Wednesday, 2 May 2012

Improving the Aigronne part II

The planned amenagement of the Aigronne valley continued rapidly this spring between Le Grand Pressigny and at least Charnizay. The work we blogged about here to improve the river flow has settled in nicely, with green algae and sediment softening the whiteness of the new stone. The "restoration" of the riverside vegetation has proved rather more controversial.

Acting to preserve the environment

Vegetation in a bad state:
     presence of unstable trees, leaning, withering, dead
     poplars in great numbers
     zones inaccessible to users (fishermen... )
     presence of trunks and branches in the bed of the river
Work done:
     Cutting down trees threatening to fall into the river in the medium term
     Creation of clearings to enable users to reach the river
     Selective removal of encumbrances on the river bed
Many of the poplar plantations in this area are way beyond any economic return, being good for nothing but firewood. Poplar is an excellent constructional timber, and according to one tradition we have heard, new parents plant poplars on the birth of a daughter, with the eventual proceeds to pay for her dowry. That would make a poplar harvest at about twenty years old, but many of these trees are much older. They are loaded with heavy balls of mistletoe (gui), and many trunks have heart rot.

Rotten poplar trunks near Le Moulin Neuf
The stump in the foreground of the picture above typifies the problem trees. It is all that remains of a poplar that crashed across the road in last winter's storms, which tipped it over roots and all. The stump has been carefully relocated, to preserve the line of the riverbank and the streamlet that empties into the river via the ditch.

It is good to see so many of these rotten old poplars waiting to be taken away. We are speculating whether some of the large piles of "lop and top" such as the one on the far bank are awaiting a mobile chipper so the scrap wood can be made into pellets for fuel.
But the scale of clearing along the riverbanks is causing some riverains some concern. Along the Aigronne. and its tributaries such as the Rémillon below La Celle Guenand, all the riverside trees and shrubs, regardless of species, have been coppiced (cut to the ground) in some places. Yohann Sionneau, the river technician, insists that his team have been removing nothing but poplars, in accordance with their policy. But, he said, some individual proprietors, working on their own stretches of river, had been rather too enthusiastic.

Bare banks - not much cover here!
Coppicing will not kill the living trees, and is necessary from time to time, but for so many proprietors to do it simultaneously is "too much" as our neighbour Anne said. The trees will regrow enough to provide some cover in a couple of years. However, before that happens the amount of shade along the Aigronne - a premier trout stream - between Charnizay and Le Grand Pressigny has been massively reduced, all at once. In hot weather the water will become warm, the oxygen level will fall and the fish will die. We have heard from someone involved with La Gaule Pressignoise (our local fishing association) that of a recent release of trout, six were picked up dead.

The trees and shrubs along the river provide an essential wildlife corridor, linking isolated patches of woodland and enabling birds, mammals and insects to find food or a mate or a nest site or somewhere to roost. The cover will grow back, but right now the banks are bald. We have not seen a single squirrel this winter - we saw them regularly last year. However we have heard three great spotted woodpeckers drumming simultaneously at different points along our still-covered stretch of riverbank. We have not yet heard an oriole, that lover of poplar plantations - many poplars have gone, but there are still plenty left for the orioles.
Wildlife corridor along the Rémillon


Susan said...

And here am I reading articles about the latest in river management techniques ie leaving fallen trees in the river to create changes in flow and protection for invertebrates and fish. Yohann and his team presumably haven't had that memo yet - or the anglers vetoed it because it makes fishing more difficult.

Also it is so frustrating when this sort of project loses complexity in translation (ie the private owners removing everything rather than acting selectively).

Part of the problem could be if the funding is not structured in a sympathetic or reliable way. Proprietors may feel they need to get it all done now in order to benefit from whatever grants there are going.

Pollygarter said...

Susan - there was a BBC Radio 4 nature program on the very topic of leaving fallen trees in river beds about a fortnight ago. The fish have coped with them for a lot longer than fishermen have been around!

GaynorB said...

Thanks for the information. We were shocked to see the scale of the project.