Image Credit: Green News Ireland
As the world celebrated Earth Day earlier this week, New York joined California and Hawaii in legally banning single-use plastic bags! In a country obsessed with plastic, this represents a major victory for the environmental movement. According to an article in Forbes, "In 2014 it is estimated that the United States used 100 billion single-use plastic shopping bags with the average American family using 1,500 single-use plastic bags each year." That is an astronomical amount of plastic making its way into landfills, parks, oceans, even the air - and those numbers don't even consider the other sources of plastic contamination, With three states leading the charge, I can only hope/imagine that more states will follow with similar bans.
We've known about the dangers of plastics for years. Back in February 2015, I wrote an article on the realities plastic (and other) waste impose on marine mammals. Four years later, this article is still frighteningly relevant. I posted it below with minor modifications, but want to emphasize the victories (like the plastic bag ban!) that have occurred since its initial publication in the Columbia Science Review. I am confident more victories will follow, and encourage everyone (myself included!) to continually find ways that we can all decrease plastic use in our every day lives.
By Alexandra DeCandia
Humans have a love affair with plastic. Lightweight, versatile, durable, and inexpensive synthetic polymers have flooded the global market since 1950. Yet the qualities that earn success in the marketplace also severely endanger the natural environment. Winds, rivers, and currents carry lightweight refuse ocean-bound, where cooler temperatures and UV-protection render it long lasting. Plastic floats in bodies of water for decades before degrading into “microplastics,” with these miniscule particles posing additional risks to ocean life. They mingle with professional fishing gear and “ghost nets” that wander around the ocean silently seizing marine mammals. Amid this plastic, limbs get entangled, digestive tracts occluded, and tissues infused with toxins.
Entanglement occurs when marine mammals are constricted or entrapped by anthropogenic debris. This may lead to strangulation, open sores, impaired behaviors, increased energy expenditure, and, in extreme cases, drowning. New Zealand fur seals, for example, get caught in stray lobster traps but aren’t strong enough to carry them to the surface. Similarly, Dugongs are unable to wriggle free from fishing nets. Even humpback whales, if not freed from tows of nets, ropes, and plastics tangled around their flukes, can die from exhaustion in their struggle to break free. Unfortunately, ocean debris acts as an anchor for these trapped animals. Even stray monofilament lines can lock animals down to the ocean floor.
Old fishing gear abandoned in the ocean can lead to entanglement. Image Credit: NOAA
The second threat stemming from the misuse of plastics is ingestion, and occurs when organisms mistake debris for food. Plastics come in all shapes, sizes, and colors, so plastic debris can mimic the look of mammalian food. Analysis of polar bear scat, for instance, revealed ingestion of debris like foil, cardboard, cigarette butts, duct tape, foam rubber, glass, paint chips, paper, plastic, wood, and even a watch band. While these items passed through the animal, others often get stuck. And since synthetic materials do not degrade as organic ones do, ingestion can yield wounds internally and externally, gastro-intestinal blockages, false sensations of satiation, toxin bioaccumulation in tissues, impaired feeding capability, and even starvation. In 2008, examination of the stomach contents of two sperm whales stranded in northern California uncovered ropes, plastics, and 134 different types of fishing nets. One whale died of a ruptured stomach; the other of starvation. Both deaths were directly caused by debris ingestion.
Marine mammals are fairly diverse, so often times the distinct behaviors, morphologies, and habitat requirements render certain risks more threatening to one type of organism over another. The order Carnivora, which contains polar bears, sea otters, and pinnipeds, dwell at the intersection of land and sea. These animals seem to approach their dual environments with a sense of curiosity. As a result, marine debris poses a particular risk of entanglement as they excitedly explore their surroundings. Pinnipeds are drawn to novel items such as plastic bags or abandoned nets, and accidentally slip their heads inside loops and holes. Then, since the animal is unable to escape, these “lethal necklaces” remain on their necks, constricting the animal as it grows.
For some species, such as critically endangered Hawaiian monk seals, entanglement has been implicated as a major threat to population growth. Even a seemingly modest rate of entanglement of 0.04%-0.78% has proven detrimental to an ailing population.
Many mammals mistake plastics for food. Image Credit: The Times
The order Cetacea consists of mysticetes (baleen whales) and odontocetes (toothed whales). Unlike pinnipeds, cetaceans are entirely marine, large bodied, and migratory. Ingestion is among the greatest threats to these animals. Nets and plastics can tangle around their bodies and prevent them from feeding. On a smaller scale, microplastics join the krill that these animals ingest or skim on the surface. When the animals filter feed, synthetic particulates enter their bodies and bioaccumulate. In the case of Mediterranean fin whales, these plastics leech toxins into their tissues. Odontocetes largely avoid these risks associated with filter feeding. However, their large-scale ingestion of marine debris does cause plastic impaction, gastro-intestinal tract blockages, starvation, and gastric rupture.
The final order, Sirenia, contains dugongs and manatees. Like cetaceans, sirenians spend their entire lives submerged beneath the waves of aquatic environments. Unlike cetaceans, they travel through coastal waters, estuaries, and inland river networks. While herbivory precludes the risk of bioaccumulation through feeding, entanglement and ingestion still pose a threat to these species.
When we think about the popularity of plastics in our society, it seems that the threat of entanglement and ingestion is inevitable. However, through the implementation of stringent legislation, recycling initiatives, incentive programs, consumption reductions, and citizen-led clean up efforts, this does not have to be the case. Education, activism, and compliance on our part can go a long way. While the ocean will never be completely devoid of plastic, we can prevent further degradation from this point forward. Through increased awareness, it is possible that marine mammals won’t have to live in an environment inundated by trash.