The number of whales struck by shipping vessels – the leading cause of death worldwide for whales – could be reduced significantly if just 2.6% of the ocean was made safer, researchers from the University of Washington and the British Antarctic Survey have concluded.

This has been the prevailing finding from a new study carried out to examine the risk to whales from ship strikes, launched to address the thousands of whales that are killed each year after being struck by vessels as well as the lack of precise global data on these kind of encounters.

For the first time, researchers have now quantified the risk for whale-ship collisions worldwide for four geographically widespread ‘ocean giants’ most at threat from shipping: blue, fin, humpback, and sperm whales.

The study, published last week in the journal Science, highlights that global shipping traffic overlaps with about 92% of these species’ ranges.

“This is the first study to look at this problem at a global scale, enabling global patterns of collision risk to be identified using an extremely large contemporary dataset of four recovering whale species,” said Dr Jennifer Jackson, a whale ecologist at British Antarctic Survey and a co-author of the research.

The team found that only about 7% of areas at highest risk for whale-ship collisions have any measures in place to protect whales from this threat. These measures include speed reductions, both mandatory and voluntary, for ships crossing the waters that overlap with whale migration or feeding areas.

“This translates to ships travelling 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 decade,” said senior author, Briana Abrahms, a University of Washington assistant professor of biology and researcher with the Centre for Ecosystem Sentinels.

While this study is the first to be conducted on an area of this magnitude, the interventions to reduce the risk of collision between cetaceans and shipping vessels remain “extremely simple”, to the point that implementing management measures across as little as an additional 2.6% of the ocean’s surface would protect all of the highest-risk collision hotspots identified in the study.

“Trade-offs between industrial and conservation outcomes are not usually this optimal,” said co-author Heather Welch, a research scientist with the National Oceanic Atmospheric Administration and the University of California, Santa Cruz. “Oftentimes, industrial activities must be greatly limited to achieve conservation goals, or vice versa. In this case, there is a potentially large conservation benefit to whales for not much cost to the shipping industry.”

The highest-risk areas for the four whale species included in the study lie largely along coastal areas in the Mediterranean, portions of the Americas, southern Africa, and parts of Asia.

The international team behind the study looked at waters where these four whale species live, feed, and migrate by pooling data from disparate sources – including government surveys, sightings by members of the public, tagging studies, and even whaling records. The team collected some 435,000 unique whale sightings in total. They then combined this novel database with information on the courses of 176,000 cargo vessels from 2017 to 2022 to identify where whales and ships are most likely to meet.

The study uncovered regions already known to be high-risk areas for ship strikes: North America’s Pacific coast, Panama, the Arabian Sea, Sri Lanka, the Canary Islands, and the Mediterranean Sea. 

It also identified understudied regions at high risk for whale ship collisions, including southern Africa; South America along the coasts of Brazil, Chile, Peru, and Ecuador; the Azores; and East Asia off the coasts of China, Japan, and South Korea.

Mandatory measures to reduce whale-ship collisions were found to be very rare, overlapping just 0.54% of blue whale hotspots and 0.27% of humpback hotspots, and not overlapping any fin or sperm whale hotspots at all.

It also found that though many collision hotspots fell within marine protected areas, these preserves often lack speed limits for vessels, as they were largely established to curb fishing and industrial pollution. For all four species, the vast majority of hotspots for whale-ship strikes – more than 95% – hugged coastlines, falling within a nation’s exclusive economic zone.

This means that each country could implement its own protection measures in coordination with the UN’s International Maritime Organisation.

In addition to speed reduction, other options to increase the safety of the ocean for the four whale species include changing vessel routings away from where whales are located, or creating alert systems to notify authorities and mariners when whales are nearby.

The authors of the study hope this research could go on to spur local or regional research to map out the hotspot zones in finer detail, inform advocacy efforts, and consider the impact of climate change which will change both whale and ship distributions as sea ice melts and ecosystems shift.

“Protecting whales from the impact of ship strikes is a huge global challenge. We’ve seen the benefits of slowing ships down at local scales through programmes like Blue Whales Blue Skies in California. Scaling up such programmes will require a concerted effort by conservation organisations, governments, and shipping companies,” said co-author, Jono Wilson, director of ocean science at the California Chapter of The Nature Conservancy. 

“Whales play a critical role in marine ecosystems. Through this study we have measurable insights into ship-collision hotspots and risk and where we need to focus to make the most impact.”

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