Conscious that this blog, which purports to be about natural history, has not actually had any posts reporting my own observations for some time, I had tentative plans to go out and collect some samples this weekend. Storm Desmond, however, had other plans for me: high winds and heavy rain from Friday evening onwards pushed local river levels up to dangerously high levels, and I was left to contemplate the capricious nature of the British climate from a largely sedentary perspective.
A screenshot of the Environment Agency’s river level gauge shows how the spate developed. We had high winds in Durham, but not excessive amounts of rain, and the steep rise in levels during Saturday reflects the time-lag between rain falling on the Pennines and arriving in the Wear at Durham. The peak in level occurred early on Sunday morning, and the subsequent pictures show the river in Durham at about 10:30 on Sunday morning. Though high, this is not the highest I can remember: that was in 2009 when the road into Durham was impassable at Shincliffe as the river had broken its banks.
A screenshot from the Environment Agency’s river level website, showing the passage of Storm Desmond through Sunderland Bridge, a few kilometres upstream of Durham City, from midday on Friday 4 December to midday on Sunday 6 December.
The River Wear in spate on 6 December 2015: the view downstream from Elvet road bridge.
The River Wear in spate on 6 December 2015: the view upstream from close to the Count’s House, showing the same clump of Japanese Knotweed that featured in my post “In praise of Japanese Knotweed” in early November. You can see how the river has risen up and covered the bankside footpath.
As I have some old-fashioned ideas about fieldworkers being part of the benthos not the plankton, I am watching river levels with interest. I have fieldwork planned in Cumbria at the end of the week and am intrigued to see what Storm Desmond has done to the algal communities. The irony being that to study the effect of spates on ecology, one has to first get into the river… or even get close to the river. This may be an issue as my route to the River Ehen passes some of the most affected parts of Cumbria.
However, questions about the effect of a spate on a river can be generalised into a broader question of how occasional catastrophic events alter ecosystems which, in turn, makes us think about problems that may arise from simplistic interpretations of the relationship between explanatory variables and response variables, discussed in the previous post. The temptation is always to interpret ecology in terms of the variables that are easiest to collect and measure when you are collecting your samples whereas, looking back at “How green is my river?” we see how late summer conditions in the River Atna are at least partly the consequence of high flows in the Spring.
Biologists have suspected this for a long time, and there is anecdotal evidence of changes wrought by individual events. I was pleased, therefore, to see that a whole issue of Freshwater Biology had been devoted to this topic. With the effects of flooding uppermost in our minds this weekend, the introduction to this issue, by Mark Ledger and Alexander Milner, reminds us that “catastrophic events” can also extend to droughts and heatwaves. One point that emerges, even from a quick scan through the contents of this issue, is the importance of long-term datasets – revisiting, again, topics that wrote about in “How green is my river?” It is more pertinent than ever because of the fiscal squeeze on our environment agencies and, ironically, the flooding that results from Storm Desmond is going to lead to calls for yet more DEFRA money to be diverted to flood defence, which can only mean less money for environmental regulation. Therein lies the biggest irony of all: a government department that trumpets the virtues of “evidence-based policy” is planning to collect less evidence. Work that one out, if you can.
Ledger, M.E. & Milner, A.M. (2015). Extreme events in running waters. Freshwater Biology 60: 2455-2460.