Effects of Roads on Animal Abundance: an Empirical Review and Synthesis

By L. Fahrig, T. Rytwinski. 2009

1,205 citations recorded by the source corpus.

The authors attempted a complete review of the empirical literature on effects of roads and traffic on animal abundance and distribution. They found 79 studies, with results for 131 species and 30 species groups. Overall, the number of documented negative effects of roads on animal abundance outnumbered the number of positive effects by a factor of 5; 114 responses were negative, 22 were positive, and 56 showed no effect. Amphibians and reptiles tended to show negative effects. Birds showed mainly negative or no effects, with a few positive effects for some small birds and for vultures. Small mammals generally showed either positive effects or no effect, mid-sized mammals showed either negative effects or no effect, and large mammals showed predominantly negative effects. The authors synthesized this information, along with information on species attributes, to develop a set of predictions of the conditions that lead to negative or positive effects or no effect of roads on animal abundance. Four species types are predicted to respond negatively to roads: (i) species that are attracted to roads and are unable to avoid individual cars; (ii) species with large movement ranges, low reproductive rates, and low natural densities; and (iii and iv) small animals whose populations are not limited by road-affected predators and either (a) avoid habitat near roads due to traffic disturbance or (b) show no avoidance of roads or traffic disturbance and are unable to avoid oncoming cars. Two species types are predicted to respond positively to roads: (i) species that are attracted to roads for an important resource (e.g., food) and are able to avoid oncoming cars, and (ii) species that do not avoid traffic disturbance but do avoid roads, and whose main predators show negative population-level responses to roads. Other conditions lead to weak or non-existent effects of roads and traffic on animal abundance. The authors identify areas where further research is needed, but they also argue that the evidence for population-level effects of roads and traffic is already strong enough to merit routine consideration of mitigation of these effects in all road construction and maintenance projects.

Subfields: Ecology, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/891e7e0d314693e96c51274562789b5731d3fe08

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Citations in the corpus

Connecting natural landscapes using a landscape permeability model to prioritize conservation activities in the United States (2012, methodology): “…habitat loss near roads because of use (i.e., human activity), we converted the annual average daily traffic (AADT; number of vehicles) using a quadratic kernel density that assumes the impact t declines with distance out to 1 km away from a road (Forman et al. 2003; Fahrig & Rytwinski 2009).”
The effects of urbanization on North American amphibian species: Identifying new directions for urban conservation (2012, background): “…responses to urbanization We assessed the degree and strength of the response by each species to urbanization and assigned one of the following four responses for each species in each study: negative, positive, neutral, and unknown (no assessment offered) (similar to Fahrig and Rytwinski 2009).”
Effects of habitat quality and access management on the density of a recovering grizzly bear population (2018, background): “Many species are negatively affected by roads (Fahrig & Rytwinski, 2009); African lions (Panthera leo), wild dogs (Lycaon pictus), cats (Felidae sp.) and apes (Gorilla and Pan sp.) are among the charismatic megafauna faced with increased roads and resulting demographic consequences (Ceia- Hasse et…”
Do species life history traits explain population responses to roads? A meta-analysis (2012, background): “1), which is consistent with previous studies (e.g. Gibbons et al., 2000; Cushman, 2006; Eigenbrod et al., 2008; Fahrig and Rytwinski, 2009; Patrick and Gibbs, 2010).”
No single solution: application of behavioural principles in mitigating human–wildlife conflict (2016, background): “However, myriad species are affected by AVCs without subsequent damage to a vehicle or human injury (e.g. Fahrig & Rytwinski, 2009; Glista, DeVault, & DeWoody, 2008; Mckenna, Mckenna, Malcom, & Berenbaum, 2001; Soluk, Zercher, & Worthington, 2011).”
The impacts of roads and other infrastructure on mammal and bird populations: a meta-analysis. (2010, background): “However, the few attempts to quantify the effects of infrastructure (UNEP, 2001; Nellemann et al., 2003b; Fahrig and Rytwinski, 2009), or to model the vulnerability of animal populations to road effects (Jaeger et al., 2005), are not based on meta-analysis, which is the statistical procedure for…”
Amphibian distribution in a traditionally managed rural landscape of Eastern Europe: Probing the effect of landscape composition (2010, background): “…(ii) have an obligate aquatic phase usually in ponds, and (iii) because of the seasonal migration between land and water habitats, amphibians are sensitive to the landscape configuration, including man-made structures such as roads that may cause high mortality (Fahrig and Rytwinski, 2009).”
Direct Mortality of Birds from Anthropogenic Causes (2015, neutral): “Meta-analyses of the indirect effects of roads have shown clear declines in local bird abundance near roads (Fahrig & Rytwinski 2009, Benitez-Lopez et al. 2010), but these responses may be at least partially driven by other road-related stressors, such as habitat loss and noise.”
Roads and wildlife: impacts, mitigation and implications for wildlife management in Australia (2010, background): “However, on the basis of numbers of declining species worldwide, amphibians may be particularly sensitive to road effects (e.g. Lesbarrères et al. 2006; Arens et al. 2007; Glista et al. 2008; Fahrig and Rytwinski 2009).”
Sampling biases shape our view of the natural world (2020, background): “The consequences of lacking data from more-diverse, intact ecosystems and their species are manifold (Fahrig and Rytwinski 2009).”
Amphibian decline, pond loss and reduced population connectivity under agricultural intensification over a 38 year period (2017, background): “…urbanization and arable cultivation (Greenwald et al. 2009; Riley et al. 2005; Trochet et al. 2016) and the heavy toll that roads inflict on amphibian populations is well documented (Fahrig and Rytwinski 2009; Garriga et al. 2012; Glista et al. 2008; Hartel et al. 2010; Rytwinski and Fahrig 2012).”
Roads and supplemental feeding affect home-range size of Slovenian red deer more than natural factors (2012, background): “Transportation routes and their associated anthropogenic disturbances (e.g., vehicles, noise, light, hikers, and hunters) may affect habitat selection and activity of individuals and demography (Fahrig and Rytwinski 2009; Forman and Alexander 1998; Trombulak and Frissell 2000).”
Relative effects of road mortality and decreased connectivity on population genetic diversity (2011, background): “Such mortality often leads to reduction in population size (reviewed in Benítez-López et al., 2010; Fahrig and Rytwinski, 2009).”