Temperate rainforest, which has been decimated over thousands of years, has the potential to be restored across a fifth of Great Britain, a new map reveals. Atlantic temperate rainforest once covered most of the west coasts of Britain and Ireland, thriving in the archipelago’s wet, mild conditions, which support rainforest indicator species such as lichens, mosses and liverworts. Today, it covers less than 1% of land, having been cleared over thousands of years by humans and is only found in isolated pockets, such as the waterfalls region in the Brecon Beacons and Ausewell Wood on Dartmoor. Two maps released by Lost Rainforests of Britain, and shared exclusively with the Guardian, show both what exists today and what could be revived in the future. The map showing the remaining fragments of rainforest in England, Wales and Scotland was compiled with the help of the public, scientists and geolocation specialists. The second map shows that more than half of Wales and nearly all of western Scotland – as well as large parts of Cornwall, the Lake District and other pockets north of Manchester – have suitable climates for temperate rainforest. Guy Shrubsole, an environmental campaigner who runs the Lost Rainforests of Britain campaign, said the 18,870 hectares (46,628 acres) that survive in England could double in size within a generation if they were allowed to naturally regenerate, spread by ecosystem engineers such as jays, which have been shown to support forest regrowth. “I think the map gives a sense of hope that 20% of Britain has the right climate for temperate rainforest,” said Shrubsole. “It is highly likely that that area would have been once covered with rainforest thousands of years ago. Ultimately, I think that’s something we need to take inspiration from and look to the past to think about what we need to be bringing back in future. “I don’t necessarily think we could cover all of the 20%. But I do think we could allow those existing fragments that we have identified to expand in size.” The organisation commissioned a YouGov poll, which found that 93% of the British public support protecting the country’s rainforest, while 85% back its expansion and 80% think public funding should support its restoration. Ecologists say that invasive species, pollution and grazing by livestock have damaged temperate rainforest in the UK, but substantive protection and careful tree-planting could see the rare ecosystems naturally generate. Previous analysis by Lost Rainforests of Britain found that 73% of England’s remaining fragments of temperate rainforest are not designated as sites of special scientific interest, despite their importance for biodiversity. Shrubsole has been encouraging members of the public to help him identify and map remaining fragments of rainforest. The RSPB, the Wildlife Trusts, the National Trust and the Woodland Trust have backed Shrubsole’s campaign, writing to the new environment secretary, Ranil Jayawardena, last month to urge him to better protect what remains and expand the rare habitat, which is also found in Chilean Patagonia, Alaska and Japan. In the letter, seen by the Guardian, leading wildlife NGOs urged the government to ensure all of England’s rainforests are put under protection to help support its commitment to protect 30% of the country, a key draft target for an international agreement on biodiversity that will be negotiated in December at Cop15 in Montreal. It also calls on the government to adopt a specific rainforest strategy to protect England’s ancient woodlands, working with landowners and farmers to help naturally regenerate the areas in accordance with the latest science. As well as Shrubsole, the letter was signed by Ian Dunn, chief executive of Plantlife; Katie-Jo Luxton, global conservation director at the RSPB; Rosie Hails, the National Trust’s nature and science director; Craig Bennett, chief executive of the Wildlife Trusts; and Sir Tim Smit, co-founder of the Eden Project. The government has previously said that much of the country’s temperate rainforest is protected and that it is committed to its safekeeping.