The Branch Line

We have all heard horror stories of construction problems caused by trees; of drains blocked by roots, of heave and subsidence, falling limbs, diseases, messy fruit falling on pavements and attracting wasps.   How many times have these excuses been made to either not plant trees at all, or to take the axe to existing ones?   Less obvious are the benefits of these same trees, of cleaner air, reduced stormwater, although we’ve all walked down tree-lined avenues thinking how lovely they are, and feeling good about the world.

Trees clean the air we breathe by settling out, trapping and holding particle pollutants from the atmosphere, absorbing  Co2 and other gasses and replenishing the Oxygen levels.    The tree canopy also reduces the ‘heat- island’ effect in summer by providing shade and reducing evaporation, whilst the roots improve water filtration, so contributing to the reduction in rate of surface water run-off.  The ecology of the area improves too, as native trees are an important habitat for insects and birds, and provide important sources of pollen and nectar for bees.

Good quality street trees, that don’t obstruct the front elevations of properties are demonstrated to reduce the crime rate:  Donovan and Prestemon (2010) have conducted extensive research with demonstrates that the influence on the crime rate depends on the size and location of street trees.  The larger trees in avenues, or in situations where they leave the view to the properties unobstructed make the place attractive and appear well maintained and well observed.  They also suggest reduced stress levels contributing to general well-being and therefore reduce the desire to commit crime.    Property prices tend to be higher for all these reasons too, so planting good specimens on new developments are also likely to recoup higher and quicker sales.

So the difference between bane or bounty is mostly about the getting the right choice of tree for a specific location.   The right tree in the right place and the benefits follow, so choose carefully and get some advice from a knowledgeable plants-person.    Otherwise the drains may be blocked and the neighbours will be complaining about wasp infested fruit that has dropped on ‘their’ side of the path, and the house will have subsided!

Ref: The effect of trees on crime in Portland Oregon.  G.H. Donovan and J.P.Prestemon 19.10.2010


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