UN Report assesses risk of plastic pollution to migratory species in Ganges, Mekong Rivers

A new report on plastic pollution and migratory species was launched on Tuesday 1 March 2022 during the fifth session of the United Nations Environment Assembly (UNEA5) in Nairobi. The report, “Risk assessment of plastic pollution to migratory species in the Mekong and Ganga River Basins”, was prepared under the UN’s Convention on the Conservation of Migratory Species of Wild Animals (CMS).

The report maps plastic hotspots and assesses the risk of plastic pollution on migratory species in the Ganges and Mekong River basins which are protected under CMS. It focuses on the impacts of plastic pollution on freshwater and terrestrial species – which has been significantly understudied.

CMS Executive Secretary Amy Fraenkel said: This study confirms that plastic pollution is adversely impacting migratory species in freshwater and terrestrial settings. It provides an important tool to assess potential risk on such species that can be used globally.”

While there are many studies that examine the impact plastic pollution poses to marine wildlife, the impacts on freshwater species are much less well studied. Research on plastics in freshwater ecosystems account for only 13 per cent of the plastics studied in all aquatic environments. Only 4 per cent of peer-reviewed studies on the impacts of plastic pollution are relevant to terrestrial ecosystems.

Together, the Ganges and Mekong Rivers contribute an estimated 200,000 tons of plastic pollution to the Indian Ocean and the Pacific Ocean every year.

Both river basins are home to 605 species protected under CMS including freshwater species, land animals, and birds. Many of them are listed as threatened or endangered by the IUCN.

Among its findings, the report concludes that in the Asia-Pacific region discarded fishing gear is a particular threat to migratory species. Of 23 species studied (5 species in the Mekong, 19 species in the Ganges, it found the following migratory species are most at risk:

Air-breathing freshwater mammals are particularly at risk from plastic pollution. Entanglement in plastic can prevent them from reaching the surface, leading to drowning.

Mekong: It is estimated that the Critically Endangered Mekong Catfish and the Mekong River subpopulation of the Irrawaddy Dolphin face lethal threats from entanglement and ingestion of plastic. Drowning because of entanglement in nets is the key threat to Irrawaddy Dolphins that are estimated to number less than 100 individuals.

The Mekong Catfish is considered a flagship species for the conservation of the lower Mekong ecosystem. It is long-lived, matures late, and is a long-distance migrant. This makes it even more vulnerable to human disturbances such as plastics and dams.

Ganges: The Ganges River Dolphin is at high risk of entanglement in fishing lines, especially in gillnets. Ingestion of microplastic is an additional threat. The Gharial, a crocodile species, is likely to become entangled in fishing nets where fisheries overlap with its habitat. It is Critically Endangered.

With nearly 500 species – birds represent over 80 per cent of the CMS-listed species in the Asia-Pacific region – there is significant evidence for bird interaction with plastics.

Migratory birds have been observed making nests out of plastics, using fishing lines and shipping debris, often resulting in the entanglement of their chicks.

Two raptor species assessed are found to be particularly impacted: In the Ganges, the Greater Spotted Eagle is threatened and may die from ingesting litter and by entanglement.

In the Mekong, the Eastern Imperial Eagle may suffer lethal injuries upon ingestion and entanglement in plastic.

Waterbirds such as the Greylag Goose, Common Shelduck, Gadwall, Northern Pintail, Common Teal, Red-crested Pochard and Tufted Duck may interact with plastic in the environment. In some cases, waterbirds ingested plastics including microplastic.

But also, waders such as the Black-tailed Godwit, Eurasian Curlew, Marsh Sandpiper, Common Greenshank, Green Sandpiper and Temminck’s Stint can become entangled where line fishing occurs.

Among terrestrial species, Asian Elephants have been observed ingesting plastic while raiding dump sites for food. The impacts of ingestion by elephants, however, largely remain unknown.

More research on freshwater and terrestrial environments is necessary to fill data gaps. Hence, the report strongly encourages more research on possible adverse impacts in freshwater and terrestrial habitats.

Recommended actions

*Upstream reduction of plastics in the commerce stream through industry and government regulations, incentives, and practices.

* More effective product design, waste management and recycling.

* Include the reduction of plastic pollution in conservation measures for migratory species.

* Need for more research on the impacts of plastics on terrestrial and freshwater species

* Education campaigns and programs to raise awareness among citizens.