In December 1918, the HMS Cassandra was headed towards Tallinn to support Estonian efforts to break away from Bolshevik rule at the end of World War I.
She hit a mine and sank off the island of Saaremaa. Most of her 400 crew survived, but 11 went down with the cruiser.
Around 100 metres deep, the site of the wreck of the Royal Navy ship was only discovered in 2010. Inside it, a hidden environmental time bomb in the form of oil.
Matt Skelhorn, who is currently on board a ship surveying the HMS Cassandra, says it is “exceptionally preserved”, like many others in the Baltic.
“It is certainly in better condition than most of the wrecks we encounter in British waters,” adds the head of the UK Ministry of Defence (MOD) Wreck Management Programme at its Salvage and Marine Operations team (SALMO), Defence Equipment and Support (DE&S).
“This poses an interesting challenge.”
The wreck is decaying at a slow rate, so it isn’t likely to collapse or cause a catastrophic spill anytime soon. But its unusually good condition also means that large amounts of oil are more likely to have remained on board than in heavily degraded wrecks found elsewhere in the world.
HMS Cassandra is already leaking small amounts, and eventually, what is still on board will be released.
“As far as we’re aware, HMS Cassandra has not thus far been at risk of catastrophically leaking. The aim of this survey is to ascertain what state the wreck is in, which will inform how we manage her moving forwards,” says Harriet Rushton, DE&S SALMO’s wreck environmental manager.
A toxic remnant of 20th century conflicts
The team are hoping that what they learn from surveying the wreck will help shape how they manage potential risks in the future for the HMS Cassandra. Working with the Estonian government, their aim is to create a proactive management plan, preventing leaks and the need to clean up a catastrophic oil spill in the first place.
It is an approach experts say could serve as a blueprint for nations looking to tackle what are known as potentially polluting wrecks (PPWs).
These wrecks contain a cargo of fuel or their own fuel that has the potential to cause environmental damage if it leaks or there is a catastrophic release. Scattered from the Baltic Sea to the South Asia-Pacific, some are already leaking, threatening marine ecosystems, fisheries, and nearby communities.
An estimated 8,500 PPWs lie beneath the waves, most dating back to World War I and II. Limited data means the actual number is likely much higher.
After 80 to 110 years, Project Tangaroa warns that they are all becoming increasingly unstable.
This global community of experts, coordinated by Lloyd’s Register Foundation, The Ocean Foundation and Waves Group, issued an urgent call to action to address this toxic global legacy of conflict at the UN Oceans Conference (UNOC3) in Nice earlier this month.
They have already been vital in connecting the UK and Estonian governments to deal with HMS Cassandra and are hoping to do the same for other governments.
“The solution to basically every issue and every point we raise is collaboration,” says Lydia Woolley, Project Tangaroa’s programme manager at the Lloyd’s Register Foundation.
A looming climate threat
There’s another layer to this urgency that is being exacerbated by human activity.
Sitting at the bottom of our oceans, these wrecks have been gradually corroding over decades. It’s natural for materials to deteriorate as a result of prolonged immersion in water.
But the rate at which wrecks have been breaking down has started to accelerate.
Rising ocean temperatures and the shifting acidity of the water – both a direct consequence of climate change – are to blame. Extreme weather events like typhoons and storm surges, also made more frequent and more intense by climate change, put added stress on these already weakened structures.
“These climate-driven changes, combined with growing ocean industrialisation, bottom trawling, and emerging threats like deep-sea mining, significantly heighten the risks associated with PPWs,” says Woolley.
The effects of human activity are shortening the already precarious fuse on these ticking environmental time bombs.
Data, data, data: The need for international collaboration
To act before a catastrophe occurs, experts and governments need detailed data. But crucial information on where wrecks lie, their condition, and what pollutants remain is patchy and often inaccessible.
The UK MOD’s SALMO team has been closely involved with Project Tangaroa since its inception.
“While we have a very good idea of how many ships sank in World Wars I and II and their approximate sinking locations, many of their wrecks are yet to be discovered,” says Skelhorn.
“This is particularly true of wrecks in deeper waters and in remote locations that are rarely surveyed.”
