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Rogue trees get criminal treatment from scientists

August 27, 2002

Rogue trees are being ‘fingered’ by gene detectives using a well-known technique to catch criminals.

Newcastle University scientists are using DNA fingerprinting to help insurers identify trees that are causing houses to subside.

Often disputes can last for several years, as when two trees of the same kind grow in an area it is very difficult to find out which one is behind the problem. This is because their roots – which can grow underneath a house and cause the subsidence – may stretch for several metres in different directions.

The scientists have set up a company, Bioprofiles Ltd, to carry out the work. It is believed to be the first company in the UK to offer this service.   It will be working for aboriculturalists – tree specialists - and building surveyors, as well as insurance companies.

Kirsten Wolff, one of the company’s directors, explained how it works:

“Houses built on clay are particularly at risk from subsidence, and more so in times of drought. Tree roots suck water out of the ground, which causes the clay supporting the house to dry out and contract.

“We would typically get involved in a dispute over which tree is responsible for the subsidence, especially when both the householder and his or her neighbour own trees which are equally likely to have roots spreading under the subsiding house. We try to establish which tree is to blame and thus indicate which insurance company should pay out.

“The problem is much easier to solve when there are different trees growing in the area.   It’s easy to tell the difference between an oak tree root and chestnut tree root, for example. It’s when you are faced with trees of the same kind in the same vicinity that the scientists have to step in.”

Dr Wolff, Reader in Evolutionary Genetics at Newcastle University’s School of Biology, and fellow scientist and company director Dr Marie Hale, begin their work by taking samples from the suspect trees and the root causing the subsidence. The team then employs three methods of genetic analysis in the laboratory to compare the samples - depending on how difficult identification is.

Firstly, they carry out a technique known as RAPD – that is, creating a DNA bar code which can be used to compare the samples. If this fails the scientists then move on to microsatellite analysis or DNA profiling, where they look for differences in the lengths of DNA fragments. The final test they can carry out is DNA sequencing, which shows the ‘nuts and bolts’ of the samples’ genetic makeup.

It takes about two weeks for a full analysis, after which the company produces a report based on its findings. This will be a vital piece of evidence for insurance companies wanting to settle the claims dispute.   

Dr Wolff, who has carried out similar techniques for plant growers eager to protect their breeding rights added: “This technique is particularly significant for insurance companies or building surveyors acting for people who live in London and the South of England or affluent areas generally, where house prices tend to be much higher and claims are therefore much bigger.”

Keith Gaston, a partner with Essex-based Gaston Whybrew Solicitors, who specialise in cases involving subsidence, said:

“This is an interesting development - cases where trees are alleged to have caused damage can result in substantial claims, and disputes often arise as to whether a particular tree has been a causative factor and if so to what extent.   

“It is to be hoped that this technique will assist in resolving disputes at an earlier stage than would otherwise be the case.”

Newcastle upon Tyne, University of