The influence of Weaver and Dale’s (1978) paper,“Trampling effects of hikers,motorcycles and horses in meadows and forests”

Abstract

Trampling of vegetation and soils by recreational activities is a recurrent concern in many lands where trail use is common. The degree of impact can vary with the myriad types of trail users. The Weaver and Dale article, “Trampling effects of hikers, motorcycles and horses in meadows and forests”, was the first to provide some insights about how different trampling agents might produce varied impacts. Weaver and Dale showed that horses and motorcycles produced greater impacts to soils and vegetation than hikers. This article appeared early in a relatively young field of study. The direct results of their research are still valuable today, but the greater impact of their paper was that it ushered in a phase of experimental trampling research that is ongoing. Because of their research and continual influence, land managers can now make better decisions about what type of recreation activity to discourage or encourage.

Keywords

Trampling recreation experimental trampling

I Introduction

Weaver and Dale’s (1978) article on the effects of recreational trampling in meadows and forests was a seminal article at the interface of physical geography and recreation ecology. This article presents the effects of experimental trampling resulting from hikers, horses, and motorcycles in forests and meadows. It was the first research paper to employ experimental trampling protocol to compare the impact of different user groups. In addition to comparing different trail users, this paper evaluated the impact on slopes versus flat ground, and in meadows versus forest. Weaver and Dale’s (1978) paper ushered in a wave of comparative trampling research. Comparative trampling studies undoubtedly play an important role in understanding recreation impacts on soils, surface vegetation, and erosion.

The breadth of the research field at the time of publication (1978) was limited. This is evidenced by the fact that of the mere 15 citations in the Weaver and Dale paper, only 10 of those cited papers discuss recreational and human trampling. Of those nine papers, six discuss trampling by hikers (Bayfield, 1973; Bell and Bliss, 1973; Dale and Weaver, 1974; Helgath, 1975; Liddle, 1975; Rogova, 1976), one discusses impacts of motorcycles (Davidson and Fox, 1974), one discusses only soil impacts for foot and car paths in dunes (Liddle and Greig-Smith, 1975), and two are bibliographies about outdoor recreation and carrying capacity (Speight, 1973; Stankey and Lime, 1973). Bayfield’s (1973) study of deterioration on paths in Scotland and Liddle’s (1975) evaluation of the ecological effect of human trampling, like Weaver and Dale’s (1978) article have become commonly cited works in recreation and trampling research. The limited works upon which Weaver and Dale built their study is indicative of this field of research at the time. Further, consider the date range of these cited works, and that the two cited bibliographies about carrying capacity dealt more with user perceptions and over-crowding than physical impacts.

II The authors

This classic paper was the culmination of research on trampling effects in the northern Rocky Mountains by the same authors (Dale and Weaver, 1974; Weaver and Dale, 1974). Dunn Dale also completed his Master’s degree at Montana State University with a thesis “Effects of trail use under forests in the Madison Range, Montana”, in 1973. It seems apparent that their initial investigations into trampling and human impact in and around trail systems motivated them to undertake the comparative study discussed herein.

Theodore (Tad) Weaver is currently a professor emeritus in the Department of Ecology at Montana State University. Donn Dale currently runs a fly-fishing guide service with his son. Figure 1 shows Donn Dale hard at work (http://www.flyfishbigsky.com/about-us/).

Figure 1.

Donn Dale hard at work. Source: http://www.flyfishbigsky.com/about-us/.

III Details of paper

The Weaver and Dale research was conducted in two vegetation types common to the northern Rocky Mountain region, the grasslands (Poa pratensis–Festuca idahoensis), and Pine forest (Pinus albicaulis). Figure 2 shows a landscape that is similar to where their research was conducted, with Festuca idahoensis in the foreground and Pinus albicaulis in the distance. They chose to locate sites in flat (0 degree) and sloping (15 degree) terrain. The soils were similar sandy loams. They set up trampling grids for each; hiker, horse, and motorcycle. The trampling agents included two hikers (91 kg and 82 kg), a 90 cc motorcycle, and three horses (500 kg, 550 kg, and 579 kg). They trampled each site 1000 times and sampled the surface and underlying soil after each successive 100 passes. The parameters sampled were: % bare ground, tread width, tread depth, and bulk density.

Figure 2.

A landscape that is similar to where Weaver and Dale’s (1978) research may have been conducted, with Festuca idahoensis in the foreground and Pinus albicaulis in the distance. Source: https://commons.wikimedia.org/wiki/File:Festuca_idahoensis_(3811039793).jpg.

Weaver and Dale found that bare ground increased with increased number of passes. Generally, the impact was greater on sloping sites and in shrub vegetation. Sites with grass cover were more resistant to impact. On level ground, they document that horses were most destructive. On sloping sites, the motorcycle was more destructive than horses. They attribute this to the motorcycle wheel spinning and skidding when going up and down hill, respectively. They found that there was no difference between motorcycles and horses in dwarf shrub sites.

