Conservationists have created a giant sponge in the Lancashire hills to stop water flooding lowland towns - and reduce greenhouse gas emissions that accelerate global warming.
Almost 3,500 pools have been dug into the peat on Holcombe Moor, near Bury, to hold back rain on the plateau.
Half a million patches of moss have been transplanted into the newly-soaked ground.
Nik Taylor, the local ranger for the National Trust, which owns the moor, said moss holds eight times its own weight in water.
"Prior to this work, intense rain would fall on this plateau and make its way through the gullies, eroding the peat, and then flow down into the valleys below and put the communities at risk," he said.
"Slowing the flow really helps to reduce the height of the river in times of flood, maybe contributing just enough to save somebody's house from flooding."
But the moss should also form a blanket over damaged areas of peat that release carbon back into the atmosphere.
In a healthy bog, the moss sucks in carbon from the air as it grows. When it dies it doesn't rot because the ground is so wet. It becomes peat, with the carbon locked away for thousands of years.
But on Holcombe moor, overgrazing by sheep and 150 years of air pollution has destroyed the fragile moss blanket, exposing the peat.
Maddi Naish, rural surveyor at the National Trust, said peatlands are "superheroes" when it comes to storing carbon.
"We're just a stone's throw from a major city so it's incredible to think we live alongside a habitat that is rarer than rainforest globally, but which contributes so significantly to tackling climate change."
The UK has three million hectares of peat, 12% of its land area.
It stores three billion tonnes of carbon, more than all the forests of the UK, Germany and France put together.
But much of it has been damaged by human activity so it is pumping the equivalent of 20 million tonnes of carbon back into the atmosphere every year - 4% of the UK's annual emissions.
The restoration of Holcombe Moor was funded by the government and the Environment Agency.
Environment minister Rebecca Pow said much more needs to be done.
She told Sky News: "We've made a commitment to restore 35,000 hectares of peatland by 2025.
"That's only in four years' time and we already have the measures in place to set that in motion."
Holcombe Moor was restored by the National Trust with the Moors for the Future Partnership, Natural England and the Holcombe Moor Commoners' Association.