Friday, 21 June 2013

Ponds and the creativity of extreme weather

2012 has become infamous as the wettest year on record in England. Infamous, at least, in England. This has been followed by a peculiarly long winter, the coldest for fifty years. Britain has had a run of wet summers. One outcome was a recent meeting by climate scientists hosted by Exeter University to try and make sense of the signals from the noise and ,perhaps, the causes. The immediate driver appears to be the jet stream, which has not been shifting as far north has it once did and, instead, acts as a conveyor hauling Atlantic depressions across the UK, one after the other. However what causes the jet stream to linger so far south remains unclear ( . Ponds make immediate and powerful indicators of the impacts of these variations in our climate. The photos above show one of the subsidence ponds at Blakemoor Farm in the summer of 2012, when it was festooned with deep banks of Celery Leaved Buttercup, to summer 2013, when it has dried out, leaving a few forlorn tufts. What is the most worrying; being awash or being dried out? Neither. The pond comes and goes and with it the vegetation. The animals are less obvious but they too wax and wane between years. The extreme year of 2012 created an opportunity for plants and animals that seldom colonised or, even if they did, dominated the ponds. The ability of a landscape to vary  has always struck me as important, although a tricky thing to measure, given how short term so much of our research is. We find it hard enough to describe what we can capture and count, letalone something as abstract as the potenital to change. The variation between years has added to the overall biodiversity, allowing wet and dry year communities to flourish. The risk is that we have not recorded enough data for sufficient years to spot any major step changes, those thresholds beyond which the stage is re-set and some of the cast of ecological characters  never re-appear.

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