Roadkill: The Hidden Environmental Hazard On Roads

Roadkill is a serious issue that has gained prominence in academic research, especially with the increasing expansion of road infrastructure. It refers to the mortality of animals caused by vehicles on roads, and it has been estimated that millions of animals are killed annually due to this issue. The impact of roadkill is not limited to animal deaths, as it also includes environmental pollution. This is a concern when roadkill carcasses are improperly disposed of near waterways, leading to potential water contamination. Additionally, roads themselves contribute to pollution, such as noise pollution, and facilitate the spread of invasive species. The negative consequences of roadkill extend beyond the environmental realm, as animal-vehicle collisions also result in human fatalities, injuries, and significant financial costs.

Roadkill impacts on endangered species

Roadkill is a significant cause of mortality for endangered species with small populations. It is estimated that roadkill is responsible for 50% of deaths of Florida panthers, and is the largest cause of badger deaths in England. It is also a primary cause of death for the Andean cat, a critically endangered species, and the koala, among many other threatened species.

In addition to immediate mortality, roadkill also has indirect negative impacts on endangered species populations. Roads create barriers to dispersal, cause habitat change and fragmentation, promote pollution (e.g. noise), alter the microclimate, facilitate the spread of invasive species, and increase human activities such as hunting and deforestation. These factors can lead to population decline and even local extinction for vulnerable species. For example, in Florida, vehicle collisions are responsible for 90% of known bear deaths and an increased risk of extinction.

Certain hotspots, such as areas with high traffic volume and proximity to bodies of water, are associated with higher mortality rates for endangered species. Understanding the conditions under which roadkill is most prevalent can help inform infrastructure management decisions to protect vulnerable species. For instance, the installation of wildlife crossings, fencing, underpasses, or overpasses can effectively reduce animal-vehicle collisions.

Data collection through roadkill observation systems and citizen science platforms is crucial for identifying vulnerable species and implementing targeted mitigation measures. These efforts can help guide road planning and wildlife protection strategies to minimize the impact of roads on endangered species.

Overall, the impacts of roadkill on endangered species are significant and contribute to population decline and potential extinction. Addressing this issue through data-driven solutions and infrastructure planning is essential for conserving biodiversity and maintaining healthy ecosystems.

Human health and safety

Roadkill poses a significant threat to human health and safety, with millions of animals killed on roads annually, from small insects to large mammals. This not only includes the direct impact on animal populations but also the potential for disease transmission to humans.

Firstly, roadkill can lead to human fatalities and injuries when vehicles collide with animals. In the United States, an estimated one to two million animals are killed in vehicle collisions each year, resulting in an animal death every 26 seconds. This leads to significant costs to society, with the insurance industry estimating that animal-vehicle collisions result in approximately $200 million in annual costs for fatalities and injuries. The Federal Highway Administration (FHWA) has reported that more than 200 motorists are killed and thousands more are injured in such collisions annually.

Additionally, roadkill can contribute to the spread of zoonotic diseases, which are known to have an animal source or vector. Direct contact with infected bodily fluids, tissues, or contaminated surfaces during roadkill removal poses a risk of disease transmission to humans. While the likelihood of pathogen survival in a deceased animal host is low, amplifier hosts like flies and ticks can also transmit diseases. The COVID-19 pandemic has heightened awareness of zoonotic spillover events, bringing this lurking danger to the forefront of scientific research and public interest.

Moreover, roadkill is indicative of a larger issue: the increasing proximity between humans and wildlife due to expanding infrastructure and roadways into forested areas. This proximity increases the potential for human-animal contact and the transmission of zoonotic diseases. Additionally, roads contribute to habitat loss and fragmentation, and ecological detriments for animals, including restricted access to food and water sources.

To mitigate these risks, several strategies have been proposed, including the construction of wildlife crossings, tunnels, and underpasses. These structures aim to reduce animal-vehicle collisions and the associated human health and safety risks while also preserving wildlife habitats and connectivity. Implementing speed limits and warning signs near wildlife crossing areas can also help reduce collision risks, although their effectiveness varies depending on enforcement and driver compliance.

