Nearly half of migratory wild animal species protected under a major United Nations treaty now have declining populations, according to a new interim update to the State of the World’s Migratory Species report. The findings will be presented to governments gathering in Brazil later this month for a major global wildlife conservation meeting.

The update shows that 49% of migratory species listed under the Convention on the Conservation of Migratory Species of Wild Animals (CMS) are experiencing population decline. This represents a rise from 44% reported just two years ago. At the same time, 24% of species are now considered at risk of extinction, an increase of two percentage points since the previous assessment.

The data will inform discussions at the 15th Meeting of the Conference of the Parties to the Convention on Migratory Species (CMS COP15), scheduled to take place in Campo Grande, Brazil from March 23 to 29. Governments attending the week-long meeting are expected to review scientific findings and consider measures aimed at improving conservation outcomes for migratory wildlife.

Migratory species play a critical role in ecosystems around the world. Billions of animals move across land, rivers, oceans and skies each year, pollinating plants, transporting nutrients, regulating ecosystems and controlling pests. Their movements also support livelihoods and cultural traditions in many regions.

Because these animals cross national borders and sometimes entire continents during their migrations, effective conservation depends on coordinated international action along their migratory routes.

Tracking changes in migratory species

The interim update was developed for CMS by the UN Environment Programme World Conservation Monitoring Centre (UNEP-WCMC) together with a range of scientific contributors. It assesses changes in conservation status for species listed under the treaty since the publication of the 2024 baseline report.

The assessment draws on the latest data from the International Union for Conservation of Nature (IUCN) Red List of Threatened Species as well as newly reported population trends in scientific literature. It provides governments with updated evidence ahead of negotiations and policy discussions at COP15.

Among the findings, 26 species listed under CMS have moved to higher extinction risk categories since the previous assessment. Eighteen of these species are migratory shorebirds.

There have also been some positive developments. Seven species have shown improvements in conservation status, including the saiga antelope, the scimitar-horned oryx and the Mediterranean monk seal.

The report also identifies 9,372 Key Biodiversity Areas that are important for CMS-listed species. Almost half of the total area covered by these sites, 47%, does not currently fall within protected or conserved areas.

Emerging knowledge and conservation efforts

Researchers report progress in mapping migratory routes and identifying important habitats used by a range of species. Work to map ocean migrations through initiatives such as Migratory Connectivity in the Ocean and BirdLife International’s identification of major marine flyways is contributing to better understanding of how species move across large ecosystems.

Advances in tracking technologies and global collaboration have also improved knowledge of migratory corridors used by sharks, rays and marine mammals. New initiatives are being developed to identify key marine areas for sea turtles.

Despite these advances, scientists warn that the overall picture remains concerning. Indicators such as the share of species with declining populations show deterioration since the first global report was released.

Amy Fraenkel, Executive Secretary of the Convention on Migratory Species, said the findings reinforce the need for stronger international action.

“The first global report was a wake-up call,” she said. “This interim update shows that the alarm is still sounding. Some species are responding to concerted conservation action, but too many continue to face mounting pressures across their migratory routes. We must respond to this evidence with coordinated and effective international action.”

Pressures along migratory routes

The report identifies overexploitation and habitat loss and fragmentation as the two most significant threats to migratory species worldwide. Activities such as hunting, fishing, infrastructure development and land conversion can disrupt migration routes or reduce the availability of key habitats.

Particular attention is being given to species listed under CMS Appendix I. These species are considered endangered across all or a significant portion of their range and require strict protection from the treaty’s member states.

Currently 188 species are listed under Appendix I. These include 28 terrestrial mammals, 23 aquatic mammals, 103 bird species, eight reptiles and 26 fish.

Countries that host these species during any stage of their migration are required under the treaty to prohibit activities such as hunting or capturing them. Governments must also protect critical habitats and remove obstacles that prevent the animals from completing their migrations.

New initiative on the taking of migratory species

Delegates at COP15 are also expected to consider a new initiative addressing the taking of migratory species for human use. Known as the Global Initiative on Taking of Migratory Species, the programme aims to help governments ensure that any use of migratory wildlife is legal, safe and within sustainable limits.

Recent analysis has shown that taking species for domestic consumption represents a greater threat in many cases than international wildlife trade.

Fraenkel stressed that preventative action will be essential if species declines are to be reversed.

“If we intervene only at the point of crisis, we risk acting too late.” said Fraenkel. “By strengthening governance, monitoring, legislation and community engagement upstream, we can reduce pressure on these remarkable animals and put them on the path to lasting recovery.”

Building on the 2024 global assessment

The interim update builds on the landmark State of the World’s Migratory Species report released in 2024. That report was the first comprehensive global assessment of migratory animals covered by the CMS treaty.

It analysed the status of 1,189 species listed under CMS Appendices I and II and linked the findings to more than 3,000 additional migratory species worldwide.

Among its findings were that 70 CMS-listed species had become more endangered over the previous three decades while only 14 showed improvement in status. Migratory fish populations had declined by an average of 90% since the 1970s, with 97% of CMS-listed migratory fish species considered at risk of extinction.

The interim update aims to ensure governments have the most current scientific information available as they prepare new conservation commitments at COP15.

Fraenkel said the tools and knowledge now available leave little doubt about the scale of the challenge facing migratory wildlife.

“We have a baseline. We have better tools. And we have growing public awareness,” she said. “The question before governments at COP15 is straightforward: will we match this knowledge with the political will and investment needed to secure the future of the world’s migratory species?”