Schools are being offered tree saplings free to plant in their playgrounds to improve air quality and cut pollution.

The Mayor of London has started a project to plant 40,000 new trees, half of them offered free to schools and the rest to create a new urban woodland at Southall in west London.

The man who brought the rent-a-bike scheme to help cut London’s air pollution is now introducing more trees to help finish the job.

Boris Johnson wants “as many schools as possible” to sign up for their own foliage projects to make their neighbourhoods greener and healthier.

That is particularly essential in the East End with its high levels of pollution along the busy A13 through Limehouse and Poplar and the A12 approaches to the Blackwall Tunnel.

Today’s tree-planting launch follows a survey carried out by City Hall with the Forestry Commission showing London’s eight million trees worth nearly £280m in the “services” they provide.

The survey included 300 volunteers who analysed and counted trees showing the carbon they store, pollution they remove and rainwater they hold.

The Forestry Commission’s London manager Craig Harrison said: “Our survey shows trees have huge benefits in the ‘services’ they provide—we all need to protect existing trees and plant new ones.”

The survey puts a price tag on the “services” such as carbon storage worth £147m, removing air pollution at £126m and storm water alleviation nearly £3m.