Even in areas where surveying regularly takes place, many have also been misidentified, Skelhorn adds, making it hard to assess potential risks and pollutants.
Assessing the consequences of pollution brings up a range of different holistic considerations, too.
“They are potentially polluting, but they’re also really dynamic, like biodiverse coral reefs,” she adds.
The wrecks can be great for local marine life, for fishermen or even for diving – and so the local tourism industry.
They may also be the last resting places for the crew who went down with these ships.
Some of them have been designated as war graves, and they have a “cultural heritage” – a status which comes with lots of different legislation.
PPWs are a “multifaceted problem”, Woolley explains, one that Project Tangaroa is hoping a better sharing of collective knowledge can solve.
By making data more accessible – including digitising archives, tracking financial resources, harnessing resources from research vessels and better modelling of potential spills – it will be easier to take on this toxic legacy.
In the roughly 18 months since the initiative was first proposed, Woolley says there have already been “loads of examples” where they have helped the right people to connect – the Estonian and UK governments are just one among many.
Navigating ‘loopholes’ and legacies
So, who exactly is responsible for cleaning up these wrecks? Right now, there’s “kind of a loophole” in the framework that would dictate that, Woolley says.
“Currently, the majority of arrangements for oil spill management have been designed to provide emergency response to contemporary incidents that involve privately owned and operated vessels – a scenario that is fundamentally different to the challenge posed by PPWs,” she explains.
“Several arrangements also explicitly exclude legacy wrecks and casualties of war from their remit.”
Some protocols are in place, like the 2007 International Maritime Organisation’s Wreck Removal Convention, which sets out an international legal framework for the removal of wrecks hazardous to the marine environment, and the International Oil Pollution Compensation Fund, a global compensation system set up to provide financial reparations for oil pollution damage.
But these only impose obligations and liabilities for oil spills from wrecks that happened after they came into force. They also only apply to privately-owned ships, not necessarily the wrecks of state-owned ships.
“Another challenge is sovereign immunity,” Woolley adds.
“The flag states of sunken state vessels, such as the US, Germany, Japan and the UK, have stated that their sunken craft are presumed to remain owned by them, unless expressly abandoned.
“As such, these PPWs are subject to sovereign immunity, meaning the flag states cannot be legally compelled to act, and intervention cannot take place without their consent.”
This means flag state cooperation is critical in the management of these wrecks, and right now it is largely dependent on goodwill, a sense of moral responsibility or overarching geopolitical factors.
Some states have taken proactive action to figure out the risks from PPWs in their own waters and sometimes in other countries. But many countries with high numbers of wrecks in their oceans don’t have the resources or finances to do this, let alone develop management plans to mitigate this risk.
They often depend on flag states to react on a case-by-case basis to emerging dangers from each individual wreck.
Though some existing resources could be applied to spills from PPWs, it would likely involve lengthy negotiations about funding, leaving coastal countries even more vulnerable.
“If you’re trying to figure out who’s responsible for months before you can do any kind of remediation, I mean that’s catastrophic,” Woolley says.
“Something, maybe potentially quite small, has escalated into something big because of not being able to respond.”
None of this can happen without an established international legal framework.
“While action has been taken on some individual wrecks – typically in response to an identified oil leak or request for interventions – the proactive, systematic approach needed to tackle this problem at scale remains lacking,” she explains.
Seven key calls to action
At UNOC3, Project Tangaroa published ‘The Malta Manifesto’ in a bid to encourage governments to act decisively before the situation reaches breaking point.
The coalition wants to transform the situation before the 100th anniversary of World War II in 2039. And the Manifesto outlines a framework to tackle the problem in this timeframe, advocating for a precautionary approach and global cooperation on long-term solutions.
In it are seven key calls to action – covering financing, standards, regional and national planning, innovation, training and data sharing – aimed at empowering governments, industry, researchers and civil society globally to address the challenge.
One of its key recommendations is the establishment of an international PPW Finance Task Force to drive international cooperation and innovative financing solutions.
“Our message is not fatalistic – it is one of urgent encouragement,” Woolley concludes.
“Thanks to the work of the global community of experts brought together by Project Tangaroa, we already know how to manage the risks posed by these wrecks – but we need the resources to put this knowledge to use at the required scale.”