Recreational Effects

Bibliography regarding the effects of recreation on natural resources and habitats of open-space lands

The purpose of this bibliography is to share information with decision makers and other interested persons regarding human impacts, primarily from recreation, on wildlife and their habitats of Front Range open spaces. By providing summaries of impartial, peer-reviewed scientific studies and interpretations, the intent of this document is to help guide decisions and directions, which are commonly passed down from elected officials to open-space departments in our communities. The articles are annotated with an italicized summary, in which quotations marks enclose passages taken verbatim from that article. A few review articles are also listed.

The intended audience includes elected officials (e.g., Boulder City Council members, Boulder County Commissioners), appointed boards that provide advice on open-space issues and policies, and other government officials, such as the Boulder City Manager. This document will be given to such individuals. It will be updated periodically by scientists affiliated with Friends of Boulder Open Space (FOBOS), which provides this text and digital files of the articles and (or) abstracts on the FOBOS website.

The scientific articles listed here represent only a small fraction of articles available on recreational impacts. We do not wish to overwhelm readers with a long document but instead to present some relevant and, where possible, recent results. All articles have long lists of cited publications that can be consulted for earlier studies. Moreover, the naturalists and ecologists on open-space staffs are familiar with these articles and many others. With this compilation, we do not intend to supplant a critical function of these experts in communicating ecological science to their managers and communities. Instead, we would like simply to facilitate the retrieval of relevant literature, so that all interested parties can quickly be “on the same page” when it comes to accessing scientific knowledge bearing on management of our landscapes and natural resources in the face of increasing recreational uses and more trails.

The City Open Space and Mountain Parks Department has now made available online copies of the many studies it has funded to look at different aspects of the system. This is an excellent portal to be able to review years of research that has been done respecting the city’s open space and mountain park lands.

Boulder County Parks and Open Space has also made many of its research studies available on line. An Excel spreadsheet with the links can be found here.

1. Effects of dogs on wildlife

adobe_pdfBanks, P.B. and Bryant, J.V., 2007, Four-legged friend or foe? Dog walking displaces native birds from natural areas: Biology Letters. Doi10.1098/rsbl2007.0374.

The presence of humans without dogs caused significant declines in diversity and abundance of birds, but the impacts of dogs, even restrained on-leash, resulted in greater displacement of birds and more severely diminished local bird fauna. Considering a zone within 50 meters (about 150 feet) of the trail as the zone of influence by dogs (all on-leash), observations indicated that “dog walking in woodland leads to a 35% reduction in bird diversity and 41% reduction in abundance. These results argue against access by dog walkers to sensitive conservation areas.” “Local wildlife does not become habituated to continued disturbance by dogs.”

adobe_pdfMiller, S.G., Knight, R.L., Miller, C.K., 2001, Wildlife responses to pedestrians and dogs: Wildlife Society Bulletin v. 29 (1), p. 124-132.

Three treatments, consisting of solitary pedestrians, a pedestrian accompanied by a dog on-leash, and a dog alone (all treatments both on- and off-trail), were used to study effects on mule deer and three songbird species. Wildlife responses varied near trails. All four species were negatively affected by off-trail users.

adobe_pdfMiller, J.A., and Hobbs, N.T., 2000, Recreational trails, human activity, and nest predation in lowland riparian areas: Landscape and Urban Planning, v. 50 (4), p. 227-236

At four lowland riparian sites in eastern Boulder County, clay eggs were used to simulate bird nests to study predation rates at varying proximity to recreational trails. Birds attacked more nests near trails than away from trails, but native predatory mammals (e.g., mice and squirrels) appeared to avoid nests near trails to some extent. “These results support the contention that recreational trails and human activity may affect nesting success for some species.”

Lowry, D.A. and McArthur, K.L., 1978, Domestic dogs as predators on deer: Wildlife Society Bulletin, V. 6 (1), p. 38-39.

Written by an employee of the Idaho Fish and Game Department, this short article describes harassment and predation by dogs that resulted in direct and indirect mortality of deer in northern Idaho where residences are interspersed throughout deer winter range.

