Wednesday, September 29, 1999 Published at 11:01 GMT 12:01 UK
City trees under subsidence threat
Trees are often blamed for housing subsidence
Environmentalists say too many trees in British cities are being cut down because of exaggerated fears of damage to house foundations.
Research from The Forestry Commission suggests that trees are frequently being axed to prevent subsidence, even when the risk is tiny.
It is usually caused by shrinkage in clay soils, which may in turn be caused by tree-roots taking the moisture from the soil.
But the commission's Tree Advisory Service says fears of damage from trees are often unfounded.
Dr Derek Patch, from the service, told the BBC: "Trees are being cut down even when there is probably no risk, because the building either has adequate foundations to accommodate movement, or the soil is not a shrinkable clay."
£375m a year
BBC Environment Correspondent Robert Piggott says the current problem dates back to 1971, when insurance companies started offering cover against subsidence.
The dry summers of 1975 and 1976 prompted a deluge of claims and a bill of more than £500m for insurance companies. Now in the UK, subsidence costs insurers £375m a year.
But insurance companies blame householders, worried about their property prices, who demand full repair and preventative measures after spotting cracks which may in fact be very minor.
Recent research by the Association of British Insurers found that the problem was almost unique to Britain.
In Australia, South Africa and America, it discovered, subsidence insurance was rare. Therefore many minor problems, which would have been put right with unnecessary tree-felling and structural repairs in the UK, were simply ignored.
The ABI says insurance companies are now investing in research so they can make sure only the right trees, for the right reasons, are cut down in future.