Cycling into the forest: what impact this has on nature

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Veronika Mitterwallner is a sports ecologist at the University of Bayreuth. In an interview with MIT Technology Review, she talks about her study, in which she and colleagues investigated the environmental impact that mountain bikes can have- including those with electric drives.

Ms. Mitterwallner, in one of the first review articles ever, you outlined the consequences that cycling can have on nature - and mountain biking in particular. How did you come up with the topic?

There were two reasons for this. Personally, I really enjoy spending time in the mountains, both on foot and on my bike. The peace and quiet and experiencing nature have a very positive, grounding and relaxing effect. In doing so, however, I have also begun to ask myself what effect I am having on my natural environment in return. At the same time, the topic was increasingly discussed in the media - from my point of view often on an emotional, not very factual level.

For both of these reasons, my colleagues and I decided that it was imperative to establish a factual, evidence-based foundation - and began to systematically compile scientific evidence on the impacts of mountain biking on natural systems. What's really new about our study, however, is that we've also done research on the ecological impacts of electrically assisted mountain bikes.

Cycling is generally considered to be environmentally friendly. Why isn't that necessarily the case with mountain biking?

Cycling mostly takes place in urban terrain or at least on paved paths, which is why one might not speak of a direct interaction with natural systems. However, a road or housing developments are also built where natural ecosystems used to be - and in the process soil is compacted, sealed and barriers are created for animal and plant species. But cycling is environmentally friendly in terms of CO2 emissions, which are vanishingly small, especially compared to cars.

Mountain biking takes place directly in natural ecosystems such as forests, meadows or mountains and thus also interacts more directly with soils, vegetation and wildlife. Even if the system is disturbed in the process, this is not necessarily hostile to the environment. Disturbances can have a positive effect on biodiversity.

Initially, it was mainly city bikes that were electrified, but now e-drives and rechargeable batteries are increasingly being found in mountain bikes as well. Are these exacerbating the negative effects on nature? Why?

Unfortunately, this cannot yet be assessed conclusively. We had to realize that the length of studies on the effects of electrified mountain biking is still very thin. In our review, we have therefore used the results of conventional mountain biking to discuss the extent to which the changes in riding behavior when using electric assistance leads to an intensification of the effects. Since the electric motor makes it possible to ride faster, longer, and farther - and also supports the overcoming of a greater altitude difference and the riding of technically more difficult passages - we see a potential for electrified mountain biking to take place in more sensitive, previously untouched systems.

This would have a negative impact especially when riding off trails, which is easier with an electric motor than without. At the same time, electrification opens up mountain biking to other groups of people than before, and you can see that sales figures are rising enormously and in some cases more e-MTBs are sold than conventional MTBs. This could also be an indication that more people are mountain biking natural systems. Whether there is some kind of stress limit for ecosystems or individual species is unfortunately difficult to say. This is hard to separate from other influences and depends on how stable the population is in each case and how tolerant the individual species is to disturbance.

You write that especially the first creation of a route is a problem. Why is that?

When the path is first laid, the vegetation is destroyed, the soil is compacted and partially eroded. Afterwards, hardly any further changes occur, except that more severe erosion takes place on the path itself as long as it is not paved - since a fortifying effect of plants and their roots is missing and the soil can absorb water more poorly due to compaction. However, it must also be said that the small-scale increase in habitat heterogeneity can promote diversity in the adjacent plant community.

What advice do you give to municipalities that want to decide to build a mountain bike trail - for tourism reasons, for example?

I would consider repurposing existing trails to prevent re-fragmentation of the landscape. Areas used for other purposes, such as former ski slopes or skid trails, could also be suitable. In addition, if the mountain bike trail is to be built in sensitive habitats or protected landscape areas, conservation assessments can evaluate whether construction is likely to endanger protected animal and plant species.

What you write also applies to the creation of a trail network for hikers or runners. Are mountain bike trails really worse?

This is difficult to evaluate. It is true that the same path networks are used to a large extent and that it is therefore difficult to separate the effects. There are studies that have separated the activities and then analyzed their effects on soils or plants, but these are difficult to transfer to reality, where it also depends heavily on the individual behavior of the respective athletes. For example, at what times they are on the road and whether they leave the path. In addition, one would have to take into account the actual proportion of mountain bikers and hikers in the terrain, which would certainly vary depending on the area.

Many cyclists see themselves as the most ecological road users. Do we need to rethink this - in view of the raw material consumption for the vehicles and possible damage to nature caused by path construction?

In my personal opinion: No, you don't have to. However, you should think about where and when you move and behave considerately towards the natural and social environment. It is always a question of proportion. The current man-made climate crisis - and the biodiversity crisis we are in - has worse consequences for natural ecosystems than mountain biking. In addition, there are studies that show that ecological awareness is increased by outdoor sports like mountain biking, which in turn can have a positive effect on our everyday and sporting behavior in relation to the environment.

(bsc)