After the long, hot days of June and July that turned so much of our countryside and our gardens an unaccustomed brown, the more variable weather (and indeed the rain) of August has been, in many ways, a relief.

So much so, that I have found myself delighted to be climbing into gumboots and getting out my umbrella for what I thought was going to be a wet Melplash show on the penultimate Thursday of the month.

In the event - as has almost always been the case - the rain held off for the duration of this marvellous show. But, as I sat at a meeting with local farmers, I found myself reflecting, not for the first time, on the extraordinary power of the forces of nature.

The astonishing achievements of human civilisations can all too easily make us forget that the entirety of the constructions of which humanity is justly so proud are in fact tiny and puny things when compared with the forces that can be exerted by nature.

Ultimately (admittedly rather a long time from now) the earth itself will be swallowed by the sun.

But even without contemplating these cataclysmic events in the distant future, and indeed without referring to the earthquakes and tsunamis which are by comparison everyday occurrences in geological time and which have the power to wipe out entire civilisations, we find that we are extraordinarily dependent on very slight adjustments of the weather.

No one recognises this more lucidly than our farmers, who can see the whole world' food-economy gyrating because of slight changes in temperature or rainfall.

Of course, it is one of the points about markets (both local and global) that they contain within themselves mechanisms and signals that enable our economies (whether in the agro-industries or elsewhere) to adapt to these changes so that life can go on more or less as normal.

But these mechanisms too, have their limits. And, the speed of adaptation to significant change in the natural world is not instantaneous.

These, of course, are the very reasons why we need to take seriously the risks caused by climate change.