Four Thinning Propositions and the “Ecological Trade-offs” Perspective

Four Thinning Propositions

At the risk of boring everyone else, we are having an interesting discussion about thinning, so continuing that… do people agree with the four propositions below, or have more to add?

1. The best thinning prescription is site-specific.  It depends on purpose, stand structure, species, moisture regime, soils, bug and disease issues (incipient or existing in the stand), and a variety of other factors, as Jim Z. has pointed out from his experience across the country.

2. Many fuel treatment prescriptions include reducing ladder fuels and reducing overall stocking.  To complete the prescription, the fuels intended to be removed have to be moved offsite, either by wheelbarrows (in fact, I’ve seen this about 30 years ago at Lake Tahoe,  because the landowners didn’t want smoke), or other kinds of equipment or by pile  or broadcast burning.

3. Many studies and experience show that time post-treatment can also influence outcomes.  The involved mechanism seems to be.. plants grow back.

3. So structuring the question, we have a) is the prescribed treatment the right treatment for the site, given the purpose? b) was the prescribed treatment carried out as prescribed? c) was the removal of fuel, as described in the prescription,  accomplished?

I think it’s fair, as well as self-evident, to say “fuel treatments don’t work if people don’t remove fuels”.  And some wildfires get there before that happens but post-thinning.  But as we can see by driving around or watching Forest’s Facebook or X feed, there are many folks working assiduously burning fuels.

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Lindenmeyer et al Perspective-  Ecological Trade-offs

So let’s move on to the recent Lindenmeyer et al. paper. Now I called the “perspective” an “op-ed with citations.”  Yes, it’s a literature review, and the 10 common questions paper was also a literature review, although it was categorized by the journal as an “invited feature.” In the abstract, the authors define “mechanical thinning” “as the partial removal of stand basal area using tracked or wheeled machines.”  This doesn’t seem like a particularly precise definition to me, as my neighbor could be lifting bucked sections into a truck (wheeled) or folks could be using this gizmo.  Is it about “how it gets to a landing” or “how it is moved from the landing” or just “when some thinned material is moved offsite?”

The title of their paper is “Ecological trade-offs of mechanical thinning in temperate forests.”  As I said above, for me the ecological trade-offs, as well as any other trade-offs that might evidence themselves, are invariably functions of a specific site, and current and future expected site conditions and practices.

As in one of the images from the paper

There are many things of interest, even in this summary.  If you think of thinning in terms of group selection, you might in fact create “important early successional environments” instead of degrading them.  But fundamentally, all of the above elements except perhaps economics and water yields are specifically addressed in specific decision documents.

If we were going to look at thinning (within specific temperate forests), we would probably want to ask scientists with experience in thinning (silviculture or applied ecology of trees), fuels experts, and forest entomologists and pathologists.  That is if our question was “when does thinning work and for what purposes?” with the purposes being improved tree health and wildfire resilience.

If we asked the question “are the benefits worth the environmental costs?” we would have to look, as the FS does in their environmental documents, at the impacts on air, carbon, soils, water and various species of wildlife and fish and ask the relevant disciplines (and comparing with the impacts of not thinning). Plus conceivably exactly how trees were removed and cut would make a difference to impacts.  If my neighbors buck and carry material to their chipper, that would have different impacts than tractor logging with (later) ripped skid trails? Will any specific thinning lead to more invasives..? The answer is always, “it depends on the site and the prescription.”

If we asked the question “is the investment worth it economically?” we would have to ask.. economists, silviculturists, fuels and forest health practitioners in the west. What can we expect to happen with or without a specific thinning prescription?

But how about thinning and PF vs. wildfire in terms of public health (smoke, evacuation stress, and others)?  We would probably need some kind of human health expert.

As it turns out, the backgrounds of all these folks is restricted to ecology (and fire behavior in Australia).

Lindemayer is a professor of ecology and conservation biology from Australia. DellaSala is a global biodiversity and climate change scientist. Elle Bowd a plant and fungal ecologist,   Beverly Law has worked on forest carbon, Philip J. Burton is a botanist and plant ecologist, Chad Hanson is both a lawyer and an ecologist, with, shall we say, a well-known point of view, Philip Zylstra,a bushfire behavior modeler , William Ripple an ecologist whose expertise in in trophic cascades.

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The language in the abstract about trade-offs is interesting..

While the benefits of mechanical thinning for fire management and drought resilience have been extensively discussed (Chagnon et al., 2025; Davis et al., 2024; Kalies and Yocom Kent, 2016), the negative environmental and financial impacts of, and carbon emissions associated with thinning are often not fully appreciated.

This may mean that trade-offs among the ecological, climate change, and economic effects of thinning are not quantified or appropriately considered in policy and management debates. Given this, we discuss impacts associated with large-scale mechanical thinning in temperate forests and the degree to which they depend on intensity, scale, and frequency of removals as well as environmental context (Fig. 1).

Apparently, to fully appreciate environmental and financial impacts.. you can do it with only the aid of ecologists, one fire scientist and no economists at all.  Count me skeptical.

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The conclusions are not very surprising considering the authors..

Given there are ecological and financial costs associated with thinning and roads, it should be prohibited in high-conservation value forests because such forests: (1) act as “controls” in active management experiments; (2) provide habitat and/or climate and wildfire refugia for old forest and complex early seral forest species, especially imperilled ones; (3) can be managed as intact, connected blocks of unaltered forest that provide connectivity for climate-forced wildlife migrations and wildlife movements; and (4) can be managed in a manner consistent with climate mitigation (e.g., carbon stored mainly in large trees and soils) and water conservation goals involving reserves and protected area networks (Law et al., 2022) (especially roadless areas). Outside protected areas, thinning can impact larger trees, forest carbon storage and carbon emissions, soils, and water, and result in the accumulation of post-thinning debris. In those situations, assessing the costs of thinning and ways to mitigate those costs, is critical to comprehensive forest management. Assessments are also necessary to determine the extent of roads needed to access sites and other areas where road closure and road removal are needed for restoration purposes. Proper cost accounting would determine when thinning reaches a cost threshold and where it is infeasible or inadvisable ecologically and economically. Recognizing self-thinning as a natural and cost-free process that enhances both carbon storage and biodiversity can help redirect management investments toward restoration of degraded forests and protection of intact forests, while ensuring significant areas act as refugia where active management impacts are absent. We encourage land managers, decision makers, and conservation groups to incorporate comprehensive analyses of the effects of thinning operations before widespread adoption of practices that are otherwise inappropriate or ineffective in certain conditions.

Hmm. “proper cost accounting” as opposed to “improper?”..”Recognizing self-thinning as a natural and cost-free process that enhances both carbon storage and biodiversity can help redirect management investments toward restoration of degraded forests and protection of intact forests, while ensuring significant areas act as refugia where active management impacts are absent. ”

Considering that the conclusions mention roadless areas (is the roadless issue relevant to the timing of this piece?), it’s interesting that the 2001 Rule itself has no prohibition against thinning.