North East butterflies act as barometer to changing climate
PUBLISHED: 08:31 28 June 2010 | UPDATED: 17:27 20 February 2013
They are the most attractive of creatures, a sure sign that summer is upon us, and yet there is so much more to butterflies than a flash of colour, as John Dean reports
Naturalists have long recognised that butterflies are barometers - that they react quicker than most species to changes in the environment. That is why they have been increasingly seen as evidence that our planet is warming up.
Supporting this viewpoint is the fact that among the 35 species listed in the North East are a number previously associated with warmer southern areas of the UK.
They are the species that can look forward to the future with some optimism but there are plenty of others that have a more uncertain future, maybe even standing on the brink of extinction in the region.
Dave Wainwright, Regional Officer for the charity Butterfly Conservation, said: The status of butterflies has been somewhat obscured by the poor summers of 2007 and 2008 but, in general, we are seeing our common species doing well and the rarer ones getting rarer.
The region has a number of common species, familiar to most people from their gardens, including Peacock, Small Tortoiseshell, Red Admiral and creatures like Painted Lady that appeared in such huge numbers last year.
Their strength is that they are generalists, capable of surviving in a range of conditions.
But there is another group - butterflies more associated with the south but which are pushing north as temperatures rise.
Dave Wainwright said: One of the factors for some species that are doing well is that the climate seems to be warming. Species that were previously at the northern end of their range have found themselves able to push ever further north.
Appearing more frequently, for example, are the likes of Gatekeeper, the Marbled White and the White-Letter Hairstreak.
Or take the Speckled Wood. Always seen as a denizen of the South, it has increasingly been sighted in northern areas, now becoming established in the coastal denes of County Durham as well as in other northern woodlands.
Among other species colonising the North East are the Ringlet and Comma, which were common in the 19th Century before numbers reduced but which returned in the late 1980s and 1990s, at about the same time as the Speckled Wood was beginning to make its presence felt.
Dave Wainwright said: We have had northward expansions before but they have tended to be staggered. We have not had such a substantial northward push as the one we have been seeing the past 25 years.
And the same is true when you look at moths, where umpteen species are being seen in the North East.
For all they may come over as fragile creatures, butterflies can prove remarkably robust, as illustrated by a potentially disastrous event in 2006.
Still a relatively rare butterfly in many northern areas, the Green Hairstreak has a number of colonies in the North East, based around its favourite plant, the bilberry.
One such area is Durham Wildlife Trusts Hedleyhope Fell Nature Reserve, near Tow Law, Weardale, but in April 2006, fire ripped through more than 10 hectares of heathland.
There were fears that the blaze would destroy the colony but, remarkably, it has survived and thrived, partly due to its resilience and also because of the survival of bilberry.
Mark Richardson, Reserves Manager for Durham Wildlife Trust, said: Numbers of the butterfly are not quite back to where they were but they should reach that level as the bilberry and the heather regenerates further.
There is a danger in assuming that the success of some species means that all is well. It isnt and perhaps the one with the biggest fight on its hands is the Small Pearl-bordered Fritillary, which was common in the region in the 19th century but had all but died out a few years ago as its habitat was lost to intensive agriculture, including overgrazing.
Today, it is estimated that there are only five colonies left in the North East, none of them larger than 100 insects, and all to be found on untouched areas of heathland along the A68.
Dave Wainwright said: The problem is that the A68 colonies are small and isolated. The big challenge is to connect them. If we can improve other areas then it gives the insects somewhere in which to expand.
Helping to create areas of habitat is the Heart of Durham Project, whose partners include Butterfly Conservation, Durham County Council, Environment Agency, the Woodland Trust, the Durham Biodiversity Action Plan Partnership and Durham Wildlife Trust.
They are working with landowners on projects including fencing marshy stream-sides, the butterflys main habitat, to protect them from over-grazing.
Also, groups including Durham Botanic Gardens and the Peartree Trust are working with local schools and Durham Wildlife Trust volunteers to grow 20,000 marsh violets to be planted out in the wild later this year, providing a food plant for the butterflys caterpillars.
As its name suggests, the Dingy Skipper is a somewhat dowdy insect that loves bare ground, the type typically found on brownfield sites once used by industry. Although it is not doing too badly in the North East, it still faces difficulties - and one of them is linked to the health of the UK economy.
Dave Wainwright said: The Dingy Skipper likes sites that are not particularly attractive and the problem is that when such sites are developed, the developers do not leave bare ground. So, although a sluggish economy is not good for the North East, it does have benefits for the butterfly.
The flower-rich chalk and limestone grasslands of East Durham are crucial for the future of a number of butterflies but the iconic species is the Northern Brown Argus.
Restricted to the magnesian grassland area because there is so much Common Rock-rose, its food plant, the butterfly is giving grave cause for concern.
Mark Richardson said: As with the Small Pearl-bordered Fritillary, the Northern Brown Argus has specific requirements. Whereas climate warming is good for some butterflies, the Northern Brown Argus is very much a northern species. The concern is that as the climate changes it will become drier and the rock rose will lose the moisture it needs. That could have a serious affect on the butterfly.
Dave Wainwright added: There is also another problem. There are reports that the Brown Argus, a separate but closely-related insect, is now breeding north of the Tees and the concern is what happens if the two meet. Will they produce hybrids and what will that mean for the pure Northern Brown Argus?