Scotland's post-industrial derelict sites are to be turned into urban forests under ambitious plans to use trees as a long-term fix for nearly 12,000 hectares of vacant land.

Glasgow and other towns and cities are understood to be looking at trees as a way of filling in large areas of derelict land.

Urban councils have long wanted to have more woods for their citizens to enjoy – and to clean both their air and their ground.

Every political party in Scotland has signed up to a campaign by the Woodlands Trust to plant more trees in urban areas.

Now Glasgow has specifically asked for the Scottish Government’s forestry strategy to have targets for planting trees on gap sites.

The Scottish Government is currently crunching responses to its own wider strategy as it continues its plans to re-wood the nation.

Less than one-fifth of Scotland, some 18 per cent, is covered in trees, about half the average for European nations. Cities – thanks to parks and gardens, public and private – can be more wooded than the national average. Tree cover was measured at 20% or above in Perth, Inverness and Stirling.

But it falls to just under 18% in Dundee, 17% in Edinburgh, 15% in Glasgow and just 10% in the city of  Aberdeen.

A spokesman for Glasgow City Council: “There are multiple benefits that can potentially be drawn from planting new woodland on vacant or derelict land.

“Urban woodland assists with carbon reduction, enhances biodiversity in places which maybe otherwise deficient, helps to manage flood risk and acts as a barrier to city noise among many other positive environmental impacts.

“But planting on derelict land also leads to aesthetic improvements for communities, while encouraging increased physical activity as people make greater use of previously unattractive spaces.”

Crucially, some abandoned ground will revert to woods if it is just left alone while some will need replanted. Sources stressed costs could be minimal - though local authorities far from always own gap sites.

The Glasgow spokesman said: “There are derelict sites that naturally regenerate into woodland with tree species such as birch, willow and alder commonly taking hold along with ground flora and urban wildlife.

“Whether to pursue planting or allow natural growth would require assessment on a site-by-site basis.

“An appropriate balance would also have to be struck between fostering urban woodland and ensuring development of sites could continue, particularly for housing.”

Experts stress the healing powers of trees - both for people and for land and air. However, city planners are also excited about the ability of small urban woodlands to protect against flooding. A 10 per cent rise in tree cover, they say, can reduce surface off-flow by 6%.

George Anderson of the Woodland Trust, which champions native trees, said: “We need more trees and they don’t have to be in the open countryside.

“Aside from the broad positives boosting biodiversity, fighting climate change and cutting flooding, urban trees create huge direct benefits for human health and wellbeing.

“We breathe easier and think happier with trees nearby.

“There is huge potential for Glasgow to improve citizens’ lives through planting derelict land.” Successive Scottish and UK governments have pursued rural reforestation, often despite opposition from those who want to keep Scotland’s hill as they are, gamekeepers and mountaineers.

Tree cover across the country has gone from around 5% at beginning of the 20th century to 17% at its end, largely thanks to commercial timber plantations and the state-owned Forestry Commission.

There is currently a target to raise that area to 21% by 2032. That would mean planting 15,000 hectares of wood a year, the equivalent of more than all the land currently categorised as vacant.

Scotland is not always achieving that rate of growth. Last month there were suggestions public-sector pension funds should throw some of their financial  weight behind reforesting.