Fire Season

November 17, 2023
Fire Season

Fire is seasonal, particularly in the boreal forests of the Northern Hemisphere where winter’s blanket of cold and moisture generally prevents burning. Fire season in the Northern Hemisphere begins in May and runs through October, with peaks in burning activity coincident with the hottest and driest months of July and August. 

The operative word in that sense, however, is “typical”. We are in a new age of fire seasons, which run hotter, longer, and more extreme than in recorded human history. While we intend for all of our letters to be objective, our understanding of fire season is also personal. We write from California, where – even in the two decades of our own direct observation – accelerating climate change has transformed our experience of late summer from one of placid clear days to, in some years, weeks of obliterating smoke, encroaching wildfires, and acute concern for our own safety. Fire is an immediate and frightening symptom of the sometimes-unseen destabilization of the global climate system. For us - and for so many around the world - fire season is no longer an abstraction. 

In this letter, Voyager examines our current, expanding fire season, its implications for the global carbon cycle, and how technology, policy, and finance can address this new reality. 

Fires in the North and the South

The generally stable climate system that has enabled human civilization is not without its dramatic outcomes. Fire is one of them. All wooded and grassy areas can burn; some areas are more prone to burn than others. Some, like the Amazon basin, have been particularly susceptible to intentional human burning to clear forests in favor of grassland. Others, like the forests of US and Canadian West, burn from causes ranging to lighting strikes, to arson, to poorly-maintained power transmission equipment. 

Globally, the world loses about more than 20 million hectares of tree cover a year, and in the 22 years from 2001 to 2022, the world lost a total of 460 million hectares of tree cover. Of that, more than one-third of losses came from fires.  

A graph of loss and loss of treesDescription automatically generated with medium confidence

Much as intentional burning in the Amazon Basin informs one’s imagination of burning forests, it is the boreal forest which loses the most tree cover from fires. From 2001 to 2022, Brazil lost an average of 457,000 hectares a year to fires. In that same time, the US tree cover loss from fires was 556,000 hectares; in Canada, the figure was 1.28 million; in Russia, it was 2.54 million hectares. 

The 2023 fire season in Canada is exceptional in a number of ways. The first is sheer volume. As of the end of September, nearly 18 million hectares has burned, equal to 20% of the total area burned in the prior 40 years. Since then, another several hundred thousand hectares have burned.

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It is also exceptional for defying the historical boundaries of fire season. Fires should be decreasing as October neared; instead, fires continued to grow rapidly given high temperatures and a strong area of low pressure forcing strong winds over dry terrain. Satellite imagery captures the burning in British Columbia and Alberta quite clearly. 

Source: European Union/Copernicus Sentinel-2

The emissions impacts of this burning is significant. As of mid-September, wildfires released 410 million metric tons of carbon dioxide – roughly the equivalent of Mexico’s emissions in 2021.  Canada’s own emissions from human activities in 2022 was roughly 550 million metric tons of CO2. Burning, then, is becoming an emissions challenge similar in scale to all human activity in a major industrial economy.

In terms of emissions impact, California’s forest wildfires are similar in scope if not in scale. The California Air Resource Board tracks emissions from wildfires as part of its greenhouse gas inventory. Its data include a sad observation: emissions from California’s wildfires have essentially erased the state’s success in reducing greenhouse gas emissions since 2008. 

Wildfires in Russia, though much less widely covered than those in the US and Canada, Russia, have planetary impacts.  For all the magnitude of Canada’s boreal forest fires this year, they have not yet exceeded the 18.8 million hectares burned in Russia in 2021. 

While northern hemisphere fires dominate in terms of total area burned, fires in the southern hemisphere are also significant. Australia’s bush fires in 2019-2020 summer not only burned an estimated 24.3 million hectares, they also killed three billion terrestrial vertebrates and produced so much smoke that they may have helped trigger a three-year La Niña event.  More than a half a million hectares burned in Argentina last year, and this year fires affected its protected wilderness areas in the northeastern part of the country. While dramatic photographs of burning hillsides in Los Angeles, orange skies in San Francisco, and thick haze over New York have dominated American media coverage, intensifying fires are shaping everyday experience worldwide.