Waterways and other natural environments

Roadkill is a significant cause of pollution in waterways and other natural environments. It is a "preventable natural disaster", according to Fraser Shilling, director of the UC Davis Road Ecology Center. Roads are known to cause damage to forests, prairies, streams, and wetlands, and they also alter water-flow patterns, increase noise, water, and air pollution, and create disturbances that alter the species composition of nearby vegetation.

Road salts, primarily chlorides of sodium, calcium, or magnesium, can be toxic to sensitive plants and animals and are a common cause of pollution in waterways. Sand can also alter stream bed environments, causing stress for the plants and animals that live there. De-icing chemicals, salts, chlorides, and nutrients from particulate pollution, such as nitrogen and phosphorus, can trigger trophic cascades in adjacent waterways. These chemicals leave the road surface in water runoff or water spray and can cause heavy metal bioaccumulation in adjacent plants.

The design, construction, and management of roads, as well as the design and regulation of vehicles, can change their environmental impact. Wildlife crossings, such as underpass tunnels, viaducts, and overpasses, can help reduce roadkill and provide connectivity between habitat areas, combating habitat fragmentation. Speed limits and "animal crossing" warning signs are also recommended to reduce roadkill, although data shows that speed zones do not reduce collisions without increased enforcement.

In addition to the direct impact on animal populations, roadkill also has economic implications. Wildlife-vehicle collisions cost California more than $200 million every year, and the insurance industry estimates that individual motorists can expect to pay at least $2,000 for vehicle repairs each time they hit a large animal.

Overall, roadkill is a significant cause of pollution in waterways and other natural environments, and it is important to implement measures to reduce its occurrence and mitigate its impact on the environment.

Road design and planning

Roadkill is a significant issue that affects wildlife and the environment. It is caused by the collision of vehicles with animals, resulting in the death of millions of animals annually and contributing to habitat loss and fragmentation. To address this problem, road design and planning play a crucial role in reducing roadkill and mitigating its environmental impact. Here are some detailed strategies and considerations for road design and planning to achieve this goal:

Wildlife Crossings and Connectivity

One of the most effective ways to reduce roadkill is to incorporate wildlife crossings into road design. This involves constructing underpasses or overpasses that allow animals to safely cross roads. These structures can be designed specifically for the local wildlife, such as salamander tunnels, bear underpasses, or deer and elk crossings. For example, in southern Florida, the use of underpasses and barrier fences has reduced panther mortality significantly along 110 kilometers of road.

Fencing and Funneling

In addition to wildlife crossings, fencing can be installed to funnel animals towards these safe crossing structures. This prevents animals from accessing the main roads and directs them towards designated passages, reducing the likelihood of collisions. For instance, Matt Aresco, a PhD student, successfully advocated for the installation of nylon fencing along a highway in Florida, saving nearly 5,000 turtles from becoming roadkill.

Avoid Road Barriers and Guardrails

Road barriers and guardrails can pose a risk to vulnerable species and increase the likelihood of roadkill. It is recommended to avoid or minimize the use of such structures to reduce the barrier effect and allow animals to move more freely across the landscape. This can help maintain habitat connectivity and reduce the negative impact of roads on wildlife populations.

Lighting and Verge Landscaping

Road lighting can be strategically used to reduce roadkill, especially in areas with high wildlife mortality rates. However, strong light pollution should be avoided in ecologically sensitive areas to minimize negative ecological impacts. Additionally, dense bushes or vegetation near roadsides should be avoided to prevent obstructing driver visibility, as it can increase the risk of wildlife-vehicle collisions.

Bus Stop Management

Proper management of bus stops is essential to reduce wildlife attraction to organic waste. Animals may be drawn to bus stop areas due to the presence of food scraps or garbage, increasing the risk of roadkill. Regular cleaning and waste management practices can help mitigate this issue.

