Can success lead to failure?

Robert Lambert asked an interesting question in his contribution to the Invasive and Introduced Plants and Animals book I’ve been reading: “Will the returned native ‘aliens’ become so abundant, so commonplace, so much a part of our cherished urban and rural landscapes, that we will no longer care enough to glance upwards, or queue at a telescope at a long-established public viewing point?” (p.177). He was specifically talking about the success of reintroduced birds of prey in Britain and the potential loss of tourist dollars, but it got me thinking about the beaver in Sweden.

After the first reintroduction in Bjurälvdalen, Jämtland, in 1922, reintroductions came fast and furious: 13 more places by 1935 had bought beavers from Norway and let them loose in Sweden. Although WWII seems to have bought the activities to a standstill, they started up again in the 1950 and 1960s — I’ve seen long lists of reintroductions in Västerbotten and Norrbotten from those decades.

All of this was immensely successful: a nationwide survey in 1977 estimated 40,000 beavers in Sweden. A ban on beaver hunting had been instituted in 1873 (ironically, 2 years after the last known beaver in Sweden was killed), so the reintroduced beavers could not be hunted. But the reintroduction had been so successful that in 1976, the law was changed to allow beaver hunting over the winter (October – 15 May in northern areas in Jakttidsförordning (1976:432)). A survey done at the end of the 1980s/early 1990s estimated a Swedish beaver population of 100,000 (!), so it was still going up.

Beavers have become visible members of the landscape. There are beaver safaris in Sweden, like one on the Vindel River near Umeå where I live, which shows that the beaver has public appeal, at least for tourists. Hunters also take an interest in beavers; according to the Jägareförbundet statistics, 888 beavers were killed in the county of Västerbotten alone last season. Other than the limited season for hunting, there are no bag limits on beavers (you can kill as many as you want).

But although some people take an interest in them, I wonder if the beaver’s star status has decreased as it became common after the last reintroductions of the 1960s. Will people notice if a common rural animal starts decreasing in number unless the decrease is drastic?  Yesterday I read a Swedish article by Dan Frendin that compared two surveys of the beaver population in an area of Värmland from 1976-77 and 2006-7. This area had 4 reintroductions in the 1920s and one in the 1960s. Frendin found a dramatic decrease in beavers – there were 61 beaver homes in 1976-77 and only 16 in 2006-7 – which he attributed to a change in vegetation regime. But as far as I can tell, the only reason we know about this is because Frendin personally wanted to follow up on his survey from 30 years before. He hadn’t expected the decrease; apparently no one had noticed it. I don’t want to imply that this decrease shows a larger problem with the beaver population in Sweden, but Frendin’s findings in combination with Lambert’s comment made me ponder how becoming common might make the beaver more invisible.

While becoming common once again was the goal of the beaver reintroduction, could being too successful lead to failure in the long run as the beaver moves from rare conservation object to common hunting object? Could the beaver be hunted to extinction again because everyone thinks there must be more of them somewhere else, as they did in the mid-1800s? Nothing that dramatic is likely since we have better ecosystem monitoring now than we did then, but it’s worth thinking about the potential cost of success.

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