London is facing "huge pressure" for new basement developments that can not only compromise existing street and garden trees but also make subsequent planting of large trees more difficult, the chair of the London Tree Officers Association (LTOA) has warned.
Jake Tibbetts told HW: "The construction of these types of basements can impact on existing trees and the current pressure for development is huge. With rising property values and demand for new housing, tree officers are having to fight harder to retain the trees we have."
The Town & Country Planning Act does afford some protection and can lead to such developments being prevented or altered, he pointed out, but: "An equal concern is the loss of potential planting sites where currently no trees are planted.
"Many of these basements extend under the footprint of the garden. If no trees exist then there is no material loss and if, as in many cases, a garden is reinstated after development then no loss of green space is considered.
"But that new garden will never be suitable for large-canopy trees due to the inadequate soil depth. If we are going to be serious about increasing canopy area we need to start considering not only existing trees but also the ever decreasing potential for new trees."
Some LTOA members are working on policy to restrict subterranean developments to 50 per cent of the front and back garden for this reason, Tibbetts added.
In March this year, the Royal Borough of Kensington & Chelsea rejected a proposed three-storey "mega-basement" underneath a £20m Holland Park property on the basis of the likely damage to mature London plane trees in the property's garden and beyond.
Capital tree loss Hampstead and Highgate
Veteran trees in the Hampstead and Highgate areas of north-west London are at risk of being chopped down to make way for basement works, according to conservation organisation the Highgate Society.
Vice-president Michael Hammerson said several trees in back gardens have already been felled as part of basement works. The society now wants to protect 800 trees that are more than 250 years old in the area.
The City of London Corporation, which manages Hampstead Heath and Highgate Wood, has also voiced concern about several planning applications seeking to fell trees.
Highgate Wood conservation manager Jonathan Meares said: "We are keen to provide support and expertise to ensure these trees receive the protection that they deserve and are recognised for their great historical and conservation importance."