2. Effects of recreational trails on habitats/wildlife

adobe_pdfSarah E. Reed & Adina M. Merenlender, Quiet, Nonconsumptive Recreation Reduces Protected Area Effectiveness

Protected areas around the world were created with the goals of preserving biodiversity and providing nature-based recreation opportunities for millions of people. This dual mandate guides the management of the majority of the world’s protected areas, but there is growing evidence that quiet, nonconsumptive recreation may not be compatible with biodiversity protection. We combined noninvasive survey techniques and DNA verification of species identifications to survey for mammalian carnivores in 28 parks and preserves in northern California. Paired comparisons of neighboring protected areas with and without recreation revealed that the presence of dispersed, nonmotorized recreation led to a five-fold decline in the density of native carnivores and a substantial shift in community composition from native to nonnative species. Demand for recreation and nature-based tourism is forecasted to grow dramatically around the world, and our findings suggest a pressing need for new approaches to the designation and management of protected areas.

adobe_pdfMiller, S.G., Knight, R.L., Miller, C.K., 1998, Influence of recreational trails on breeding bird communities: Ecological Applications 8 (1), p. 162-169.

Bird species diversity, composition, and abundance were assessed in proximity to recreational trails on City of Boulder open space in 1994-95. In both grassland and forest ecosystems, areas with increasing distance from trails harbored more species, more individuals, and higher nest survival of young birds, for many important bird species. A nest predator (magpie) fared better closer to trails.

Blumstein, D.T. Fernandez,-Juricic, E., Zollner, P.A., and Garrity, S.C., 2005, Inter-specific variation in avian responses to human disturbance: Journal of Applied Ecology, v. 42, p. 943-953. (doi:10.1111/j.1365-2665.2005.01071).

Transient human activity disturbs birds, leading to declines in species numbers.

Stenhouse, R., 2004, Fragmentation and internal disturbance of natural vegetation reserves in the Perth metropolitan area, Western Australia: Landscape and Urban Planning, v. 68 (4), p. 389-401.

A close association was found among recreational path density, high levels of fragmentation, weed infestation, and low vegetation condition.

3. Effects of horses on soil stability and erosion

Deluca, T.H., Patterson, W.A., Friemund, W.A., Cole, D.N., 1998, Influence of llamas, horses, and hikers on soil erosion from established recreation trials in western Montana, USA: Environmental Management, v. 22 (2), p. 255-262.

Horses turn up more soil than hikers leading to more sediment yield and thus creating more erosion.

Cole, D.N. and Spildie, D.R., 1998, Hiker, horse, and llama trampling effects on native vegetation in Montana, USA: Journal of Environmental Management, v. 53, p. 61-71.

Horses, more than hikers, expose soil and have greater impact on relative cover of resident vegetation. The study area included two types of forest vegetation.

4. Effects of horses on spread of weeds

Wells, F. and Lauenroth, W.K., 2007, The potential for horses to disperse alien plants along recreational trails: Rangeland Ecology and Management, v. 60 (6), p. 574-577.

Because it is common for horses to graze in “weedy” pastures and because their feed may be contaminated by alien plants, horses may be an important cause of introducing invasive plant species far into previously non-invaded wildlands. In this study, seedlings were grown from samples of horse dung collected along a recreational trail in the White River National Forest (Colorado). In replicate plantings, 85% of seedlings were alien species. “Our results make clear that horses used on recreational trails represent a potentially important dispersal vector for alien plants in western wildlands.”

5. Effects of dogs on spread of weeds

Sime, C.A., 1999, Domestic dogs in wildlife habitats effects of recreation on rocky mountain wildlife. A Review for Montana. Montana Chapter of The Wildlife Society.

A Wildlife Biologist for the Montana Fish, Wildlife, and Parks (Kalispell) writes, “domestic dogs do pick up and transport seeds in their hair and paws. While the scale of noxious weed seed transport by dogs is small compared to that of motorized vehicles, dogs can travel and deposit seeds in locations far removed from roads and trail systems. Because these areas are not traveled as frequently as roads, emerging weed plants may go undetected and not be treated in a timely manner.”

6. Effects of other or general disturbances on the spread on non-native plant species

Note: Trails, especially those created by gouging or tilling or in any way moving or removing soil, represent one of the most common and widespread disturbances on open-space land. There are numerous examples of noxious weed invasion along the edges of open-space trails.

Bradford, J.B. and Lauenroth, W.K., 2006, Controls over invasion of Bromus tectorum: The importance of climate, soil, disturbance, and seed availability: Journal of Vegetation Science, v. 17, p. 693-704.

Frequent soil disturbance causes more cheatgrass in invaded areas, and higher seed availability causes faster invasion. Disturbance and cheatgrass invasion are connected primarily by the ways in which disturbed soils acquire and utilize water.

