areas supports clean water, healthy fish and wildlife habitat, and opportunities to connect with nature. The argument goes that the Metro levy approved by voters said nothing about bikes (or dogs) being excluded. True, there was no exhaustive list of things excluded. That does not imply that bikes are permitted. It is more in tune with the spirit of the levy that significant natural resource spaces be protected for wildlife and water quality. In fact, those conservation values are the basis for their protection. We are so lucky that green spaces were formed before they were all gone, as they are near many other cities.

Think of it this way: Would a majority of voters approve a bond measure that funded land acquisition specifically for downhill mountain biking? Not likely. There may be a few sub-areas in large natural areas suitable for dogs and for bikes, but leashes and wheels do not mix safely. Each would require their own acreage. Wanting to protect natural areas from dogs and bikes is not being selfish.

Intentional Protections

Forested natural areas have certain conservation easements, environmental overlays, and/or other legal protections. Any use must be consistent with goals for conservation and sustainability. There is little doubt that lawsuits would challenge any mountain biking trails planned in a protected natural area, regardless of promised corporate donations or pledged trail-building volunteers.

Call to Action

Let's Protect our Natural Areas, and minimize human impact by allowing only passive recreation. We might allow individuals, and at most, small groups on foot. It makes it very simple, and unambiguous.

Please consider writing your Metro councilor, the Metro president, and/or Portland city councilors to express your concern for allowing mountain bikes in natural areas.


City of Portland
Ananda Fritz, Amanda@portlandoregon.gov
Nick Fish, Nick@portlandoregon.gov
Dan Saltzman, Dan@portlandoregon.gov
Chloe Eudaly, Chloe@PortlandOregon.gov

Additional Reading

  • Portland's Off-Road Cycling Master Plan [LINK]
  • Buxton to Stub Stewart MTB trail Mountain Bike Trail, Banks, Oregon [LINK]
  • Sandy Ridge Trail System [LINK]
  • Gateway Green, a 25-acre former Multnomah County jail site [LINK]
  • Green Grand Rapids report [LINK]
  • Sierra Club Policy on Bicycles [LINK]
  • International Mountain Biking Association Environmental Impacts of Mountain Biking [LINK]
  • Salmonberry Trail Project [LINK]
  • PDX Green Loop Project [LINK]

John Miller

John Miller is a retired computer scientist living in Southwest Portland. His interests range from transit systems, to stained glass, to recreational mathematics.

John served as chair of his neighborhood for eight years, as president of Southwest Neighborhood Inc, as chair of the Multnomah Country Citizen Involvement Committee, and as the only citizen member on Metro's Regional Urban Growth Goals and Objectives PAC. John was lecturer and system co-ordinator at Lewis & Clark College, and was System Architect for Metro. He volunteers with Cycle Oregon on the week long ride, and with Travel Portland's Visitor Information Center. John writes here out of personal concern for the natural world. He has an ancient StumpJumper bike with fat tires.