The devastating Los Angeles fires in the very heart of a built-up urban interface sparked global interest, including in Australia as communities, media and governments asked how the fires happened and could such a catastrophe happen here.
One year on from the fires researchers have focused on understanding the causes and impacts of the fires as well as evaluating vulnerabilities and resilience features that contributed to the patterns of destruction and the efficacy of emergency management.
Causes and impacts
Despite occurring during the winter months that typically see less wildfires, extremely dry conditions, combined with strong winds (reaching almost 160 km/h) created hazardous fire conditions. Dozens of fires ignited in early January 2025, two of which grew to become the Palisades and Eaton Fires which spread through adjacent suburbs.
The fires burned 37 000 acres and destroyed more than16 000 structures, driven by intense house-to-house fire spread, known as conflagration. According to Swiss Re, the fires were the costliest wildfire event ever globally with insurance losses estimated at $40 billion. Some sixteen times greater than Australia’s Black Summer Bushfires.
US building codes relating to the wildfire urban interface became operational in 2008, however, much of the building stock destroyed was built before then which meant wildfire resilience measures were not uniformly adopted.
Rapid urban growth has also increased wildfire exposure across the United States, with a study concluding that exposure grew 40% between 1990 and 2010.
Deaths were reported at 31, however, research found 440 indirect deaths linked to the fires from factors such as poor air quality, stress, disruption to health systems and mental health impacts. A further study found a 46% increase in visits for heart attacks to a Los Angeles hospital in the first 90 days following the fires when compared to the same period over the previous seven years.
Built environment vulnerabilities and resilience
Investigations led by the Insurance Institute for Business and Home Safety (IIBHS) determined key factors that contributed to the loss of structures were lack of structure separation, connective fuels and building materials used, concluding that:
- Each additional 10 ft (3 m) of separation between structures increased the likelihood of no damage by 7-13%, up to 30ft no matter the structure type, After 30 ft, the impact of additional separation flattened off.
- Vegetation and other flammable materials and household items adjacent to buildings such as decks, garbage bins, hot tubs and pergolas acted as connective fuels, creating significant vulnerability to structures.
- Vegetation growing alongside non-combustible fences compromised its resilience. Where there was 25% fuel coverage in the 1.2 m directly surrounding a structure there was an 87% to 100% chance of damage or destruction.
- Most structures inspected included at least one resilient building feature. However, few had adopted a comprehensive resilient system allowing flames, radiant heat and embers to exploit building vulnerabilities.
- Often resilient characteristics, such as non-combustible exterior wall cladding were paired with vulnerable ones such as windows, doors, vents or eaves increasing the overall vulnerability of the structure.
- Structures with four resilient components were 54% more likely to experience no damage regardless of separation distance, this reduced to 36% likelihood of no damage with only one or two resilient components.
A recent Berkeley Fire Research Lab study analysing data from five of the most destructive Californian fires before 2022 identified similar results suggesting that home retrofitting and defensible space can double the number of homes and other structures that survive a wildfire. Notably, the study found that removing all combustible material within 1.2 m of homes could reduce structure losses by 17%, compared with 5% for retrofitting alone.
The study also found that separation distance between structures is the most influential factor driving structure loss, especially in densely built areas.
Resilience implications
Research overwhelmingly found a systematic approach to wildfire resilience is key, underscoring that no single resilience measure is sufficient on its own.
At the household level, a combination of resilience measures including building codes, retrofitting, adequate structure separation and the removal of connective fuels has been proven to have the greatest impact on reducing risk. The IIBHS conclude that when resilience measures are adopted on a neighbourhood-wide scale the number of structure ignitions can be reduced, slowing fire spread and reducing impacts.
Much debate following the fires has centred around new Californian regulations to limit flammable materials within 1.2 m (5 ft) of homes, known as Zone 0, to create an ember-resistant area to prevent structure ignition. According to CAL FIRE the purpose of Zone 0 is to:
Reduce the likelihood of structure ignition by reducing the potential for direct ignition of the structure from flame contact, by embers that accumulate at the base of a wall, and/or indirect ignitions when embers ignite vegetation, vegetative debris or other combustible materials located close to the structure that result in either a radiant heat and/or direct flame contact.
