Plastics are popular in part because they’re accessible, sturdy, and durable. For this same reason, when they find their way into the environment, they tend to last. As plastic waste accumulates around the world, many people are concerned about the negative impacts in the long term. However, few global actions have been taken to combat plastic pollution — and actions that have been taken haven’t fully addressed the problem. 

This report aims to understand how plastic pollution is impacting freshwater and land-based  migratory species in the Asia-Pacific region. The authors note that this area has high rates of plastic use and pollution, largely ineffective waste management, and a lack of environmental knowledge among consumers. 

They focus on the Ganges and Mekong River basins, as plastics typically enter rivers before polluting the ocean or remaining in freshwater environments. As a result, though most plastic research focuses on marine environments, the authors emphasize the importance of understanding river ecosystems. The Ganges and Mekong are both major sources of marine plastic, with the former contributing 172,000 tonnes of plastic to the Indian Ocean and the latter contributing 40,000 tonnes to the South China Sea each year.

The Challenges Of Studying Plastic Pollution

Plastic size ranges from macroplastics (bigger than 2.5 centimeters) to microscopic nanoplastics (1-1,000 nanometers). Research on the impacts of plastic varies depending on factors like the size of the pollutant and the environment being studied. Furthermore, common study methods can’t account for particularly tiny pieces of plastic.

According to the authors, most plastic enters the environment on land as macroplastics, either intentionally as litter or because of large-scale mismanagement. Common types of macroplastics are product packages and discarded fishing gear, which can be ingested by animals or cause entanglement. Plastics also cause toxic chemicals to spread into the environment, and they can lead to the spread of non-native, “invasive” organisms who dwell on their surface.

Smaller forms of plastic, especially microplastics, are harder to remove from the environment. Some of these debris are designed to be small (e.g., small consumer product fragments like a medicine cap) or come about when macroplastics break down. Small plastic debris can also be ingested, and microplastics are known to cause high levels of chemical exposure.   

The authors look at migratory species because they note these animals are highly vulnerable to plastic exposure (added the problem is that many migratory animals are endangered). For example, they may ingest plastic when they travel to new regions, and they may also transfer plastics to new environments. Migratory species include birds, but they can also include invertebrates, fishes, reptiles, and mammals.

Invertebrates

In freshwater environments, invertebrates have been known to ingest microplastics. One example is the Asian clam — in at least one study, researchers found plastic particles in their tissues. One of the biggest concerns with both freshwater and terrestrial invertebrates is that they’re consumed by other animals. This means that when invertebrates are contaminated by plastics, they transfer these plastics to their predators, causing harm up the food chain.

Fishes

Because they dwell in water, fishes are especially susceptible to plastic waste from the fishing industry. For example, one study of eight freshwater fish species found that 73% of individual fishes had microplastics in their gut, mostly from fishing cages and nets. Because of their body shapes or traits, certain fishes are highly susceptible to plastic entanglement (for example the sawfish, which has sharp, protruding teeth). 

Finally, certain fishes (including sturgeons) are susceptible to chemical pollution, which can impact their reproduction. The authors note that plastic pollution may make them more susceptible to chemical exposure.

Mammals

There are limited data on migratory land mammals, but anecdotally, Indian elephants have been observed ingesting plastic. The authors describe the case of one elephant who died as a result of plastic ingestion (plastic bags were found in the animal’s stomach). Cows, sheep, goats, and camels who dwell near rivers may accidentally ingest plastic that, in turn, can cause stomach blockages.

For air-breathing aquatic mammals, getting entangled with plastic waste may prevent them from reaching the water surface. Furthermore, these mammals are at risk from ingesting plastics either directly or by consuming other animals. According to a recent study of the Ganges River, the Ganges River Dolphin was the second-most vulnerable animal in terms of plastic entanglement and harm from fishing gear (the Three-striped Roofed Turtle ranked first).

Reptiles

The authors say that many reptile species are at risk of becoming entangled in plastic, although they cannot verify this with scientific data. Certain species of aquatic turtles have been seen consuming or getting entangled with plastics. This can cause infections, growth problems, injuries, starvation, and drowning.

Birds

Birds are particularly vulnerable to plastic exposure as they interact with it in various ways. For example, many birds use plastics in nest construction. This becomes a problem when twine or other plastic string is used (the authors describe one young bird who was entangled with plastic in their nest). However, many birds benefit from using plastics as nesting materials, as it’s easily accessible, it can increase their visibility for mating purposes, and it can provide camouflage.

When birds become entangled with plastic string or fishing wire, it can cut off their blood supply, prevent feeding and flight behaviors, and cause other problems. Some birds ingest rubber bands when foraging, mistaking them for earthworms, while birds who skim food off the ocean’s surface may accidentally eat floating plastic. In addition to harming themselves, birds may hurt their offspring when they regurgitate plastic to feed them.

Addressing Plastic Pollution In Asia And The Pacific

The authors call for a concerted effort to combat plastic waste in the Asia-Pacific region that involves multiple stakeholders and takes into account the region’s economic, social, and environmental differences. Industry needs to minimize plastic use and improve how they dispose of the plastics they do use, while government policies, such as bans and taxes, should be effectively enforced. Animal advocates can also get involved in educating local consumers about making sustainable choices and demanding better waste management infrastructure in their communities. Regional fishers are an important stakeholder group to target, as the fishing industry is a major source of plastic waste.

Finally, the report also calls for targeted conservation efforts for species most vulnerable to plastic pollution. This may include developing local wild animal reserves and organizing community clean-up efforts.