As explained under the ecological value banner, I have separated the environmental value to a trees ability in curbing human activity in terms of damage to the environment or in benefits to reducing energy requirements.
There is a plethora of ‘calculators’ and other information regarding tree values in the environmental criteria available online and within research. In many ways it is now considered The most important value and has as such dominated research. Having opted for the rural tree valuation to use particular existing tree valuation systems, (including the Helliwell & Frank/Reeves systems), it limits many of the online calculators asides from one innovative and now widely used valuation system itrees, which due to the international recognition of the US Dollar is arguably the most recognisable tree valuation system in the world.
The method of calculation is complex but has been developed into a base system that is easily available, user friendly and free. This is contrary to most other tree valuations and is perhaps indicative of the difference of attitude towards arborists and foresters and connection with trees in the psyche between the UK, (and Europe) and North America. Trees are still habitually treated as a subjective issue in terms of property value in the UK and this is not the case in the US, where the research works backwards from the given fact that trees add value.
One problem is that the calculator gives a cost per annum based on age and thus it is necessary to add together preceding years and determine life expectancy.
Thus to correctly determine the value over a lifetime it is essential to discover the age of the tree and life expectancy of the tree. This is possible without exposing tree ring counts by way of felling and thanks to the UK having excellent historical records, particularly in accurate mapping it is possible to determine an estimated age of 75 – 90 years for these 2 trees. I am thus assuming an estimated age of 82 for the trees.
[Whilst I have not used it on the trees in question I wanted to divulge a quick method of tree health analysis, which also acts as a very basic aid in determining the life span of a tree. The O’Neill factor. This is very simple and unscientific but can allow a forester the means top determine whether a tree needs further investigation – All trees display their annual growth on branches, albeit difficult to find on mature broadleaved trees than on fast growing coniferous trees.
Simply divide the growth in cm in the last 2 growing season against the previous 2 years growth. Often if possible, it is better to lengthen the quantity of growing seasons, particularly for more mature specimens. However the result will be <1 or >1. <1 = the tree is decelerating in growth. >1 = the tree is accelerating and thus still young.
Trees often have differing stages of life and the above calculation is better used in formative years. ]
Life expectancy of Tilia species varies dramatically according to situation – an ancient remnant small leaved lime can live to up 400 years old. However an urban large leaved lime can assume a life expectancy of 100.
Thus I have allowed for this difference in the assumption also that future maintenance to the tree to help enable an increased longevity will not take place, (contrary to the expected life expectancy in the ‘sustainable’ value).
Therefore I calculate that without additional factors, (disease, extreme weather event or human interference), these trees may survive for a further 165 years.
The calculated cost is £56.60 per tree / per annum (having accrued an average price of 59p per annum since establishment, when the trees environmental value totalled £8.22, to the date of valuation = £2549.40 per tree). From henceforth I am not going to calculate further increases in environmental value above the £56.60 per annum.
I have removed storm water run off benefit value from these figures as I had included this in the ecological value, (contained within the Frank Reeves system).
The total Environmental value, (includes the benefits from reduced consumption as a result of tree’s presence, CO2 storage and air quality improvement), = £11888.40 per tree.
It is necessary to include a discount due to the proximity of the two trees to one another, where the canopy of the trees is reduced accordingly by 15%, (bearing in mind also the increased canopy on other aspects).
The Environmental Total = £20210.28
SUB TOTAL £30697.11