Home and Garden
What can you feel but never touch? And what can you see the effects of but never actually see? What is so essential that without it, both you and your garden would be dead - but, in excess, can kill you?
The answer, possums, lies in the sky. And I'm not talking about vapour trails or so-called chemtrails. I'm talking about sunshine and vitamin D.
Without light from sunshine, plants couldn't grow and we'd starve. And without vitamin D - which we, as mammals, also get from sunlight - we'd have all sorts of health problems.
But you'd have to be living in a cave to not know that the ultraviolet radiation (UVR) in sunlight can also cause skin cancer, which plagues us as the most commonly diagnosed cancer in New Zealand, as emphasised by research findings from Otago University this week.
Published in the New Zealand Medical Journal last Friday, the paper highlighted, once again, that our melanoma rates - along with those of Australia - are among the highest in the world.
UVR, we are reminded, is a "known carcinogen", and in high UVR areas, such as New Zealand, excessive exposure is "estimated to cause over 90 per cent of skin cancers".
However, while most of us know about the need for sun protection, the research findings have highlighted inadequate UVR exposure prevention programmes in early childhood centres that "could be putting children at risk of skin cancer later in life".
Which is why shade, and not just hats, sunscreen and protective clothing, is surely essential at these centres.
The research paper found that even if parents sent their kids to centres with hats and sunscreen, prevalent practices meant they might not put either on or use them effectively.
But shade, as we know, covers kids even if they don't wear their hat or apply sunscreen. And young kiddies are reliant on adults to lead the way and make sure they have protection.
Which is where trees come in. Sad as it might seem, skin cancer has highlighted just how valuable trees can be in providing shade, especially for kids at childcare centres and schools.
Awnings might provide instant cover, but trees provide a holistic answer. They not only cost less but, in time, can look good and provide summer shade while still allowing warm winter sun to filter through. They can also provide flowers and fruit to attract birds.
The secret to successfully using trees for shade is to have the right tree for the right place, and to use it for maximum effect.
That's where a shade audit can help. If you haven't heard of shade auditing, which is used widely in Australia, then check it out online. It makes an assessment of a site and how it is used.
It's a planning process anyone can learn to use to assess the UVR exposure risk at a particular site - from outdoor spaces such as playgrounds and school grounds to parks and even your own garden - and plan for shade and minimising overexposure to harmful rays.
Although audit results can identify challenging issues, often the solutions simply require some lateral thinking and strategic changes. Sometimes it means providing more shade in different places, or simply changing activity times.
Trees can provide excellent playground shade, but it needs to be when the kids are out playing, when the UVR is most intense and when the youngsters are most vulnerable. Often, that means having trees and shade right overhead in the middle of the day.
Another essential consideration is shelter. As most of us know, even during a Nelson summer the air can be chilly - and with no accompanying shelter, it can be too cold for kids to want to stay in the shade.
And then there are changes during the day and the seasons. The midday sun casts a different shadow compared to that in the morning and afternoon, and to that during autumn and winter.
The good news is that auditing outcomes don't necessarily mean spending lots of money. Instead, any problems can be solved through better use of existing shade, adding more shade, and rescheduling activities.
Before the trees grew and provided shade in Nelson's Trafalgar St, I used to watch in horror as thousands of families and young children, including my own, stood in the searing midday December sun watching the annual Santa Parade. Changing the parade time to the end of the day, when the UVR was less intense, would have been a sensible solution had the trees not grown to provide the shade they now offer.
Similarly, early childhood centres can plan to limit or change their lunch and playtime activities during summer, and public playgrounds can be better served by having trees to protect kids, and their parents, from UVR and possible future melanoma. Which is why I found it such a tragic irony to see the beautiful old spreading elm tree by the Takaka children's playground cut down by the Tasman District Council last week, on the same day Otago University published its findings.
The tree had suffered scorch damage when the adjacent library burned down in October 2010. Council horticulture officer Kathy Curnow announced last week that, after monitoring its health and noting "a marked decline", the call was made to remove the tree.
Many, like me, will remember it as a valued part of the town and playground landscape, providing welcome shade from the hot Takaka summer sun.
As Nelson tree advocate the late Ron Flook, instigator of the New Zealand Notable Tree Scheme, would say, people often don't value a tree until it is gone.
And when they do, it's worth remembering that if the tree was, say, 50 years old, it will take that long for a replacement elm to provide the same amount of shade.
To read the University of Otago paper on sun protection at early childhood centres, go to www.otago.ac.nz/news/news/otago065200. For more on shade auditing, refer to www.webshade.com.au/what. To do your own shade audit, go to www.sunsmart.com.au.