Ship routes overlap with 92% of whale habitats 

The collision of cargo vessels with whales is one of the leading causes of death for these majestic marine creatures. Despite high-profile accidents and localized research efforts, a comprehensive global picture of the risks posed by shipping to whales has remained elusive – until now. 

A study led by the University of Washington (UW), with contributions from University of California, Santa Barbara (UCSB) researchers, reveals that global shipping routes overlap with 92% of the migratory ranges of blue, fin, humpback, and sperm whales.

Global risk assessment 

Published in the journal Science, the study offers the first global map of ship-strike risks for these four large whale species. 

“Most ship-strike studies are done at a regional scale, which is critically important but doesn’t provide the full picture worldwide,” said co-author Rachel Rhodes, a project scientist at UCSB’s Benioff Ocean Science Laboratory. 

“By taking this broader perspective, we can identify the highest-risk areas globally and strategically direct research and conservation efforts where they’re needed most.”

Whales and ships: A deadly intersection

Cargo vessels, often the size of skyscrapers and over ten times the length of an adult blue whale, dominate the oceans. Any whale crossing their path faces almost certain death. 

As shipping lanes increasingly intersect with whale migration routes, the likelihood of collisions grows. 

According to Professor Briana Abrahms, this translates to ships traveling thousands of times the distance to the moon and back within these species’ ranges each and every year. 

“And this problem is only projected to increase as global trade grows in the coming decades,” said Abrahms.

Success in local conservation efforts

While the outlook may seem grim, successful initiatives like Whale Safe off the California coast demonstrate the potential for mitigating these risks. 

Whale Safe is a collaborative effort between researchers, citizen scientists, and shipping companies to reduce collisions by slowing vessels in whale-rich waters. 

Tracking whale presence and providing data on ship compliance with slow zones have helped lower collision rates since the program’s launch in 2019.

“Getting the vessels to slow down works,” said UCSB marine ecologist and co-author Douglas McCauley, whose lab developed Whale Safe. 

Lack of adequate protection for whales

The Santa Barbara Channel, a vital migration corridor for blue, fin, and humpback whales, overlaps with major shipping hubs in Los Angeles, Long Beach, and Oakland. 

Federal guidelines encourage ships to voluntarily reduce their speed from May to December to protect endangered whales.

Despite these localized successes, the study found that only 7% of the highest-risk areas globally have measures in place to protect whales from ship strikes.

Mapping whale-ship collision hotspots

To estimate collision risks, the researchers first needed to map whale habitats on an unprecedented global scale. 

This involved compiling data from government surveys, public sightings, tagging studies, and even historic whaling vessel logbooks to track where blue, fin, humpback, and sperm whales live, feed, and migrate. 

The team combined this information with the routes of 176,000 cargo vessels tracked between 2017 and 2022 using data from ships’ automatic identification systems and algorithms developed by Global Fishing Watch.

Identifying high-risk regions 

The study revealed several new high-risk regions, including areas off southern Africa; the coasts of Brazil, Chile, Peru, and Ecuador in South America; the Azores; and East Asia, particularly near China, Japan, and South Korea. 

“These are vast areas of the ocean where whales may quietly be being killed,” Rhodes said. “This may be a silent contributor to why we aren’t seeing more optimistic recoveries for some at-risk whale populations.”

The research also reaffirmed known hotspots, such as the Pacific coast of North America (including California), Panama, the Arabian Sea, Sri Lanka, the Canary Islands, and the Mediterranean Sea.

Urgent need for policy changes

The team discovered that mandatory measures to prevent whale-ship collisions are exceedingly rare, covering just 0.54% of blue whale hotspots, 0.27% of humpback hotspots, and none for fin or sperm whales. 

Even marine protected areas often lack speed regulations for vessels, as they were initially established to address issues like overfishing and industrial pollution rather than shipping-related risks.

Encouragingly, 95% of the hotspots identified lie within nations’ exclusive economic zones (EEZs), meaning individual countries have the authority to implement protective measures. 

“From the standpoint of conservation, the fact that most high-risk areas lie within exclusive economic zones is actually encouraging,” said lead author Anna Nisi, a UW postdoctoral researcher. 

“It means individual countries have the ability to protect the riskiest areas.” 

Expanding protective measures to cover an additional 2.6% of the ocean’s surface would safeguard all the identified collision hotspots, the researchers estimate.

Protecting whales from ship strikes 

The experts hope their study will inspire local and regional research to refine hotspot maps, inform advocacy efforts, and address the impact of climate change, which will alter whale and ship distributions as sea ice melts and ecosystems shift.

“Protecting whales from the impact of ship strikes is a huge global challenge,” said Jono Wilson, co-author and director of ocean science at The Nature Conservancyù’s California Chapter. 

“We’ve seen the benefits of slowing ships down at local scales through programs like ‘Blue Whales Blue Skies’ in California. Scaling up such programs will require a concerted effort by conservation organizations, governments, and shipping companies.”

Whales play a critical role in marine ecosystems, supporting biodiversity and contributing to ocean health. By identifying ship-collision hotspots and prioritizing these areas for conservation, this study offers a path forward to ensure their survival in an increasingly industrialized ocean.

Video Credit: Global Fishing Watch 

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