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Climate change drives (micro)evolution in Finland

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For want of snow, the tawny owl of Finland has become more brown in the past half-century, according to new research published February 22 in Nature Communications. Finnish researchers scored tawny owls (Strix aluco)—a raptor common to all of Europe—on the color of their plumage, specifically how brown (dark) or gray (pale) their feathers were. (Scientific American is part of the Nature Publishing Group.)

Since the owls do not seem to show a sexual preference for either darker or lighter feathers, the main driving force for any change in plumage would be natural selection, in this case, most likely, whether a dark or a light coat helped in catching more voles, the raptor’s primary food. Over the course of the study led by bird ecologist Patrik Karell of the University of Helsinki—from 1981 to 2008—the brown owls started to increase in numbers.

More specifically, more brown owls survived Finnish winters. The reason? Unknown for sure, but Finnish winters have become milder in recent decades thanks to climate change—with much less snow. Less snow means less chance of brown owls standing out against a white landscape as they stalk their prey—or falling prey to the dread Bubo bubo (the eagle owl). Or it may be that the brown coloration is also tied to the owl’s physiology, like the strength of its immune system or how much food it needs to eat.

In fact, since at least 1961, the proportion of brown tawny owls caught by ornithologists throughout Finland has increased, adding more circumstantial evidence in support of the finding.

At the same time, there is no direct evidence yet to support any of those possible explanations for why brown owls would do any better than gray owls, even in milder winters, as the researchers admit. In fact, browner and grayer owls have roughly the same level of survival through winter these days (an improvement for the browns and stasis for the grays).

Nevertheless, the Finnish tawny owl may join a relatively short list of animals that have been shown to have evolved in response to human-induced changes to the environment. There is the famous peppered moth of the U.K., which flipped from light-colored to dark-colored as a result of the discoloration of its habitat by coal soot in the 19th century and then back again towards the end of the 20th century as those conditions cleared up. More recently, the bottom-dwelling tomcod in the Hudson River have rapidly evolved a resistance to polychlorinated biphenyls—better known as PCBs and once used in electrical equipment—that were dumped in the river by General Electric in the middle decades of the 20th century. And a wide range of animals and plants are changing behaviors or range—and potentially ultimately their very genetics—in response to the changing climate as a result of greenhouse gas emissions from fossil fuel burning.

But the more biologists look, the more often the human scientists are finding that our own species is directing evolution for other species, albeit unwittingly.

Image: Courtesy of Dick Forsman





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  1. 1. Elderlybloke 3:28 pm 02/24/2011

    This happened to moths when the Industrial Revolution occurred in Britain a wee time back.

    Link to this
  2. 2. Wayne Williamson 5:33 pm 02/24/2011

    I wish the photos were better…all I noticed was how similar in color to the tree bark(past and present) they are…did the tree bark change colors to?
    (I’m assuming that the one on the left is an older photo)

    Link to this
  3. 3. Venomlust 8:43 pm 02/24/2011

    "At the same time, there is no direct evidence yet to support any of those possible explanations for why brown owls would do any better than gray owls, even in milder winters, as the researchers admit. In fact, browner and grayer owls have roughly the same level of survival…"

    So, then, what gives with the title of this article? Figured you’d get more views if it had something to do with climate change?

    Link to this
  4. 4. Postman1 9:17 pm 02/24/2011

    Glad to see you on line! I was thinking about you when I saw the news on the earthquake. Hope all is well in your part of NZ. Anything we Americans can do?

    Link to this
  5. 5. Postman1 11:21 pm 02/24/2011

    Another article which I just read, pointed out that corals around Japan are rapidly moving north, up to twelve miles a year. Also, in Alaska, shrubs and trees are migrating north into the tundra. Life does know how to adjust and is always in a state of fluctuation to the greener side of the fence.

    Link to this
  6. 6. bucketofsquid 12:24 pm 02/25/2011

    Very good point that calls into question the color balance of the images. It doesn’t mean much in regards to the actual story but I’ve done a lot of color adjustment of images and I couldn’t say for sure if the trees in each image were the same type or not. If they are the same type of tree then there would be a reason to wonder about bark color changes. If they are different types of tree then maybe the owls choose the tree type that best matches their own coloring. Or it may just be coincidence.

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  7. 7. kristi276 5:48 am 02/27/2011

    The study clearly show how the external forces, climatic change, has a direct bearing on how species undergo physical change in order to adapt their survival mechanisms. The ability for species to adapt to a changing environment in order to assure its survival. When the environment was a landscape encased is ice the plumage of the owl reflected that environment and so its plumage had to blend in to assure its success in hunting. Now when, as the study pointed out, the environment is less snowy and more gray, the response of the owl was to change accordingly to blend in and assure a successful hunt for its self and its offspring. The destruction of the ecosystems by man has not abated and has only increased, how will this effect the species that is native to the north and south polar regions. What will Finland’s tawny owl look like as the climate change increase in the next fifty years, would it be called Finland’s Chestnut owl?

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