The Steadily-Dying Sierra Nevadas

Drought, Bark Beetle Infestation, Climate Change Imperil Sierra Pine Forests

Dying trees pepper the Yosemite landscape.
Dying trees pepper the Yosemite landscape.

Like over 600 other environmental lawyers, professors, law students and regulators, I attended the 25th annual Environmental Law Conference at Yosemite last weekend.  As always, the Conference–sponsored by the California State Bar’s Environmental Law Section–was a big success, filled with inspirational speakers and thought-provoking panels.

But the major topic of conversation–during the Conference proceedings, in hallway conversations and on outdoor hikes in Yosemite National Park–was not about the speakers or the Conference.  Rather, it focused on the alarming state of Yosemite and the Sierra Nevada in general.  The pine forests of California are dying at an alarming rate.

Forestry experts know that the causes of this ecosystem epidemic are chronic drought, bark beetle infestation and climate change.  These phenomena operate in a perverse, symbiotic way: California’s chronic, five-year drought has made the pine trees of the Sierras especially vulnerable to the ravages of the bark beetle, a pernicious species of insect that has become the forests’ principal enemy.  (California is home to some 19 different types of pine trees.)  Conversely, the growing presence of the bark beetle in the Sierra Nevada range makes the pine forests more susceptible to the adverse effects of the ongoing drought.  And the once-severe, freezing Sierra winters that previously kept the bark beetle population in check are becoming steadily warmer, thus allowing the beetles to survive and multiply year-round.

My layperson’s observations indicate that, both in Yosemite and in many other areas of the Sierra Nevada, one of every three or four pine trees is dead or dying.  It’s a truly dispiriting sight–unlike anything I’ve previously seen in my 60 years of visiting Yosemite and the Sierras.  And the pine forests’ dramatic decline in just the past year is shocking.

These same forestry experts tell us there’s nothing we can do to staunch the spread of disease and death in California’s pine forests.

Which leads to a further dilemma for environmental regulators and forest managers: what to do about the plethora of dead trees?  Should we engage in vast timber harvesting to clear them from the Sierras, thus facilitating the environmental damage that widespread logging will inevitably trigger?  Or do we leave the dead trees in place, where they will exacerbate the already-increased threat of cataclysmic forest fires?  And should the human response to these tree deaths vary in National Parks as compared to the public lands of the Sierra Nevada generally?  There are no easy answers or fixes to be had here.

To be sure, this forestry crisis is not limited to the Sierra Nevada range.  According to a recent San Francisco Chronicle report, bark beetle infestation has ravaged 45 million acres of forests in the Western United States in recent years, including 15 million acres of U.S. Forest Service lands.

The once-splendid pine forests of California and the American West are dying at an alarming rate, right before our eyes.  Sadly, all we can do is watch, and mourn their passing.

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Reader Comments

7 Replies to “The Steadily-Dying Sierra Nevadas”

  1. I hadn’t attended the annual conference in three years and was heartened to know that the weather forecast was finally showing cooler, autumn-like temperatures. As I passed through Coarsegold and approached Oakhurst, my heart sank at the sight of rust-colored hillsides of dead pines. And every successive ridge showed more swaths of rust. When I reached Fish Camp, my nose and eyes told me something new was in the air, too. A friend called it “bark beetle dust”.

  2. I don’t think the assumption that beetle-killed trees increase the occurrence, area burned, and/or severity of wildfires has been borne out by recent studies.

