[Paine in the Neck]

Most beaver dams have a lifespan of decades at most, making essentially no difference in the carbon cycle.

In the long run, nothing makes any difference to the carbon cycle. That's why they call it a 'cycle'. ;-}

[TigersEye]

In the long run, nothing makes any difference to the carbon cycle. That's why they call it a 'cycle'. ;-}

Yep.

Beavers build dam; carbon is sequestered.

Beavers abandon dam; carbon is released.

Net change = 0

It doesn't take a rocket surgeon.