Saturday, 30 March 2013

2012 - a disaster for butterflies

Chalk hill blue

Another report recently published by the excellent organisation Butterfly Conservation has shown just how bad last summer was (as if we needed reminding!) for our wildlife in general, and in this case particularly butterflies. Eye catching statistics such as “one of the UK’s rarest butterflies the black hairstreak saw its numbers fall by 98% and the white-letter hairstreak fell by 72%”.  The report goes on "Despite the horrific weather in 2012 over 1,500 dedicated volunteers still managed to collect data from over a thousand sites across the UK. Their amazing efforts enable us to assess the impacts of wet summers on butterfly diversity." I admit that the report did also say that one or two species did buck the trend such as the meadow brown which was up in numbers from the previous year.
However, this all resulted in newspaper headlines such as “Butterflies suffer devastating year after UK’s wet summer” and “Disaster year for butterflies”. You have to admit, a 98% decline in a species in just one year does sound pretty appalling – but is it? The last dreadful year similar to 2012 was 1976, which ironically was caused by drought. So, were butterfly numbers permanently affected following this drought? No, not really.
The importance of these surveys are to gauge long term trends, which does show that many butterfly and moth species are in fact declining which is worrying and an important story to tell. The fact that populations jump up and down in number from year to year, depending on a wide range of reasons, is of course interesting too, but this has been ever thus and should be treated accordingly. Of course for some of our very rare species, an awful breeding season could be the final nail in the coffin, but for most it is just a bad year and no more than that. We need to be careful that all we ever read in the press is more and more depressing news as far as the countryside is concerned.
The summer of 2012 was in fact an incredible summer for the chalkhill blue in parts of the south of England. Phenomenal numbers emerged on some areas of the South Downs at the beginning of August, in scenes seldom witnessed since Victorian times. On one particular place near Eastbourne for instance, a conservative estimate for the whole site reckoned there to be around 820,000 chalk hill blues, which in certain favoured places were recorded at a density of up to 33 per square metre!!
Not much mention of this in the press.  

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