Botanical climate control

Having plants around you, whether in native bushland or manicured gardens or pots, is good for you. I've blogged before on the benefits of plants in hospital rooms a few weeks ago, and the evidence is stacking up for a range of benefits you get from being near to greenery.

Plants can give you better overall health, satisfaction with life, and reduced stress. More explicitly, there are correlations between gardening and preventing dementia and reducing the risk of heart disease.

‘Contact with nature’, as it is sometimes called, can even contribute to curing social ills such as violence and crime. A study in Chicago showed that crime rates were halved in housing blocks with more greenery.

And this is all aside from the obvious benefits of oxygen, food, medicines, clothing and shelter...

As we respond to accelerated climate change, it’s worth remembering that plants are net consumers of carbon-dioxide and long-lived species are good stores of carbon. However it’s not an easy solution.

Our horticultural scientist, Dr Cathy Offord, has estimated that each Australian would have to plant at least 24 eucalypts a year, and look after them until their trunks are a metre round, to offset the amount of carbon we each use each year (on average 7.7 tonnes).

Trees might help us battle climate change in other ways. A study in California published last year on ScienceDaily showed that carefully planted shade trees can significantly reduce our electricity use.

As researcher Geoffrey Donovan put it: ‘Everyone knows that shade trees cool a house. No one is going to get a Nobel Prize for that conclusion’. But where do you plant to get the biggest impact and does it make a difference?

Well, in California at least, trees planted within 12 metres of the south side (equivalent to our ‘north side’) or within 18 metres of the west side of a house give you about the same energy savings due to the way shadows fall. Trees on the east side have no effect on electricity use.

Apparently one tree planted on the west side of a house can reduce your carbon emissions from air-conditioning in summer by 30 percent over 100 years. That’s a long time to wait, but as I said at the start, trees have lots of other benefits – and they look nice.

Image: Trees planted near a house not only look good but they store carbon and reduce electricity costs. *This posting is from the Radio Archives (April 2009).