Monday, 9 November 2015

When is pond not a pond? An existential crisis and the probolem of choosing the best

Here is an example of how the Druridge Bay field ponds fluctuate in area depending on the rainfall. This might be an even more existential questions: can you have a pond that has no water in it, is it still a pond? Yes it is, although I am not sure how long you can go before saying it is no longer a pond. My personal preference would be years. I am sure there will be ponds in some desert habitat that only fill very rarely with long hard dry years in between. The pond in the photos above is just in the field to the right hand side of the entrance to Ellington Caravan Park. It is wet most years and well established. On the left is the pond in mid July 2012. Yes, those are rain drops smudging the lens. Still, it is not lashing rain so this must have been a particularly dry day given the deluge of 2012. On the left July 2014. No water an there had not been for a while, instead carpet of weeds that weave a distinct carpet over the exposed earth. Mayweeds and annual meadow grass, bistorts and cudweed. In 2012 the plant life was dominated by other species growing luxuriantly in the damp summer, although the overall tick list was much the same.

Which is the better pond? That could be a classic question asked of conservationists. Is it the overflowing quagmire of 2012 with thick tufts of toad rush and even underwater starworts? Or maybe the dried out mayweed and cudweed carpet of 2014. Both are good, both are typical of the Druridge fields. The differences between years do not matter, they are part of the natural disturbance and change. The real challenge will be if the local wildlife is exposed to weather conditions so different to anything they are used to that they cannot cope. The plants seemed to cope with 2012 but I do not know about the invertebrates because I was not monitoring them Butterflies took a massive hit, but butterflies like it sunny and dry. I am worried that the invertebrates may have been hit harder than we know, especially those with flying adult stages to their life history

Saturday, 7 November 2015

Extreme weather and a not at all extreme graph: how rainfall influences the extent of the Bay's ponds

The first blog graph. I like a good graph, although these days it is very easy to create endless variety of rubbish graphs in colour and 3D.

This one shows how the areas of ponds varies between years and seasons at a site on the Bay, in particular the effects of extreme weather

Our autumn has been peculiarly warm, disconcertingly so. The fog is clammy rather than cold and there have been very few days when any wind strong enough to have shaken the leaves down. Instead I have stood in Newcastle and listened to the crisp patter of aspen leaves falling so neatly and gently you’d think it was a cheesy CGI effect. Unusual weather seems to be the norm. 

The example in the graph is from up on Druridge Bay at Blakemoor Farm. Every November and May between 2010 and 2013 I walked a zig zag route across the Blakemoor fields, a nine mile trek to find every pond and wetland down to the smallest pools of around 1m2. Their areas were measured and in the graph you can see the total area for ponds in four types of fields The black area is the ponds in amongst the dune grassland, the dark grey from the arable fields or cereal and oil seed rape, the pale grey from permanent pasture and the white the area of ponds in amongst natural wetland. In all four cases the areas change markedly with the local rainfall. Over the three years of walking back and forth the Bay was hit by a distinct sequence of extreme weather; unusual drought from 2009 to March of 2012, then sudden and sustained rainfall resulting in a record breaking wet year and finally a 2013 heat-wave.

Much of the contemporary work on pond has been spurred by concerns at the loss of ponds from the British landscape over the last 100 years. The seasonal change at Blakemoor show a more complicated story, even the suggestion that extreme wet year can be good for the pondscape. However the damp and cold probably did more harm throughout the summer than any benefit provide by more and larger ponds.

Druridge Bay continues to reveal surprises and challenges about even such familiar habitats as the farm pond