Soil erosion on mountain trails as a consequence of recreational activities. A comprehensive review of the scientific literature.

This article reviews the scientific literature on trail erosion and the magnitude of the erosive processes that occur on mountain trails due to recreational activities, mainly due to hiking. This work is necessary as a result of the increase in hiking and biking in forest, scrubland and grasslands, and the soil and vegetation degradation induced by these activities. We analysed results that have been compiled in the scientific literature, as well as other issues such as the geographical and temporal distribution of the research, the methods applied, the journals where the research was published, the types and quantity of uses of the pathways and the measures undertaken for damage mitigation. This paper highlights that there is a need for harmonization of methods. The results show that soil erosion rates are highly variable, high, and non-sustainable. Trail erosion research is growing at a rate of 3 papers per year and is published in a small group of scientific journals. Six journals published 47% of the papers on trail erosion, which show a high concentration in environmental journals. There are few papers published in the soil science and geomorphology disciplines, although the research topic and the science background are in these two disciplines. Reported world soil losses from trails ranged from 6.1 Mg ha-1 y-1 to 2090 Mg ha-1 y-1, all of which are not sustainable. Trail erosion has mainly been investigated in the USA and is a new topic in other regions of the world. There is a need to implement mitigation measures to avoid land degradation, and this should be researched in the near future as right now most of the research describes and quantifies the problem but does not provide solutions: mitigation, rehabilitation or restoration. From a pure scientific approach, we claim that there is a need to research the connectivity of flows and the role of the trails on runoff generation and then sediment yield at pedon, slope and watershed scales. There is a need to research the mechanisms of the soil erosion process in trails: trampling effect, wheel impact, factors and seasonal and temporal changes.

Three topographical approaches to survey soil erosion on a mountain trail affected by a forest fire. Barranc de la Manesa, Llutxent, Eastern Iberian Peninsula.

Soil erosion on mountain trails threaten the sustainability of soils and vegetation. There is a wide theoretical knowledge about the effects produced by mountain recreational activities, but particularly for soil erosion there is a shortage of field data. This is why it is necessary to properly survey the soil losses on mountain trails. The most widely applied method in scientific literature is the Cross-Section field survey as is easy-to-apply and low-cost. However, there is a doubt about its accuracy and the development of the new technologies may improve the quality and accuracy of the measurements. Aerial and terrestrial photogrammetric methods are difficult to apply when vegetation is present but, an opportunity arises to apply this method when fire takes place. This paper analyses the soil losses in a recently fire-affected land to check the accuracy of the three methodologies to assess soil loss on mountain trails. The results obtained show an average soil loss between 1287 and 1404 Mg ha-1 of trail erosion for the three methodologies applied, which implies that the Cross-Sectional-Area method, aerial photography and terrestrial photography provide very similar values. Therefore, the conventional Cross-Section field surveys method is useful and adequate to evaluate the impacts generated on mountain trails as it provides accurate measurement and can be repeated any time and below different vegetation covers. The terrestrial photogrammetric methods are accurate too, but they can only be used when there is very little vegetation cover such as in semiarid and arid landscapes or after forest fires. Moreover, they are more expensive and time consuming.

Soil erosion on the "El Portalet" mountain trails in the Eastern Iberian Peninsula.

Leisure activities in natural areas have experienced a large increase in popularity. In Mediterranean ecosystems, research on soil erosion in agriculture and forest fire affected land has been well developed but trail erosion has not been widely studied. In this work we evaluated two trails in the eastern Iberian Peninsula to assess soil erosion rates and provide new data. The study area is located in a semi-arid Mediterranean climate (around 400 mm y-1) and in limestone terrain with scarce soil development. The average erosion rates were 24.39 Mg ha-1 y-1 and 40.40 Mg ha-1 y-1 for the "Barranc de la Cova de la Hedra" and "Casa del Racó" study trails, respectively. These are non-sustainable rates due to the shallow soils and slow soil development in Mediterranean ecosystems. We found that the depth at the centre of the trail and the maximum depth measured could quickly and easily assess soil erosion rates in the mountain trails. Measuring the width and depth in the centre of the trail can assess 91% of the total erosion and reduces the time of the survey by 80%.