How mountain bikers promote – or damage? – plant diversity

This article was published in our newsletter. Sign up here.

 a mountain biker cycles over dyed plant seeds.

A hike up onto the Kybfelsen rocks is rewarded by a spectacular view of the city of Freiburg and of the Upper Rhine Plain. At an altitude of around 800 metres, the Kybfelsen rocks are a popular destination for locals and tourists alike. It is not only hikers who make their way up to the top – plenty of mountain bikers are also out and about.

Mountain bikes – seed transporters

When mountain bikers go off-road, one side effect is that they scatter plant seeds over wide areas. Plant ecologist Dr Gesine Pufal from the University of Freiburg and Fabio Weiss, an environmental science student, have explored exactly how this happens. They scattered dyed seeds of different shapes and sizes around this popular mountain biking region and then cycled along the route themselves. On damp forest paths, they found that mountain bikes can transport seeds which stick to their tyres for distances of up to 500 metres. If the seeds stick to the frame or saddle of the bike, they can be carried for up to five kilometres. They discovered that flat and needle-shaped seeds adhered particularly well, while round seeds quickly fell off again.

dyed plant seeds on the tyre of a mountain bike

Plants find new habitats

When seeds are transported over considerable distances to other areas, this can have positive but also negative effects on biodiversity. For example, mountain bikers may leave the path and pick up the seeds of cow parsley, a plant commonly found by the side of paths. If the seeds then happen to be deposited on a meadow, the fast-growing cow parsley could crowd out other plants and disrupt the delicate ecosystem.

“Transporting seeds can also have a beneficial impact on biodiversity, however”, says researcher Dr Gesine Pufal. If the seeds of rare plants are taken far away and germinate at a new site, they may find a permanent new habitat. “That said, the bike obviously does not choose the seeds it picks up”, the plant ecologist points out.

Mountain bikers urged to respect the environment

Dr Gesine Pufal, whose research at the University of Freiburg focuses among other things on humankind’s impact on biodiversity, therefore recommends that mountain bikers stick to the paths, especially in wet weather and when cycling in conservation areas. “To avoid spreading seeds between different habitats, cyclists should also clean their bikes between different tours”, advises the plant ecologist. She adds that this is already common practice in countries like New Zealand which face huge problems with introduced species.

University of Freiburg

Founded in 1457, the University of Freiburg offers undergraduate, doctoral and post-doctoral degree courses in all the major disciplines: the humanities, economics, natural and engineering sciences, medicine, law and theology. More than 24,000 students from over 100 nations are matriculated in 180 degree programmes at eleven faculties.