New Steel et al. Paper: Mega-disturbances Cause Rapid Decline of Mature Conifer Forest Habitat in California

The Rim Fire in the Stanislaus National Forest U.S. Forest Service photo.

I don’t think the findings of this paper will be surprising to many TSW readers. I usually try to excerpt from the discussion, but this paper also has a management implications section. The basic story is that ideas developed around mesic forests may not work in dry forests. “Protected” areas, including important endangered species habitat, may be lost to wildfire, beetles or drought, or any combination thereof, whether due to AGW, historic fire suppression, human ignitions or any combination of the above.. what is, is. Here’s a link in case it’s not posted on Treesearch yet.

***Note: some of what these authors claim is contrary to the “science-based” claims of many MOG advocates. It’s easy to say your claims are based on “science”; it’s a bit harder to dig into the existing scientific studies and what they show; especially if they disagree. The authors also question static conservation approaches (if this reminds you of Botkin’s 1992 book Discordant Harmonies, the idea has been around for a while), e.g, “Thus even today, in both law and in practice, the scientific conservation of endangered marine species continues to be based on the idea that nature undisturbed is constant and stable . . .” I wonder whether resistance to change from this static worldview is perhaps a form of scientific/philosophical comfort with the status quo or that the momentum of law and policy is just too strong for the few voices saying “maybe not.” Anyway, back to the paper.***

Such “static” conservation approaches are heavily embedded in existing wildlife and ecosystem conservation policy (Leopold et al. 2018), as well as land management plans (e.g.,USDA 2004) in North America. Yet recent disturbance patterns and their cumulative impacts have demonstrated that efforts to resist change are often falling short in dynamic ecosystems, such that achieving the specific conservation objectives and possibly the intent outlined in policy documents may no longer be feasible in disturbance prone areas (Davis et al. In Press). In fact, continued attempts to resist change may be counterproductive where a hands-off approach (but continued fire suppression) creates a higher likelihood of rapid, transformational, and undesirable changes in the form of large scale type conversion and habitat loss from disturbance (Rissman et al. 2018). In our study region spotted owl Protected Activity Centers are often managed using a static conservation approach but our analysis shows they have recently experienced more declines in canopy cover (49% relative to 2011) than outside of their borders (40%). This observation suggests that conservation of habitat for old-forest dependent species may require a more dynamic approach that increases resilience to disturbance while maintaining valuable habitat features such as large, tall trees.

This is from the last section of the Discussion.

Rapid loss in mature forest habitat in the southern Sierra Nevada and longer term trends in fire-related forest decline throughout California (Stevens et al. 2017, Steel et al. 2018) suggest that existing forest management paradigms may be inadequate for maintaining mature mixed-conifer forests under current and projected future disturbance dynamics (North et al. 2022). If these rates of decline continue, we are likely to see near total loss of southern Sierra Nevada mature conifer forests in the coming decades. This would be much more rapid than the time horizon of mature forest loss estimated by Stephens et al. (2016b) (by 2089, or ~75 years). However, Stephens et al. (2016b) did not consider drought-related mortality, and only analyzed fire activity up through 2014, which missed the record fire year of 2020 (Safford et al. 2022). It is worth noting that the extreme fire activity documented in California during 2020 was likely not a one-off anomaly; recent observations indicate similar, if not exacerbated fire activity in 2021 (Shive et al. 2021).

The region has also reentered extreme drought (Williams et al. 2022) with implications for both drought and beetle mortality and severe wildfire. More optimistically, total loss of mature forests in this region could be delayed until mid-century if we enter a period of cooler, wetter years, if surviving mature forests within these fire footprints have gained resilience to future disturbances, or if recruitment of mature hardwood species compensate for losses of large conifers. Hardwood species may become a greater component of the Sierra Nevada landscape as conifers decline (Restaino et al. 2019, Steel et al. 2021b). Oaks, especially California black oaks, are relatively resilient to both wildfire and drought, and are utilized by species such as the spotted owl and fisher (North et al. 2000, Aubry et al. 2013, Green et al. 2019). However, loss of mature forest habitat, on any likely timeline, is unsustainable given that the recruitment of conifer or hardwood mature forests takes many decades to centuries. Stephens et al. (2016a) emphasize that policies prioritizing forest resilience over other resource concerns may be needed to meaningfully address the current backlog in forest management and shift course from forest decline to sustainable disturbance dynamics. Indeed, our analysis showed that areas of higher canopy cover are more at risk of loss, and that large areas of relatively homogenous moderate and higher density forests, like PACs, are at risk of larger declines if resilience needs are not addressed. Recognizing the dynamic nature of habitat in these forests, and prioritizing the restoration of these dynamics over the attempted strict preservation of existing habitat, may help minimize the impacts of these changes and maintain habitat functionality in the long term (Fabritius et al. 2017, Stoetzel et al. 2020, Gaines et al. 2022).

3 thoughts on “New Steel et al. Paper: Mega-disturbances Cause Rapid Decline of Mature Conifer Forest Habitat in California”

  1. I am not sure I can really comprehend the scale of million acre fires. But in my efforts to do so, I would say this research makes a lot of sense. And not just size of fires but where they occur – such as along a major highway from Sacramento to Lake Tahoe. For the most part this loss of our nation’s beautiful natural resources is sad. I don’t know the answer to it, I only know the status quo is destructive, from a lay persons Pov.

  2. Is this a problem? It appears that the Region 5 Forester from 2007 to 2021 did such an outstanding job of forest preservation that he was made Chief of the USFS.


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