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  • Could we be seeing the end of some of the great animal migrations? Fishing, fences and development are fast-tracking extinctions.

    This article has been republished from The Conversation under Creative Commons licence CC BY-ND 4.0 and is written by Richard Fuller (Professor in Biodiversity and Conservation, The University of Queensland), Daniel Dunn (Associate Professor of Marine Conservation Science and Director of the Centre for Biodiversity and Conservation Science (CBCS), The University of Queensland) and Lily Bentley (Postdoctoral research fellow (The University of Queensland). It was originally titled ‘The world’s spectacular animal migrations are dwindling. Fishing, fences and development are fast-tracking extinctions’.

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    Godwits – designed to fly

    As with other flying birds, godwits have many physical features that work together to enable them to fly. They need lightweight, streamlined, rigid structures for flight.

    In 1875, trillions of Rocky Mountain locusts gathered and began migrating across the western United States in search of food. The enormous swarm covered an area larger than California. Three decades later, these grasshoppers were extinct.

    This fate is all too common for migratory species. Their journeys can make them especially vulnerable to hunting or fishing. They may move between countries, meaning protecting the species in one jurisdiction isn’t enough. And it’s hard for us to even know if they’re in trouble.

    Today, we get a global glimpse of how migratory species are faring, in the first-ever stocktake produced by the United Nations Convention on the Conservation of Migratory Species. The report shows falling populations in close to half (44%) the 1,189 species tracked by the convention. The problem is much worse underwater – 90% of migratory fish species are threatened with extinction.

    Their decline is not inevitable. After all, the migratory humpback whale was headed for rapid extinction – until we stopped whaling.

    Why are migratory species at higher risk?

    Every year, birds weighing about 300 grams leave Siberia and fly non-stop to Australia. Some bar-tailed godwits fly 13,000 km without stopping – one of the longest known continuous migrations

    Their journeys are critical for their life cycles – to find food, mates or a better climate. To undertake these journeys, animals must be in good condition with plenty of fat stores, and they must have safe flyways, swimways and pathways.

    On land, roads and fences carve up migratory routes for animals like wildebeest. At sea, fishing trawlers chase migrating schools of fish and often accidentally collect sea turtles, albatrosses and whales. On seashores, development or land reclamation take away vital resting points for migrating shorebirds.

    What the report shows us is that migration between countries is getting harder and harder. While a few species are benefiting greatly from farming and artificial wetlands, many more are being severely harmed.

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    Wildebeest migrating in Africa

    Even the largest migrations can be stopped by fences or other barriers.

    Overexploitation is the top risk

    Human exploitation of migratory species – taken as food, bycatch or exterminated as “pest” species – is the main reason why these species are in decline.

    Animals often migrate in large groups, making them an appealing target for hunting or fishing. This is why we no longer have species such as the passenger pigeon, once numbering in their billions but hunted to extinction in 100 years.

    Marine species are often out of sight, out of mind. But this report is a huge red flag for ocean ecosystems. Oceanic shark and ray populations have fallen 71% since 1970, which coincides with an 18-fold increase in fishing pressure. Bycatch in commercial fisheries is a huge problem for sharks, turtles, mammals and birds, but it can be massively reduced with existing technology, if deployed across all fleets

    Overexploitation can be stopped. In 1981, Australia and Japan agreed to stop hunting Latham’s Snipe, a migratory shorebird that travels between the two countries. It’s the same story for humpback whales, which have returned in large numbers – and created a new industry, whale-watching.

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    Dead manta rays

    Populations of sharks and rays have plummeted since 1970 – and fishing pressure is to blame.

    On fences and stepping stones

    Direct killing of migratory animals isn’t the only threat. Clearing forests and grassland for farming destroys habitat. Light pollution can mess with navigation, climate change plays havoc with the timing of migration, and underwater noise pollution can confuse marine migrants. Even simple actions like building fences, roads and dams can disrupt migrations over land and through rivers.

    Many migratory species need stepping stones: resting sites linking up their whole migratory route. If just one site is lost – or if animals are intensely hunted there – the whole chain can collapse.

