Grasslands More Resilient Carbon Sinks Than Forests?: Behind the Study

Study Figure 1: Grassland (A) and forest (B) retreat or expansion in response to 21st century climate changes. Blue indicates expansion; red indicates contraction. Forests retreat in all future climates except those associated with aggressive emissions reductions (RCP 2.6)/Sharon’s note: see places where trees are increasing, many under 2.6 and even some under 8.5

You all may have seen the news report “Grasslands More Reliable Carbon Sink Than Trees” I’m not exactly sure whether this site is a source of UC Davis press releases, or a more broad climate communications site.

Their basic argument is that because forests have most of their carbon above ground, and they burn up that carbon in wildfires (the video has a very nice graphic that depicts this), then grasslands are better because their carbon doesn’t burn up. First, note that this statement claims that this scientific information is relevant to policy in terms of California’s cap and trade program.

A study from the University of California, Davis, found that grasslands and rangelands are more resilient carbon sinks than forests in 21st century California. As such, the study indicates they should be given opportunities in the state’s cap-and-and trade market, which is designed to reduce California’s greenhouse gas emissions to 40 percent below 1990 levels by 2030.

So we are talking investments conceivably in the next 10 years to reduce GHGs. But what was most peculiar to me was how they went about figuring this out, and some of their results. First of all, they referred to RCP 8.5 as a “business as usual” scenario. If this were a NEPA document, we might say that there is scientific controversy around that claim. Many would say that it’s a “useful worst case scenario” not “business as usual”. Of course, you don’t have to have a Ph.D. in atmospheric physics to think that people might disagree about what’s likely to happen in the future, and that prophecy is unlikely to have a meaningful probability distribution.

Most interesting to me, though, were their efforts to predict where trees would go away and be replaced by grasslands under that climate scenario. This can be seen in the figure above, and also a figure I couldn’t copy that is a placeholder for the video for the paper here.

Tree or grass people might wonder, how could you possibly predict that, given what we know of trees and grasses? Well, it’s possible to link a variety of models. I think the authors did real nice work in explaining their paper, using an open source journal and describing the limitations of their work.

Here’s the first sentence of their results and conclusions:

In contrast to the conventional paradigm, we show that the inherent resilience of grassland vegetation to drought and wildfire (figure 1) translates to a more reliable C sink than forest ecosystems (figure 2) in response to 21st century climate changes.

But their caveats include:

Factors such as species traits, biodiversity, rapid evolution, and human management intervention could alter our model-based findings from the projections provided here. Consequently, our results indicate the potential direction of change as opposed to predictions that consider the full ensemble of ecological, physiological and management factors that can alter pathways and responses of ecosystems to climate change.

(my bold, human management intervention like fire suppression?) In what sense is it realistic to model the carbon impacts of future wildfires while not considering fire suppression?


Future work could focus on such factors as the evolutionary history of trees to fire, the physiological adaptations of ecosystems as well as regional species to fire, drought and climate change, the effects of biodiversity on ecosystem resilience as well as a comprehensive analysis of the goods and services provided by forests and grasslands.

The research was funded by the National Science Foundation. I wonder if on their research panels, there is ever a thought of “is there a point at which running models has little real world data that the information produced is not worth funding, or we should be clear that it is basic science with no real-world relevance? NSF doesn’t have to care whether its research is policy relevant, because its mission in broader than that, it’s mission is to “advance the progress of science” but as I’ve argued before, if researchers make the claim that it is, perhaps there should be some kind of standard. For those of you who haven’t seen my effort in this direction here’s a link to Eight Steps to Vet Scientific Information for Policy Fitness.

On wonders whether if the California policy makers had (1) framed the questions they felt they needed answered relevant to their cap n trade program (2) reviewed existing literature on grasslands, forests, trees, drought, fires and climate change, would they have prioritized this kind of study?

7 thoughts on “Grasslands More Resilient Carbon Sinks Than Forests?: Behind the Study”

  1. Science seems to work like a Pedulum in a blowing wind. Wasn’t it just a while ago, last week or so ? where we were told by the tree hugging crowd that planting a trillion trees would save everything ? Seriously every single social media site and group on those sites on a feel good page plastered the trees save the day story all over the net & now this ? Below is a video from one of the most radical former Environmentalist who now says there is no hope.

    • yes, that was another great one in terms of modeling, scale and ground truthing or lack thereof.

      It’s a great gig, anyone can model anything at any scale and come up with different answers, and get funding to do it. Without any pesky ground-truthing, literature review of the directly involved disciplines, or (horrors!) actually collecting any data that might prove your model wrong. And if I were to ask NSF and other funders whether they have any limits to the pontification to data ratio in the studies they fund, they would probably say that I’m “against science.” Like I said, it’s a good gig for some, not so much if a policy maker or manager who is actually supposed to use this stuff in real-world decisions.

      • “Like I said, it’s a good gig for some, not so much if a policy maker or manager who is actually supposed to use this stuff in real-world decisions.”

        Which is what has disappointed me with the a lot about the environmental movement who talk a great speech (How can you fault anyone who says because they care), but rarely step up and show everyone else what they have actually done. For example in the video, Paul Kingsnorth says they are viciously against industrialization of the wild, but have no problem with industrialization with solar or wind turbine infrastructure where forests need to be cut down. Saw a recent photo in New England what a giant massive patch of forest was removed for a Solar Farm and that’s okay because in their imagination that’s going to save us. Same massive patch cleared for rare earth mining and there’s all heck to pay in the form of violence, destruction of private property, etc.

        • Hey Kevin: News Flash! “Environmentalists” are not some monolithic, homogeneous group of people.

          There are plenty of “environmentalists” who actually do have a problem “with industrialization with solar or wind turbine infrastructure where forests need to be cut down.”

          Also, I’m still waiting for Sharon to dissect some pro-industry science and research. There’s a lot of it out there, so picking a few studies shouldn’t be that hard.

          • But depending on your perspective, this very study could be considered “pro-industry” as it suggests encouraging (via state funding) ranchers to engage in “good carbon” practices.

        • I agree Kevin. If we were totally rational, we would sit down and say “OK, people impact the environment, so where and how are we going to get needed resources and minimize our joint impact on the environment?” With today’s technology? And what future technology do we want to invest in? And to what extent are we going to force people to do things they don’t otherwise want to do (e.g. move to cities, take public transportation, stop air travel, and so on?)

          Just saying “no” to everything is not a realistic policy either. Any energy source has impacts.

          • Sharon: “Just saying “no” to everything is not a realistic policy either. Any energy source has impacts.”

            Well, not everything needs a scientific study. Sometimes we just need people who have real world outdoor experience in what works and just plain common sense. I’ve seen so many intellectuals who were lacking common sense.


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