impacts to habitat – Ryann O'Carroll

How Roads Impact Wildlife – The Environmental Impact

rocarroll Wildlife June 13, 2020June 26, 2020environmental issues, environmental polluntants, impacts from habitat fragmentation, impacts from noise, impacts from pollution, impacts from roads, impacts to habitat, impacts to wildlife, indirect effects, mitigation strategies, road ecology, roads, solutions for wildlife, wildlife 0 Comment

Roads have become increasingly common across our globe as people utilize them to travel to places they want to go, increasing the reliability on cars for transportation needs. These large and wide networks of roads we know today severely alter a landscape and can impact wildlife in numerous ways. As seen in my previous blog posts, roads can cause impacts to wildlife such as mortality, wildlife-vehicle collisions, and limit their movement from place to place; however, roads can also shift the population demographic of a wildlife species and become a source of pollution into the environment. Roads impacts extend well beyond the surface of the road itself, causing many ecological impacts to the environment and the wildlife within it.

Habitat Fragmentation & Alteration

Roads can cause direct mortality to wildlife, causing other factors to occur such as wildlife shifting their population demographic farther away from the road, losing vital habitat space. Roads also pose a number of indirect effects onto wildlife, such as habitat fragmentation and alteration. This is due to either wildlife not being able to cross a road due to the risks of mortality or through avoiding the road altogether, shifting their habitat farther away.

Roads also create barriers that limit the movement of wildlife, one of the main issues being barriers prohibit gene flow. An example of this was seen when a group of researchers studied the genetics in timber snakes; snakes that were blocked in their movement from roads had a much lower genetic diversity than other snakes across continuous habitat types. Along with this, the male timber snakes are known to follow pheromone trails to find mates; roads disturb this trail and make it difficult for the males to be able to find mates, affecting reproduction and survival of the species.

Wildlife being affected from habitat fragmentation and alteration are also susceptible to not being able to access specific habitats. An example of this is during dry seasons; when there is a drought occurring, road prohibit wildlife from reaching vital water sources. Roads can also prevent some wildlife from reaching nesting sites, such as turtles; these species end up laying their eggs in habitats where there is more predation, meaning their is a decreased chance of reproductive success and survival of the species.

Constructing a road also alters the habitat altogether. If a road is running through a forest, the road creates an edge habitat along the parts of the road that fringe the forest itself. This can have severe consequences for wildlife, especially birds; when an edge habitat is created, birds become more susceptible to predation. This is due to predators being able to prey on birds much easier in the edge habitat, as the forest canopy at the edge offers less protection to the birds and their nests. Other wildlife susceptible to edge habitats are turtles; some species of turtle prefer to nest along edge habitats because it is an ideal habitat for their nest. However, turtles utilizing the edge habitat are now posed to a greater risk of mortality when crossing roads, and their hatchlings could also be susceptible to this when they disperse after hatching from the nest.

Pollution

While roads can alter habitats and cause fragmentation to occur, they can also channel pollutants onto the environment. Debris from tires on the road can cause things such as a decreased amount of time to metamorphosis for the wood frog species. Salt that is used to deice roads runs off the road and into adjacent ponds that can decrease the survivorship of species such as spotted salamanders and wood frogs. Deicing salts can also change frogs behavior and decrease their performance in locomotion. Frogs are one the species that have been shown to have greater skeletal abnormalities when they are closer to roads; researchers suggest this is a result from the road contamination. This is turn affects the frogs fitness, making them potentially less adept to catch prey or elude themselves away from predators.

Roads polluting the environment extend far beyond introducing chemicals into the environment; they also introduce noise and light, which can be detrimental to wildlife as well. The noise from traffic on a road can effect species of bird, causing declines in bird populations living in proximity habitats close to the road. However, not all species of bird are equally affected, such as how birds having song frequencies similar to that of a car frequency being found as absent from habitats near roadsides. Noise from a road can also change bird species’ community composition, meaning that some species of birds are differentially excluded from a particular habitat near a road.

