Author: welch.338

Wildlife Crossings Cross One Risk Off the List

As urbanization spreads and the human population of earth grows, roads and highway systems are expanding to keep up with urban sprawl. It is well known that habitat loss is one of the more detrimental anthropogenic impacts to wildlife. But what about roads specifically can be so harmful to animals? And is there anything we can do to mitigate these impacts?

First of all, the sheer stress that traffic noise elicits can have quite the negative impact. Birds are one unlucky recipient of the brunt of negative effects of roads. Obviously, most birds do not need to cross a busy street on foot and can instead just fly right over. However, birds often have to compete with the loud, low hum of traffic noise when emitting calls to find a mate or defend their territories. Traffic noise has even been shown to cause changes in breeding patterns, increase stress levels, and change how birds interact with their offspring (Halfwerk et al., 2011).

Furthermore, roadways by design fragment wildlife habitat and act as a literal barrier for animals that can prove fatal to attempt to cross on foot. Collisions with vehicles are all too common in cities, as I am sure we all are familiar with seeing an animal laying on the side of the road after an unfortunate encounter with a car or truck. Deer, opossums, squirrels, and even mountain lions (among many other animals) are all examples of creatures who too often meet unfortunate ends while trying to cross a street to find food, a mate, new territory or to escape predation.

So, what can be done to mitigate the impacts roadways have on wildlife? While the impacts from traffic noise are harder to alleviate, there is a solution to help with the fragmentation roads cause and danger associated with attempts to cross them. Enter: wildlife crossings!

Wildlife crossings are exactly what they sound like: a corridor designed to link habitats on either side of a roadway or other barrier, which will help restore landscape connectivity and give wildlife a safe way to cross the street. The first wildlife crossing was built over 60 years ago in Florida. Now, wildlife crossings are often incorporated into early highway planning stages and may even be added as retrofits to existing highways (Clevenger, 2005).

“Wildlife crossing 3” by afagen is marked with CC BY-NC-SA 2.0. To view the terms, visit https://creativecommons.org/licenses/by-nc-sa/2.0/?ref=openverse

Construction has recently started on what will be the world’s largest wildlife crossing, which will span 10 lanes of Highway 101 traffic in Los Angeles. The $87 million project is expected to be completed in 2025 and was primarily designed to give mountain lions a safe way to pass from the Santa Monica mountains, over the freeway, and into the Simi Hills of the Santa Susana mountain range. The population of mountain lions in this area also is suffering from inbreeding and a resulting lack of genetic diversity due to being surrounded by roadways and isolated to their “urban island”, which further underscores the importance of this project (Mossburg, 2022).

California Governor Gavin Newsom has pledged to contribute $50 million to other similar projects around the state (Mossburg, 2022). This project will also likely kick forward other wildlife crossing projects across the country (and perhaps the world). It is time to start incorporating wildlife considerations into our roadway plans to allow for safe passages. Next up, how to deal with all that traffic noise…

 

REFERENCES:

Clevenger AP. (2005) Conservation Value of Wildlife Crossings: Measures of Performance and Research Directions. GAIA 14(2):124-129.

Halfwerk W, Holleman LJ, Lessells CM and Slabbekoorn H. (2011) Negative impact of traffic noise on avian reproductive success. Journal of Applied Ecology 48:210-219.

Mossburg C. (2022, April 25). Construction starts on world’s largest wildlife crossing to let animals roam over 10 lanes of L.A. highway. CNN. Retrieved from https://www.cnn.com/2022/04/23/us/california-wildlife-crossing-scn-trnd/index.html.

Microplastics in Fish: Not a Microproblem

Plastics are everywhere. We humans use them in everything – from toys to food packaging to medical supplies and beyond. As a manmade material, plastics do not readily break down in the environment once we are finished using them. To make matters worse, there is an abundance of teeny, tiny pieces of plastics in our world. These tiny bits can occur as a byproduct of the production of plastic goods, or they may be a result of litter in the environment breaking down into smaller and smaller pieces (Barboza et al., 2020). Because they are so small, they spread easily. Today, little pieces of plastic are found everywhere: in our soil, on our beaches, in rivers and oceans, and even scarier… inside the bodies of animals.

“Microplastic” by Oregon State University is marked with CC BY-SA 2.0. To view the terms, visit https://creativecommons.org/licenses/by-sa/2.0/?ref=openverse

These miniscule bits of plastic measuring less than 5 mm are also known as microplastics, and they truly are ubiquitous in today’s environment. (So much so that they are now considered a contaminant of concern on a global scale (Barboza et al., 2020).) Ingestion of microplastics has been documented in over 700 marine animal species, including sea turtles, whales, dolphins, and fish (Wootton, 2021). This either happens when animals mistake microplastics as food and ingest them by accident, or they ingest another smaller prey organism that also has microplastics inside of its body (Wootton, 2021). Fish may also take in microplastics passively as they filter contaminated water through their gills. As a result, microplastics have been found in the digestive tracts, muscle tissues and even the gills of fish (Barboza et al., 2020).

So why should we care if fish are accumulating small particles of plastic in their bodies? Recent studies have demonstrated that there are multiple toxic impacts of microplastic ingestion in fish. These impacts include impaired development, decreased feeding and body mass (Naidoo and Glassom, 2019), damage to cells, changes in behavior, impaired reproductive capacity, and even death (Barboza et al., 2020). There are documented instances of neurotoxicity (or damage to the nervous system) as a result of microplastic ingestion in fish. Oxidative stress, or an imbalance of antioxidants and free radicals in the body, has also been found to result from accumulation of plastics in the body, and may lead to cell and tissue damage in fish (Barboza et al., 2020). All of these impacts have the potential to harm the overall population of a particular species of fish, and ultimately alter food webs.

Conceptual model illustrating capture, retention and internalization of microplastics by fish species (Barboza et al., 2020).

If none of that grabbed your attention, perhaps this will: since microplastics have been found in the edible muscle tissues of fish, humans are also at risk of accumulating small bits of plastic in their bodies after eating a fish meal. Further studies into human risk assessment of microplastic ingestion are warranted, and perhaps microplastic daily intake limits may be in our future once the research is more solid (Barboza et al., 2020). Also, if food webs are altered enough by reduced populations of fish impacted by microplastics, maybe your favorite type of fish will be a lot harder to come by in the grocery store years down the line. For now, take note next time you are on a walk around your neighborhood and see the tiny pieces of a broken up plastic bottle cap – think about the impacts to the fish in a nearby waterway once a heavy rain washes those microplastics downstream. If nothing else, perhaps this thought will motivate each of us to choose to use less plastic in some capacity in our daily lives.

 

References:

Barboza LG, Lopes C, Oliveira P, Bessa F, Otero V, Henriques B, Raimundo J, Caetano M, Vale C and Guilhermino L. (2020) Microplastics in wild fish from North East Atlantic Ocean and its potential for causing neurotoxic effects, lipid oxidative damage, and human health risks associated with ingestion exposure. Science of the Total Environment 717:1-14.

Naidoo T and Glassom D. (2019) Decreased growth and survival in small juvenile fish, after chronic exposure to environmentally relevant concentrations of microplastic. Marine Pollution Bulletin 145:254-259.

Wootton N, Reis-Santos P and Gillanders BM. (2021) Microplastic in fish – A global synthesis. Rev Fish Biol Fisheries 31:753-771.