Why is LA on Fire?

In Daniel Abraham and Ty Frank’s science fiction novel Mercy of the Gods , the protagonist posits that every person has a pathological move they make when faced with disaster. I’m pretty sure this idea has no scientific basis, but I love it as a framework to understand what I do when I’m stressed. My pathological move: I analyze. In my mind, understanding why something is happening is the first step to doing something about it. I find it calming. 

This week, unprecedented wildfires are burning structures in Los Angeles. I lived in Venice and Pasadena while working at SpaceX and JPL. It’s been horrifying to recognize places I love, including the homes of friends and JPL itself, have already burned or are at risk. 

The prevailing narrative I’ve seen about why this is happening is that dry conditions and hurricane-force Santa Ana winds have created an unprecedented ‘perfect storm’ in which fires can spread uncontrolled. At a surface level this is true, but it’s only a partial truth. Let’s dig deeper.

Is this wind and humidity truly unprecedented? The Santa Ana winds happen when the hot, dry, high pressure air over the deserts flows towards the low pressure areas off the coast. As the air descends and air pressure increases, the air warms, making it hotter along the coast than in the desert. Since the winds accelerate as they are forced through mountain passes, the Santa Anas can reach gale strength.  

The current consensus is that climate change is not making Santa Anas worse. In fact, while this week’s winds are strong and dry, this happens fairly often in LA. If we examine the last twenty years’ red flag warnings, which are issued when the combination of dry air and strong winds make fire conditions dangerous, we can see no clear trend. (Note that instead of number of warnings, I’ve partitioned this analysis by the square kilometers of warnings issued times number of hours issued, as I feel this more accurately represents fire risk).

If these winds and humidity have happened before without massive fires threatening LA, why is this year different? Did we just get unlucky enough to have three massive fires threatening metro areas at once?

Thing is, California’s natural state involves frequent wildfires.

Nearly every ecosystem in California either needs periodic fires to be healthy, or is adapted to survive fires. In fact, it has been estimated that prior to modern forest management practices, between 17,000 and 48,000 square kilometers of land burned annually in California. Compare this to the 17,800 square kilometers of land that burned in 2020’s fire season, the most since we began tracking in 2000. 

Unfortunately, when the land is prevented from burning as often, biomass fuel builds up. Compare the amount of tree cover in these photos of Yosemite in 1913 and 2021. 

The amount of fuel available directly correlates to the heat of the fire. Areas that haven’t burned recently burn much hotter when they do burn.

There’s a massive difference in destructive capability between a brush fire which scorches the bark of the larger trees while burning back the undergrowth, and a megafire which immolates the trees themselves. Unfortunately, the longer the first is delayed, the more likely the second.

To combat this issue, fire departments engage in fuel management , deliberately starting fires under favorable conditions, or thinning forests with chainsaws, herbicides, grazing animals, or even by hand.  In 2023, California spent hundreds of millions of dollars to treat more than 2000 square kilometers. While undoubtedly helpful, this does not compare favorably to the 17,000 that might have burned naturally. 

Additionally, firefighters create fuel breaks, which are areas devoid of vegetation that can be used to contain a wildland fire. These breaks are relatively expensive to create, and can be bypassed by megafires, which can throw burning embers thousands of meters to start fires well across the break.

Unfortunately, both these practices can get tougher to perform closer to populated areas. Sensitivity to smoke or perceived risks to structures can mean that controlled fires can’t always be set, and public opposition can be strong. 

But wait. Why are said structures built in fire areas in the first place? Shouldn’t a home which has a significant risk of burning be impossible to insure, and therefore never have been built?

Since 1968, the FAIR Plan in California has made it possible to insure homes in California which cannot obtain coverage in the voluntary markets. The FAIR plan explicitly was created to “provide basic fire insurance coverage for high-risk properties when traditional insurance companies will not.” Why was this seen as a good idea?

After World-War two, suburban growth exploded, funded by the FHA. Cities like LA began to sprawl into the urban-wildland interface, increasing wildfire risks.

 Simultaneously, the practice of redlining was used to prevent Black homeowners from obtaining access to credit because of where they lived, making home ownership much more difficult. In 1965, things in LA came to a head in the Watts Riots. $40 million in property was burned during the riots. 

Both these factors - wildfire risks along the urban-wildland interface, and civil unrest in urban areas - caused difficulties obtaining property insurance. While I can’t find this directly written, the 1968 timing of the FAIR plan (Coinciding with the federal Fair Housing Act) and the similarity in names makes me wonder if the motivation was to ensure that insurance redlining wouldn’t replace loan redlining in California. While a great reason, the guaranteed availability of state-sponsored insurance along the urban-wildland interface has resulted in nearly sixty years of building in fire risk zones.

200 years of limited burning and sixty years of development with market risk signals artificially expressed by a state program made a great tinderbox. Climate change makes things even worse.

It’s well known that Climate Change creates increased temperatures, and that hotter, drier summers lead to a longer and worse fire season. 

However, it isn’t fire season right now. In fact, the high temperature in LA is around 70 degrees F. Also, though LA has gotten very little rainfall this winter, California isn’t currently in a long drought. 

Climate change has a lesser known effect which is possibly more impactful in this case: it can indirectly impact the amount of fuel available. For example, the tree-killing effects of bark beetles in Californian forests is one reason fuel management has gotten so difficult. Dead trees dry out and burn far more easily. Bark beetles have exploded in population primarily because slightly warmer winters allow them to thrive.

California residents will remember that the last two years have had unexpectedly wet winters followed by unexpectedly hot, dry summers. This ‘hydroclimate volatility’ is directly attributable to climate change, and combines explosive winter plant growth with a summer kiln-dry. We know that more fuel makes fires burn hotter and more intense, and that this year has been unprecedentedly bad for the above volatility. 

So, in short:

• For the past hundred-and-fifty years, we haven’t been letting the land burn the way it naturally might. Fuel has built up.

• Sixty years ago, we implemented insurance policies that let people build and buy homes in fire-prone areas while artificially suppressing market signals of risk

• Climate Change is making much more dry fuel available via tree death and ‘hydroclimate volatility’

• The above situation, combined with a relatively dry first half of winter and unluckily strong Santa Anas, made for a perfect (fire)storm

Ow. 

In an upcoming post, I’ll take a look at how risks of climate disasters like wildfires will impact different parts of the US. Subscribe to be emailed when it’s posted!

For now, friends in LA, stay safe. My heart goes out to anyone breathing smoke right now and everyone who has lost a home.