Along with noise polluting the environment, light can as well. Some species of wildlife rely on light to control biological activities, and this can be impacted by lights along a road. For example, robins use sunlight as a cue to begin their morning songs and can mistake lights on a road for the sun and begin their song in the middle of the night. Lights from roads can also alter flying routes for bats, as well as expose some frog species to artificial light during the night that could delay their metamorphosis time. Along with this, sea turtle hatchlings use light in order to navigate themselves to the sea and can become confused by lights on a road and go toward a road instead of the ocean; this can cause the hatchlings to die from dehydration, predators, and /or wildlife-vehicle collisions, and they will never reach the ocean. This goes for the females that nest their hatchlings as well, sometimes becoming disoriented from road lights and have a difficult time getting back to the ocean.

A final note on pollution from roads is that is can facilitate the spread of invasive species when land is cleared for a road. An example of this was seen in Australia with cane toads; these species of toad are very invasive in the continent and use roadside areas to move, causing an increase in their range as a population. Along with this, species such as fire ants may also build their mounding nests by areas cleared for roads because this is an ideal habitat for them. Roads can facilitate the invasion of invasive species, and alter or fragment a habitat; all of this impacts are detrimental to both wildlife and the land they live in.

Mitigation Strategies

There are numerous solutions and mitigation strategies being developed to help decrease the amount of harmful impacts our roads cause to wildlife. In instances where the pattern of mortality can be predicted for a specific are during a specific time of year, roads are either closed or reduced in their speed limits to decrease the rates of wildlife mortality. Another solution is creating artificial nesting sites for gravid species that need them; this can reduce species from needing to potentially cross a road, the distance they need to travel, and/or their chances of mortality.

A main issue with roads is the traffic volume on them. Though decreasing traffic volume is not very likely to be effective for a mitigation strategy, constructing alternative methods to cross a road could become more successful. For example, culverts can be used for smaller animals to allow for a safe passage under a roadway; this has been shown to be highly effective in decreasing mortality rates of wildlife. For bigger animals, overpasses can be used to cross a road; this overpass would need to have specific features of the wildlife’s environment, such as vegetation planted over it to mimic the habitat type.

There are many factors that need to be taken into consideration when ensuring wildlife can effectively and efficiently cross our road structures. We need to implement and create new ways to protect and preserve our wildlife, as well as the environment they live in. From this post, we have learned that roads not only impact wildlife through things such as mortality or vehicle collisions, but roads also create very real and severe threats to the environment that in turn affect wildlife. We as humans have a job of conserving our planet, and that includes the wildlife within it. Without the wildlife, there would not be an environment for us to destruct upon, as wildlife naturally disperse seeds, nutrients, and vital resources the environment needs to keep going.

“We are part of the environment, just as much as wild animals are. They do not seek to kill us, we seek to kill them. It’s surely our responsibility to do everything within our power to create a planet that provides a home not just for us, but for all life on Earth.” – David Attenborough.

How Roads Impact Wildlife – Habitat Fragmentation

rocarroll Wildlife June 6, 2020June 10, 2020adverse effects to wildlife, habitat fragmentation, impacts to habitat, impacts to wildlife, major transportation infrastructures, road ecology, roads, solutions for habitat fragmentation, solutions for wildlife 0 Comment

Driving down a long and windy road can sometimes feel like the best thing in the world: music cranked all the way up, windows down and the sun shining down on the world with the hills and trees lining the fields in the distance. This is a beautiful sight especially during the summertime, however, what about the the part of the land you’re driving on, now covered with tar? Most people don’t think of this when they’re driving, but roads have a huge ecological impact to the land they are implemented in; this in turn effects the environment and the wildlife living within the habitats of the land. Habitat fragmentation is a major issue when it comes to placing major transportation infrastructures (i.e., roads, highways, interstates, railroads, etc.) into the environment, but how do they exactly affect the land and the wildlife within it?