A History of Suppression Meets a Climate Inevitability

Attributing the causes of wildfires is straightforward in some senses, and complex in others. Immediate causes can be tracked back to acts of arson, lightning strikes, or faulty equipment providing the necessary heat and sparks for ignition.  Some are malice, some are accident, some are nature. The effects are the same. 

Medium-term and longer-term causes are worth analyzing. Once cause, particularly for the US West, is conflicting priorities in vegetation management. Steady, years-long accumulation of brush, small trees, and dead wood leaves forests filled with fuel that can ignite and burn intensely. Removing this vegetation – which small natural fires can also do on their own – is useful, but also fraught. Fuel reduction, like prescribed burning and mechanical thinning can be effective in some types of forests, but not all. As the Public Policy Institute of California notes, “Some argue that California is not doing enough to manage its forests and that more trees must be removed. Others are concerned that this approach could weaken important environmental protections.” 

Drought is another obvious driver, particularly apparent in the American West. Climate change continues to reduce steady precipitation, desiccating both ground and vegetation. Following a burn, destabilized soils do not as easily absorb water and are prone to slides, compounding fire’s effects long after the burn.

Of course, the biggest cause is the changing climate. In its August analysis of fires in eastern Canada, the World Weather Attribution Initiative found that the area’s record-warm May and June period (more than 0.8 degrees Celsius above the prior record) more than doubled the likelihood of extreme fire conditions. This, as the WWA describes it, is “fire weather”. 

In addition, the WWA noted “Climate change made the cumulative severity of Québec’s 2023 fire season to the end of July around 50% more intense, and seasons of this severity at least seven times more likely to occur.” Proximate conditions matter, and so does policy – but it is climate, above all, that drives today’s fire seasons. 

Policy, Insurance, Finance 

Fire is already re-writing the US risk landscape. This past June, two giant insurers announced that they would no longer write new policies in California, in large part because of wildfire risks.  One of the insurers, Allstate, said that “The cost to insure new home customers in California is far higher than the price they would pay for policies due to wildfires, higher costs for repairing homes and higher reinsurance premiums.” Fire is not the only factor in California, but it may be the decisive factor in many areas prone to frequent and often catastrophic losses. The scale here is important: according to the US Fire Administration, between 1990 and 2010, the so-called wildland-urban interface border between developed and open land grew by 33% to 190 million acres. At that same time, the number of homes in these areas increased 41%.  Today, 99 million people, or 1/3 of the US population, now live in the wildland-urban interface.

Policymakers are in something of a bind, too. They can only compel so much coverage from companies that are in the risk business, and they can only take on so much risk themselves without risking their balance sheets and bond ratings. 

Policymakers can, however, find areas where they can be risk-on to the benefit of preventing uncontrolled wildfires, rather than just responding to them. A useful example from California is the state’s $20 million “Prescribed Fire Liability Claims Fund Pilot” which will cover losses from any prescribed burn or cultural burn that escapes control. 

This pilot is a compelling use of public funds. Providing liability insurance to prescribed and cultural burn activities will allow the practice to expand and be used more frequently. A well-informed, and well-evolved, risk environment for beneficial practices that still have tail risks will enable more innovation in managing fire pre-emptively, rather than just responding to it. 


Within an imperfect - and evolving - regulatory and financial response to fire, Voyager sees three applications of technology to the problem. They are preventing fires, mitigating their spread, and addressing their damage. 

