Whales in ship strike hotspots could be saved by protecting just 3% more ocean

Protecting a little bit more of the ocean could lead to big changes for whales.

Hundreds of thousands of large ships sail the oceans every year, carrying passengers, goods and commodities around the world. The size and speed of these vessels is enough to plough through the waves – and any wildlife in their path.

Each year, it’s estimated that tens of thousands of whales are struck by ships. The consequences range from lacerations to broken bones and even death. New research has mapped where the risk of collision risk is at its highest, identifying new hotspots around Africa’s southern coast and elsewhere.

Despite the threat to whales, less than 7% of these ship strike hotspots currently have protections. While this situation won’t change overnight, protecting just an additional 2.6% of the ocean would help to eliminate many of these high-risk areas while only increasing shipping time by a small amount.

“Trade-offs between industrial and conservation outcomes are not usually this optimal,” said co-author Dr Heather Welch. “Industrial activities must often 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 findings of the research were published in the journal Science.

Finding whale ship strike hotspots

Since the 1990s, worldwide shipping traffic has quadrupled. Increasing globalisation and the rise of online shopping means that more goods than ever before are travelling by sea. By 2050, it’s expected that the volume of maritime trade will be three times higher than it is today.

Alongside cruise ships and fishing vessels, this means the ocean surface is increasingly crowded. To ensure that large vessels don’t collide with each other they’re fitted with technology such as the automatic identification system (AIS) to record their position.

To see what impact the ships might be having on whale populations, the researchers combined the AIS route data from 176,000 vessels with over 435,000 whale sightings. They focused on four species in particular: the blue whale, fin whale, sperm whale and humpback whale.

In total, the researchers found that almost 92% of the ocean had at least some large ships sailing through it.

The researchers then narrowed this down to sites in the top 1% of risk for whale ship strikes. Many of these areas are found along coastlines, as the upwellings of nutrients along continental shelves feed the prey of whales. This mean that whales are feeding in the path of ships hugging the coastlines.

The largest proportion of risk was focused in the Indian Ocean, where around 22% of whale strike hotspots were found. This is due to the large numbers of ships passing through the Suez Canal and the Cape of Good Hope into a region of ocean inhabited by many whales.

The different species each had their own hotspots, with the ocean around Sri Lanka representing a particular risk for blue whales while humpbacks are most vulnerable to ship strikes in the Arabian Sea. 

The study also identified hotspots in areas where much less is known about these incidents. The seas around Namibia, South Africa, Mozambique and Madagascar formed one lesser known region, as did the waters around the Azores in the Atlantic Ocean.

Dr Anna Nisi, the study’s lead author, said that the identification of new hotspots was not a particular surprise.

“Whale-ship collisions have typically only been studied at a local or regional level, like off the east and west coasts of the continental USA, so patterns of risk remain unknown for large areas.”

“Our study is an attempt to fill those knowledge gaps and understand the risk of ship strikes on a global level. It’s important to understand where these collisions are likely to occur because there are some really simple interventions that can substantially reduce collision risk.”

Reducing the risk of whale ship strikes

There are two main approaches to reduce the risk of ships injuring or killing whales.

The first option is to simply slow ships down, as slower vessels give whales more time to dive or swim away. Some studies have estimated that ships slowing to 10 knots can reduce whale mortality by up to 30%.

The alternative is to reroute ships away from collision hotspots. The World Wide Fund for Nature estimates that moving ships in the Mediterranean away from the Hellenic Trench, a known sperm whale feeding area, has reduced the collision risk by around 27%.

But for the majority of whale ship strike hotspots there aren’t any measures in place at all.

New protections will also be needed in areas that aren’t currently collision hotspots. At the moment there’s a very low risk of whales in the Arctic being hit, but rising temperatures are expected to open new routes through this region in the coming decades. At the same time, higher temperatures are expected to drive more whale species polewards.

This makes it important to act sooner rather than later to minimise the potential future threat to whales in the Arctic.

The team are hopeful that new protections for unprotected hotspots could come as part of 30 by 30, where many countries have pledged to conserve 30% of their seas by 2030. They are hopeful that the additional 2.6% of protected areas needed to eliminate the high-risk hotspots should be achievable as part of wider conservation goals.

“Measures to reduce whale-ship collision risk can also benefit other species that overlap with those management zones,” Anna adds. “This includes other whale species that were not the focus of our analysis, as well as many other marine species who are susceptible to collisions with vessels.”

“These measures also can result in reduced underwater noise pollution, which negatively affects many marine species.”