In our leafy locale they are all around us. Trees lining the streets, trees in the our gardens, trees in our treasured green spaces such as Littleheath Woods, Croham Hurst and Bramley Bank, trees in and around the golf course and trees in the grounds of our schools. Have you ever wondered how many trees there are in our area or what is the point and benefit of Trees?
Whilst the numerical answer could be obtained from a forensic and time consuming search of Google Earth an organisation called Forest Research has launched a Citizen Science project which aims to build an urban tree canopy cover map for Britain on a Ward by Ward basis. Using a piece of computer software called ‘i-Tree Canopy’, which was developed in the US, Forest Research estimates an average canopy cover of 15.8% for English towns and cities. Examination of the canopy cover at a ward level can help improve management of urban trees and identify which areas within a town or city could benefit from future tree planting.
Within the Croham Valley area we have two Wards: Selsdon and Addington Village (S&AV) and South Croydon (SC). Using the i-Tree Canopy software and analysing 1000 random points in each ward it is assessed that S&AV ward has a tree canopy cover of 37.5% (with a potential error of 1.53%). By comparison the adjacent ward of Selsdon Vale and Forestdale has a tree canopy cover of 46.7% (with a potential error of 1.58%)
The i-Tree Canopy software assesses the practical benefits of the trees, in quantity and monetary terms, of their capacity for annual removal of Carbon Dioxide, Ozone, Nitrogen Dioxide and Particulates of 2.5 microns or less, the annual sequestration of Carbon Dioxide and the amount of stored Carbon Dioxide:
Selsdon and Addington Village Ward (S&AV) cover at 37.5%
Tree Benefit Estimates (GB £s, Tonnes and lbs):
Abbrev. Benefit Description Value Amount
CO Carbon Monoxide removed annually £15.24 437 lb
NO2 Nitrogen Dioxide removed annually £26.25 1.19 T
O3 Ozone removed annually £1,366.81 11.86 T
PM2.5 Particulate Matter* removed annually £2,825.45 1,152 lb
SO2 Sulphur Dioxide removed annually £4.59 1,50 1,501 lb
CO2seq Carbon Dioxide sequestered annually in trees £92,518.27 2,424 T
CO2stor Carbon Dioxide stored in trees (total) £2,323,481.02 60,899T
*less than 2.5microns
Of particular benefit to us Humans is the ability of trees to remove minute particles of pollution from the air. We are subjected to pollution from many sources. The World Health Organisation (WHO) considers airborne particulates a Group 1 Carcinogen. Fine particles with a diameter of 2.5 microns or less can penetrate into the lungs and blood stream causing heart attacks, respiratory disease and premature death. Particulates of 2.5 microns or less include the soot produced during the combustion of solid and liquid fuels: vehicles are a major source. (As a guide, in old money, 1 inch equals approximately 25,000 microns.)
The role of trees in managing surface water is not to be underestimated, especially In light of recent flooding in parts of the UK. Broadleaved trees can slow down the rate at which rain hits the ground. The trees roots penetrate the ground and create passageways for rainwater to permeate the earth. The root system stabilises the soil and protects the ground against erosion.
The Lancet recently published research which was funded by the World Health Organisation into Green Spaces and Mortality: Green Spaces were found to have a beneficial effect on health and well being. So much so that ‘Interventions to increase and manage green spaces should therefore be considered as a strategic public health intervention.’
Croydon Council are now proposing further revisions to the recently agreed Local Plan. These revisions concern the provision of 46,000 new homes in the Borough of Croydon over the next 20 years to satisfy the ambitions of the London Mayor and we have been asked to comment on three ‘Strategic Spatial Options’. Strategic Spatial Options 1 and 2 both involve using Green Belt land for infrastructure development such as schools or a new tram depot to support the population increase. Strategic Spatial Option 3 in addition to the use of Green Belt land as above, involves the further use of Green Belt land in New Addington, Selsdon and Sanderstead for 5,300 homes. Whilst it could be argued that analysis of these three sites will show that they are largely free from a high degree of tree canopy cover I would suggest the concept of building on the Green Belt should be challenged. Support the idea in this Local Plan consultation and we will see, over time, the gradual erosion of valuable Green Belt. We need more trees and green spaces, not less.
You can find out more about Forestry Research and UK Urban Canopy Cover at www.forestresearch.gov.uk/research/i-tree-eco/urbancanopycover/ where you could select a local ward to take part in this exciting piece of Citizen Science and help Forest Research build their map of urban trees. If you would like to immerse yourself in some local woodland you can find out all about Littleheath Woods at www.folw.co.uk or contact me on 020 8651 1140.
Chair, Friends of Littleheath Woods