A tree inventory valuation provides useful information about the trees within a defined area.
Characteristics of individual trees are collected and recorded. These include the trees’ position, the species, and often the cultivar, size, and condition (additional information may also be recorded). More often than not, they are used for operational purposes, where work is needed or scheduled, or risk assessments need to be made.
But tree inventories can provide the basis for a more extensive and probing analysis of the urban forest, with the data available subjected to a greater degree of analysis than was possible only a few years ago.
With three basic pieces of information about an individual tree (species, height, and diameter at breast height), an assessment can be made as to the likely benefits and ecosystem services the tree is delivering. It is possible to calculate the amount of carbon stored in the tree, the amount of carbon sequestered annually, the amount of pollution intercepted, and the amount of avoided stormwater runoff that will be achieved by the presence of the tree.
From the same analysis, it is possible to calculate the value to society of the benefits provided, and to express these in monetary terms, as well as providing an asset value for the tree itself.
Applied at tree population level, with all trees on the inventory subjected to the same analysis, it is possible to provide the above information about the whole population. So, from three pieces of information (a constant feature in most tree inventories), a picture emerges of what the trees on that inventory are contributing as a whole. This is seen in terms of benefits and ecosystem services, as well as a defendable asset value for the population under consideration.
But this is only the beginning of what is possible. From the data gathered, it is possible to assess the diversity of trees in the population and to assess its resilience to threats from pests and diseases, as well as those posed by climate change. It is widely recognised that the more diverse a tree population, the more resilient it is. Tree inventory analysis allows an examination of diversity to take place, illustrating which species are over-represented and which are under-represented. This can provide a basis for strategic tree planting.
A deeper analysis may be carried out if the area represented within the inventory is sub-divided. For example, a local authority area may be subdivided into political wards. Providing there is a location for each tree on the inventory, and this is almost always included, then another series of analytical observations can be made. It is possible to compare these sub divisions with each other and understand where inequalities exist and where further tree planting is possible and necessary.
So from information which is already recorded, the use of the tree inventory can be extended well beyond its original purpose, providing valuable information about the tree population it represents, and thereby creating the baseline for further urban forest planning and development at a strategic level.