The survey by the City of Trees initiative, which is run by the Community Forest Trust, is believed to be the largest of its kind outside the United States, where the methodology was developed.
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 this summer and autumn, in order to calculate the environmental and economic benefits that trees provide, as well as highlight any risks to tree health.
Their work found that:
- Greater Manchester has 11.3 million trees providing canopy cover of 15.7% - close to the urban average for England, with hawthorn, sycamore and English oak predominating;
- Trees remove 847 tonnes of pollutants and intercept 1.65 million cubic metres of storm water run-off each year;
- They also sequester 56,500 tonnes of carbon each year, and currently store 1.57m tonnes of carbon;
- The value of these services equates to £33.33m a year.
But it also highlights that around 1 million trees are in danger of being lost due to pests and diseases such as ash dieback and horse chestnut bleeding canker.
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.
City of Trees technical oficer for green infrastructure Bryan Cosgrove said: "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."