Among the tens of thousands of Coloradans who fled the state’s most destructive blaze a year ago were some of the nation’s foremost experts on fire behavior and natural disaster recovery.

Brad Wham, a disaster reconnaissance specialist, watched in horror on Dec. 30, 2021, as the Marshall Fire chewed through mulch on medians around him as he drove away from his Louisville home.

An engineer who has traveled to Japan and New Zealand to study earthquake damage to help communities prepare for future temblors, Wham returned to his own devastated city to find his home intact despite embers the size of dinner plates in his townhome’s window wells. Assured his place was safe, the University of Colorado assistant research professor jumped on his bike and pedaled into a snowstorm to start documenting the destruction.

He soon assembled a national team to discern how the region could rebuild to withstand the next conflagration. They joined a race by fire scientists to understand how global warming is changing such disasters, including how buildings themselves act as fuel during a wildfire.

The lessons have relevance beyond Colorado’s borders.

Some of America’s fastest-growing areas are in arid Western states prone to wildfires. About 1 in 3 homes are being built in areas that abut land with flammable vegetation — what scientists call the wildland-urban interface, or WUI. And about 60 million homes are within a kilometer of areas that have burned at some point in the past 24 years, scientists found in a 2020 analysis. The study’s authors cautioned: “We’ve been living with wildfire risk that we haven’t fully understood.”

This destruction is intensifying as the West endures its worst drought in 1,200 years. About two-thirds of the 97,196 homes destroyed by wildfire between 2005 and June 2022 burned in the last five years.

A year after the Marshall Fire, authorities have yet to determine the cause.

The team co-led by Wham chose to study the fire because the grasslands where the blaze likely ignited are separate from the communities that burned — unlike other burn zones in the West where the torched homes mixed with wildlands, said Erica Fischer, a structural engineer and assistant professor at Oregon State University who was the research team’s other co-leader.

She added another draw was that “we’ve never seen this level of housing damage due to a grassland fire.”

To understand how the blaze unfolded and how residents and policymakers can address the growing threat, the group flew drones over 14 charred neighborhoods within the 9-square-mile burn zone. The interdisciplinary team’s work was published five months later and echoed past studies that pointed to ways fast-growing Western states could build more fire-resistant communities.

“It is possible that using different materials would have given people more time to evacuate,” Wham said in May, as he lifted his voice above the sound of an excavator removing chunks of foundation from a cul-de-sac on Cherrywood Lane. The street is nestled in one of seven hard-hit neighborhoods where researchers conducted their ground surveys. “And they could have led to slower burn rates, which would have helped firefighters and reduced the spread of the fire.”

Their findings offer policymakers a stark choice: design communities so firefighters can safely defend them from fast-moving wildfires, or leave residents and firefighters vulnerable to further losses.

“There were a number of communities that were abandoned by firefighters because they could not stop the spread of the fire and it wasn’t safe for them to be there,” Fischer said.

Fischer pointed to the International Wildland-Urban Interface Code and the National Fire Protection Association’s Firewise USA program as examples of what works. Both were created about 20 years ago to educate homeowners and help fortify communities.

Twenty-six counties and about 186 sites, including communities, ranches and other areas, in Colorado participate in the voluntary Firewise USA mitigation program, which teaches homeowners how to gird their property to “withstand ember attacks.”

Wham and Fischer’s conclusions mirror evidence that prompted creation of such preventive codes and programs: Wooden fences, decking and vegetation within 5 to 30 feet of homes act as conduits for fire to move from house to house and should be replaced with fire resistant materials, such as steel, or removed altogether.

“Our building codes are designed to make sure structures are safe to get people out, they are not designed for property protection,” Fischer said. “We need to rethink how we are designing our communities and our buildings across all hazards.”

Wham and Fischer’s data is unique in that it shows how a relatively affluent community chooses to rebuild, Fischer said. Many homes destroyed by the conflagration were newer than those previously studied. And the area’s household income is nearly twice the national median; 2 out of 3 residents hold a college degree.

The team is continuing its field work, together with the Federal Emergency Management Agency, to figure out how to most effectively mitigate fire risk in neighborhoods with homes closely spaced together. They’re studying satellite images to see which homes first caught fire and collecting data from the wreckage to draw their conclusions. The group will soon release information showing urban homeowners how to lessen their risk, Fischer said.

Similar studies are taking place across the West, as scientists learn more about how homes located in the WUI — where plants such as trees, shrubs and grasses are near, or mixed with, homes, power lines, businesses and other human development — act as fuel during a wildfire.

“Once a home in your community catches fire, your exposure to that hazard changes,” Fischer said. “Embers can travel up to 5 miles — think about how many homes are within 5 miles of your house — that’s a lot of people you are relying on to mitigate their property.”