Impacts to the Land & Wildlife

Looking at the image above, what do you see? Roads cause a lot of fragmentation in the land, as you can see from the small patches of habitat in between the sections of crossing roads. A literature review I recently read about habitat fragmentation gave prime examples of how the land and wildlife are impacted by this. Habitat fragmentation is one the largest and most single pervasive threat to biodiversity across the world; it is the destruction of habitat, as well as altering and/or fragmenting large areas of habitat into smaller patches. Roads play a major role in habitat fragmentation because they cause a large dividing of the landscape into smaller patches of habitat; roads also cause interior habitat areas to turn into edge habitats, meaning areas in the interior of the land had characteristics unchanged and have now become altered and have edges that do not resemble what the habitat used to look like or be. As of 2003, 3.9 million miles of roads have caused direct habitat loss to our landscape in the U.S., and this has only increased with the number roads we currently have in the U.S. In terms of how habitat fragmentation affects wildlife populations and species, fragmentation forms the landscape to have altered habitats or areas that have developed fundamentally differently due to being shaped from natural disturbances, such as major transportation infrastructures; this is turn causes wildlife populations and species to adapt to these altered habitats over time.

These impacts of habitat fragmentation from roads have adverse effects to wildlife, and include, but are not limited to, the following: increased isolation of populations and species causing adverse effects on genetics and diversity, changes to vegetation the animals forage or feed on, changes to the quality and quantity of food, changes in temperature, changes in the flow of energy and nutrients, changes to available shelter or cover, increased edge effects that could cause species that do not normally interact to now interact, and increased opportunities for humans to exploit resources or wildlife (i.e., poaching). All of these impacts occur from having a road placed in the middle of a landscape, causing a chain reaction to occur that creates habitat fragmentation to loss of wildlife populations and species. How can this issue be solved so we don’t lose more habitat and wildlife as new roads are created?

Solutions to Habitat Fragmentation

Now that we’ve discussed the issues roads cause to wildlife, from mortality and collisions in my early blog posts to how habitat fragmentation impacts wildlife as well, what are the solutions to help reduce the effects habitat fragmentation has on the land and wildlife? The good news is not all species are necessarily affected by it; species that do not travel very far can only be truly effected if the area they’re in is disturbed, and species that have good dispersal are only affected by the amount of habitat they have access to. However, this does not mean all wildlife are safe from roads causing habitat fragmentation, or habitat fragmentation in general. I was able to find an article discussing the practical considerations of how to address the issue of habitat fragmentation. The main issue of habitat fragmentation is that it is causing wildlife populations and species to decrease in size and amount, causing wildlife to become isolated and not be able to reproduce to keep their populations growing. Barriers such as guardrails or even buildings cause limitations to wildlife movement as well; habitat fragmentation is pushed even further when a road is placed and then there are barriers placed around the road, causing the wildlife to find new corridors to their habitats. One of the main solutions to this issue is utilizing urban green-space to reduce habitat fragmentation and keep intact the connectivity between habitat patches as development continues into the future. In existing urban areas, such as landscapes having a lot of roads or other major infrastructures, green-spaces can be utilized by implementing things such as footpaths, canals and rivers to offer more corridors for wildlife to access instead of using roads to move from habitat to habitat. In urban areas that are becoming newly developed, habitat fragmentation can be counteracted by protecting the already existing patches of habitat that are high in quality and species diversity; this would in turn allow wildlife to still have access to a valuable piece of habitat and allow for the wildlife to not be limited in their movement.

Another great solution to this issue is using habitat network maps; this is a leading development by Forest Research where they develop and apply landscape ecology techniques to combat against fragmentation. Groups of people within this research organization that are concerned with fragmentation have created habitat network maps to evaluate the connectivity of existing wildlife patches and target where to implement new patches when planning urban development. These solutions to the issue of habitat fragmentation will not only help reduce the effects roads have wildlife, but also wildlife increased movement from habitat to habitat and give them more corridors to access as well. The more wildlife movement there is, the more genetic and species diversity will be seen, causing wildlife populations and species to increase rather than decrease. Roads pose serious and adverse effects to wildlife, especially when they’re habitat becomes fragmented an destroyed in the process of implementing the road. If road ecology researchers took more of this into consideration when planning to implement roads in the least destructible way possible, this would in turn benefit the landscape and wildlife in the process.