Female leatherback turtles are among the most fearless creatures in the world, traveling up to 10,000 miles after nesting to find food in distant seas. They are known to venture from tropical Southeast Asia to the cold waters of Alaska, where jellyfish are abundant.
But such a long journey poses dangers that can be deadly: fishing nets intended for other species, poachers, pollution and waters warmed by the climate crisis, forcing the turtles to travel even further to find their prey.
These turtles are just one of hundreds of migratory species – those that make remarkable journeys across land, rivers and oceans every year – that are at risk of extinction due to human interference, according to a landmark report released Monday by the U.N. agency.
Of the 1,189 creatures listed in the Convention on the Conservation of Migratory Species of Wild Animals (CMS), more than one in five are threatened.
This includes species from all possible animal groups – including whales, sharks, elephants, wild cats, birds of prey, birds and insects.
About 44% of listed species are experiencing population declines, the report said. Most worrying is the state of global migratory fish: almost all, 97%, of the fish listed are at risk of extinction.
The report is the first inventory to assess the status of migratory species and their attempts to survive in a world dramatically changed by humans. It found that the two biggest threats were overexploitation and habitat loss due to human activities such as clearing of land for agriculture, roads and infrastructure. These activities also disrupt the paths of migratory species, sometimes making it impossible for them to complete their journey.
About 58% of monitored areas considered important for migratory species are experiencing unsustainable levels of human pressure, according to CMS.
Climate change and pollution also pose major threats. Higher temperatures not only force some species to travel further, but can also cause animals to move at different times of the year. This can mean missing out on prey or a reproductive partner.
A particularly blatant example is the narwhal. Famous for their spiral-shaped tusks, these mythical sea creatures spend summers in mostly ice-free coastal areas before migrating south to deeper Arctic waters.
But as the oceans warm and annual sea ice expansion occurs later and later, scientists have found that some narwhals are delaying their journey and risk becoming trapped in sea ice with no openings to breathe when the ice pack freezes in the fall.
Global warming can also lead to the destruction of habitats such as coral reefs for marine life.
Light pollution also makes migration more dangerous for some species, particularly birds. At the McCormick Place Lakeside Center, a Chicago building on the shores of Lake Michigan, more than 40,000 dead birds have been recovered since 1978, the report said, after they were attracted to and collided with the light streaming from the windows.
Some mass whale strandings have been linked to noise pollution, while plastic pollution has been linked to the mortality of albatrosses, large migratory seabirds.
The report highlights how creatures who undertake these often spectacular journeys also play a critical role in maintaining the Earth’s delicate ecological balance.
“These animals are primarily part of the ecosystems in which they occur,” CMS Executive Director Amy Fraenkel told CNN. “And we have a lot of evidence that removing these species as they decline will have an impact on the ecosystems in which they occur, and not in a good way.”
Take bats, for example. It can be hard to imagine them as creatures that make the world more beautiful. But those that migrate play a crucial role as pollinators for a variety of fruits and flowers – pollinating more than 500 species of flowering plants, the report says.
The bats spread seeds that help maintain healthy forests, and they regulate the spread of insects by eating large quantities of them.
But bats are threatened by deforestation, which destroys their habitat, and by hunting – their meat is considered a delicacy in some countries. Noise pollution also distracts foraging bats and makes them less efficient hunters.
The report contains some good news. There are 14 species that recorded positive trends, including blue and humpback whales. But overall the picture is alarming.
“Today’s report shows us clearly that unsustainable human activities are threatening the future of migratory species – creatures that not only act as indicators of environmental change, but also play an essential role in maintaining the function and resilience of our planet’s complex ecosystems,” says Inger Andersen, executive director of the United Nations Environment Program, said in a statement.
The report was presented on Monday at a major UN wildlife conservation conference in Samarkand, Uzbekistan.
Reducing the threat to migratory species requires a global effort, experts say, because so many animals making these regular journeys cross international borders, whether on land, sea or air.
“Migrant species play a special role in nature because they do not recognize political boundaries,” said Anurag Agrawal, a professor of environmental studies at Cornell University. “Instead, their movements are sewing up large parts of the planet. Their conservation therefore requires international cooperation.”