Preventing fires

  • Better detection of dry vegetation and drought conditions, and better prediction of high winds and fire storms. Numerous satellite imagery and analytics providers play a role here, as does better weather forecasting.  
  • Better detection of combustible material. This includes trees and vegetation likely to burn (diseased and dead trees), infrastructure prone to sparking fires (such as aboveground utility wires), and wooden structures and structures in close proximity to vegetation. Example companies include Overstory and AI-Dash
  • Vegetation management itself, via an integrated detection of risky assets and infrastructure.
  • Companies creating the foundation of granular data and financial incentive alignment for physical change. These include measurement, reporting, and verification (MRV) companies, risk prediction companies, and insurance / reinsurance companies. Examples of startups include Kettle and Vibrant Planet.
  • More accurate carbon sensing and management to enable financial incentive alignment for fire prevention among landowners, forestry managers and regulators.
  • Regular vegetation clearing along with bioenergy with carbon capture and storage power generation.  This is a way of valorizing forestry waste by producing carbon-negative electricity. Arbor Energy is tackling this problem – and solution. 

Mitigating fires’ spread

  • Vegetation management, which can both prevent fire and create a co-benefit economic stream from forest products.
  • Fire detection once breakouts have occurred. Example companies include Pano and Dryad, which provide value through containing risks as quickly as possible once they emerge. 
  • Drones and other approaches for fire suppression. Rain, a wildfire intelligence system for autonomous aircraft, is one example.  

Addressing fire damages

  • Hardened infrastructure that can better withstand fire. Firemaps, a home hardening service, is one example.  
  • Better and more responsive reinsurance. This includes better maps and spatial understanding of fire risk, as well as faster and more accurate payment for loss and damage after fires have occurred. 
  • More thoughtful planning and construction and permitting for new builds. This is primarily a policy response, and it is particularly important in the wildland-urban interface. 
  • Better air quality sensors and better indoor air pollution control systems for populations subjected to wildfire smoke. The latter will have benefits even when fire is not an air quality risk. 

A Fire Imperative: Managing Carbon and Removing It

We are in an age of fires so large that they emit they can emit as much carbon dioxide as the entirety of annual economic activity in a large industrial country. That carbon, once stable in the biome and now warming the atmosphere, contributes to further warming, and further emitting. As California demonstrates, wildfires already imperil – or negate – decades of improving net greenhouse gas emissions in major economies. Fires change the carbon equation, so to speak: they make humans’ carbon ledger that much bigger, and that much harder to manage. 

With today’s forests at risk of moving from carbon sink to carbon source, Voyager believes we should pursue better forest management at every level: averting fires when possible, reducing their intensity, and creating the financial incentives and technological infrastructure to reduce their damage to proximate assets and to the global climate system. It is no longer enough to expect forest carbon to persist in a stable fashion. 

That change in expectation leads Voyager to another carbon imperative: removing carbon. In a new era of longer, hotter, more intense, and more destructive fire seasons, there will be times and places where carbon is emitted outside of human purview. We must respond by placing that carbon back inside our control. That means removing carbon from the atmosphere, at gigaton scale. The economics, policy, and business models of carbon removal are themselves complex, but also essential – and a topic for an upcoming Voyager letter. 

Fire Seasons Past and Future

Smoke from the California wildfires of 2020 smothered San Francisco, obliterating sunlight, and coloring the whole sky an eerie dark orange in early September 2020. The San Francisco Fire Department tweeted: “We know the smoke, darkness and orange glow is scary. Stay calm and try to stay indoors; it’s going to get better.” 

For some, the alarming experience catalyzed their decision to work on climate stabilization: we know several companies founded in the weeks and months after what many in the Bay Area still refer to as the “Orange Sky Day”. Voyager was one of them – after years working on other means of systemic decarbonization, we made the decision in late 2020 to launch Voyager Fund I, recognizing the confluence of technological opportunity, market demand for decarbonization, and the arrival of talented company-builders focused on climate stabilization. The urgency and commercial opportunity in decarbonization have never been more obvious, and a generation of ambitious founders is working to moderate the fire seasons of future decades.