Having been an arborist for fifty years I thought I might add a professional perspective to Mr Degan’s comments on the proposed removal of invasive trees from Whippendell Woods (Letters, January 31).

READ MORE: Letter: We can't afford to lose more trees

Yes, trees are being lost worldwide and the rate is probably unprecedented, but this should not precipitate ill-considered responses to ecologically sound management. Watford Council’s argument about returning woodland to what it once was is not specious but founded on accepted and scientific woodland management practice. The world is indeed a different place now and much of this is attributable to the ongoing effects of climate change. Establishment and subsequent proliferation of exotic trees in native ecosystems is a direct consequence of warmer and wetter climatic conditions.

Non-native exotic trees are often able to out-compete native woodland trees and become invasive because they are not exposed to predators, pathogens and diseases that would have been present in their place of origin. They are harmful to native trees and by extension woodland because this confers a competitive advantage. Further, many invasive species, notably Norway maple and western hemlock, are shade-tolerant species that also cast considerable shade of their own and so prevent the natural regeneration of desirable woodland trees. Our own native oaks now barely regenerate anywhere in a woodland environment.

Mr Degan refers to removing healthy trees and replacing them with ‘native’ sprigs as though this is a harmful practice. The removal of invasive species is ecologically sound and helps to preserve woodland integrity. In the Hertfordshire local area, Norway maple would swiftly establish and displace desirable species which provide food and habitat for indigenous fauna. The arrival of exotic (invasive) tree species is not nature’s way of adapting to climate change. Historically, the invasion of such trees has been facilitated by the burgeoning trade in ‘plants for planting’. The same pathway has enabled the current catastrophic introduction of exotic pests and diseases to which our native trees have no natural defence.

Mayor Taylor has apparently had the temerity to refer to healthier woodland, which has caused Mr Degan to infer that this means the woodland trees are sick due to air pollution. Whilst air pollution can harm tree health, this is not the thrust of the Mayor’s response. I am sure that he is highlighting the fact, probably after discussions with professional arborists, that removing undesirable invasive species will promote healthier woodland.

In closing, I would take issue with the assertion that Whippendell Woods would be best left alone. Woodlands respond well to sound forestry practice and almost all English woodland has been historically managed for food, fuel and other resources. Unmanaged woodland soon falls into a state of degradation, to the loss of the local ecology and man’s needs.

Shane A Lanigan

Chartered Arboriculturist