Four-year soil erosion rates in a running-mountain trail in eastern Iberian Peninsula

During the last decades, the use of mountain trails for running is more and more popular. New trails are opened to allow the runners to practice and compete. This form of human impact on the landscape is new as the new trails do not follow the conservation strategies in design and maintenance as traditional mountain trails constructed by farmers, shepherds and muleteers do. This impact of sport events in nature is not measured and we know little about this impact on vegetation, fauna and soils. We surveyed in September 2018 a trail that was opened in September 2014 and was used for four official mountain trail races, and for training by local runners. Our interviews with organizers and users show that 1054 runners passed during the competition days (4 races in 4 years) and over the 4-year period the trail was used approximately 43,800 times by a runner. We measured the current topography and calculated the soil lost. The results show extremely high erosion rates in the sloping terrain, with the highest rates in the north-facing slope, reaching up to 180.29 Mg ha-1 y-1, while in the flat section of the trail soil erosion rates are 107.56 Mg ha-1 y-1 and in the south-facing slope trail 128.93 Mg ha-1 y-1. Our study demonstrates that (i) soil erosion rates on trails can be easily estimated by measuring the deepest trail position enabling fast and cheap surveys; and (ii) that there is a need to establish conservation strategies on new trails to avoid non-sustainable soil losses in the Mediterranean mountains due to the sport activities such as the mountain trail races.