Sunday, 10 January 2016

Changing Climate

As I've already stated numerous times, the summer of 2015 was awful for dragonflies (here in the north anyway), mainly down to the weather pattern for the whole year, not just the summer itself.

It's amazing to think that 2015 ended up as being one of the wettest years on record, considering we had hardly any rainfall in the first six months which led to usually shallow ponds being devoid of any water whatsoever when the first damsels and dragons should have been emerging, and this combined with the cold nights right through to July, would have the effect of either killing off many aquatic larvae or at least retarding their growth through lack of available food through abnormally cold water temperatures, with the cold water not being particularly conducive to emergence anyway.

Now I know one of the most consistent things about British weather is its inconsistency, no two consecutive summers are the same, so there's a good chance this year will be better altogether (fingers crossed), but what of the changing climate? It's well documented the world as a whole is changing, and whether you believe it to be man made or just the natural cycle there is no doubt the planet is heating up. So what does climate change actually mean for the future of our Dragons and Damsels?  
 
Well, as it happens I recently followed a link on Twitter which led to a scientific paper on the potential effect of climate change on British odonata, based on a study of records collated between 1980 and 2012.
Written by leading experts including Steve Cham and Dave Smallshire (who's Dragonfly book I just got at Christmas).



It was interesting reading (as is the book) with so many detailed factors taken into consideration but the conclusion was pretty much inconclusive, so no startling scare-mongering headlines on climate change for the Daily Mail to exploit (not that it would stop them).
 
Being a bit thick, I had to read it with the aid of a dictionary to semi-understand what they were on about but I did learn some new dragon-jargon in the way of science mumbo-jumbo, my favourites being :

Lentic – of standing water
Lotic – of running water
Phenological shift – A change in the time of growth and breeding of a species

Biotic homogenization- the process by which species invasions and extinctions increase the genetic, taxonomic or functional similarity of two or more locations over a specified time interval.

All good stuff, but here’s a summary of some of their findings in terms I can understand myself :

Of 36 British breeding species which were studied, 8 have significant negative distribution trends over the period, whereas 19 have been positive.
Before the study was made one of the things they expected to find was that species with longer flight periods would have greater ability to respond to environmental change as they have a greater opportunity for dispersal . . . . but this proved not to be the case.
They also expected to find that species which overwinter as larvae would suffer more than those which remain dormant as eggs, seeing as larvae can be washed away in floods to unsuitable habitat which will affect their development . This also proved not to be the case.

So what did they find? Well, they found that positive trending species (the biggest gainers being Emperor and migrant hawker) come about for two reasons. Climate warming has increased habitat suitability for those dragonflies with lower thermal tolerance, meaning southern species used to warmer climes will drift north. But the increased distribution of many species since the mid-2oth  century can be as much attributed to far improved water quality over the period due to the dismantling of heavy industry, mining and the introduction of environmental laws.
I remember as a lad there were pitheads visible in all directions as you travelled through the northeast and we used to play on the slagheaps which are now parks and nature reserves, so it stands to reason that dragonflies among other wildlife would benefit greatly from this and start to spread into previously uninhabited areas.


Red-veined Darter
I photographed this one as a migrant at Kibblesworth in 2006, With the change in climate they are become
established breeders in the south of England so how long before we see more of them oop north?
On the other hand there is a negative effect on those species with a northern bias, as they require more specific breeding habitat and due to the changing climate find they have to share their landscape with more species as a result of the northward charge of southern species. Moorland (common) Hawker and Black Darter being the two most noteworthy, though the decline of another two of the greatest losers over the period, scarce blue-tailed damselfly and common clubtail, are most likely to do with destruction of suitable habitat in their limited range rather than climate change.

Black Darter
Appears to be one of those species losing out, but a good year for them in Gateshead, with more noted
than ever before late in the season.

So there we have it. Though a large number of dragonfly species have increased their range in the UK between 1980 and 2012, it is as much a response to increased water quality as it is climate change.
Here in the North East we have a paltry number of species to look forward to each year so I'm all for a positive effect of colonisation due to climate change or whatever, but the long term forecast is as much a mystery as a whodunnit? with the last page missing, there are so many theories being bandied about. Some say our summers are going to get hotter, some say wetter, some say cooler and drier. Whatever the future holds, it's just as I said at the beginning, where our weather is concerned, the only certainty is the uncertainty. 
Here's to the next summer, and whatever it brings ;-)
   
And for anyone interested, here's a link to the actual paper I took the info from :

https://peerj.com/articles/1410/?td=tw



 

 

 

3 comments:

  1. I'm looking forward to my second year of Dragon hunting. My copy of that book turned up today so I've started preparations.

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    1. Yip same here, and it HAS to better than last year :-O

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