    Once identified, key areas have to be protected, which is where we often get stuck. But there are glimmers of hope. Last year conservation of these areas in the ocean got a boost when the world’s nations agreed to better protect the high seas beyond national jurisdictions, which fills a planet-sized gap in biodiversity governance.

    What the report didn’t cover

    This is a groundbreaking report, but it has limitations. First, it only covers species listed under the UN convention, a tiny fraction of all migratory species. Listing unlocks stronger protections and urgently needs to be rolled out to more species.

    For instance, around 60 migratory fish species are covered – but more than 1,700 others are not. Of these unprotected species, almost 25% are threatened, near threatened or there’s not enough data to know.

    That’s to say nothing of insects. To date, only one insect is listed on the convention, the famous monarch butterfly which migrates from the United States to Mexico. But millions of tonnes of insects migrate through the airspace each year, and we have largely no idea what they are, where they’re going or how they’re faring.

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    Monarch butterfly swarm

    Monarch butterflies (Danaus plexippus) get the press on migration – but many more insect species migrate.

    Can we save these species?

    We now know much more about why migratory species are in decline. But we’re still not acting to protect them adequately.

    More than 90% of the world’s migratory birds aren’t adequately protected by national parks and other protected areas. Only 8% of the world’s protected land is joined up, preventing migrating animals from moving safely across their routes. Because of this, animals have to make daring sorties across unprotected land or sea to complete their journeys.

    So what can be done? Agreements between countries can create more action, but in practice, each country needs to actually do what it has already promised.

    Policymakers can turn to a bevy of new tools, including Important Bird & Biodiversity Areas and the Migratory Connectivity in the Ocean system, to provide easy access to knowledge on how migratory species use and move through the world.

    Animal migrations have collapsed on our watch. We need to do all we can to stem the losses and begin recovery if we want future generations to be able to experience nature in all its glory.

    Related content

    This Connected series article On the move includes teacher support material about the technology used for monitoring migration.

    The following articles below provide additional information about animal migration and how scientists and citizen scientists track the animals.


    Marine species


    Monarch butterflies

    Activity ideas

    Bird hotel is an active game that demonstrates the importance of estuaries for bird migration. Discover how one primary school teacher adapted this activity for their science unit on the New Zealand longfin eel.

    Tracking E7 – learn about the migratory flight of bar-tailed godwits from New Zealand

    Useful links

    Find out more about some of the research mentioned in this article:

    Read the first-ever UN report on the State of the World's Migratory Species released in 2024.

    See this Guardian news story Bar-tailed godwit sets world record with 13,560km continuous flight from Alaska to southern Australia from October 2022.

    The 1981 Agreement between the Government of Australia and the Government of Japan for the Protection of Migratory Birds in Danger of Extinction and their Environment.

    Visit the United Nations Intergovernmental Conference on Marine Biodiversity of Areas Beyond National Jurisdiction website.

    Find out more about using radar to study insect movement on The Radar Entomology Web Site.

    Claire A. Runge, et al., Coordinating Domestic Legislation and International Agreements to Conserve Migratory Species: A Case Study from Australia, Conservation Letters, Vol 10, 2017.

    Read about Protecting the most important habitats for birds on the BirdLife website.

    MiCO, Migratory Connectivity in the Ocean, is developing a system that aggregates and generates actionable knowledge to support worldwide conservation efforts for numerous migratory species and the oceans on which they depend.

    Read more in these The Conversation articles:


    This article was written by Richard Fuller (Professor in Biodiversity and Conservation, The University of Queensland), Daniel Dunn (Associate Professor of Marine Conservation Science and Director of the Centre for Biodiversity and Conservation Science (CBCS), The University of Queensland) and Lily Bentley (Postdoctoral research fellow (The University of Queensland). The article was originally published in The Conversation, 13 February 2024. Read the original article.

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    The Conversation

    The Conversation is an independent source of news and views, sourced from the academic and research community and delivered direct to the public.

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      Published 10 April 2024 Referencing Hub articles
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