A disturbance in the forest

The forests of Scandinavia look beautiful in the autumn. What secrets do they hold?

Color changes are beginning. The red coloration you see here is surprising, because it is mostly North American species that turn red – European species are overwhelmingly more likely to turn yellow. The explanation for this pattern remains a matter of active debate – take a look at this recent publication. The short answer is that red leaved-species have defenses against certain species of plant-eating (herbivorous) insects, and that such defenses were globally common in the Tertiary (65 – 2.6 million years ago). However more recent climate change has disproportionately caused the extinction of such insects in Europe, potentially leading to the loss of red-leaved species whose phenotypes became gradually less adaptive. There are still, of course, some red-leaved species in Europe – as you can see here. But the overall yellow-ness of these forests is very obvious as one walks around.

The second thing to notice is that these forests are very highly disturbed. Roads and old fences criss-cross the woods, and many are actively being harvested for timber. The result is that most trees are young, and quite small – very different from the character of an old-growth forest with a more diverse range of tree ages, sizes, and species.

And of course forests are not even that common in many places – most have been removed to clear land for agricultural purposes. In Denmark, for example, forests became so scarce that timbers for naval shipbuilding were unavailable - leading to the replanting of many forests in the hope of providing timbers more than a century later. (Unfortunately the development of steel warships rendered this plan obsolete.) But much Scandinavian wealth is predicated on the past use of large expanses of forested land. As economies and values shift today, the legacy of this land use presents a unique challenge to these small countries. The balance is difficult – agricultural sustainability requires land-clearing, but provisioning of ecosystem services requires conservation of forests. It is still unclear, at the level of basic research understandings, how to best balance these goals.

Of course the United States has similar issues. Below is an image of a clear-cut forest in Oregon. The only difference is that our country has more land to begin with, and more ‘wiggle room’ to balance tradeoffs inherent to these difficult decisions.

We are also lucky to still have some old-growth forests in our country – such forests are almost entirely absent in northern Europe. Experiencing such places provides a powerful reminder of what landscapes might have been, and invaluable reference data source as we try to understand the impacts of our land-use choices.

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2 thoughts on “A disturbance in the forest

    • I would love to walk through a Danish urskov if you know of any nearby!

      What I meant was more that Denmark does not have very much preserved forested land, and current policies don’t adequately promote conservation. According to this year’s Natur- og Landbrugskommissionens statusrapport (http://www.naturoglandbrug.dk/statusrapport_2012.aspx?ID=51058) on page 266, only 13.5% of Denmark is forested; most of this forested land is under private ownership and is highly fragmented across the landscape (no contiguous large blocks); and regulations do not require active conservation management. So some opportunities for change the coming decades. :)

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