What the whalers did not achieve in the centuries they hunted them for their oil, could be done by the huge ships that transport the oil, computers or toys that human societies need. A new global risk map, published in the journal Scienceshows how thousands of cargo ships pass through sea areas where the remaining whales breed, feed and migrate. The cartography highlights the coastal areas of the most developed countries or the shortest possible routes connecting their ports. The Galician coast, the Strait of Gibraltar and the Canary Islands are among the areas at highest risk. Worst of all, human authorities only limited speed on 0.5% of that map.
The study, conducted by biologists from five continents, is based on two impressive databases. On the one hand, information from 435,370 sightings of specimens of four large whale species: blue whale, fin whale, humpback whale and sperm whale. On the other hand, the routes and movements of 175,900 large non-fishing vessels – over 300 tonnes – between 2017 and 2022. For this they relied on the AIS system (acronym for Automatic Tracking System) carried by all ships, large and small, which locates them via satellite and allows maritime traffic to be regulated. Then, supported by powerful computers, they overlaid both maps, obtaining the most complete picture of the risk of collision between cetaceans and cargo ships.
The map shows how 91.5% of the areas where whales live or migrate are also the preferred routes of large ships. And these are not occasional crossings, but rather areas of very intense traffic. For example, they calculated that in blue whale habitats, ships travel a distance equivalent to going to the Moon and back 4,600 times a year. The risk to the whale is slightly lower, only 2,600 times.
To compare the real risk posed by so many miles, they took one of the most studied areas as a reference: the California Current ecosystem, on the west coast of the United States. Anna Nisi, biologist at the University of Washington and first author of the research, explains it: “It is an area where collisions between whales and ships have been studied in depth. It is estimated that around 80 cetaceans (including fin whales, humpback whales and blue whales) die each year in this region due to these collisions. The figure would be between 2 and 8 times higher than the limit for obtaining the maintenance or recovery of these animals on those coasts. Nisi acknowledges that it is not possible to obtain a similar calculation on a global scale, but it is possible to obtain the relative risk of collision and, therefore, the potential for death.
“Collisions with shipping vessels are a major cause of human-caused whale mortality, along with entanglements in fishing gear. It varies depending on the species and there are other threats, such as climate change and exposure to pollution,” recalls the researcher.
As on the streets, there are black spots in the sea too. The authors focused a second phase of the study on the 1% of areas where ship AIS data overlapped most with cetacean sightings. A first piece of information reminds us of those who arrived first: in the Southern Ocean, where merchant ships rarely dare to pass, there is no hot spot (or hot spot in English slang). In the other sea for the brave, the Arctic Ocean, only 0.56% of the total hot spots are found. Large-scale international maritime traffic began in the 19th century, but has accelerated in recent decades,
quadrupled compared to 1992. Furthermore, it is concentrated in a few areas: Indian Ocean (21.6%), North Pacific (14.5%) and Mediterranean (13.3%) where the risk is greatest. And it’s not in the high seas, almost all the black spots are close to the coast. Those bordering eastern China, southern Asia and the western United States are among the most dangerous. In Europe, the waters off Galicia, the Strait of Gibraltar and the southern Mediterranean are among the most dangerous for three species. The Canary Islands appear prominently on the high threat map for the fourth, the sperm whale.
A blue whale, the largest animal on the planet, looks like a sardine on the keel of this container ship docked in the port of Colombo, Sri Lanka.Sopaka Karunasundara
The biologist Briana Abrahams also from the University of Washington, and senior author of the research, highlights two possible reasons why whale habitat and shipping routes overlap so much: “In many cases, the ideal feeding habitat for whales is found near the coasts, where upwellings produce waters rich in nutrients where its prey develop and gather. The coasts are also the places where the highest density of maritime traffic entering and leaving coastal ports is observed.” Nisi completes the latter: “Maritime traffic usually delimits the coasts when ships transit between ports, which generates a high risk in those areas. The California coast is a great example of this.”
In the Spanish case, the scientific director of the environmental organization MEER Fabian Ritter, recalls that “there is a lot of traffic on the Spanish coasts, including international sea routes for merchant
Ritter, who has been studying the situation of cetaceans in the Canary Islands for years, underlines how ferries, especially those traveling at high speed, are extremely prone to colliding with whales and other marine species. “Therefore, in very touristy areas, these boats can dominate.” The expert, who did not participate in the study Science it then focuses on the case of the Canary archipelago, “which hosts the densest network of high-speed ferries in the world”. According to Ritter, it is estimated that, in total, high-speed ferries travel more than 1.4 million kilometers within the archipelago every year. “Given that the Canary Islands are home to an extraordinary diversity of species – 30 species of whales and dolphins have been documented here – it is not surprising that the risk of collisions with ships is extremely high,” says the scientist.
Slow down and get around
The International Whaling Commission has published its plan to reduce collisions and mitigate its impact on the survival of cetaceans. To be implemented this decade, the program proposes two fundamental measures: reduce the speed where the whales are present and, if the risk is very high, detour the ship. While waiting for these mitigation measures, the newly published risk map reveals that there are hardly any areas where these limitations have been implemented. For the fin whale and the sperm whale the value is zero hotspot where the obligation to change route or limit speed has been applied. The percentage rises to 0.27% in the case of the humpback whale and 0.54% for the blue whale. The figures rise to a commendable 7% if we consider the areas where it is advisable, but not obligatory, to slow down. The American west coast is the one that concentrates the limitations.
“Just as land traffic is regulated in areas where protected species, such as the lynx, live, we must do the same at sea,” says Natacha Aguilar de Soto, researcher at the Spanish Institute of Oceanography (IEO/CSIC), in a study e-mail. which has been investigating the situation of cetaceans in the Canary Islands for years. “We are developing technological projects to improve the detectability of large cetaceans through thermal detection, with the collaboration of fast shipping companies.” Collision prevention courses are also provided for bridge personnel. “This should be mandatory for all shipping companies transiting cetacean habitats, worldwide. But more is needed: dynamic measurements of changes in path and speed. ”Speed kills, that’s why we go slower in front of schools,” says Aguilar de Soto, who was not involved in the study on Science and leaves a final reminder: “It is necessary that the company is informed that it buys everything made in China kill the whales.”
The NOAA (American Federal Oceanic and Atmospheric Agency) scientist and co-author of the research published in Science Heather Welch recognizes that finding a balance between the needs of the economy and those of nature is rarely easy: “Often, industrial activities must be limited as much as possible to achieve conservation goals, or vice versa. “In this case, there is a potentially large benefit for whale conservation at little to no cost to the maritime industry.” It is the latest result of this work: if the brakes were forced to intervene on 2.6% of the sea surface, the danger would be reduced in all critical points at risk of collision on the map.
What measures can be taken to reduce ship collisions with whales?
Santos, a marine biologist involved in advocating for cetacean protections. She emphasizes the importance of implementing regulations to mitigate the risks to whales caused by shipping traffic, akin to how traffic rules are enforced for the protection of terrestrial wildlife.
The high mortality rate of cetaceans, which are increasingly threatened by ship collisions, highlights the urgency for intervention. The research suggests that while local efforts such as speed restrictions and rerouting of vessels are critical, broader regulations need to be enacted globally to safeguard whale populations.
Additionally, awareness among maritime operators and the public about the significance of these measures can play a pivotal role in protecting these majestic marine mammals from further decline. Moving forward, collaboration between researchers, environmental organizations, and maritime authorities will be essential to develop and enforce effective strategies to reduce ship-whale collisions, ensuring these species can thrive in their natural habitats.