| Topic: | Re:Re:Re:Re:Re:Re:Re:How Many Trees Will Go from the High Road for CS9 and where? | |
| Posted by: | Kevin Howard | |
| Date/Time: | 26/10/17 10:53:00 |
| The notion that you can measure the impact of the removal of a tree down to a precise percentage is totally bogus. Tom Pike quotes a figure of 2% based on the weight of CO2 that trees will absorb but they have more or less zero impact on CO2 levels. On a local basis the effect will be neutralised almost immediately by air flow. Quite how much air quality is improved by trees on Chiswick High Road is very complex and difficult to measure precisely. It may be the case that the canopy of trees actually makes air quality worse in dry non-windy conditions. But it is reasonable to assume given what we know of trees that a mature tree in the right area will take out a significant proportion of particulates will be harmlessly washed away when it rains. As for the claims that cycle superhighways elsewhere have reduced pollution this is another example of spuriously exact numbers being quoted when the reality is much more complex. I've looked at the air quality data for the stations around other recently implemented cycle superhighways and only a very selective and unscientific use of the data would allow you to conclude definitively that they have contributed to better air quality. Aside from the relatively limited dataset and the difficulty of getting a proper base for comparison there are so many other variables that attributing any change to a single factor is clearly wrong. Changes in vehicle type due to anticipation of punitive measures against diesels and the T-Charge, an upgrading of the bus fleet, an absence of roadworks and overall economic activity will all have a significant impact. Any reduction in traffic by displacement just means that pollution has been moved elsewhere. If CS9 goes ahead there is a good chance that pollution will seem to reduce on Chiswick High Road at the same time but the main reason for this will be that only low-emission buses will be permitted just as the cycle superhighway is opened. This will mean there will be a big drop in particulates as measured on the High Road. However, the polluting buses have just been moved somewhere else so overall pollution hasn't been reduced and the actual impact of CS9 on air quality will have been masked. As it will mean more vehicles on Chiswick High Road at anyone time I struggle to see how anyone can make a convincing argument that its net effect in isolation won't be to increase pollution. |