Trail width increased with the number of passes. This experimental setting supported earlier findings by Dale and Weaver (1974) showing that trail width increases with the logarithm of the number of users. Trail widths were generally greater on sloping sites and with horses.

Trail depth increased with increasing use, was greatest on slopes, was greater where stones were absent in the substrate, and was greatest with horses. The increased trail depth on slopes was attributed to the increased potential for erosion on sloping sites. Soil compaction, in addition to erosion, is a factor that determines trail depth. Soil compaction was greater on slopes, and as a result of the impacts of horses.

The results that revealed the gradation of lower impact hikers to higher impacts of motorcycles and horses had strong implications for trail management, which were discussed. For their study, Weaver and Dale limited the speed of the motorcycle to ∼20 km/h. They note that if the motorcycle was driven less conservatively, the damage could be greater.

With greater impact on sloped sites, they recommended that slopes over 15 degrees should not be used for trails. One intriguing conclusion they reached was,

Motorcycle damage was greatest when going uphill while hiker and horse damage was greatest when going downhill; where a choice is available, wear on trails would be minimized if motorcycles ascended gentle slopes and descended steep slopes while hikers and horses ascended steep slopes and descended gentle slopes. (Weaver and Dale, 1978: 456)

Weaver and Dale reported that horse impact was greater because of the greater weight of the horse being distributed on a relative small and hard hoof. This finding has been corroborated by many other research efforts. Many of the citations of their work are related to this finding that horse impact is substantially greater than hikers.

IV Influence on later publications

Weaver and Dale’s paper has had a lasting impact on recreation ecology and anthropogeomorphology research. The impact of this work has received steady attention since publication, and it seems that this classic paper is gaining more attention in recent years. Web of Science shows this paper having 85 citations. Web of Science provides histograms of the number of citation per year for first-tier (Figure 3) and second-tier citations (Figure 4). A first-tier citation is one which cites the article directly, and second-tier citations are citations of articles that cited the original work. These two histograms show how Weaver and Dale’s work has had a direct influence on many articles and a larger indirect influence on the research field. They also show that interest in the article has remained steady, with a slight increase in citations in the more recent years. The second-tier citations show that this particular field of research is gaining more interest and seeing more publications – a trend that I expect to continue.

Figure 3.

First tier: direct citations of Weaver and Dale (1978) per year as of April 14, 2016 as reported on Web of Science.

Figure 4.

Second tier: citations of papers that cited Weaver and Dale (1978) per year as of April 14, 2016 as reported on Web of Science.

Scanning thorough the 85 papers cited on Web of Science, this classic paper has informed studies about the impact of humans, horses, bicycles, and off-road vehicles. The locations and environments of concern in these studies influenced by Weaver and Dale’s paper include; forests, mountains, coasts, heathers, meadows, grasses, subalpine zones, and herbaceous plants; some of which are located around trails, campsites, and sensitive habitats.

Weaver and Dale’s (1978) paper influenced a range of research topics. The most direct influence is that it began the discussion about the variation of trampling impacts on soils and surface features from various recreational user groups. Understanding that different types of recreation activities yield different types of impacts is paramount to making positive management decisions. Some of the comparisons that Weaver and Dale’s paper likely inspired include: hiking, horse riding, and mountain biking (Pickering et al., 2010); hiking, skiing, and horse riding (Torn et al., 2009); hikers, horses, and llamas (Cole and Spildie, 1998); horses, hikers, motorcycles, and mountain bikes (Wilson and Seney, 1994); pedestrians and cyclists (Vogler and Butler, 1996); hikers and pack animals (Barros et al., 2013); hikers, mountain bikers, and off-highway vehicles (Lei, 2004); off-road vehicles, hikers, and horses (Sack and da Luz, 2003); and hikers and mountain bikers (Thurston and Reader, 2001). The author of this paper (Ross Martin) has conducted an experiment comparing the impact of a cyclocross bike with narrow tires and a mountain bike with fat tires (under review). Some general management-centric observations gleaned from these comparative studies are that horse impact greater than hiking or biking (Pickering et al., 2010), motorized vehicles, including motorcycles, present the greatest impact (Lei, 2004; Sack and da Luz, 2003; Wilson and Seney, 1994), and wheeled trampling from motorcycles or mountain bikes presents a very different pattern of impact than feet or hooves (Thurston and Reader, 2001; Vogler and Butler, 1996; Wilson and Seney, 1994).

As evidenced by the wide range of comparative trampling studies, Weaver and Dale’s (1978) research has had a lasting impact on studies of recreation and surface erosion, and that legacy continues to the present day.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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