Assessing the Environmental Impacts, Condition and Sustainability of Mountain Biking Trails in an Urban National Park.

Mountain biking is a popular recreational activity in natural areas, with thousands of formal trails designed, constructed and maintained by land managers. Increasingly, there are also rising numbers of informal trails created by riders. A challenge for land managers is identifying, assessing, and then mitigating environmental impacts created by trails, including in protected areas. Here we assessed mountain biking trails in a large, popular national park on the Gold Coast, Australia, addressing the currently limited research comparing the extent, environmental impacts, condition and sustainability of these trails. Impacts from the 31.4 km of formal and 33.7 km of informal trails through the forests in Nerang National Park (1659 ha) included soil erosion (16.48 m3) and loss of vegetation along and adjacent to the trails (90,955 m2). Formal trails were six times more popular and wider on average (1.1 m vs 0.7 m) than informal trails, but less incised than informal trails (4.6 cm deep vs 6.3 cm). Generalised Linear Models showed that Trail Grade, slope and alignment best-predicted trail condition, highlighting the importance of good trail design in minimising trail impacts. It is recommended most of the informal trails are closed and rehabilitated, as they were not well-designed, increase fragmentation and have environmental impacts, with some traversing ecologically sensitive areas. In addition, some formal trails need to be upgraded to deal with erosion and other impacts. More broadly, the increasing demand for mountain biking must be addressed, including exploring opportunities to promote areas outside of national parks while minimising environmental impacts and other challenges associated with the creation and use of informal mountain bike trails in protected areas.