Icelandic cloud casts ominous shadow

MY heart missed a beat. In a half-asleep daze I had switched on the radio at 6am. I could hardly believe the dramatic news: "United Kingdom airspace has been closed due to a volcanic eruption in Iceland". An ash cloud heading our way. Wow.

As events have unfolded since the news broke on April 15, most people have been thinking about the implications for travel and transport. Uppermost in my thoughts have been our butterflies which depend for their very existence on direct heat from the sun. In the past, volcanic eruptions such as Krakatoa had a considerable effect on our butterfly populations. Could it be about to happen again?

In the four days of no flying following 9/11, US scientists took the opportunity of studying the temperature effects of removing the layer of vapour trails and pollutive plane emissions. To their surprise, the clearer air pushed up temperatures by one to two degrees.

We know that some of our butterfly species need extremely high ground temperatures. Could vapour trails be reducing the heat butterflies need and be pushing them towards extinction? The caterpillar of Yorkshire's rarest species, the pearl-bordered fritillary, even needs high temperatures for digestion to take place.

So having lost that that layer for some time, could it be making any difference or has it simply been replaced with a layer of ash? Even on sunny days, the sky has looked very hazy. Has it been a meteorological haziness or an ashy one?

On Day Two of no flying, I took a close look at my car. It wasn't terribly obvious until you caught it at an angle to the sun, but there were dirty streaks down the windscreen. I felt them; definitely gritty. I examined a patch under a x12 hand lens. Amazing! You could clearly see tiny flecks of grey ash interspersed with shiny spicules of glass, and deep yellow granules which I took to be sulphur. I took a damp tissue and wiped it across the window. It came away ashy black. Ash from a thousand miles away.

Icelandic volcanoes have a long history of affecting Britain and indeed the whole of the northern hemisphere.

They probably contributed to the "Year without a Summer" in 1816 which led to the 1817 Irish potato famine. And here lies the crux of the problem. Ash in the atmosphere reflects the sun's heat and cools the weather. If the current volcano carries on for a year or two, which is not impossible, that could lead to problems for our farmers and food producers, not to mention our butterflies.

However, for the moment, our butterflies have been enjoying the unusually long spell of quiet high pressure weather. Hibernating species like the peacock, small tortoiseshell and brimstone have emerged in good numbers and there have been red admirals reported from Leeds and Skelton (Middlesbrough). We usually think of the red admiral as an annual immigrant from the Mediterranean, and although it can hibernate, it has to wake up to feed every few weeks, which usually spells doom in a typical English winter, so few survive.

Other species recently recorded have included green hairstreak at Otley Chevin, a holly blue at Baildon (Shipley), speckled woods in Leeds and Sheffield, and the first orange-tips in Leeds, York, Scarborough and as far north as Richmond. Small whites have also been spotted in Skipsea, Church Fenton and Silsden (near Keighley). An early wall was also seen in Crossgates, Leeds. Moths have also been emerging in unusually good numbers.

Howard M Frost is Butterfly Conservation's voluntary organiser of butterfly recording in Yorkshire and can be contacted via their website, www.yorkshirebutterflies .org.uk where you can find the latest butterfly and moth news updated day by day.

CW 24/4/10