What's Wrong with the Zombie Forest Narrative

A recent NYT article leaves out the historical impact of fire suppression

Hello Wilderness readers! I turned in my book yesterday, so now I am back at it. Thanks so much for sticking with me. There’s a lot of great stuff coming up. For now, please share this far and wide, or become a paying subscriber. It really helps!

There is no such thing as a zombie forest.

On March 6th, the New York Times published an article called Mapping California’s Zombie Forests. The first line reads:

“A warming climate has left a fifth of the conifer forests that blanket California's Sierra Nevada stranded in habitats that no longer suit them, according to a study published last week by researchers at Stanford University.”

I spent seven years in the field as a wildland firefighter, four of those as a hotshot. I’m also (reluctantly) an academic. For the past four years I’ve been researching climate change, the history of fire suppression, Indigenous burning and kincentric practices, and fire policy in the United States. I am going to go ahead and say very loudly that calling any forest a zombie forest is irresponsible.

Giving complex ecological issues catchy names tends to flatten the collective understanding of the processes that have led up to an issues and continue to exacerbate it, especially when we consider the historical narratives surrounding wildland fire, wildfires, and prescribed burning.

The article continues:

“In these “zombie forests,” older, well-established trees — including ponderosa pines, Douglas firs and sugar pines — still tower overhead, but few young trees have been able to take root because the climate has become too warm and dry for them to thrive.”

This is only partially true. While climate change is clearly a factor in forest die-off, there are many other factors that have led to these forests dying. In the NYT piece:

“Until the 1930s, low-intensity fires that did not kill many large trees occurred regularly, which meant tree seedlings could more easily re-establish themselves in those regions after the fire. However, decades of aggressive wildfire suppression that began in the 20th century led to a buildup of vegetation in forests that was primed to burn.”

Yes. And: low-intensity fires were removed from California landscapes well before the 1930’s. Indigenous Californians had cyclically applied low-intensity fire throughout nearly all California ecosystems for thousands of years, and it was in the 1700s that many tribes were violently taken from their lands, primarily by Spanish colonizers, and forced into the Spanish Mission system. One could easily argue that this was the initiation of fire suppression— Indigenous Americans, taken from their home territories, were a major reason why many landscapes throughout California (and the United States) were (and are) fire adapted.

Throughout the 18th and 19th Century, California tribes were violently disbanded and Indigenous Californians were enslaved, first to the Spanish and then, at the time of the Gold Rush, by other Europeans and white Americans.

Before the turn of the 20th century, there were already established fire-suppression patrols in California. In 1905, the California Bureau of Forestry was established and these patrols were increased. This was the beginning of formal fire suppression in California.

As Indigenous fires decreased, and fire suppression increased, the number of trees on the landscape increased.

Compare these photos of Yosemite Valley, from most recent to oldest.

A recent photo of Yosemite Valley

The Queen of England visits Yosemite in 1983

Yosemite in 1886

As you can clearly see, the number of trees increased over time. It’s fair to assume that the 1886 picture was also a representation of increased tree crowding, because it was after the Gold Rush and over 100 years after the Spanish built the first mission in California.

What the New York Times article (and the ‘Zombie’ tree narrative) doesn’t seem to account for is that these forests have been in transition well before our planet began to warm, and that this transition, and the continuing effects of fire suppression, have had a larger impact on landscapes than climate change.

---

There are other factors at play.

We also must take into account the die-off of forests that has occurred over the past 30 years due to increased numbers of bark beetles. Diana Six, an entomologist at the University of Montana, has argued that these bark beetles infestations are a result of fire-suppression. The reasoning is multi-pronged:

• Bark beetle populations have increased due to shorter winters

• Low-severity fire applied cyclically also kept bark beetle populations in check.

• Frequent application of low-severity fire reduces the growth of new trees, therefore allowing established trees to reach maturity without having to compete for nutrients and water, therefore leading to healthier tree populations.

• Bark beetles have always served a purpose in forests. They target weaker trees and therefore increase overall tree health throughout the forest.

• Fire also targets weaker trees and essentially enacts the same function.

Six (and other scientists) argue that fire-suppression created the perfect environment for bark beetles.

---

It could be argued that, even without climate change at play, these forest die-offs could be occurring. The issue here is that there are too many trees, and that the only real “forest management” tactic regularly employed by federal agencies like the Forest Service and BLM is, in fact, fire suppression. We are clearly seeing the consequences of that.

---

The NYT article briefly mentions prescribed fire, but only to note that “the changing climate is making intentional burns more complicated to carry out.”

This is irresponsible. Yes, climate change does complicate the application of fire, but for decades there has been an exorbitant backlog on fuels reduction (effectively thinning and prescribed fire) work within federal agencies. Additionally, federal and state agencies (like Cal Fire) often interfere with the work of nonprofits trying to implement prescribed fire.

Prescribed burning must be implemented on a large scale, along with other fuel mitigations.

In a 2021 paper¹ several scientists and ecologists argue that:

“Past forest management, including widespread harvest of fire- and climate-tolerant large old trees and old forests, fire exclusion (both Indigenous and lightning ignitions), and highly effective wildfire suppression have contributed to the current state of wNA forests.”

(note that wNA stands for Western North American here)

Climate change is, of course, a factor here, but it is not the primary factor. These scientists (and many others) argue that “scaling-up a broad variety of fuel reduction treatments can tip landscape dynamics in favor of more benign fire behavior and effects.”

These fuel reduction treatments need to include low-severity fire. In fact, many scientists and researchers argue that thinning alone doesn’t work without being implemented in tandem with low-severity fire, because low-severity fire has a regenerative effect on soils and plants, and can also help fire adapted species (like many pine species) germinate properly.

---

There is no such thing as a Zombie forest.

That’s a categorically pessimistic way to look at the situation. That said, it is true that the warming climate could prove inhospitable to some tree species in their traditional regions. But how can we know that without implementing large-scale mitigations that could increase the health of these forests?

Daniel Mathews, who wrote the book Trees in Trouble suggests the possibility of reseeding areas with more drought and heat tolerant species variations.

Trees are essential. But we have too many of them.

Our obsession with trees being the most superior carbon filters is a little bit baffling to me. They aren’t, Specifically, pine trees are not the best carbon filters, because when they burn they release most of their accumulated carbon back into the atmosphere.

Grasslands are the best choice when it comes to storing carbon. Because nearly all of their root systems are underground, grasslands hold onto their stored carbon even when they burn. These “zombie” forests were once home to understory grasses of many different types, all of which helped to store carbon.

---

Okay, friends. That’s all I have for you today. Please, don’t believe everything you read, ok?

1. Hessburg, P. F., S. J. Prichard, R. K. Hagmann, N. A. Povak, and F. K. Lake. 2021. Wildfire and climate change adaptation of western North American forests: a case for intentional management. Ecological Applications 31(8):e02432. 10.1002/eap.2432