I'm a Beaver Believer!

The speaker for this talk was Ben Goldfarb, who was wearing a tshirt with a picture of a beaver on it, over the word "dam".
He's just written a book called Eager: The Surprising Secret Life of Beavers and Why they Matter.
When people think about environmental degradation, they often think of things like deforestation. They very rarely think about beavers and their dams. But beavers create wetlands, which are incredibly important for biodiversity, being spawning grounds for fish, watering holes for animals, and homes for birds and insects.
Ben Goldfarb did some of his research by looking at the journals of early explorers across North America, and comparing their descriptions of the land with later descriptions, when the beavers had been almost hunted out of existence. Beavers, he said, can be incredibly important in mitigating flooding - they slow the water down and spread it over flood plains, in contrast to human intervention in rivers which tends to make them into swift flowing channels that wash nutrients out to sea. In modern farmland, slowing down the water also makes the nitrates and other agricultural pollutants settle out of the water.
And they don't eat fish - CS Lewis has a lot to answer for, concerning the image of beavers that whole generations of children have grown up with. They are completely vegetarian. In areas where people are trying to re-introduce beavers, anglers are often opposed to the schemes for this reason.
The history of the beaver in the book is mostly about the United States, and Ben Goldfarb said that up until the Civil War just about every major event in US history had some link to the beaver. For instance, the Hudson Bay Company at one point wanted to make the North West of the US unattractive to settlers who would be competing with them in Canada - so they decided to make a "fur desert" by exterminating all the beavers. And it turns out that, when you make a fur desert, you also make a real desert as the land dries out. Beaver fur was in great demand to make hats at the time.
Before beaver fur became so sought after, beavers were hunted for their scent glands (you can tell the sex of a beaver by sniffing it - males smell like motor oil, females like old cheese, apparently), and castorium is still used in some perfumes and other products.
By about 1900, people across the US were realising that the destruction of the beavers had been a big mistake, and there were attempts to re-introduce beavers - including dropping them in remote areas by parachute! I think everyone in the audience was imagining them in little harnesses with little helmets on, though in fact they were inside crates which were constructed so that they opened when they landed.
And beavers are not that small. In length, they're similar to an otter "though they're in another weight class", he said.
One of the questions at the end was about how beavers interacted with otters, and Ben Goldfarb said that otters liked being around beavers because they could catch the fish in the beaver ponds, but sometimes they would kill the baby beavers, so the beavers weren't as keen to have otters around.
When they're being used as part of a flood mitigation scheme, humans have to regulate the flow of water by putting pipes through the beaver dams, so that the ponds stay at the right level. These are known as Beaver Deceivers!
There is a problem in that the best habitat for beavers is also the best habitat for humans, who moved in when the beavers were wiped out, so reintroduction has to balance the needs of human inhabitants and farm land alongside the beavers - but beavers are so beneficial to the environment, mitigating flooding, raising the water table, stopping nutrients from being washed out to sea, increasing biodiversity, and at far less cost than human management of the landscape to get the same results - that it's totally worth it.
And beavers are a "gateway drug" of re-introduction of species. After all, if you have beavers, then you might want to try lynx, and maybe even, one day, wolves!