Trees under threat






Arboricultural surveys


Making an assessment of all the trees on a site that may be developed is a usual first step in preparing the plans for a development. The assessment is made by arboriculturists who are likely to follow the British Standard BS 5837:2005, “Trees in relation to construction—Recommendations”. This assessment becomes a part of a planning application for a development. The assessment may be part of a comprehensive Arboricultural Report on the implications for development on a site. (The Recommendations have recently been updated to BS 5837:2012, “Trees in relation to design, demolition and construction – Recommendations”. It is offered at £178 from 1st June, 2012. It supercedes BS 5387:2005.)


BS 5837:2005 is generally supportive of trees and their retention on development sites but this publication is an expensive document, (36 pages, £178), prepared for the professions, so few among the general public are likely to know its ins and outs. However, the nature of the tree data in the assessment can be set out briefly here, though not comprehensively, and there is a lot of important detail within the document that needs to be understood.


The BS recommends an arboricultural assessment be completed before any site plans are drawn up. The Arboricultural Survey will comprise a standard data set entered for each tree, similar to the table below.


The main categories to which trees will be assigned are:

Category R.  Deemed to be of no value within 10 years of the assessment and should be removed. Criteria are defined in the BS.

Category A.  Trees of high quality and value capable of making a significant contribution to the area for 40 or more years.

Category B.  Trees of moderate quality or value capable of making a significant contribution to the area for 20 or more years.

Category C.  Trees of low quality, adequate for retention for a minimum of 10 years expecting new planting to take place; or young trees that are less than 15 cms in diameter which should be considered for re-planting where they impinge significantly on the proposed development.


Also, trees in categories A, B, and C will be assigned at least one sub-category relating to distinct values:

1.  Arboricultural values;

2.  Landscape values;

3.  Cultural values, including conservation.

A tree may be considered worthy of one, two or all three of these sub-categories.


The BS recommends that except for trees deemed to fall into category R, for removal, it should be assumed that a tree will fall into the high category and be deserving of the greatest protection and of retention unless there are reasons for the tree to be assigned to a lower category.


There is also a recommendation that where trees form cohesive groups, the trees should be assessed as groups. However, where trees in groups are open-grown or where there is a need to make differences clear, the trees should be assessed both individually and as a group. The criteria for assessing groups of trees are similar to those for assessing individual trees.


Making the assessment is not a science only, and it is possible that different arboriculturists may come to different conclusions as to the merits of a tree or group of trees. Someone campaigning for trees would want to know what the Arboricultural Survey includes as tree data and, if they seem inadequately to reflect the importance of the tree or trees, they can be queried and, if necessary, challenged. The council tree officers working in planning will be able to show and explain the complexity of the BS 5837:2005 more than is set out here.


There may be scope for discussion around what seems to be an area where subjectivity or different levels of experience necessarily play a part. A second opinion, from an arboriculturist, may be sought and presented to the local planning authority.


Many individual trees in private ownership are protected by Tree Preservation Orders. The government has made revisions to these regulations and has published a short document advising on the Main Changes.