Rabbits and hares are prodigious excavators and tunnel builders. But it wasn’t until I had taken the same route to walk the dog over several years that I realised how rapidly they can have an effect on their environment. On one stretch of the walk the path leads through a deeply sunken lane. A few years back the earthen banks of the lane were sheer, reinforced by exposed tree roots. But the rabbits and hares have built their warrens under the tree roots, encouraging the sandy soil to erode downwards and the trees to collapse. The result is that the lane, whilst still sunken, no longer has such sheer banks. If I were the farmer whose fields are gradually being reduced in size, I’d be a bit peeved. But he doesn’t seem to be bothered. Could it be that he thinks the erosion is worthwhile in return for an occasional saddle of hare on the dinner table? In any case, frequent visits to the countryside and observation of the way landscapes and perspectives change with the seasons and through such standard practices as crop rotation or felling and planting trees have led me to understand that any sort of impression of permanence is an illusion.