Data has been collected from more than 6,000 trees across Greater Manchester by a team of 57 surveyors who visited nearly 2,000 plots. The results show that there are an estimated 11,321,386 trees with 15.7 per cent of Greater Manchester beneath tree canopy.
The data also highlights that approx. 1 million trees are in danger of being lost in Greater Manchester due to pests and diseases such as Ash Dieback and Horse Chestnut Bleeding Canker.
Greater Manchester's trees act as a filtration system for harmful air pollutants – removing 847 tonnes of pollutants each year. They assist with excessive storm water, intercepting 1,644,415 cubic metres of storm water run-off per year.
Added to this they sequester 56,530 tonnes of carbon each year and the current carbon of all the trees in the region is 1,573,015 tonnes.
The total annual economic value of air pollution filtration, stormwater attenuation and carbon sequestration in Greater Manchester's trees is £33,298,891.
The survey was carried out across Greater Manchester this summer and autumn collecting data such as tree species, width, height and diameter.
The data is fed into the i-tree software system, which processes the information and provides insightful results about the economic value of trees, trees under threat and where there is potential to plant more.
· It would cost over £4.7 billion to replace all Greater Manchester's trees
· They produce 122,450 tonnes of oxygen each year
· The most common species of tree in Greater Manchester are Hawthorn, Sycamore and English Oak
The data can be used to protect existing trees, as well as identifying new land for planting – assisting with initiatives such as The Northern Forest and Greater Manchester Spatial Framework - providing guidance for planners and developers.
The results will also inform the Greater Manchester Tree and Woodland Strategy, which will be published in spring next year.
A further report will also make recommendations for managing woodlands to enhance biodiversity and create homes for wildlife especially those in serious decline.
Bryan Cosgrove at City of Trees said: "The i-Tree figures show the crucial role our trees and woods play in combatting climate change and ensuring our city region is more resilient for the future.
"By putting a price on Greater Manchester's trees and woods we can ensure they are valued not just in terms of their amazing aesthetics but as natural assets providing a wealth of important environmental and economic benefits."
He added: "The statistic showing trees at risk from pests and disease are extremely worrying and shows the need for us to act now, planting more trees and protecting and preserving the ones we have".
The i-Tree Eco project All Our Trees has been supported by United Utilities, Viridor, Forestry Commission, Environment Agency, Salford City Council, Woodland Trust, Heritage Lottery Fund, The Greater Manchester Forest Partnership and The Greater Manchester Combined Authority.
Surveying the trees
Laurence Adams is one of 57 tree surveyors who has spent the last few months in various parts of Greater Manchester researching.
With no formal background in environmental science, Laurence worked in small teams with other surveyors, who were often trained ecologists.
The teams were given allocated plots each day, in one geographical area, such as Rochdale and they would travel to the GPS points on the map and then survey all the trees in an 11.3metre radius around that point.
Laurence said: "Sometimes you would be in a suburban area and you would find street trees or you would need to access people's back gardens to survey the trees there. Other times the location might be on the edge of the motorway and you would have to find a way of surveying those trees. At one point as we were right on the edge of the M62.
"We took measurements such as tree height, the size and condition of the tree crown, the thickness of the trunks, the estimated age of the tree and species as well as, whether there was any other space around the tree to plant more.
"Sometimes the trees would be on their own but there were instances where teams would find a group of trees together which may take up to two days to survey.
"It's a fascinating project and I am much more familiar with trees now, than when I started. I think oak trees are my favourite. They are the kings of the forest, among the biggest, strongest and slowest growers and they are connected to our heritage.
"Putting aside their environmental benefits, being around trees is also one of our best ways to re-connect with nature in the city and, speaking as a relative beginner, the more you learn about them, the more you realise what fascinating creatures they are. It's really important that we share our streets and green spaces with them."