Habitat Loss and Fragmentation

When planning roads, it is crucial to consider the potential habitat loss and fragmentation that may occur. Roads can bisect contiguous land, affecting the movement and survival of various wildlife species. By carefully selecting road locations and incorporating wildlife corridors or crossings, the impact on habitats can be minimized.

Collaboration and Research

Collaboration between ecologists, biologists, engineers, and transportation planners is vital for effective road design and planning. By combining expertise and utilizing research findings, such as wildlife distribution data and habitat connectivity models, roads can be strategically designed to minimize their ecological footprint.

In conclusion, road design and planning have a significant impact on reducing roadkill and mitigating its environmental consequences. By implementing wildlife-friendly features, such as crossings, fencing, and lighting, and by considering habitat connectivity and fragmentation, roads can become safer for both wildlife and humans. Additionally, ongoing research and public awareness are crucial for addressing this issue and driving the development of more sustainable transportation infrastructure.

Data collection and reporting

Data Collection:

• Identify hotspots: Use spatial analysis techniques, such as heat maps, to identify areas with high concentrations of roadkill. These hotspots are often influenced by environmental and road conditions, such as high traffic volumes or proximity to bodies of water. By identifying these hotspots, we can determine the priority areas for data collection and targeted mitigation efforts.
• Record wildlife-vehicle collisions (WVC): Collect data on the locations of WVC incidents, including vehicle crashes and animal carcasses on the roadways. This information is crucial for understanding the scope and severity of the problem.
• Monitor animal behaviour: Observe and record animal behaviour around roads, such as their crossing patterns, habitat preferences, and seasonal activities. This helps in identifying areas where animals are more likely to cross and allows for the implementation of targeted solutions, such as wildlife crossing structures.
• Involve volunteers and agencies: Collaborate with volunteers, agency staff, and local communities to report WVC incidents. This can include training individuals to recognize and report roadkill, as well as encouraging the use of reporting platforms, such as online forms or telephone requests, offered by local governments.
• Use technology: Employ technology, such as off-road automatic cameras, to monitor wildlife distribution near highways and the usage of crossing structures, such as bridges and culverts. This provides valuable data on wildlife movement and the effectiveness of existing crossing structures.
• Sample and categorize roadkill: Collect data on the species and categories of animals affected by roadkill. This includes distinguishing between mammals, birds, reptiles, amphibians, and invertebrates. Additionally, pay special attention to threatened or endangered species, as roadkill can significantly impact their population decline.
• Consider observability: Take into account the varying levels of observability between different taxa. For example, larger mammals may be easier to spot and report compared to smaller amphibians or invertebrates, which can lead to underestimating the impact on certain species.

Reporting:

• Create a centralized database: Compile the collected data into a comprehensive database that is accessible to relevant stakeholders, such as conservation organizations, researchers, and government agencies. This database should include information on the species affected, locations of incidents, and environmental factors contributing to roadkill hotspots.
• Analyze and visualize data: Utilize analytical tools to identify patterns and trends in roadkill data. Create visual representations, such as maps and charts, to communicate the findings effectively to the public, policymakers, and conservation groups.
• Report to authorities: Share the collected data and analysis with local, regional, and national authorities responsible for transportation planning and wildlife conservation. This information can inform policy decisions, infrastructure improvements, and the allocation of resources for mitigation measures.
• Engage the public: Raise awareness about roadkill pollution and its impact on wildlife and the environment. Share data and success stories of effective mitigation strategies through public platforms, social media campaigns, and educational initiatives.
• Collaborate with researchers: Encourage academic research on roadkill pollution and its mitigation. Share data with researchers to contribute to scientific studies, publications, and the development of innovative solutions.
• Monitor and evaluate mitigation efforts: Implement mitigation strategies, such as wildlife crossing structures, reduced speed limits, or fencing, and continuously monitor their effectiveness. Evaluate the impact of these measures on reducing roadkill and protecting vulnerable species.

Frequently asked questions