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The Butterfly Effect

August 7, 2018

Reading Graham Lawton’s article about biodiversity in last week’s New Scientist, I am feeling a little guilty that an injured shoulder and a busy schedule has prevented me and my gardening partner, Kathryn, from looking after the small wildflower meadow at our local community. Unfortunately, just letting the plants take care of themselves doesn’t work and, trying to encourage as much species diversity as possible requires carefully timed cutting. We didn’t cut the meadow when we should have and now, in a very short time, the stronger plants have taken over – at least I think they have.

 

As Graham points out in his article, much of the evidence for biodiversity loss is anecdotal. To prove the theory, there would have to be meticulous sampling, repeated year after year. Around this time last year, I surveyed the meadow and recorded over 60 species. Casting my eye over it this year, it looks like we’re down on the finer species and up on the toughies such as broad-leaved dock and spear thistle. But, then again, we usually cut the flower heads off the dock and thistle to keep them in check so the finer species could well be there, I’m just not looking hard enough.

 

Last year’s survey showed up a reasonably healthy population of kidney vetch especially on the margins of the more closely mown areas and kidney vetch is the primary larval food of the Small Blue butterfly, a priority conservation species in the UK. I’m pretty sure I saw a Small Blue flitting about the meadow last year. So, though it might not seem all that important there are more docks and thistles this year, it certainly is important to the Small Blue butterfly.

Doing the survey on the meadow last year took me back a long time to the year I spent studying for my HNC in habitat surveying with the Scottish Wildlife Trust and to the day we spent on a hillside somewhere near Glasgow counting butterfly orchids. The count had been taking place every year and that particular year was our turn to make a contribution. Butterfly orchids are pollinated by night-flying moths so, without seeing or catching the moths, we can make an assumption that, if the orchids are thriving, then so are the moths. If the moths go into decline, the orchids will probably follow, and vice versa.

 

The relationships between the kidney vetch and small blues and between the butterfly orchids and the moths is really what defines the importance of species diversity and how the loss of one species can have a knock-on effect on others.

Despite the fact there aren’t enough reliable surveys to prove it outright, Ed Turner, curator of insects at Cambridge University’s Zoology Museum is in no doubt that insects are in massive decline. In June, Chris Packham tweeted he hadn’t seen a single butterfly in his garden. Entomologist, Simon Leather, measures his sense of major insect decline by the rarity of insect splats on car windscreens and, come to think of it, he may have a point. I think there are less insects splattered on my windscreen these days. And now, because of one injured shoulder, there may well be less Small Blue Butterflies - at least in my neck of the woods.

Graham’s article ends on a hopeful note – that good conservation intervention can rapidly turn around population decline. So, if I get back on the case, I should be able to re-establish our cutting regime in time to encourage the kidney vetch to thrive again next year. Kidney vetch likes to grow alongside coastal footpaths, which is why it is so important I get back to a regular cutting regime and make sure the grass paths are able to support them. If you want to grow kidney vetch in your garden, you could try putting them in a rockery but the soil will have to be very poor otherwise they won’t flower. They are short-lived perennials so you may need to collect the seeds each year or disturb the soil around them in autumn to allow the seeds somewhere suitable to land.

 

Our little wildflower meadow isn’t particularly pretty. Tough, Scottish, coastal, perennial wildflowers aren’t as attractive as the cornfield annuals such as cornflowers and poppies - and kidney vetch isn’t exactly a beauty. I doubt many of the people who come to the garden to tend to their vegetable plots have even noticed any difference in what most people would consider a big patch of weeds. But, if that really was a Small Blue I saw last year, at least he or she will appreciate the resumption of our efforts.

 

Kidney vetch image by Arnstein Rønning [CC BY-SA 3.0  (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons

Small blue butterfly image by Bob Embleton / Small blue butterfly (Cupido minimus) from Wikimedia Commons

 

 

 The Plant Listener

Explaining the processes upon which all plant rely for their survival and how we can use that knowledge to influence our horticultural practices

Available in paperback and kindle from Amazon

ISBN No: 978 1 9997243 0 6

 

 

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