    (See, e.g., Garrett W. Meigs et al., Do Insect Outbreaks Reduce the Severity of Subsequent Forest Fires?, 11 Environmental Research Letters (2016), doi:10.1088/1748-9326/11/4/045008 (finding that, “[i]n contrast to common assumptions of positive feedbacks, we find that insects generally reduce the severity of subsequent wildfires” and suggesting that “higher severity insect outbreaks reduce the abundance of live vegetation susceptible to wildfire while altering vertical and horizontal fuel distributions, particularly as trees defoliate, die, and transition from canopy to surface fuels,” reducing the risk of canopy fires); Sarah J. Hart et al., Area Burned in the Western United States is Unaffected by Recent Mountain Pine Beetle Outbreaks, 112 Proceedings of the National Academy of Sciences 4375, 4375 (2015) (stating that “[t]he assumption that [beetle] outbreaks raise fire risk is driving far-reaching policy decisions involving expenditures of hundreds of millions of dollars,” and finding that, “[c]ontrary to the expectation that an MPB outbreak increases fire risk, spatial overlay analysis shows no effect of outbreaks on subsequent area burned during years of extreme burning across the West”).

    1. Thanks for this, Nell. I was not aware of this new comprehensive research, though I was aware of more modest studies with related findings. It’s been pretty clear that “salvage logging” of dead and “dying” trees has not been a science-based response to fire risk more generally, and this provides more evidence of that in the context of insect infestation. I hope the Forest Service and other agencies understand the implications of this research. Unfortunately, everything else Rick says in his post is accurate. The mass die-off of pine trees in the Sierra Nevada over the past four years has been a catastrophe- and one of the most visible manifestations of climate change in California.

  3. Richard,
    Thanks for this.
    A recent conversation with the FS silviculturalist on the Sierra National Forest and others is that pine mortality in large areas in the pine belt approaches 90-95%. Even assuming that this and the operation other factors related to climate change do not increase the probability of stand replacing fire in the central Sierra, it remains a concern. As does the opportunity for regeneration. Is this the early stage of habitat type conversion? It may be too early to tell, but in my conversation, it is clear that this is a concern to many forest scientists.

  4. I would like to qualify my esteemed colleague’s assessment of the state of the Sierra forests. In addition to having studied law, I have a PhD in forest ecology. In my view there is a lot of misinformation about the state of the Sierra forest and a lot of misplaced hysteria. Better approaches can be found if we take Aldo Leopold’s advice and “think like a mountain,” i.e. long-term, landscape scale, and in terms of systems.

    The bark beetle outbreak is a symptom of the state of forests. It is the result of the forests being under a lot of stress. The reason for that stress is the result of well-meaning decisions by many people over many years. But the cumulative effect causes the results you see.

    The basic problem is that there are too many trees on the landscape. Places that had 20 trees per acre a century ago now have 260 trees. This is largely the result of fire suppression. It is also the result of well-intentioned actions in recent decades that have led to the loss of forest industry capacity in California. And well-meaning regulators make decisions that create obstacles to doing real ecosystem management. In part this comes from specialization – water professional think about water; air professionals think about air. If instead we could think about these problems holistically and at an appropriate scale, we can find solutions that solve many problems plus save California taxpayers a lot of money.

    Salvaging trees that have died from bark beetle may cause more problems than they solve. Of course it is important to remove trees that pose a direct threat of falling on people, buildings, roads, and power lines. But building new forest roads can harm water quality and further fragment the landscape. Heavy logging machinery may damage fragile regeneration coming along. Research out of Colorado has found that dead trees elevate fire risk only as long as needles remain on the tree; once needles fall, stands of dead trees can have a lower fire risk.

    Salvaging dead trees only postpones the day when we can start doing ecosystem restoration in our forests. An experiment of new silvicultural approaches for forest ecosystem management – guided by UC Berkeley professors — cannot be implemented because forest companies have more material than they can handle from trees that have died from fire, drought and insects. As long as we harvest dead trees before living trees we are not doing the forest ecosystem management that could make forests more resilient to fire, drought, insects and climate change.

