Tree-related subsidence: Pruning is not the answer

Abstract

Building subsidence is a major problem in the UK and has been for many years. Most subsidence problems are tree-related and the cost to the insurance sector runs into hundreds of millions of pounds a year. Subsidence damage ranges from minor cracking to significant structural damage and trees are sometimes viewed negatively because of their role in subsidence damage. There are over 150 million urban trees in Britain and a significant majority of these are legally protected by tree preservation orders or by virtue of the fact that they are in conservation areas. There has been simplistic and erroneous advice available for a number of years that is based on a false premise that pruning offers a means to control tree water use sufficiently to provide a remedy for tree-related subsidence. This paper presents a factual account of the biology involved in how trees use water, together with the results of recent research into the subject, that cogently dispose of the false premise that has dominated the subject since the 1970s. A simple 'model tree' is presented in the context of clay soils, climate, building guidelines, the housing stock and management options. Recent case law in this area is placed in the context of the legal framework surrounding the issue and the effect of tree removals on the nation's urban tree population is discussed. [PUBLICATION ABSTRACT]