Animal health

The one simple act of ingesting plastic, can have the following stream of effects:

Ingestion

Birds

Birds are known to ingest waste pollution, especially plastic. Plastic can block the gastrointestinal tract, leading to choking. Swallowed plastic can make birds feel full, reducing nutrition and causing starvation[26][16]. As plastic breaks down, trace elements and toxins can be released, damaging vital organs.

Many seabirds eat plastics by mistake, as the odour emitted by bacteria on the plastic is very similar to the smell of their food. Seventy three percent of albatrosses world-wide are threatened with extinction. Ingestion of plastic in this species has been well documented in the Northern Hemisphere where it is considered a major threat. However, only recently has it been demonstrated that this problem is also significant in the Southern Hemisphere. A study of beach-cast albatrosses from twelve species, received by wildlife hospitals in Australia and New Zealand, had a high proportion birds that died from plastic ingestion.

The albatross is also attracted to single-use light sticks, a significant cause of injury and death[19]. The flesh-footed shearwater eats more plastic relative to their size than any other marine creature[17], contributing to the potential extinction of this species[1][17]. The shearwaters are attracted to hard plastic, rubber and balloons, with studies showing that 79 percent of chicks had plastic in their stomachs[1].

Some species of seabird in Australia encounter large areas of plastic in the Pacific Ocean during their annual migration to the northern hemisphere. In 2016, nine red phalaropes were found dead on the north coast of British Columbia, Canada. All the birds had ingested plastic and were emaciated[8]. Other studies have shown that half of petrel species regularly ingest human-generated waste[25].

Birds also ingest fishing line, sometimes with fishing hooks, which can be caught in the mouth or further along the gastrointestinal tract, leading to injury and potential death[27].

Marine turtles

Waste pollution in the ocean is a major threat to marine turtles. Turtles can ingest waste, become entangled in waste or be contaminated by toxic waste[34] . For example, green turtles and hawksbill turtles often consume soft, clear plastic, such as plastic bags, as it resembles jellyfish[28][29].

In February 2021, a high volume of dead and sick baby turtles were reported to be washed up on Capricorn Coast beaches. Post-hatchlings, which had been tagged, had ingested fragments of floating hard plastics and soft plastics and this issue is being further investigated[35].

Just a single piece of debris can be large enough or the right shape to cause fatal gut impaction or perforation in turtles. Marine turtles that ingest just one piece of plastic have a 22 percent chance of dying[34]. Of the green turtles and hawksbill turtles washed up dead in South East Queensland, 33 percent had marine debris in their gastrointestinal tract and 90 percent of this debris was plastic, including pieces of balloon.

Balloons (even latex balloons advertised as ‘biodegradable’) do not degrade quickly in water[12]. A 2014 study found that balloon fragments are found at high levels in the ocean and on beaches around the Great Barrier Reef. In turtles they cause infection, intestinal blockage, internal injury, malnutrition and increased buoyancy. These can result in reduced growth rates, lower reproductive output and death[22].

Young turtles, which forage near the ocean surface (pelagic zone), are at particular risk of ingesting buoyant plastic and other light debris[28]. They are more likely to ingest marine debris than larger turtles that feed near the bottom (benthic zone).

Because of their susceptibility to marine waste, turtles are good proxy indicators of how the marine environment is functioning. Queensland waters and nesting beaches are home to six of the seven species of marine turtle, including the flatback turtle, which only nests in Australia Recovery Plan for Marine Turtles in Australia, Commonwealth of Australia 2017); Queensland Marine Turtle Conservation Strategy 2018).

Fish and other marine animals

Microplastic can be ingested by a wide range of fish and animals, including vertebrates and invertebrates, filter feeders, suspension feeders, detritus feeders and predators. Ingestion can occur at the surface, throughout the water column and at the ocean floor. For example, commercial shellfish (oysters, muscles and scallops) have been found to have many types of microplastics, including fibres, fragments and pellets, in all tissues[30]. It has also been found in the guts of fish, including species intended for human consumption, and those with critical ecological roles[3][6].

One study on phytoplankton exposure to plastics found that biomass (total weight of organisms) and community structure (number/diversity of species present) were both affected, with a decrease in chlorophyll and structural changes in offshore waters[21]. Another study found that a significant percentage of freshwater macroinvertebrates (e.g. larvae and snails) close to a wastewater treatment plant contained microplastic[36].

It is also clear that plastic ingestion affects whales, with microplastic found in stranded whales[2]. As with other species, prey preference and feeding strategies can alter the way whales ingest microplastic[2].

Entanglement

Entanglement in waste pollution is one of the major threats to marine life, especially birds[5][9][13][15].

