No Longer Extinct, Beaver Populations in the Netherlands Now Threaten Their Dikes

They were extinct in the Netherlands in the early 19th century. But in 1988 beavers were reintroduced to the region, and now there's over 7,000, reports the Guardian.

But unfortunately...

Beavers are increasingly digging burrows and tunnels under roads, railways and — even more worryingly — in dikes. For a country where a quarter of the land sits below sea level, this is not a minor problem — especially as beavers are not exactly holding back when digging. 'We've found tunnels stretching up to 17 metres [equivalent to 60 feet] into a dike... That's alarming,' says Jelmer Krom of the Rivierenland water board... If a major dike gives way, it would cause a serious flood affecting thousands of people...

[T]heir entrances are under water, and as yet there are no effective techniques for mapping them. During high water, special patrols go out at night with thermal-imaging cameras to spot where beavers are active, but this method doesn't always yield the desired results. Also, when a beaver that's causing problems is found, it can only be killed in exceptional circumstances, because beavers are a protected species in the Netherlands. Moving it doesn't do much good either, as the beaver tends simply to return.
Current mitigation efforts include mesh reinforcements (as well as sealing burrows) — and also removing the thickets of willows on the riverbanks to make them a less appealing habitat.

Thanks to Slashdot reader Bruce66423 for sharing the news.

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