INTRODUCTION TO THE THYER TREE VALUATION METHOD
The Thyer Tree Valuation Method was developed in Sydney, Australia during 1984.
It was distributed for public use in 1985 and there have been minor modifications since.
The method is summarised and presented as a one page worksheet for ease of use.
Personnel engaged in tree valuation should be qualified, experienced and knowledgeable in
arboriculture and landscape assessment. They should also be trained in the use of this method.
The method allows the calculation of monetary values for trees. It was designed to value trees on
public or community owned land in city, town and suburban locations. It is assumed that tree values
may be affected by the zoning and permitted uses of the land on which they grow. The method is not
intended for use within bushland areas, or on rural land except near residences.
The valuation is an expression of the positive qualities of the tree, the contribution that tree
makes to the landscape, and the extent to which this is appreciated.
The calculated value is a statement of the importance of the tree to the environment and human
community, not just to the owner of the tree. Owners and neighbours may calculate different values
depending on their opinion of, or problems with a tree. Values calculated for trees on private land
indicate the value of those trees to the community.
Damage caused by the tree, cost to repair that damage, and cost to repair or remove the
tree must be valued separately.
The method combines four factors to establish a Significance Index for each tree :
1. Size measures of height, side view of canopy area, dripline diameter, and girth.
2. Age of the tree.
3. Physical assessment of the tree and location.
4. Social benefit and how the tree is appreciated.
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