Councils, Indigenous Land and Sea Rangers, and community groups such as Tangaroa Blue and the Surfrider Foundation, remove tonnes of marine debris from beaches annually. However, entanglement still occurs, with seabirds, freshwater birds and land birds routinely entangled in plastic and other synthetic materials[27].

Entanglement is also a major threat to marine turtles. It has been estimated that between 5000 and 14,000 turtles were captured in ghost nets (discarded nets) across northern Australia in an eight year period[33]. Another study estimated that approximately 20,000 turtles have been caught by derelict fishing gear and other marine debris arriving on the northern coast of Australia[14]. This estimate does not take into account the beach waste that entangles nesting females or emerging hatchlings[22]. Northern Australia has some of the highest densities of ghost nets in the world, with up to 3 tonnes washing ashore per kilometre annually[33]. See the Recovery Plan for Marine Turtles in Australia, Commonwealth of Australia 2017 which demonstrates how the government is dealing with this issue.

Toxicity

Many wastes can be toxic. In Queensland, the Regulated Waste Classification and Waste-related Environmentally Relevant Activity (ERA) regulations are used to identify and manage the risks associated with various wastes.

Microplastics are found in a wide range of species, from plankton to large fish but their impact on living organisms in Queensland requires further research. Nanoplastics were identified in 2016[11] and are created when microplastic breaks up. They are less than a thousandth of a millimetre in size, smaller than a human cell. Unlike microplastics, nanoplastics are small enough to accumulate in the bloodstream and cell membranes of a range of organisms, even passing the blood/brain barrier[31].

Although there is little Australian research in this area, nanoplastics are believed to have various toxic effects, including neurological damage and reproductive abnormalities[7]. Microplastics and nanoplastics are also believed to have indirect toxic effects when heavy metals and other pollutants attach to the plastic[23]. Espinosa, et al. (2018) found that continued exposure of the plastic to fish had detrimental effects on their immune system.

Plant growth can also be affected when plastic is added to soils[32]. Research on earthworms and plants exposed to microplastics found:

• adverse effects on wheat vegetative and reproductive growth
• alterations to roots and leaves in spring onions
• increased mortality and decreased growth rate of earthworms
• damage to gut, immune responses, body weight and gut microbiome in earthworms.

Fire

Fires started from discarded cigarette butts cause widespread damage to wildlife as well as humans. Media reported up to 500 million animals may have perished in the 2019–2020 Australian bushfires, some of which started due to littered items, including cigarette butts. Dumping green waste in nature reserves or parks may serve as a fuel, increasing the bushfire threat. Pets and livestock also suffer the effects of bushfires[18].

Habitat destruction

Dumping waste can cause or accelerate the destruction of wildlife habitat. When green waste is dumped on top of native or local plants, those plants may die due to lack of sunlight or lack of competitive advantage. Invasive weeds in the green waste may overtake reserves and forests, significantly altering the biodiversity of an area.

Dumping contaminated green waste and soils can pose biosecurity risks to animals and plants. It can also spread pests, such as fire ants and yellow crazy ants, to otherwise pristine areas, competing with native species and damaging ecosystems. Further biosecurity issues, including policy and programs, can be found on the Queensland Department of Primary Industries website.

Marine litter can also cause habitat destruction. Plastic can smother coral, and there is evidence that waste affects the composition of aquatic ecosystems[10][20][24]. Plastic waste on the ocean floor can reduce the exchange of gas between sediment and water, leading to low oxygen levels and suffocation. Anoxic (low oxygen) conditions have been observed in sediments under sunken plastic bags. This can adversely affect the animals that live in on the ocean floor, especially in soft sediment communities. Experiments have shown that changes to organic matter can occur after only two months (or three months for biodegradable plastic bags)[4].

Injury

Many injuries to animals are a result of waste pollution. Sharp and broken materials can cut wildlife, pets and livestock. Discarded fishing gear, such as fishing hooks left on beaches, and other debris injure wildlife. If swallowed, sharp objects can also cause internal injuries. The Currumbin Wildlife Hospital collects and records hooks and dangerous material that have either maimed or killed wildlife.

Littered food can negatively impact animals, which can get sick after eating rotten food or be attracted to roadsides and suffer vehicle strikes.

Contamination of water with waste pollution can lead to fish kills and other animal deaths. Germs, bacteria and viruses can spread on waste pollution, infecting scavenging animals.

Additional information

• Using expert elicitation to estimate the impacts of plastic pollution on marine wildlife
• Marine Litter Changes Benthic Habitats
• Dead, sick baby turtles wash up on central Queensland beaches after eating plastic - ABC News

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Last updated: 10 May 2021