Originally directed by the Legislature in 2020, the impending legislation stalled until the 2025 fires, when the Californian Governor directed the completion of the Zone 0 regulation by the end of 2025. Public debate over the issue has since pushed expected completion to 2026. Despite this, some Californian cities have already implemented Zone 0 policies, with some offering grant programs to support implementation.
The new regulation will build upon existing defendable space policies dating back to 1965, which mandated a fuel reduced area extending to 10 m surrounding a property, and which were supplemented in 2008 with a requirement for fuel reduction to around 30 m or to the edge of the property. These regulations include maintenance of grass, space between vegetation, removal of fallen leaves and clearance space around sheds and wood plies. The key difference is that in Zone 0 there should be no fuel, while in the outer areas, fuel is to be minimised and managed.
It is proposed Zone 0 will apply to all new construction in California’s State Responsibility Area. For existing structures home and business owners will have three years to clear the vegetation and other combustibles within 1.2 m around the structure. CAL FIRE has estimated that 17% of all structures (some 2 million houses) across California will be affected by the regulations.
Regulations are proposed to include combustibles such as wood-based mulch, woody plants, dry grass, synthetic lawns, stored timber, storage sheds, wooden gates and fences attached to a structure, small trees and other landscape materials within the first 1.2 m of the structure and any attached decks. Trees would be allowed within the zone if they are pruned and maintained appropriately.
A recent UCLA expert panel debate noted that while combustible materials near structures pose clear fire risks, vegetation management is more complex. Reducing tree canopy may contribute to extreme heat exposure, and communities have resisted vegetation removal due to aesthetics and cost, framed in the media as ‘anti-garden policy’. Some residents argue well-watered plants in Zone 0 offer protection, but recent IIBHS research confirms even hydrated vegetation will ignite under extreme fire conditions.
Observations for Australia
Australian experience has seen significant bushfire losses within urban areas. For example, in 1967 fires burned to within 2 km of Hobart CBD claiming 62 lives and in 2003 fires burned into Canberra suburbs destroying close to 500 homes.
Similar to California, many Australian properties were not designed to withstand bushfires, and the number of homes in at-risk areas continues to increase. The risk of conflagrations in Australia compared to California, however, must be better understood. The two environments are different and significant risk factors such as structure separation may differ.
Natural Hazards Research Australia funded research led by UTAS investigating the wildfire urban interface found that creating defensible space around a home can reduce house losses. Finding that guidelines for the creation of defensible space should identify the closest area surrounding a home as a stand-alone zone (similar to Zone 0), to ensure focus on this critical area.
A systems approach to household resilience requires clear, evidence-based measures that prioritise efficacy and efficiency. While guidelines exist to address existing buildings, their implementation remains largely voluntary, highlighting the need for incentives to encourage adoption. Fire agencies play a crucial role to communicate these measures, but systemic change is essential to ensure widespread resilience.
To help remove barriers to improving the resilience of Australia’s building stock the Productivity Commission recently recommended the development of a nationally consistent climate resilience rating system for housing and for a national strategy to improve the resilience of Australia’s housing stock over coming decades.
In its submission to the Productivity Commission inquiry on net zero transformation, the Centre noted that a resilience rating system could be mandatory for all new properties at the time a property was sold or leased. For example, California now requires sellers in areas of high wildfire risk to report completed retrofit works. Such rating systems should consider both physical attributes of a structure and features surrounding a structure such as garden design.
Transparency of household resilience alone, however, will unlikely be insufficient to overcome barriers to improving the resilience of existing housing stock. Incentive measures such as subsidies, low-interest loans, insurance discounts and build back better provisions in insurance policies should all be considered.
Natural Hazards Research Australia is continuing to support Australian fire services to explore implications of the Los Angeles fires through new research focused on understanding the risk of conflagration in Australia.
In short, Australia needs:
- National Resilience Strategy for housing stock inclusive of the management of bushfire fuel on private land
- Resilience rating system, mandatory for all new properties and when properties are sold or leased
- Incentive measures such as subsidies, low-interest loans, insurance discounts to promote retrofitting to enhance property resilience.