Monitoring and modelling walking track impacts in the Tasmanian Wilderness World Heritage Area, Australia

A program has been developed for monitoring the condition of unimproved walking tracks on a 1000-km track system in Western Tasmania, and it has been used as the basis of an eight-year study of track-impact development. The monitoring technique involves measuring track depth and two track-width indicators at permanently marked and widely dispersed sites, each site comprising ten transects located at 2-m intervals. Sites have been ‘typed’ on the basis of track slope, drainage and substrate characteristics, and the typing scheme has been tested and refined by assessing the relationship between type-usage groups and observed impacts. Analysis reveals that track depth and rates of erosion are strongly influenced by track type and to a lesser extent by usage, while track width is influenced mainly by usage and track bogginess. me-invariant variable ‘usage gradient’ was introduced to compensate for the fact that usage levels on most walking tracks in Western Tasmania have varied over time. Data derived from multiple inspections at 2–3 year intervals since 1994 from over 250 sites have been used to derive impact/time curves for different type-‘usage gradient’ groups. Each of the impact variables can be approximated by the formula m=αtB, where m is the expected value of the impact variable, t is chronological time, and α and B are constants characteristic of the impact variable and type-‘usage gradient’ group in question. The typing scheme and impact-development model have the potential to be used for systematically describing and predicting impacts over extensive systems of ‘typed’ tracks. The implications of these findings for the ongoing monitoring, siting and management of walking tracks are discussed.