THE other day I heard somebody observing that some deciduous trees were starting to change colour and drop their leaves early this year and suggesting that this was a sign that we were in for a bad winter.
In Ireland and all over the world, there are dozens of ways in which events in nature are used for long-range weather forecasting. And this traditional lore is still widely believed, despite the fact that it’s practically all nonsense.
Long range weather forecasting is not something human beings can do, not yet anyway, despite the fact that a huge amount of effort, ingenuity and computer time has been devoted to it since people became aware of the dangers of climate change.
Not long ago an eminent source from one of our eminent universities stated that a feature of climate change in Ireland would be hotter, drier summers, particularly in the eastern part of the country. Every summer since 2000 has been unusually wet and cool, with the exceptions of 2003 and 2006.
We can’t do it and neither can the natural world. Yet every spring there are articles in the papers and items on radio in which sages who observe the behaviour of dolphins or frogs predict what sort of summer we’re going to have. And in the autumn I listen to neighbours saying there’s an unusually heavy crop of wild berries in the hedgerows and this means we’re in for a hard winter.
The implication behind this kind of thinking is that an all-knowing nature can forecast what the weather is going to be doing in several months time and make provision for hungry birds and animals by providing extra supplies of food.
In fact a bumper crop of hedgerow berries reflects what happened months in the past. A mild May will ensure a greater amount of insects to pollinate the hawthorn blossom which will result in more haw berries in November.
But observing wildlife can tell you what the weather is doing at the moment and, in some cases, what it’s going to do in the next few hours.
If the swallows are flying low over the field it means the insects they’re feeding on are also flying lower than usual. The normal reason for this is a large amount of water vapour in the atmosphere preventing the insects from climbing to the altitude they want. This could mean it’s going to rain in the next hour or so.
Larch trees are deciduous. If their needles are attacked by caterpillars then the following year they will produce modified needles that are shorter and thicker. These needles are less efficient at their primary job of photosynthesis, but are better at resisting caterpillar attacks. If the caterpillars fail to reappear for the next couple of years the larch notes this and reverts to the original long, thin needles.
It has also been shown experimentally that if you plant two identical young trees side by side and go out regularly in the winter and shake one of them vigorously, imitating a strong wind, then next spring it will produce thicker and sturdier growth than the unshaken tree.
We can’t really call this memory but it is something very similar. But, although trees may be good at remembering the past, they can’t foretell the future.
* dick.warner@examiner.ie
a d v e r t i s e m e n t
This appeared in the printed version of the Irish Examiner Monday, August 31, 2009
