Mark Ballantyne

The impacts of trail infrastructure on vegetation and soils: current literature and future directions.

Reflecting the popularity of nature-based activities such as hiking and mountain biking, there are thousands of kilometres of recreational trails worldwide traversing a range of natural areas. These trails have environmental impacts on soils and vegetation, but where has there been research, what impacts have been found and how were they measured? Using a systematic quantitative literature review methodology, we assessed the impacts of trails on vegetation and soils, highlighting what is known, but also key knowledge gaps. Of the 59 original research papers identified on this topic that have been published in English language peer-reviewed academic journals, most were for research conducted in protected areas (71%), with few from developing countries (17%) or threatened ecosystems (14%). The research is concentrated in a few habitats and biodiversity hotspots, mainly temperate woodland, alpine grassland and Mediterranean habitats, often in the USA (32%) or Australia (20%). Most examined formal trails, with just 15% examining informal trails and 11% assessing both types. Nearly all papers report the results of observational surveys (90%), collecting quantitative data (66%) with 24% using geographic information systems. There was an emphasis on assessing trail impacts at a local scale, either on the trail itself and/or over short gradients away from the trail edge. Many assessed changes in composition and to some degree, structure, of vegetation and soils with the most common impacts documented including reduced vegetation cover, changes in plant species composition, trail widening, soil loss and soil compaction. There were 14 papers assessing how these local impacts can accumulate at the landscape scale. Few papers assessed differences in impacts among trails (7 papers), changes in impacts over time (4), species-specific responses (3) and only one assessed effects on plant community functioning. This review provides evidence that there are key research gaps including assessing informal trails, comparing trail types, landscape and temporal scale impacts, functional responses and impacts on threatened ecosystems/species. A more diverse geographic spread of research is also required including in regions experiencing rapid growth in tourism and recreation.

Ecotourism as a threatening process for wild orchids

Orchids are a charismatic and highly diverse group of plants, many of which are threatened by human activities. Nature-based tourism is contributing to the decline of some wild orchid populations, although this has rarely been discussed in the tourism literature. We therefore provide a scoping assessment to demonstrate that tourism contributes to the loss of some orchids in the wild by direct collecting, habitat clearance and trampling, and/or indirectly by increasing the impact of other threats such as weeds, pathogens and climate change using data on Australian threatened orchids. Increased recognition and more research are required into the role of nature-based tourism in the declines of these and other species of threatened plants as well as into the ways in which impacts can be mitigated.

Tourism and recreation listed as a threat for a wide diversity of vascular plants: a continental scale review.

Tourism and recreation are diverse and popular activities. They may also contribute to the risk of extinction for some plants because of the range and severity of their impacts, including in protected areas: but which species, where and how? To evaluate the extent to which tourism and recreation may be threatening process for plants, we conducted a continental level review of listed threats to endangered vascular plants using data from Australia. Of the 659 vascular plant species listed as critically endangered or endangered by the Australian Government, tourism and recreation were listed as a threat(s) for 42%. This is more than those listed as threatened by climate change (26%) and close to the proportion listed as threatened by altered fire regimes (47%). There are plant species with tourism and recreation listed threats in all States and Territories and from all but one bioregion in Australia. Although more than 45 plant families have species with tourism and recreation listed as threats, orchids were the most common species listed as at risk from these threats (90 species). The most common types of threats listed were visitors collecting plants in protected areas (113 species), trampling by hikers and others (84 species), damage from recreational vehicles (59 species) and road infrastructure (39 species). Despite the frequency with which tourism and recreation were listed as threats in Australia, research quantifying these threats and methods to ameliorate their impacts are still limited. Although this lack of information contributes to the challenge of managing tourism and recreation, impacts from visitors will often be easier to manage within natural areas than those from larger scale threats such as altered fire regimes and climate change.

Differences in the impacts of formal and informal recreational trails on urban forest loss and tree structure

Recreational trails are one of the most common types of infrastructure used for nature-based activities such as hiking and mountain biking worldwide. Depending on their design, location, construction, maintenance and use, these trails differ in their environmental impacts. There are few studies, however, comparing the impacts of different trail types including between formal management-created trails and informal visitor-created trails. Although both types of trails can be found in remote natural areas, dense networks of them often occur in forests close to cities where they experience intense visitor use. To assess the relative impacts of different recreational trails in urban forests, we compared the condition of the trail surface, loss of forest strata and changes in tree structure caused by seven types of trails (total network 46.1 km) traversing 17 remnants of an endangered urban forest in Australia. After mapping and classifying all trails, we assessed their impact on the forest condition at 125 sites (15 sites per trail type, plus 15 control sites within undisturbed forest). On the trail sites, the condition of the trail surface, distance from the trail edge to four forest strata (litter, understory, midstorey and tree cover) and structure of the tree-line were assessed. Informal trails generally had poorer surface conditions and were poorly-designed and located. Per site, formal and informal trails resulted in similar loss of forest strata, with wider trails resulting in greater loss of forest. Because there were more informal trails, however, they accounted for the greatest cumulative forest loss. Structural impacts varied, with the widest informal trails and all formal hardened trails resulting in similar reductions in canopy cover and tree density but an increase in saplings. These structural impacts are likely a function of the unregulated and intense use of large informal trails, and disturbance from the construction and maintenance of formal trails. The results demonstrate that different types of recreational trails vary in the type and range of impacts they cause to forests. They highlight the importance of careful consideration towards management options when dealing with trail networks especially in areas of high conservation value.

