The 561-hectare valley around Snaizeholme, near the town of Hawes, is now almost completely barren.

The Woodland Trust is aiming to plant 291 hectares with saplings, creating the largest continuous native woodland in England, and protecting local red squirrels.

The first of 100,000 trees will go in the ground this weekend in phase one of the scheme. More trees than needed will be planted as not all will survive in the windswept, rainy upland valley.

The Trust has been fundraising to buy the area and save the depleted land, whose "stark" conditions are "repeated" across the broader area.

Total tree cover in the Yorkshire Dales National Park is now less than 5%, with ancient woodland - the best type for wildlife - making up just 1% of that cover.

Al Nash, who is spearheading the project for the Woodland Trust, said: "I love the Dales but the one thing it lacks in many areas is an abundance of trees."

They plan to give nature a "big boost... creating a vibrant mosaic of habitats and a rare opportunity to create a sizeable wildlife haven for the north of England".

"Woodland birds will have a home here for the first time in centuries, and open scrub woodland should benefit endangered species like the black grouse."

It will also help tackle climate change, he said. "The work we do here will restore an entire ecosystem, lock away carbon for years to come, and help improve water quality".

Now the charity is trying to raise £8m for a decades-long programme to restore the forest, providing habitat for threatened species such as woodland birds and black grouse.

By slowing the flow of water on the hillsides, trees can also improve the wetland environment, giving space for otters and kingfishers to thrive, while reducing the risk of flooding for residents nearby.

There is also a plan to plant trees next to an existing ancient woodland where red squirrels live, expanding their home.

Existing dry stone walls currently in place will be maintained to offer shelter for small mammals and lizards, the trust said.

Planted trees will be mostly native broadleaved species such as alder, silver birch, downy birch, willow, aspen, rowan, hawthorn and blackthorn, with montane species on the higher slopes.

Sky News last month reported that a tree-planting project by National Highways had failed. The Woodland Trust says its "complex planting project" has been "very carefully planned". It is using different tree varieties to suit different conditions, with higher densities in tougher areas to ensure enough survive.

The Trust hopes the new forest in Yorkshire will eventually surpass in size the current largest continuous woodland, another of its sites in Heartwood in Hertfordshire.

Watch the Daily Climate Show at 3.30pm Monday to Friday, and The Climate Show with Tom Heap on Saturday and Sunday at 3.30pm and 7.30pm.

All on Sky News, on the Sky News website and app, on YouTube and Twitter.

The show investigates how global warming is changing our landscape and highlights solutions to the crisis.