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Landmark report on migratory species underlines threats to Asia’s wildlife

A boatload of fish caught on the Tonle Sap River in Cambodia. Image by Anton L. Delgado.

  • A U.N.-backed report has found that nominally protected migratory species face the rising risk of extinction amid habitat loss and overexploitation worldwide.
  • Of the 1,200 species listed in the Convention on the Conservation of Migratory Species of Wild Animals, half were found to have declining populations and one in five were threatened with extinction.
  • The report found that “species occurring in Asia are the most threatened overall” and that “early indications suggest that the scale of unsustainable and illegal take may be even higher in Southeast Asia.”

Populations of protected migratory species are plummeting worldwide and “levels of extinction risk are rising,” according to a landmark report that emphasized the devastating threats facing Southeast Asia’s transboundary wildlife.

The release of the United Nations-backed report, branded as the first comprehensive, global study on migratory species, coincides with the Conference of the Parties for the Convention on the Conservation of Migratory Species of Wild Animals, or CMS COP14 in short.

The borderless nature of migratory species makes them ideal showrunners for these negotiations on multicountry conservation efforts.

Besides the cultural significance of many of these species, migrating wildlife also play a critical role in ecosystems. For example, migratory fish transfer nutrients between marine, freshwater and terrestrial ecosystems, while migratory birds and bats disperse seeds and pollinate flowers.

Of the roughly 1,200 species listed on the convention, nearly half are suffering population declines, and one in five are threatened with extinction. While the migratory species report studied each major animal group, fish were by far in the direst state, with 97% of fish species listed on the convention at threat of extinction.

A haul of fish caught from the Tonle Sap River in Longvek city, approximately 40 kilometers (25 miles) north of Phnom Penh. Image by Anton L. Delgado.

The Living Planet Index monitored nearly 16,000 populations of more than 1,700 different migratory species from 1970 to 2017, finding an overall average decline of 15% across all species.

“It really is the first time this data has been brought together,” Kelly Malsch, author of the study, and a leader at the U.N. Environment Programme’s World Conservation Monitoring Centre, said at a press briefing leading up to the report’s release. “We weren’t really sure what we would find. So, understanding and really providing that baseline information for how migratory species were doing, how those under the umbrella of the convention [were doing], was really important to us.”

On top of the challenges facing the animals protected by the convention, the report also found that nearly 400 unlisted species are also under threat and “may benefit from international protection” under the convention.

“A future step, one of the areas for more data, would be to look more at the regional level and also at the national level,” said Amy Fraenkel, executive secretary of the convention, in response to a question by Mongabay at the same briefing. “This was a global report. But it takes a lot more effort, even [more than] we did on this report, to get to this level of resilience with the data … It is certainly something to think about for the future.”

A collection of snares discovered by rangers in Cambodia’s Phnom Tnout–Phnom Pok Wildlife Sanctuary. While community rangers discovered and dismantled these snares, studies suggest thousands more are left undiscovered. Image by Anton L. Delgado.

‘Unsustainable pressure’

Habitat loss, degradation and fragmentation is listed as a “principal threat” to migratory species.

There are more than 16,300 landscapes considered “key biodiversity areas.” The majority of these areas, nearly 9,500 landscapes, received this classification in part because they provide habitat for migratory species. The report studied the threat data for about nearly 3,100 of these areas – finding that almost 60% were under “unsustainable levels of human-caused pressure.”

But by and large, the report found that overexploitation is the largest human-caused threat to the survival of migratory species.

Nowhere is this more prevalent than in Asia.

Just over 770 of the approximately 1,200 species listed in the convention are found in Asia. The report’s analysis of the Red List of Threatened Species, published by the IUCN, the global wildlife conservation authority, found that “species occurring in Asia are the most threatened overall” and that “early indications suggest that the scale of unsustainable and illegal take may be even higher in Southeast Asia.”

There were 133 signatories to the migratory species convention as of September 2023. The Philippines is the only listed “party” member of the 10-country Association of Southeast Asian Nations (ASEAN), the others being listed as “non-party” nations.

Non-party nations have not signed or ratified the convention and are therefore not bound to the environmental treaty. While only The Philippines has signed, half of ASEAN – Indonesia, Malaysia, Myanmar, Thailand and Vietnam – have agreed to Memorandums of Understanding with the convention.

The skulls of two banteng, a species of wild cattle native to Southeast Asia, are kept at BeTreed Adventures in Cambodia’s Preah Vihear province. The animals died after being caught in snares. Image by Anton L. Delgado.

“Hunting is more likely to be unsustainable in regions affected by political instability or poverty, or in areas where infrastructure has been expanded,” the report said.

The Mekong River and basin is a case in point for the study’s findings and exemplifies the plights of migratory species. The nearly 5,000-kilometer (3,000-mile) river flows through six countries and supports the livelihoods of millions of people.

But as a habitat, the Mekong Basin faces a myriad of threats, from a boom in hydropower dam developments to basinwide droughts. Overfishing in each of the Mekong countries, as well as in Cambodia’s Tonle Sap Lake, often referred to as the beating heart of the Mekong River, is crippling wild populations of migratory species.

At the same press briefing, Malsch cited the Mekong giant catfish (Pangasianodon gigas) as an example of a culturally significant and ecosystem-defining species under significant threat in Southeast Asia.

“Across the board, there will be endangered and critically endangered species that are needing more attention, more support, more protection. There are a few key examples in Asia, such as the Mekong giant catfish,” Malsch said. “These are species being impacted by habitat challenges, loss of their key areas that they need to survive. It is something that is needed across the board to focus on.”

A Mekong giant catfish is measured in a rearing facility before being released into Cambodia’s Tonle Sap Lake. Image by Anton L. Delgado.

Zeb Hogan, program lead for the U.S.-funded conservation project Wonders of the Mekong, has worked with this species of giant catfish for more than two decades and is one of the authors of a recent study that found an “alarming decline” of fish species in Lower Mekong Basin fisheries.

“Due to their migratory nature, large size, and high commercial value, they are among the most vulnerable of Mekong fish,” Hogan said of the giant catfish, in an email response to Mongabay.

“Loss of migratory fish would be devastating to the millions of people who depend on them for food and livelihoods,” Hogan said. “There is also a close link between fish biodiversity and fisheries production. As species are lost, there is often a parallel loss in fish harvest. Ultimately, protecting migratory fish provides massive benefits to rivers, people, and aquatic life.”

The solutions proposed in the report range from tangible to idealistic, from identifying important habitats for migratory wildlife and establishing catch limits for non-marine species, to tackling global plastic pollution and following through on international carbon emissions reductions.

The report concluded by emphasizing the “urgent need for action,” and specifically in the case of declining migratory species, for action to “protect their key sites.”

“The good news is that, although some important data gaps remain, the main drivers of population declines and species loss are known, and so too are the solutions,” the report concluded.

Banner image: Fish caught from the Tonle Sap River, by Anton L. Delgado.

Illegal hunting a greater threat to wildlife than forest degradation


Chevalier, M., Ngor, P. B., Pin, K., Touch, B., Lek, S., Grenouillet, G., & Hogan, Z. (2023). Long-term data show alarming decline of majority of fish species in a Lower Mekong Basin fishery. Science of The Total Environment891, 164624. doi:10.1016/j.scitotenv.2023.164624

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