||Recreational use of nature areas is increasing worldwide. All trail-based activities have a certain degradation effect on vegetation and soil, and conflicts between conservation values and recreation may occur. Controversy still exists regarding the relative impact of mountain bikers compared to hikers on trails. In Norway, mountain biking is allowed on existing, multiuse trails outside of protected areas, but within protected areas restrictions vary, whereas hiking is allowed. A governmental proposal suggests to allow for mountain biking on trails in national parks in line with hiking, but restrictions could be introduced if effects from biking are more severe than from hiking and in conflict with conservation values. For managers, knowledge about the effects of opening trails for new user groups in national parks is highly needed: will mountain biking cause other and more severe effects on trails, and thus provoke higher and other trail maintenance needs, or are effects similar to that if hikers? In this study, we investigated trail degradation from increased use of trails from hikers and ountain bikers under different climatic conditions. Two study sites were selected, one located in an oceanic climate zone and the other in a continental zone. In each site, two trails were selected, one to be predominantly used by hikers and one by mountain bikers. The trails were natural-surfaced, occurring in natural vegetation, and with a variation in topography and plant communities. We contacted local groups through different channels (personal contact, e-mails, announcements on Facebook groups) and encouraged the use of the study trails throughout the summer of 2019. Mountain bikers were informed of the designated biking trails only, and we created Strava segments that were distributed to bikers. The oceanic biking trail was used for a local Endoru race from May-August, whereas the continental trail was part of a mountain bike race in end-August. Hikers were informed of the designated hiking trails only, and we mounted information signs in each end of the trails encouraging people to take a detour.Passes were counted with TRAFx counters.