Shrub facilitation is an important driver of alpine plant community diversity and functional composition

Facilitation often occurs in environments where extreme climatic factors favour positive rather than negative species interactions. This includes larger ‘nurse’ cushion plants in some alpine environments that shelter other species from abiotic filters such as abrasive winds and low temperatures. This type of facilitation can contribute to higher alpha (within habitat), beta (between habitats) and gamma diversity (across the community), by facilitating species with less stress tolerant but more competitive functional traits otherwise excluded from these communities. We assess whether shrubs play a similar role in facilitation, using the dominant prostrate shrub Epacris gunnii in a high conservation value plant community along the highest ridgeline in the Australian Alps. Differences in alpha and beta diversity, species and functional composition were compared in and out of shrubs using point sampling and quadrats. Shrub habitat enhanced alpha (species richness per plot) and beta diversity resulting in greater gamma diversity for the community as a whole, with twice as many species associated with the shrub than open quadrats. There were also differences in functional composition with vegetation in shrub quadrats being taller with larger leaves. It seems that E. gunnii creates micro-refugia that assist in the range expansion of more productive but less stress-tolerant species, including some endemics, in the community. Alpine shrubs can therefore occupy a similar facilitative role to that of cushion plants in alpine plant communities and therefore may also be important drivers of diversity and functional composition.

Sustained impacts of a hiking trail on changing Windswept Feldmark vegetation in the Australian Alps.

Damage to vegetation from tourism and recreation includes the impacts of hiking trails, which may favour trampling-tolerant plants over those that are more sensitive to this type of disturbance. To assess how continued use of a hiking trail coupled with changes in local climate affect a rare Australian alpine plant community, we compared plant composition at different distances from a trail in 2013 during wetter conditions with that 10 years prior during a drought in 2003. In both years, only a few trampling-tolerant graminoids and cushion plants were found on the trail surface, which runs along the ridgeline. Species richness and cover in both surveys generally increased with distance from the trail, but there were differences between the windward and leeward sides of the trail. This included increased abundance of some species but continued disruption of shrub succession on the leeward side of the trail. There was an overall increase in species richness between the two surveys, and changes in the abundance of many species independent of trampling effects, possibly reflecting the more favourable/wetter conditions for plant growth in 2013. These results suggest that changes in climatic conditions can affect community composition, but that this has not negated the impact of the hiking trail on this rare community. With average temperatures increasing, and snow cover declining in the Australian Alps, it is likely that there will be even more changes in the Windswept Feldmark, including the potential colonisation of these ridges by more competitive species, such as graminoids, at the expense of the dominant shrub and some herbs that are already adversely affected by trampling. Longer term monitoring of this rare community is imperative to better understand community processes in relation to the impacts of trail use and climate change. Management options to reduce these impacts are discussed.

Comparing the impacts of different types of recreational trails on grey box grassy-woodland vegetation: lessons for conservation and management

Tourism and recreation are popular in natural areas but can damage plant communities, including those of high conservation value in protected areas. This includes impacts from recreational trails, but what type of trail has the most impact and why? We compared the impacts of five different trails (narrow, intermediate and wide bare earth trails, intermediate gravel trails and wide tarmac trails) on the endangered grey box grassy-woodland (Eucalyptus microcarpa (Maiden) Maiden) in Belair National Park near Adelaide in South Australia. First, the extent, width and area of recreational trails in the remnant woodland were mapped. Then, vegetation parameters were recorded in quadrats at three distances from the edge of trails in the woodland, with 10 replicate sites per trail type and single quadrats at 10 control sites (i.e. total 60 sites, 160 quadrats). All trails resulted in vegetation loss on the trail surface and along the edges of the trails, as well as changes in vegetation composition, including reductions in shrubs and bulbs close to the trail. The most common types of trail were bare earth trails with an average width of 2.5 m (50% of trails) which resulted in the greatest soil loss (>88 000 m3) and vegetation loss (33 899 m2 or 3.4 ha) in the 167 ha woodland remnant overall. Wider (5.4 m) hardened tarmac trails, however, were associated with low species richness, high cover of exotic grasses and few herbs, shrubs and bulbs compared with vegetation away from trails and closer to other trails. Therefore a mixed approach to the provision of trails may be most appropriate, with hardened trails used in areas of highest use, but in some circumstances leaving trails unhardened may be more appropriate where they are likely to remain narrow and where there is less likely to be erosion and/or safety issues.