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Shoreline litter and aquatic debris primarily threatens wildlife through entanglement and ingestion. Additionally, many of the species that are most vulnerable to these risks also happen to be endangered or threatened, including sea turtles, fish, marine mammals, and birds.
Entanglement is most often caused by items such as plastic strapping bands, rope, wire, fishing lines, six pack rings and other similar items. Meanwhile, abandoned fishing gear such as lines, nets, traps and pots pose another threat in the form of ghost fishing. This is a phenomenon where these items continue to catch fish and trap marine mammals, turtles, and seabirds long after they’ve been discarded. Derelict fishing gear and nets can also drag along the ocean floor, damaging delicate corals and impacting the many animals that depend on that environment.
Entanglement can happen accidentally, or because the animal is attracted to the items out of curiosity, hunger, or some other natural behaviour. Some wildlife, especially birds, even uses pieces of litter to build their nests and shelters, which can then entangle their young. Entanglement often impairs an animal’s ability to move or swim, causing it to drown, be unable to find food, or escape predators. When an animal tries to free itself from entanglement and happens to survive, it may cause itself serious wounds that become infected and lead to loss of limbs. Sadly, the animal is most often suffocated or strangled.
Ingestion occurs when animals swallow litter items, the results of which can be devastating. Doing so often interferes with an animal’s ability to eat, breathe and move, leading to starvation, choking or fatal poisoning depending on the item. Generally, animals swallow litter items because they resemble a typical part of their diet.
For example, trumpeter swans swallow tiny pebbles of grit to aid with digestion, but have also been found to eat lead shotgun pellets by accident, a highly poisonous substitute. Similarly, turtles will mistakenly eat plastic bags as they strongly resemble their common prey, jellyfish. This then clogs the turtle’s digestive tracts and leads to starvation. Furthermore, the air trapped within these plastic bags makes it nearly impossible for turtles to dive deep into the water.
Plastic pellets and discarded plastic that has broken up into smaller and smaller pieces over time, is a particular concern as the indigestible substance can fill an animal’s stomach. This can lead to malnutrition, or stopping of eating altogether because the animal feels “full.” These small particles can be ingested by a wide range of animals at the bottom of the aquatic food web, creating the potential to disrupt feeding and digestion all the way up the food chain. For birds in particular, this change in diet can lead to a loss of the fat stores critical for migration and reproduction.