Collisions between whales and cargo ships are a significant threat to whale populations, often leaving them little chance of survival. Now, a study published in Science highlights the global scale of the issue: it turns out that shipping routes overlap with 92 percent of the migratory ranges of blue, fin, humpback, and sperm whales.

While ship-strike studies done on a regional scale are essential, they do not give us a full picture of ship strikes worldwide, said co-author Rachel Rhodes, a project scientist at University of California Santa Barbara’s Benioff Ocean Science Laboratory. 

Enter this study, which focused on the four large whale species on a global scale. 

Describing the analysis as the first global map of ship strike risk for the four whale species, Rhodes said, "By taking this broader perspective, we can identify the highest-risk areas worldwide and strategically direct future research and conservation efforts where they’re needed most.”

Mapping the Risks

To generate the map, the research team pooled data from government surveys, public sightings, tagging studies, and historical whaling logs. They combined this with the movements of 176,000 cargo vessels tracked between 2017 and 2022, uncovering high-risk regions worldwide where whales and ships intersect.

While well-known hotspots such as North America’s Pacific coast, Panama, the Mediterranean, and the Arabian Sea remain high-risk zones, the study identified new areas of concern, like southern Africa, Chile, Peru, Ecuador, the Azores, and East Asia off the coasts of China, Japan and South Korea.

Rhodes said that whales might be killed at the latter areas. "This may be a silent contributor to why we aren't seeing more optimistic recoveries for some at-risk whale populations." Despite the dangers, mandatory collision-prevention strategies are almost nonexistent, overlapping with just 0.54 percent of blue whale hot spots and 0.27 percent of humpback hot spots. None overlapped with fin whale or sperm whale hot spots.

Challenges in Conservation

Although many high-risk zones arefound within marine protected areas, this do not translate into better protection for the whales. This was because such areas generally do not impose speed restrictions for ships, being originally designed to address overfishing and pollution.

In addition, most high-risk areas are situated along coastlines, meaning that they were within a nation's exclusive economic zones. Describing this fact as encouraging, UW postdoctoral researcher and lead author Anna Nisi said that it meant that "individual countries have the ability to protect the riskiest areas."

Lessons from the Pacific Coast

In recent years, efforts have been made to reduce the number of whale-ship collisions. For instance, along the Californian coast, Whale Safe is a collaboration between researchers, citizen scientists and cargo ship operators which encourages vessels to slow down during whale migration seasons.

It utilizes vessel tracking, whale monitoring, and data-sharing to alert shipping companies and ensure compliance with voluntary slow zones.

Urgent Action Needed

The researchers emphasize the need for global conservation efforts and hope that their study could bring about more efforts to map out hot spots in more details and inform advocacy efforts. By identifying high-risk zones and emphasizing practical solutions, the study provides a roadmap for safeguarding whales amidst growing global trade.