Do you remember that story, back in fourth of fifth grade, you heard at a sleepover with friends? Two of the friends you had known since 2nd grade but one girl was someone else’s friend, or neighbor, or cousin and she was rumored to have slightly more street cred on account of her parents were divorced, or her mother had died, or her brother was in jail. And when the last pizza had been eaten and all the lights were out and you were huddled in sleeping bags on the living room rug or the back yard, she started with that spooky story in that absolutely chilling and unforgettable voice:
And of course, even at 10, you knew the story was impossible and that ghosts weren’t real and that even if they were people don’t ever make arms out of solid gold, and you might have mumbled so all the way through at intervals but once Elvira leaped from the grave and shouted “YOU GOT IT!” and that terrifying story was over you couldn’t wait to think about who you were going to tell it to next. All the other kids must have too because pretty soon the story was all over school and was starting to get little adjustments, like the woman had been murdered for her golden arm, or it was actually a golden leg. It was a self-reproducing meme that was perpetuating itself like a virus through the primary grades. And even today, just saying the words has a kind of ring to it, and you can remember something of that chill. And it doesn’t matter whether its true, because its not that kind of story.
Which brings us naturally to the topic of beaver dams, water temperature and fish.
Mr. Krevosky said Barber’s Hollow Brook is but one of several small headwater brooks in town where the positive effect of 46-degree groundwater in a stream has been compromised by beaver dams that dramatically raise stream temperature.
Todd A. Richards, biologist for the Division of Fisheries and Wildlife, agrees that beaver impoundments have an impact on cold-water fish resources, but adds it’s only one point that makes an already bad situation worse.
He said beaver may not have as much impact in hilly and mountainous terrain, but their impact on streams with minimal flow and minimal change in grade is considerable.
“Beavers have a place, and historically, beaver populations were kept in check by wolf, cougar and native Americans. Obviously that is no longer the case. We are losing trout fisheries in areas that previously were not impacted by beaver and that has to be taken into consideration in restoring cold-water fish resources,” he said.
I believe Eisenhower was president when Clyde the ranger stuck his thermometer in the top inch of pond water and observed beaver ponds are warmer than flowing streams. He published a paper on it and of course the paper said what everyone wanted to hear, (that beavers, not progress and concrete, were ruining our streams) and so it went into all those biology text books and field guides. Never mind that if you ask an experienced trout fisherman where he loves to frequent after lots of beer and persuasion he will eventually say the beaver dam. Folks are so used dull easy hatcheries with fish dumped out of the truck that they don’t remember their grandpa or believe their friend Billy anymore.
So the meme of beaver ponds raising temperatures and ruining things for fish perpetuates itself. Michael Pollock was very perplexed by this temperature canard because it ran against everything he saw and observed. He tracked down the origins of the temperature meme to the root of its roots and learned the truth about its single thermometer in the top inch of the pond- origins. He ran expensive experiments funded by the federal government with sensors all the way down the depths of the beaver pond and proved it was completely, entirely and in all other ways untrue.
Okay now, follow this closely. The right of the graph is the mouth of the stream, so the water comes out of the ground colder and gets steadily warmer as it passes to the sea. Except for that one patch on the middle where it says AREA OF PERSISTENT BEAVER DAM BUILDING. How can this be? The water you see in the stream is only part of the story. The majority of that water is underground, beneath the soil, where it never gets warmed by the sun. This colder water passes through the bank wall in a process called hyporheic exchange which cools the temperatures. The placement of a dam increases hyporheic flux by increasing the downward hydraulic gradient across the dam.
End result cooler temperatures in ponds and below beaver dams and happy fish.
This data has been published and discussed in scientific forums. It has been quoted and re-quoted in fish journals from Washington to Norway. It doesn’t matter. Biologists like Mr. Krevosky and Mr. Richards would rather stay up late telling each other scary tales of beavers ruining streams for fish like “Whoooo stole my golden arm???” Of course they invited the media who comes to the sleepover and very responsibly write down every bogus thing they say as if it were fact.
“Previously enterred woman seeks valuable false limb. News at 11:00“
I have zero patience with the fact that this story comes from the fisheries of Massachusetts of all places. It is obviously a brick in the consistent argument, ‘The stupid voters ruined our lives when they took away our traps and infested us with icky beavers! Better change the law right away”. This bad-penny persuasion shows up every few months, usually proceeding a new last-ditch effort to overturn the will of the voters some way or other. Mark your calendar because we’ll be talking about this again soon, I guarantee it.
Oh and if the name of Mr. Krevosky sounds familiar, it should. I wrote about him 4 years ago on this website for famously claiming that beaver dams were ruining Massachusetts by promoting Purple Loosestrife. Here’s a taste of that column, which was fun.
Enter Mr. Glenn E. Krevosky of EBT Environmental Consulting. He has a theory, and like all good theories, it blames the rodent. He says that beaver dams cause flooding, destroy native plants and then make space for Loosestrife to take over. If there were fewer dam beavers, (he has persuasively shouted to the media), we could rid ourselves of this purple menace once and for all. Of course I went immediately to research his copius studies proving this brilliant hypothesis, and saw that the sum total of all literature published in peer review journals on this theory is zero. No research whatsoever. Nada. Not that this has troubled the media, mind you. They are perfectly happy to write down what someone from a very environmental sounding company says. (Of course I couldn’t find EBT consulting either, so who knows what E.B.T. stands for? Everybody Blames Them?)
Some things never change. I still couldn’t find anything about EBT on the internet. Obviously the digital age, along with certain beaver-related scientific facts, continues to elude him.
