Migrating whales need specially managed blue corridors

Often when people think about the mass migration of animals, they picture herds of wildebeest galloping across the Serengeti plains or flocks of geese flying south for the winter.

But as Melanie Lancaster, senior species specialist for WWF’s Global Arctic Programme, explains, vast underwater migrations also take place in the Earth’s oceans—and these migratory routes need to be safeguarded to protect marine species like whales.

Many cetaceans — from diminutive dolphins to massive blue whales — swim astonishing distances seasonally to take advantage of sheltered bays, food hotspots, and other areas that offer the conditions they need to survive.

The underwater migration routes they use, known as blue corridors, can span thousands of kilometres, often crossing national borders and extending into the high seas.

For species that live within the boundaries of a single country, the responsibility for their conservation ultimately belongs to that country’s government. For far-ranging whales, including those that migrate from the tropics to the Arctic, conservation is more complicated — yet no less essential.

Across the globe, whales face a multitude of threats during their migrations. The top three are shipping, fishing and climate change. Depending on their routes, whales risk entanglement in fishing nets and lines, collisions with ships, distress, disorientation and displacement from underwater noise pollution, shifts in and loss of prey, and increasing predation risk due to the effects of the climate crisis. Protecting some of their habitats through marine protected areas and other measures is a good start. But it is not a complete solution.

Networks of protected and conserved areas—which incorporate elements of ecological connectivity, such as migratory corridors—are necessary to maintain ocean health and function. Although widely promoted by scientists and now finally getting some traction among policy-makers, in practice, migratory corridors for whales have never been integrated into the systematic design and implementation of such ocean networks. Instead, whales are left to “swim the gauntlet” of threats during their migrations twice a year—a conservation strategy that is far from effective.

A triple whammy of threats

Holding the champion position for the longest migration of all mammals on the planet, the North Pacific grey whale swims 11,000 kilometres every spring from the warm equatorial waters of Mexico to the icy Arctic Ocean. These whales face a multitude of threats during their migrations.

Leaving the sheltered lagoons of Mexico, the whales, including females with young calves, travel north along the US west coast. Stopping over to feed off the coast of Oregon, they are stressed by underwater noise from ship traffic. They then continue up Canada’s coastline into Alaska and swim through the Bering Sea, known as America’s “fish basket” because it supplies almost half the seafood consumed in the US. Here, some whales become entangled in fishing gear. Upon finally reaching Arctic waters, it seems they have, in recent years, been greeted by a lack of food: Arctic marine heatwaves and other climate change–related effects are thought to have diminished grey whale prey.

This loss of food at the end of a long migration was believed to be a primary cause of an unusual mortality event declared by the US government from 2018 to 2021, during which time more than 500 malnourished grey whales washed up along the coasts of their blue corridors. The size of the grey whale population dropped by half, from around 28,000 to 14,000.

Yet the Arctic Ocean is a summer feeding destination for almost a quarter of the world’s whales. Blue corridors are conduits for thousands of whales finding their way from the tropics to the Arctic’s icy cold, food-rich waters every summer. In addition, three whale species—narwhal, beluga and bowhead whales—live there year-round.

Conservation strategies

As climate change heats up Arctic waters and industrialization creeps northward, whales — like the North Pacific grey whale — need space to adapt to new conditions. They cannot be fenced in by shipping lanes and fishing trawlers. They need adequate protective measures that include migratory corridors as critical habitats.

For the three Arctic whale species, dynamic and flexible measures to safeguard them on their migrations are especially important. We still have large gaps in our knowledge of when and where these populations migrate. Because they hug the sea ice during their migrations, reductions in ice thickness and extent across the Arctic directly affect their migratory behaviours.

Considering that Arctic shipping volumes have doubled over the last 10 years while both commercially important fish stocks and fishing fleets have pushed deeper into Arctic waters, now is the time to recognize migratory corridors as essential components of ocean connectivity and marine species conservation, and to include these in ocean protection measures.

This is not just an Arctic opportunity, but a global one. Under the UN’s Kunming-Montreal Global Biodiversity Framework, 196 nations around the world have already committed to protecting and conserving at least 30 per cent of the world’s oceans — and ensuring sustainable use of the remaining 70 per cent — by 2030. This is a heavy lift for governments, the private sector and civil society, but it’s an essential one.

At the 16th meeting of the Conference of the Parties to the Convention on Biological Diversity in October 2024, we will have the first chance to see whether national commitments towards this target, including by Arctic states, measure up to the task.

I’ve been lucky to see the blows of humpback whales off the coast of southeastern Australia as the whales migrated from Antarctica to give birth in calm tropical waters. Across the country, there is great excitement each year as we welcome the whales back. We must not let whales and other migratory ocean species, like turtles and sharks, become the tragedy of the commons because their lives span multiple political boundaries. We must take collective responsibility to protect these species by ensuring that our oceans remain connected.

This article originally appeared in WWF Arctic’s latest issue of The Circle, “Making Waves: Getting it right for Arctic whales.“