    New research out of UC Berkeley has found that managing fire, rather than suppressing it, makes wilderness areas more resilient to fire, with the added benefit of increased water availability and resistance to drought. (Gabrielle Boisramé, Sally Thompson, Brandon Collins, Scott Stephens. Managed Wildfire Effects on Forest Resilience and Water in the Sierra Nevada. Ecosystems, 2016.) In addition, a promising forest management strategy developed at the Sagehen Creek Field Station can improve wildlife habitat as well. This strategy was developed through a collaborative of scientists and stakeholders ranging from environmentalists to loggers. The resulting plan focuses on the pattern of trees remaining after harvest – a pattern that is similar to the pattern after managed fire. The plan created pockets of dense cover as well as openings; big old trees were left; wildlife habitat improved; fire risk reduced. And the plan also made plenty of merchantable timber available.

    Managing our forests in a more holistic way could provide a lot of benefits. It could reduce the cost of fighting fires; it would save lives and homes, fish and wildlife, scenic vistas and recreation values.

    My hope is that as we think about what to do with our forests, we resist reacting to the latest threat. That can cause more harm than good. A better approach is to be strategic, proactive and holistic in our thinking.

  5. NEW study: Does increased forest protection correspond to higher fire severity in frequent-fire forests of the western United States? available here:

    ABSTRACT: “There is a widespread view among land managers and others that the protected status of many forestlands in the western United States corresponds with higher fire severity levels due to historical restrictions on logging that contribute to greater amounts of biomass and fuel loading in less intensively managed areas, particularly after decades of fire suppression. This view has led to recent proposals—both administrative and legislative—to reduce or eliminate forest protections and increase some forms of logging based on the belief that restrictions on active management have increased fire severity. We investigated the relationship between protected status and fire severity using the Random Forests algorithm applied to 1500 fires affecting 9.5 million hectares between 1984 and 2014 in pine (Pinus ponderosa, Pinus jeffreyi) and mixed-conifer forests of western United States, accounting for key topographic and climate variables. We found forests with higher levels of protection had lower severity values even though they are generally identified as having the highest overall levels of biomass and fuel loading. Our results suggest a need to reconsider current overly simplistic assumptions about the relationship between forest protection and fire severity in fire management and policy.”

    In general, our findings—that forests with the highest levels of protection from logging tend to burn least severely—suggest a need for managers and policymakers to rethink current forest and fire management direction, particularly proposals that seek to weaken forest protections or suspend environmental laws ostensibly to facilitate a more extensive and industrial forest–fire management regime. Such approaches would likely achieve the opposite of their intended consequences and would degrade complex early seral forests (DellaSala et al. 2015). We suggest that the results of our study counsel in favor of increased protection for federal forestlands without the concern that this may lead to more severe fires.
    Allowing wildfires to burn under safe conditions is an effective restoration tool for achieving landscape heterogeneity and biodiversity conservation objectives in regions where high levels of biodiversity are associated with mixed-intensity fires (i.e., “pyrodiversity begets biodiversity,” see DellaSala and Hanson 2015b). Managers concerned about fires can close and decommission roads that contribute to human-caused fire ignitions and treat fire-prone tree plantations where fires have been shown to burn uncharacteristically severe (Odion et al. 2004). Prioritizing fuel treatments to flammable vegetation adjacent to homes along with specific measures that reduce fire risks to home structures are precautionary steps for allowing more fires to proceed safely in the backcountry (Moritz 2014, DellaSala et al. 2015, Moritz and Knowles 2016).
    Continued –


  6. If I had written this article I would have ordered the tree die off explanation in a different matter. As an air pollution meteorologist who has attended the conference in the past, I explain the tree die off as directly linked to climate change. Climate change has caused megadrought in the west, weakened the trees that are now susceptible to girdling of the tree by the pine bark bettle. In the opinion of many meteorologists and climatologists and documented in journals supported by the American Meteorological Society the western mega droughts are and forecast to continue due to man caused climate change.

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About Richard

Richard Frank is Professor of Environmental Practice and Director of the U. C. Davis School of Law’s California Environmental Law & Policy Center. From 2006-2010, …

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About Richard

Richard Frank is Professor of Environmental Practice and Director of the U. C. Davis School of Law’s California Environmental Law & Policy Center. From 2006-2010, …

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