9-1 Significant Tree Assessment Valuation Method and Criteria

​​​9-1.1 The RNZIH Standard Method of Evaluation

A standard evaluation method has been developed by the Royal New Zealand Institute of Horticulture (RNZIH) for the assessment of all trees proposed for inclusion in district plans.

In this adapted form there are 13 categories (A-M). Each category asks specific questions of the assessor. Each category must be regarded as a specific question and answered without reference to other categories.

The categories are given ratings of 1 to 4. Each rating requires a clear decision. Any expansion of the rating values leads to subjectivity and fractional differences of opinion.  The following assessment must be used in the context of the value of that tree or group of trees to the local community. The scoring is carried out using the form shown in Appendix 9-2.

9-1.2 Category A: Size of Tree

The height and the width of the tree are measured and the tree is then assessed for size.  This is done by taking the larger dimension, i.e. height or width, and doubling. The lesser dimension is subsequently added. This figure will give the visual area of the tree.

Small​​
1-25
1 point
Medium
26-60
2 points
Large
61-86
3 points
Exceptional
86
4 points

The terrain may slope or be level without affecting the measurement method.

9-1.3 Category B: Importance of Position

This is used for assessing the trees’ visual importance or proximity to the public. There is a need to recognise the value of trees that are adjacent to well-used footpaths or walkways in urban situations. For ease of definition the rating of this category is divided as follows (with vehicle counts for types of routes as a guide).

Minor Significance (local transport corridor or private garden), fewer than 3000 vehicles per day (vpd)
1 point
Significant (collector transport corridor) 3000–10,000 vpd
2 points
Very Significant (minor arterial transport corridor or suburban and sub-regional centres) 10,000–20,000 vpd
3 points
Major Significance (major arterial transport corridor or city centre) > 20,000 vpd
4 points

9-1.4 Category C: Presence of Other Trees

This category evaluates the proximity of other trees in the area.  The rating is as follows.

Forest or woodland park
1 point
Grou​p or small park (10+ trees)
2 points
Small group (2-9 trees)
3 points
Solitary specimen
4 points

9-1.5 Category D: Occurrence of the Species

Trees of importance in this category are assessed according to the frequency of the species in the local area. This category makes allowance for regional geographic differences such as climate.

Common
1 point
Infreque​​nt
2 points
Rare locally
3 points
Rare regionally
4 points

9-1.6 Category E: Role in Location or Setting

This category assesses the visual and spatial quality surrounding the trees, i.e. the visual or spatial role of the tree in the setting. Does it contribute to the scene in a special way?  Would the removal of the tree detract from the scene? Is the tree complementary to its surrounds?  Is the tree an intentional part of a composition? The rating is as follows.

Minor significance
1 point
Significant
2 points
Very Significant
3 points
Major Significance
4 points

9-1.7 Category F: Useful Life Expectancy

The health and condition of a tree are indicators in this category. Simply put – does the tree look healthy in foliage, branch or bark? Are there any bad cuts or wounds liable to infection or rot? This category is divided into human life-span generations (in broad terms) for ease of reference. The question to be asked is whether the tree will be expected to be there for the next generation or generations to enjoy.

0 – 30 ​years
1 point
30 – 60 years
2 points
60 – 90 years
3 points
90 + years
4 points

9-1.8 Category G: Form

This is assessed by observing the appearance of the tree. Is it a well-shaped tree with a well-balanced branch system? A sturdy well-developed trunk is also visually important in the overall appearance of the tree.

Poor Form
1 point
Fair For​m
2 points
Good Form
3 points
Excellent Form
4 points

9-1.9 Category H: Scientific Value

This category is for trees that have interest due to a genetic purity lost in the countries of origin, their value as a source of propagation material, or their uniqueness as rare cultivar or forms of a species. Trees without great stature or even a common species could be of great scientific interest. Specialist knowledge is required for the scientific evaluation and should be fully documented.

Min​or Significance
1 point
Significant
2 points
Very Significant
3 points
Major Significance
4 points

9-1.10 Category I: Historic Value

This category is used for awarding trees their own particular historic distinctions. These include trees that have historic associations with early pioneers of historic events or places. It is important that trees in this category are given documented reasons for the evaluation.

Minor Significance
1 point
Significant (locally)
2 points
Very Signif​​icant
3  points
Major Significance
4 points

9-1.11 Category J: Cultural Value

Trees of spiritual, tribal, or other cultural values that are well documented or widely recognised. This category includes trees that are very large (notable) or very old for the species, but not recognised in Category A or commemorative trees without historic associations.

Minor significance
1 point
Significant (loca​lly)
2 points
Very Significant (locally)
3 points
Major Significance (locally, nationally)
4 points

9-1.12 Category K: Functional Value(s)

This assesses the values of protection of soil by stabilisation, noise amelioration, shelter and shade, and fruit production, where these values are primary functions of the tree(s) in their location, i.e. the tree(s) are there for that reason.

Minor Significance
1 point
Significant
2 points
Very Significant
3 points
Major Significance
4 points

9-1.13 Category L: Ecological Value

This is assessed as distinct from scientific and botanical value. It is related to habitat values for flora and fauna (particularly native) and is assessed on a stand basis so that single or isolated trees would score 1 in all cases. The species diversity of a stand is also important in this respect. Stands that serve as links between natural features and other larger stands can also be assessed here.

Minor Significance
1 point
Significant
2 points
Very Significa​nt
3 points
Major Significance
4 points

9-1.14 Category M: Stand Landscape Value

This is assessed distinct from individual trees so individual or isolated trees would score 1 in all cases. The essential aspect is the overall significance of the stand in its environment. Is it visually significant? Does it screen or buffer development? Does it contribute to the city-wide tree framework or green network?

Minor Si​​gnificance
1 point
Significant
2 points
Very Significant
3 points
Major Significance
4 points

9-1.15 Method of Finding the Score for the Evaluation

The rating figures for each category entered on the registration form are now multiplied category by category.  A x B x C x D x E x F x G x H x I x J x K x L x M = Total Points.  Please note that in whatever order the individual category scores are multiplied, the final score remains the same. This represents the sum of the evaluation for amenity purposes and clarification for listing.

For individual trees or groups of up to nine trees, the qualifying score should be the average of individual scores. For groups of 10 or more trees, the qualifying score should be the average score for the 10 best typical trees of the group. (If required, individual scores for other trees in the group could be assessed.)

Thus for individual trees or groups of up to nine trees, the score obtained shall achieve or exceed for:

Category 1 – 1000 points

Category 2 – 500 points

For trees protected as a condition of consent – 250 points.

9-1.16 Method of Applying a Monetary Value

A monetary value is obtained by multiplying the evaluation score by the unit value.  A value of $45 per unit has been adopted, based on the 1998 cost of purchase and establishment of a tree scoring 1. 

The value of an individual tree, in a group or stand of more than 10 trees, shall be the unit value multiplied by the average score for 10 typical trees as established in the registration procedure. The stand value will be the individual value multiplied by the number of trees.

Page reviewed: 15 Apr 2016 3:29pm