Knick, S.T. and Rotenberry, J.T., 1997, Landscape characteristic of disturbed shrubsteppe habitats in southwestern Idaho (USA): Landscape Ecology 12, 287-297.

There is a strong connection between disturbance of grassland and shrubland and the invasion of cheatgrass.

Larson, D.L., 2002, Native weeds and exotic plants: relationships to disturbance in mixed-grass prairie: Plant Ecology, v. 169 (2), p. 317-333 DOI:10.1023/A102604810307.

The effects of soil disturbance of mixed grass prairie by prairie dogs, roads, and constructed trails were studied in national parks in North and South Dakota. Exotic species were more likely than native weeds to have spread beyond the disturbed areas into native prairie.

7. Review articles and other resources

Boyle, S.A. and Samson, F.B., 1985, Effects of non-consumptive recreation on wildlife: A review: Wildlife Society Bulletin, v. 13, p. 110-116.

From 74 cited scientific articles, the authors categorized original reports of impacts, including 91 reports on impacts related to hiking/camping and wildlife observation/photography. Of these, 65 reports documented negative effects (16 concluded indeterminate or no effect).

adobe_pdfCollinge, S.K., and others, 2004, Scientific principles for management of City of Boulder open space lands.

For decision-makers, this document articulates the scientific principles that may inform policies to implement the Visitor Master Plan, summarizes consequences of alternative actions regarding these policies, and states the relevance of the precautionary principle.

Montana Chapter of the Wildlife Society, 1999, Effects of recreation on Rocky Mountain wildlife: A review for Montana. [Highly relevant to Front Range wildlife and habitats. Each chapter was reviewed by several experts.]

  • Overview, Chapter 1
  • Amphibians and reptiles, Chapter 2
  • Birds, Chapter 3
  • Small mammals, Chapter 4
  • Semi-aquatic mammals, Chapter 5
  • Ungulates, Chapter 6
  • Carnivores, Chapter 7
  • Domestic dogs in wildlife habitats Chapter 8
  • Vegetation, soils, and water, Chapter 9
  • Online bibliography, Chapter 10

adobe_pdfLenth, B.E., 2006, The effects of dogs on wildlife: Masters thesis, Fort Collins, Colorado State University. (abstract attached)

adobe_pdfTaylor, A.R. and Knight, R.L., 2003, Wildlife responses to recreation and associated visitor perceptions: Ecological Applications, v. 13(4), p. 951-963. (abstract attached).

adobe_pdfFletcher, R., McKinney, S., and Bock, C., 1999, Effects of recreational trails on wintering diurnal raptors in a Colorado grassland, The Raptor Research Foundation, Inc. Study on Boulder OSMP land.

This study compared prairie sites with a riparian corridor, with and without pedestrian/biker trails in the riparian corridor. In sites with no trails, species richness, perching frequency, and abundance of raptors was greater. Eagle abundance was strongly affected by the presence of trails.

Meany, C., Ruggles, A., Clippinger, N., and Lubow, B., The impact of recreational trails and grazing on small mammals in the Colorado piedmont (Boulder OSMP study along South Boulder Creek)

Population density of Preble’s Meadow Jumping Mouse was 31% lower on sites with trails than on sites without trails.

Cole, D.N. and Schreiner, E.G.S., 1981, Impacts of backcountry recreation: Site management and rehabilitation: U.S. Department of Agriculture Forest Service, General Technical Report INT-121. (title page attached)


adobe_pdfDogs on the Trail, Even on a Leash, Give Birds a Fright

adobe_pdfImpacts of Rec Trails on Exotic and Ruderal Species Distribution in Grassland Along the Colorado Front Range

adobe_pdfHabitat Fragmentation and Pollination

adobe_pdfInfluence of Recreational Trails on Breeding Bird Communities

adobe_pdfRestoration Ecology to the Future: A Call for a New Paradigm

adobe_pdfRelationship between Human Disturbance and Wildlife Use in Urban Habitat Fragments

adobe_pdfRecommended Changes to the Trail Study Area Planning Process for Public Review

adobe_pdfEstimating Visitation to Boulder Open Space and Mountain Parks

adobe_pdfVisitor Characteristics and Beliefs about Boulder Open Space and Mountain Parks

adobe_pdfWhat are the “novel ecosystems” emerging along the Colorado Front Range?

adobe_pdfPrairie dogs and dust storms: Managing novel ecosystems