Written by Peter Holt, Director of The SHIPS Project CIC
Many years ago, the waters of Plymouth Sound were in much better health than they are today, the sandy areas were covered in seagrass down to 7m depth, the two rivers that flow into Plymouth Sound were full of native oysters and the fish life was abundant. Seagrass was so readily available at that time it was used as a packing material for upholstering furniture and as sound insulation. However, the Industrial Revolution and the modern world changed all that. China clay extraction started on the hills behind Plymouth in 1830 and the runoff killed all the oysters within just 10 years. In the 1930s almost all the seagrass died in Plymouth Sound, as it did everywhere from the Atlantic coast of America to Denmark and Sweden, and the cause of this die-off is still unclear.
The loss of species in Plymouth Sound was reported as far back as 1889 when it was noted that ‘many animals that were plentiful in the Sound twenty years ago had now deserted it’.
The heavy metal pollution from the many copper and arsenic mines along the Tamar River has now stopped and the vast quantities of raw sewage from the city are no longer pumped straight into the sea. Money is being spent on restoring the seagrass beds in Plymouth Sound to provide an important habitat for other species and there is a will to restore the oyster beds too. Alongside these restoration efforts, The SHIPS Project believes that we also need to start tidying up the seabed.
Plastic pollution in the ocean is commonly recognised as a significant threat to biodiversity, impacting marine life and ecosystems. However, the detrimental effects of plastic waste are multifaceted, and are now seen to directly impact the preservation and conservation of historical artefacts, submerged archaeological sites, and cultural landmarks. The impact of plastic pollution intersects culture, heritage, and nature, and underscores the urgent need for comprehensive solutions to address this global challenge. Through the use of marine technology, industry and academic support and a team of volunteers, Plymouth Sound is being cleaned up to get the seabed back to a state more favourable for its marine life. Heritage has not been forgotten; while busy tidying up the seabed the SHIPS team is still keeping an eye out for clues that will lead them to their next shipwreck discovery.
For many years The SHIPS Project team have been locating and investigating sunken shipwrecks on the bottom of Plymouth Sound. They have been successful in their search so far, finding many wrecks including the remains of the Napoleonic frigate HMS Amethyst, the 68-gun warship HMS Conqueror and an unknown WWI aeroplane. While mapping the waters of Plymouth Sound using a new high-resolution sonar, the team found a huge number of tyres and other polluting junk dumped on the seabed. The junk was getting in the way of locating a particular shipwreck and this led to the idea of removing some of the tyres, which led to The SHIPS Project CIC starting the 1000 Tyres clean-up project.
The land around Plymouth in southwest England has been occupied for more than 15,000 years, with the first visitors coming for the mild weather and an abundant seafood supply. The modern city overlooks the broad expanse of Plymouth Sound with its rocky shores and shallow, sheltered water that opens to the south onto the English Channel. There is evidence of trade with the Mediterranean in the Bronze Age, the area was occupied by the Romans, the Saxons and then the Normans, and Plymouth grew from a small medieval fishing village into the City it is today. The waters of Plymouth Sound and its rivers have always been a resource providing transport links, a haven for ships and a reliable source of food from the sea. Where there is shipping there are shipwrecks and more than 1000 have been recorded within the harbour, their remains still to be found under the sand amongst the shallow reefs and kelp-covered rocks.
But where there are people there is rubbish and, until recently, the Sound has been the repository for all of Plymouth’s refuse. So, Plymouth Sound, now a marine park and Marine Protected Area, is a curious mix of marine habitat, underwater museum and rubbish dump.
The SHIPS Project is a non-profit organisation that was started to locate and investigate this underwater museum. One of the great benefits of cultural material underwater is that it is protected by being hidden from view and the material can survive for millennia in the right environment. The seabed is littered with the remains of shipwrecks and lost cargoes which are usually only seen by underwater explorers. On the flip side, the drawback with underwater cultural material is that most people do not get to see it or even know it is there. There is always a great public interest in shipwreck objects but they are hard to locate and there is also a reluctance to recover underwater finds because of the expense of conserving them. The objects will have spent years absorbing salt from the sea which unless it is all removed will surely cause their destruction once they dry out.
The search for this lost heritage is done on a backdrop of marine habitats with many different environments present within the Sound, from shallow rocky foreshore to large areas of sandy seabed, and a deep channel runs across the northern edge of the Sound that has sheer rock cliffs and thick mud in the quieter, deeper areas. Every habitat has its own variety of marine life and its own role to play in the complex interactions between the species. The habitats define their marine life but they also define the archaeology to be found there, because wave action, chemicals, and the marine life itself will affect shipwreck remains. In the high-energy environment of the foreshore, you will only find the more durable materials made from iron, copper, and the more robust pottery. There will be these same materials in deeper water perhaps under the sand, but there will also be more delicate objects made from pottery and glass. If timber from a wooden ship becomes buried in mud then it can survive for centuries because it is protected from erosion and the effects of marine organisms, but once exposed the timber soon degrades. So what you can find in any location depends very much on the marine habitat, the water currents and the wave energy found there.
Searching this seabed using marine geophysics instruments provides a list of locations to be investigated by the team’s divers or underwater drones. Many of the objects detected on the surveys turn out to be junk, dumped rubbish that could be from any age. Some of the rubbish is old enough to be considered archaeology but far more of it is modern and much of it is made from polluting materials, such as road tyres. The tyres are found everywhere in Plymouth Sound with over 1300 located so far and only a quarter of the seabed area mapped. The tyres found with small holes in their sides were once used as cheap fenders for ships but many others are found intact, and these are thought to have been dumped to dispose of them. The first car arrived in Plymouth in 1900 and just 20 years later the first tyre was dumped in the sea, based on the oldest tyre the team have found so far. The adverse effect of the tyres on marine life is only now starting to be revealed and the full extent of their harm may never be known. As well as the tyres, plastic rubbish like bottles and packing material gets blown or washed into the Sound. Efforts are being made to stop plastic from entering the water and to recover the floating debris from beaches, but some of the plastic sinks to the seabed where like the underwater heritage, it disappears out of sight. Now the SHIPS team are taking a proactive approach to this problem in a large-scale experimental clean-up operation in Plymouth Sound. With the help of industry, academia, and a host of volunteers they are removing tyres, plastics, lost fishing gear and other man-made pollutants from underwater and the foreshore. The long-term benefits of doing the 1000 Tyres clean-up may never be proven but the tyres and pollutants should not be in the sea, and it is cheaper to remove and recycle them than to spend money proving all the harm they do.
By removing tyres from the ocean, we not only safeguard our precious cultural heritage and protect vulnerable biodiversity, but we also take a crucial step towards a cleaner and healthier marine environment for generations to come.
By recognising that plastic pollution is an intersectional issue, we can work together to turn the tide on ensuring a sustainable future for our oceans, and the people who depend on them.
The SHIPS Project CIC is a volunteer non-profit organisation that undertakes research and exploration of maritime historical sites and events, both on land and underwater. The SHIPS Project also runs The 1000 Tyres Project as an environmental direct-action campaign to clean up Plymouth Sound. The SHIPS Project is based in Plymouth, England, and the focus of our work is centred on that city.
For more information please see: 1000Tyres.org