Tuesday 18 August 2020

River Rodents Good

Christmas 2 years ago I kited the idea [not original to me] that beavers Castor fiber might have a part to play in flood control. The problem being that rain doesn't fall with convenient uniformity - say 10mm every 3rd night between 0200-0400hrs. Rather than 100mm in a single night on top of 300mm of snow. The problem is gravity and mass: when water starts to travel downhill it can be amazingly destructive; gathering speed and debris as it goes. The idea is that beaver dams form a porous impedance to the flow of water: any statistically lumpy build-up in a storm can be slowly dissipated over the following days.

It seems that the idea of re-introducing beavers to the landscape of the WEA is widespread and that Beaver Bombers have been taking action in England without prior approval or sanction. Most recently a colony of beavers on the River Otter, which debouches into the sea at Buddleigh Salterton in Devon, have been allowed to remain by the Minister of the Environment. A single beaver documented in 2013 has now become the progenitor of about 50 individuals. Presumably there was at least one other beaver of the opposite sex. The local ecologists claim the impact has been, on balance, good.

  • Water flow has been improved and bankside erosion decreased
  • Otters Lutra lutra certainly prefer the fish which are multiplying in the beaver ponds
  • And kingfishers Alcedo atthis also are making a come-back
  • The anglers otoh are unhappy because beaver dams are impenetrable to anadromous fish like salmon "saddened that the minister has decided to favour an introduced species over species already present and in desperate need of more protection"
  • Treehuggers are also dissing the idea because riparian trees are important for retaining riverbanks and beavers chop 'em down.
I have  sympathy with the salmon-side of the argument. Kingfishers, I love; and Dau.II watches otters hunting the River Lee from her quayside apartment in Cork. But the less sexy species have rights too: gravelly invertebrates that like a lot of oxygen beaten into the water, for starters. tbh, it seems a bit arbitrary. I was just waving the muskrats must go flag and now we're to be all for releasing other rodents. Where?

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