Manmade materials including bricks, concrete, glass and industrial waste could make up as much as half of some Scottish beaches, according to new research showing how human activity is affecting the natural world.
The natural sands making up the beaches along the Firth of Forth are now mixed with significant amounts of human-made materials. These have been swept from the land into the water by erosion of coastal industrial sites and infrastructure and the dumping of waste.
A survey of six beaches, led by a team from the University of Glasgow, found that these mineral-based materials, known as anthropogenic geomaterials, now make up far more of the beach surface than previously realised.
A paper published in the journal Sedimentology shows that up to half of the coarse sediments on Granton Beach near Edinburgh are composed of these materials.
On average, materials of human origin made up around 22% of the pebble-sized or above sediments on the beaches surveyed.
Granton Beach
Brick fragments were the most common at five of the sites, but Granton was dominated by concrete.
The research shows for the first time the extent to which anthropogenic materials have joined materials produced by natural processes on beaches.
The team say that the modification of the natural composition of the beaches is significant enough that it warrants a new scientific classification, suggesting that they be called “Anthropogenic Mixed Sand and Gravel”, or MSG-A beaches.
University research
John MacDonald of the University of Glasgow’s School of Geographical & Earth Sciences, a co-author of the study, said: “Much of the world’s urbanised coast is made up of unconsolidated post-industrial and landfill materials.
“As climate change increases the frequency and magnitude of coastal storms, more human-made waste materials are likely to be mobilised and enter beach systems.”
The team combined physical surveys of beach sediments and aerial drone surveys to scrutinise the makeup of six sites representing different coastal conditions on the north and south banks of the Forth.
At Torryburn, Ravenscraig, and Fife Path on the north side, and Carriden, Granton, and Prestonpans on the southern shore, the team collected samples of beach materials at low, mid and high tides and identified the origins of the rocks, pebbles and grains they picked up. They also used drones to build up detailed 3D models of the terrain of each beach.
They found evidence of varying degrees of anthropogenic materials across the beaches, from 2% at Ravenscraig to nearly 49% at Granton’s mid-tide zone.
They also discovered that, on average, 22% of the beaches’ coarse sediment fraction consisted of human-made material, including fragments measuring between 11mm up to 256mm.
However, very few were in the “fine fraction” below 11mm, suggesting that the materials are deposited into the Forth as larger fragments and have not yet been worn down by wave action, a conclusion supported by the team’s observation that more of the smaller fragments were found on beaches with higher wave energy.
Unpredictable effects
The researchers warn that increased buildup of anthropogenic materials on and around Scotland’s beaches could have unpredictable effects in the years ahead, as climate change accelerates coastal erosion.
Professor Larissa Naylor, a co-author of the study, said: “Research like this casts new light on how human activity is affecting the natural world.
“It is vital in helping us to understand how our beaches are changing and better enabling us to manage our changing coasts.”
The team has already carried out repeated surveys to track how the beaches change over time, and how they vary.
Postgraduate researcher Yuchen Wang, who carried out the research as part of her PhD at the University of Glasgow, said: “It’s very likely that if these six beaches have accumulated so much coarse sediment through human activity, others around the country and indeed around the world are likely to be similarly affected.”
