As Europe's biggest conservation charity, we have a responsibility to do everything we can to fight climate change, which poses the biggest threat to the places, nature and collections we care for.
The National Trust is planning to create new woodland equivalent to 42 Sherwood Forests as part of efforts to achieve "net zero" emissions by 2030.
The organisation, which cares for countryside, coasts, castles and stately homes, is aiming to plant and establish 20 million trees over 10 years to tackle the climate crisis.
It made the announcement, which it says is one of the biggest woodland expansion and tree planting projects in the UK and will cost around £90-100 million, to mark its 125th anniversary.
By the end of the decade, new trees and natural regeneration of woods will cover more than 18,000 hectares (44,000 acres), an area one-and-a-half times the size of Manchester - or 42 Sherwood Forests.
And it will mean that 17% of the land the National Trust looks after will be wooded, an increase from 10% today.
The focus will be on planting on farmland - including in upland areas - that the trust owns, rather than in country estates, but director general Hilary McGrady said they would be working with farmers to deliver the targets.
It is a level of tree cover which the charity says is needed on a nationwide basis to meet Government targets to cut greenhouse gas emissions, and will deliver additional benefits such as public access and habitats for nature.
Other initiatives to help the nearly six million member-strong trust achieve net zero emissions include maintaining peat bogs, which like trees absorb and store carbon, investing in more renewable energy, and cutting its carbon footprint.
Efforts will focus on the National Trust's own pollution, but Ms McGrady acknowledged the impact of visitors, many of whom travel by car to the organisation's properties.
She said the trust was beginning to try and measure the impact of visitor emissions and find ways to encourage more sustainable transport.
The charity, which was founded in the 19th century to protect and care for natural and historic places, also said it plans to work with other organisations to create "green corridors" that connect people in urban areas to nature.
It will also continue work to protect nature, such as clean up rivers and reintroduce species such as water voles and beavers, Ms McGrady said.
She said: "It's our 125th year and the National Trust has always been here for the benefit of everyone.
"That is why we are making these ambitious announcements in response to what is needed from our institution today.
"As Europe's biggest conservation charity, we have a responsibility to do everything we can to fight climate change, which poses the biggest threat to the places, nature and collections we care for."
And she said: "People need nature now more than ever. If they connect with it then they look after it.
"And working together is the only way we can reverse the decline in wildlife and the challenges we face due to climate change."
A year-long campaign to connect people with nature will include schemes to celebrate Britain's blossom season, watching dawns for property rooftops and even dancing outdoors.
Emily Beament is the PA environment correspondent.