The Return of the Beaver

[A] Beavers were trapped out of most of Europe by the sixteenth century, and the landscapes that remained came to be treated as natural. [B] That is the difficulty with reintroduction: the reference point is a country that had already lost the animal that made much of it. A river without beavers runs in one channel and moves quickly. A river with them is a chain of ponds, wet ground and dead standing trees, which looks, to a farmer or a fisherman, like damage. [C]

[D] The measured effects have surprised both sides of the argument. Flood peaks downstream of a beaver reach are consistently lower, because water is held and released slowly, and this is now the commonest reason given for supporting reintroduction. Fish numbers, which opponents expected to fall, rise for most species and fall for a few. What does not resolve so neatly is the cost. The animals fell trees people planted, flood fields that are farmed, and block culverts, and those costs fall on individuals while the benefit falls on everybody downstream. That is a distribution problem rather than an ecological one, and the schemes that have worked are the ones that treated it as such.