Impacts of off-road vehicles (ORVs) on macrobenthic assemblages on sandy beaches

Sandy beaches are the prime sites for human recreation and underpin many coastal economies and developments. In many coastal areas worldwide, beach recreation relies on the use of off-road vehicles (ORVs) driven on the shore. Yet, the use of ORVs is not universally embraced due to social conflicts with other beach user groups and putative environmental consequences of vehicle traffic on sandy shores. Such ecological impacts of ORVs are, however, poorly understood for endobenthic invertebrates of the intertidal zone seawards of the dunes. Consequently, this study quantified the degree to which assemblages of intertidal beach invertebrates are affected by traffic. The study design comprised a series of temporally replicated spatial contrasts between two reference sites (no ORVs) and two beaches with heavy ORV traffic (in excess of 250,000 vehicles per year) located in SouthEast Queensland, Australia. Macrobenthic assemblages on ORV-impacted beaches had significantly fewer species at substantially reduced densities, resulting in marked shifts in community composition and structure. These shifts were particularly strong on the middle and upper shore where vehicle traffic was concentrated. Strong effects of ORVs were detectable in all seasons, but increased towards the summer months as a result of heavier traffic volumes. This study provides clear evidence that ORVs can have substantial impacts on sandy beach invertebrates that are manifested throughout the whole community. Demonstrating such an ecological impact caused by a single type of human use poses a formidable challenge to management, which needs to develop multi-faceted approaches to balance environmental, social, cultural, and economic arguments in the use of sandy shores, including management of "beach traffic."