Trees are a Hot Topic—But I Bet Not in the Way You’re Thinking…

By Elizabeth Baldwin

A new report suggests that in Europe (and it’s specific that this is not going to be true in every region), trees grown since 1750 may have actually increased global warming.  And this is also going to be a shout out to planting hardwood over softwood.

The report suggests that softwoods like Pine and Spruce are darker in color and therefore absorb more heat than broadleaved woods like Oak, Ash and Birch.  Apparently the choice of softwoods also impacts significantly on “albedo,” which is the amount of solar radiation reflected back into space.  Finally, they release less cooling water into the atmosphere through evaporation.

The report had some very interesting statistics:

  • Europe lost nearly 190,000 sq km of forests between 1750 and 1850.
  • From 1850 to today, Europe’s forests have grown by about 386,000 sq km.  They now cover 10% more land than they did before the industrial revolution.  That’s definitely good news!
  • Approximately 85% of Europe’s trees are managed by humans.  (Personally I think that particularly fascinating.  I’ve always looked at Sweden and Finland in particular as nothing but giant plantations, but I hadn’t considered how controlled the rest of the region was as well.)
  • For the last 150 years or so, as foresters began to control the woods more aggressively, the planting of faster growing softwoods has increased.

Here’s where the report is really interesting—they reviewed over 250 years of forest management history in Europe (everything from the species planted to how we harvest and use the wood) and their conclusion was that human management can result in far less carbon being stored than what nature would be putting into the bank.  And they believe that the temperature increased slightly because of these choices.

The researchers from the Laboratory of Climate Science and Environment in Gif-sur-Yvette, France, say that because the conifers absorb more heat and reflect less back, temperature increase may equal up to 6% of the global warming that has been attributed to the burning of fossil fuels.  The report warns that with many countries moving to more and more plantations and more and more softwood forests, this could become a real issue in the future.

It was noted in researching responses to the report, that tropical regions will have a different condition.  Tropical trees will release more water in the air which makes it cooler and can also feed cloud cover that reflect light back.

This is a new way to consider for management, comparing not just forests vs. non-forested areas, but on how the forests are used.  The group’s new model includes a historic 3D representation of the forest canopy, allowing researchers to see differences in how various tree species interact with the atmosphere and how selective harvesting vs. clear cutting or timing of cutting can impact the results.

This just goes to show that we’re always learning better ways to utilize, manage and protect our resources and that nothing is black and white when you’re talking green.  You always need to dig into the details and consider all impacts…and of course, we’re still learning what some of those impacts might be.

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