Can Both Things be True? We Need to Protect Mesic Forests for Carbon and We Will Lose Them Due to Climate Change?


This is from a classic 1992 paper on genetics in reforestation under climate change. The Douglas fir near my house don’t appear to be suffering, 30-ish years later.

Here’s an article in Mongabay, which attempts to explain this very complicated article in Nature.

  • Landscapes are showing signs of losing their ability to absorb the amount of carbon they once could, a new study revealed. That would pose serious obstacles to the fight against climate change.
  • The study reviewed the productivity of carbon storage of different ecosystems between 1981 and 2018, finding that many fluctuated greatly and were at risk of turning into permanent scrubland.
  • Researchers identified a concerning “spiraling” effect, in which landscapes absorb less carbon that in turn worsens climate change, which then destabilizes additional landscapes and puts them at higher risk of turning into scrubland.

One reason for this, the researchers said, is that landscapes have a “memory” of which years had high carbon storage and which were low. Low years are more likely to be followed by additional low years, meaning that as carbon storage potential diminishes, a landscape is more likely to permanently become scrubland.

The phenomenon can be thought of as a “spiraling” effect, researchers said, in which landscapes absorb less carbon that in turn worsens climate change, which then destabilizes additional landscapes and puts them at higher risk of turning into scrubland.

“If we destabilize the carbon net uptake, that will destabilize climate even more,” said lead author Marcos Fernández, researcher at the Center for Ecological Research and Forestry Applications (CREAF). “It’s like a positive feedback loop. As you destabilize the carbon balance, then the climate becomes more unstable, as well.”

The most-affected regions include the Mediterranean Basin, South and Central Asia, East Africa and the west coasts of North and Central America. More specifically, mapping suggests that Kenya, India, Pakistan, Russia, Kyrgyzstan and Iraq are losing their ability to store carbon while in the Americas, it’s the Northern Triangle, Mexico and the west coast of the United States that are the most affected.


“For the first time, we’ve demonstrated that for certain regions of the world, the land might be reaching a tipping point in terms of its ability to host significantly forested land and absorb significant amounts of carbon,” said co-author Patrick McGuire, a staff meteorologist at the University of Reading and the National Centre for Atmospheric Science in the UK.


“We need to take care of our land better and not let all the trees get cut down and converted to cropland,” McGuire said. “Trees can hold a lot more carbon than crops or grasslands.”


The question is “how did the authors come to that conclusion?” The article was fortunately published with a sharing token from Mongabay, so perhaps you can access it.  Sadly I can’t copy the paragraphs that describe the authors’ thinking. but it’s something like if we measure variability in carbon uptake from year to year that might mean “ecosystems” are in trouble.  They talk about Net Biome Production or NBP.

We can access and copy the peer reviewers comments, though, and they explain perhaps better.. .

Fernandez-Martinez et al. take an interesting and novel approach by analysing changes in the interannual variability and autocorrelation of NBP to infer potential early warning signals for a “destabilization” of the terrestrial carbon sink.

Now it could be that internannual variation of NBP might be early warning signals for “destabilization” but first we’d have to define what destabilization means..  and some of us might want to see some evidence that points in that direction.  I don’t think there is any evidence of a link, just conjecture that there might be with calculations using data from Cams and Carboscope.

Anyway, it appears that CAMS and Carboscope are estimates of carbon in the atmosphere.  TRENDY appears to be a vegetation simulation.

My take: they  took two models at the global level for veg and atmospheric carbon. They used a term “destabilization” without making clear exactly what they meant.  And concluded that trees could die.

What is interesting about these kinds of papers is that they take datasets of unknown quality, define things without understanding or describing mechanisms, and then.. ask for monitoring to see if the results mean anything in the real world.

Last sentence of the paper..

Hence, regions showing increased variability and autocorrelations should be monitored in detail to properly understand the mechanisms and consequences behind these changes given that increasing variability and autocorrelation have been shown to act as early-warning signals preceding abrupt phase transitions in simulations of ecosystem functioning.

