Wildlife (and weeds) on track - October

My first site visit of October took me to a rural stretch of railway near Corby which included a stunning brick viaduct across a wide valley – the bridge has been repaired so often with so many different colours of brick that it’s hard to tell which are the original bricks!
On the wildlife front, we saw a stoat running along near the track, a hedgehog, a pheasant and several different butterflies.

We also saw a set of beehives made from tyres around the edge of a field, a reminder that we ignore the needs of pollinators at our peril at a time when many bee colonies are being decimated by the use of neonicotinoid pesticides, resulting in difficulties for many food crops which rely on bees for pollination.
A less welcome sight was the presence of Himalayan Balsam, one of several invasive plants which spread rapidly around the railway network. It is a criminal offence to spread these species but the wind and the burrs which stick to you as you try to walk in a position of safety encourage its spread nonetheless. The worst culprit is Japanese Knotweed, which begged the obvious question: why is it not viewed as an aggressive weed in Japan?
It turns out the reason is climate: Japan has very cold winters which kills the rhizomes (roots) so knotweed has to self-seed itself annually. In England, the rhizomes easily survive our mild winters and so the problem gets worse every year. This also means that any soil where the knotweed has grown is considered to be hazardous waste because the weed can grow back from even a tiny piece of root, resulting in serious difficulties when construction work would disturb the soil.
I know of one scheme which had to relocate a planned substation to another location because the original site had knotweed. This made it impossible to build without either several years delay (to spray the weed repeatedly with weedkiller) or replacing all the soil up to 5m deep to remove all traces of the weed, which could had destabilised a retaining wall next to the site and resulted in significant disposal costs.
This month I also spent a week inspecting rock slopes In Scotland, which was made difficult by another plant which is pretty in gardens but a serious weed when loose in the wild: rhododendron. Some parts of the slopes were completely inaccessible because the rhododendron was so thick and you could make no progress through it to see the ground beneath. The moral of this story is: beware of importing species when you don’t understand the ecosystem!

See also:
Wildlife on Track - September

If There Is No Home for Nature