Edges - their effect on vegetation and wildlife (Australia)

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The "edge effect" is a term used to describe the various consequences, on vegetation and wildlife, that occur as a result of one type of vegetation sharing a border with another. These edges may be natural, such as forest grading into woodland, streamside vegetation passing through an arid zone, burnt and unburnt areas; or induced, such as pasture abutting forest or a road through a forest.

Edges may have a variety of effects on wildlife. For example, when thin, narrow strips of roadside vegetation and larger, square forest blocks in northern Victoria were compared, they shared only one common bird species, the Willie Wagtail (Bennett, 1993). This can be attributed to the large amount of edge habitat typical of roadsides and its consequences for the fauna of this habitat.

Managing edge effects can improve the quality and long-term viability of wildlife habitats.

An increase in traffic or human activities is not often considered. Many wildlife species rely on the seclusion of undisturbed habitat in order to breed successfully. For example, the Wedge-tailed Eagle has been known to abandon its nest due to disturbance (J. Robinson pers. comm.).

Edge effects are likely to be most influential on narrow strips or small areas of habitat. Consequently, they are an important issue in the management of corridors and small bush blocks. Larger areas are also vulnerable where disturbance, track construction and other activities create edges.

Noise disturbance along highways: Kuranda Range Road upgrade project (Australia)

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A review of scientific literature was undertaken in order to identify known effects to wildlife caused by exposure to traffic noise. The research project was designed to collect daytime noise-level data along the Kuranda Range Road, north of Cairns, with the primary aim of accurately representing third-octave noise conditions through the rainforest adjacent to the road at heights of one and fifteen metres above the forest floor under varying microtopography. A secondary objective was to delineate any acoustic refugia (areas of relative quiet shielded from traffic noise) along the current road and examine potential impacts on these from the proposed road upgrade.

Distribution and abundance of roadkill on Tasmanian highways: human management options (Australia)

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An obvious sign of potential human impact on animal populations is roadkill. In Tasmania, this impact is perceived as relatively greater than in other Australian states, and is often noted by visitors and locals alike, such that calls for management action are common in the popular press. The goal of this three-year study was to assess the frequency and distribution of species killed on Tasmanian roads. Seasonal surveys were completed along five major routes, for a total of 154 trips. Over 15 000 km of road were surveyed and 5691 individuals in 54 taxa were recorded for an average roadkill density of 0.372 km-1. Over 50% of encountered roadkill could be identified to species, with common brushtail possums (Trichosurus vulpecula) and Tasmanian pademelon (Thylogale billardierii) the most common species identified, both in overall numbers and frequency of trips encountered. The 10 most common taxa accounted for 99% of the items observed. The seasonal occurrence, relationship with vehicle speed, and clustering in local hotspots for particular taxa all suggest that mitigation measures, such as vehicle speed reduction in specific areas, may be effective in reducing the number of animals killed. Mitigation measures, however, will not apply equally to all species and, in particular, success will depend on changing human behaviours.

The impacts of off-road vehicle noise on wildlife (USA)

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The noise of off-road vehicles is among their least-endearing qualities to hikers, mountain bikers, and other non-motorized recreationists. The noise of ORVs can do more than simply annoy humans, however. ORV noise can cause significant adverse impacts to wildlife in at least two ways. First, exposure to ORV noise can result in hearing impairment or even loss, with severe consequences for animals dependent on their sense of hearing for finding prey, avoiding predators, and interacting with other individuals of the same species. Second, wildlife exposed to ORV noise often experience stress and other disturbance effects.

Over time, such impacts can lead to altered movement patterns, behavioral changes, and long-term stress impacts, all with potentially significant adverse results.

Roads and traffic: effects on ecology and wildlife habitat use, applications for cooperative adaptive management (USA)

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Since the 1960s, there has been a dramatic increase in both the number of vehicles on our Nation’s roadways and the number of roadway miles. From 1960 to 2003, State motor vehicle registrations tripled from nearly 74 million to over 231 million; the total miles of public roads increased from 3.5 to nearly 4 million; and the annual vehicle distance traveled grew from 719,762 to 2.8 million miles. In addition, the sale and use of off-highway vehicles also has skyrocketed. With the construction of new roads, increased use of motorized vehicles, and increasing dispersal of the human population to more rural areas, wildlife populations are losing habitats. As they are being forced to navigate through temporally and spatially fragmented habitats, they are losing genetic diversity and experiencing increased mortality from a variety of sources. The objective of this task is to provide simultaneous monitoring of (1) the daily, seasonal, and annual movements of wildlife species of interest (initially elk), and (2) the use of motorized vehicles in western Colorado. The resulting data will provide natural resource managers with crucial information on the relationships between elk habitat use and movements, as well as the density and distribution of roads and concomitant use of motorized vehicles. Close collaboration with local management agencies provides options for manipulating accessibility of public lands and observing wildlife responses.

Synthesis of noise effects on wildlife populations (USA)

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This report contains a partial summary of a literature review dealing with the effect of noise on wildlife emphasizing the effects on birds. Beginning with studies in the Netherlands and, later, in the United States, a series of studies have indicated that road noise has a negative effect on bird populations (particularly during breeding) in a variety of species. These effects can be significant with ‘effect distances’ (i.e., those within which the density of birds is reduced) of two to three thousand meters from the road. In these reports, the effect distances increase with the density of traffic on the road being greatest near large, multilane highways with high densities. A similar effect has been reported for both grassland and woodland species. It is important to note that 1) not all species have shown this effect and 2) some species show the opposite response, increasing in numbers near roads or utilizing rights-of-way. It is important to determine the cause of this effect and to utilize additional or alternative methods beyond population densities as the sole measure of effect distance, because the latter is susceptible to variation due to changes in overall population density. Recommendations for further study are given, including alternative measures of disturbance in birds.