(so far observations in the “real world” have not entered in.

Here’s my fave:

Given the main role of climate change as a driver of these changes in their temporal behavior, mitigating climate change is needed to prevent further unforeseen changes in land C sinks.

I think you could probably say that without all this data. Here’s my take:

-Climate change affects trees (among other things)

-Trees sequester and store carbon

-With climate change, tree species may slow down growth or may be unable to live, and be replaced by shrubs or grass or desert.

-And we don’t know exactly what will happen one way or the other- nor can we really, because trees and forest ecosystems are so complex.

-Nevertheless, mitigating climate change is a good idea.

There.. was that so hard?

If we thought western mesic forests were in danger, perhaps we could look for signs that those trees were in serious trouble. What signs would those be?

5 thoughts on “Can Both Things be True? We Need to Protect Mesic Forests for Carbon and We Will Lose Them Due to Climate Change?”

  1. ““If we destabilize the carbon net uptake” — by failing to manage for resilience and thus consigning them to decline and death?

  2. Bonnicksen has written that forests, tree species, move to higher elevations and north with climate warming and down slope and south when climate cools. I have no memory of reading what the flat land vegetation does as glaciers retreat or advance. Likely the semi tropical move south with climate cooling and north with climate warming. Odd, but that is likely why tree species are still here. Wind blows seed to favorable sites which change with climate.

    Dr. Hansen’s research papers and his mapping tree species historically on that plot of land by examination of subsoil pollen are on file at Oregon State University Valley Library. University of Oregon archeologists’ examination of human presence now go back 16,500 years from evidence found deep in the soil of dry Eastern Oregon caves, and now are examining 400+ tubs of human coprolites for what was consumed. Pollen is one of the markers in the food consumed and now being examined 16,500 years later.

  3. Excellent summary Sharon! Common sense “will out” with a small reminder one constant we can depend on is change.

  4. Sharon, in response to your original post question, “If we thought western mesic forests were in danger, perhaps we could look for signs that those trees were in serious trouble. What signs would those be?”

    Here are some signs:

    Anecdotally, several years ago Jerry Franklin told me that his research on the Wind River Experimental Forest on the GP was showing that the hemlock were dying, likely due to drought stress. I’m not sure he published that before he retired, but I bet some of his students are carrying on that work.

    If the douglas fir and hemlock are dying in the “douglas fir/hemlock zone,” that seems like pretty good evidence to me that our western forests – even the very carbon-rich ones – are in trouble.

    • Yes, and it says in the article you cite…

      “Bennett led a recent study which estimated approximately a quarter million Douglas-firs had died off between 2016 and 2019, with the die-off getting worse in the years since.

      The prevailing theory is that wildfires have cleared the way for Douglas-fir trees to take root in new places, specifically lower elevation, hotter, drier areas.

      “And so when a drought comes along, and of course we’ve had plenty of droughts in the last several years, the trees get particularly stressed for lack of moisture. And they become very vulnerable to various types of insects. And the insects get into the trees and basically finish them off,” explained Bennett.

      That die-off leads to a cycle spiraling downward as the dead or dying trees add to a buildup of fuels loads in the forest for the next fire.”

      It sounds kind of like the “grand fir/white fir” problem in central Oregon…in that you can’t really separate a unique fire history from climatic factors because they are so intertwined.

      But are these specific droughts due to climate change? Can we tell that over natural variability?

      I’m not saying that there aren’t circumstances where tree die off can be attributed to climate change, say in Alaska, but it’s hard to imagine how folks could untwist all the historical and climatic changes to get one answer.

      But if you think that DF in SW Ore is all about climate change (not that you, SJ, specifically do) how would that score with the belief “the best thing to do for climate is not to try to make stands more resilient, but leave them alone to die from drought and bugs and be sent to Tree Valhalla on the winds of a cleansing fire…”


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