The detonation of wartime bombs left on the seafloor around the UK must end to stop the deaths of whales and dolphins, campaigners say. The offshore wind industry is expanding rapidly and this may lead to a sharp rise in such explosions as the seafloor is cleared before construction. A quieter “burning” technique is already available, say the campaigners. The seas around the UK are estimated to contain 100,000 tonnes of mines and bombs. They are relics of the second world war, as well as explosives lost accidentally or during training exercises. They are routinely disposed of using a counter charge placed next to the bomb to explode it, and there are an estimated 50 detonations a year. Marine mammals are sensitive to loud noises as they use their hearing to navigate and communicate. A 2015 study found that each explosion in Dutch waters deafened 15 porpoises, and possibly as many as 60. An alternative method, used by the Royal Navy since 2005, is far quieter and involves using a small charge to penetrate the bomb casing but without detonating it. The technique, called deflagration, causes the explosive inside the bomb to burn. Recent tests conducted by the National Physical Laboratory led its scientists to conclude: “The deflagration method shows considerable promise for noise abatement in [bomb] disposal.” The campaign has been funded by Eodex, a company that provides deflagration services, It is voluntarily supported by a number of marine charities and the campaigner and actor Joanna Lumley. Underwater bomb disposal operations have caused the deaths of marine mammals. At least eight porpoises were deafened and died in August 2019 after explosions were used to clear second world war mines in a German marine protection zone in the Baltic Sea. Small charges had been used to try to scare the animals out of the area, but the porpoises remained in the strait during at least five of the 42 blasts, according to a government report. In 2011, at the Kyle of Durness in Scotland, 39 long-finned pilot whales became stranded in the bay at high tide, with 19 eventually dying. A government-funded report found nearby bomb disposal operations in the days leading up the tragedy were “the only external event with the potential to cause” the whale strandings, although it could not rule out “navigational error”. “We’ve got to have windfarms and green energy, but not at the cost of marine life,” said Liz Sandeman, co-founder of the Marine Connection charity and a member of the government-sponsored Underwater Sound Forum. More than a dozen whale, dolphin and porpoise species can be seen in UK waters and already suffer harm from “wall of death” fishing nets and pollution. “It seems completely nuts to me that we are allowing these giant explosions to cause considerable harm to some of our most precious whale and dolphin species when there is a viable alternative available,” said Lumley. In October, the prime minister, Boris Johnson, pledged to quadruple offshore wind capacity by 2030 so it can power every UK home. The UK’s official conservation advisory body, the Joint Nature Conservation Committee, said in June: “The scale of offshore wind installation planned over the next decades in some of these areas raises the potential for unprecedented disturbance.” Developers clearing bombs already have to try to reduce the risk of harm by looking out for marine mammals ahead of explosions, and using scare charges, but the effectiveness of these measures is contested. “If you have a pod of whales under the water, you’ve got no idea they’re there,” said Sandeman. “Bubble curtains” are also used sometimes, but are designed to absorb the continuous, lower level noise from drilling the sea bed, rather than loud bangs, the campaigners said. A government spokesman said: “We recognise the impact that underwater noise from clearing unexploded ordnance can have on vulnerable marine species. We are working closely with the Marine Management Organisation (MMO), nature conservation bodies and marine industries to reduce underwater noise but must ensure any clearance method used is both safe and effective.” He said the MMO, the marine regulator, could require the use of deflagration if it can be shown to be “100% safe or effective”. “We welcome the development of new technologies which can help to make [unexploded bombs] safe and reduce environmental impacts,” said Luke Clark at RenewableUK, the wind industry trade body. “Detonation is only used as a last resort if there is no other way to ensure the safety of our workers and operations.” “Climate change poses the greatest threat to our ocean habitats and wildlife, so it is vital that we rapidly develop solutions like offshore wind and that we do so in an environmentally sensitive way,” said Clark.