Science
Mosquito season is upon us. So why are Southern California officials releasing more of them?
Jennifer Castellon shook, tapped and blew on a box to shoo out more than 1,000 mosquitoes in a quiet, upscale Inland Empire neighborhood.
The insects had a job to do, and the pest scientist wanted every last one out.
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Their task? Find lady mosquitoes and mate.
But these were no ordinary mosquitoes. Technicians had zapped the insects, all males, with radiation in a nearby lab to make them sterile. If they achieve their amorous quest, there will be fewer baby mosquitoes than there would be if nature ran its course. That means fewer mouths to feed — mouths that thirst for human blood.
“I believe, fingers crossed, that we can drop the population size,” said Solomon Birhanie, scientific director for the West Valley Mosquito and Vector Control District, which released the mosquitoes in several San Bernardino County neighborhoods this month.
Sterilized male Aedes mosquitoes are released from a box in Rancho Cucamonga.
(Myung J. Chun / Los Angeles Times)
Controlling mosquitoes with mosquitoes
Mosquito control agencies in Southern California are desperate to tamp down an invasive mosquito — called Aedes aegypti — that has exploded in recent years. Itchy, unhappy residents are demanding it. And the mosquitoes known for fierce ankle biting aren’t just putting a damper on outdoor hangouts — they also spread disease.
The low-flying, day-biting mosquitoes can lay eggs in tiny water sources. A bottle cap is fair game. And they might lay a few, say, in a plant tray and others, perhaps, in a drain. Tackling the invaders isn’t easy when it can be hard to even locate all the reproduction spots. So public health agencies increasingly are trying to use the insects’ own biology against them by releasing sterilized males.
The West Valley district, which covers six cities in San Bernardino County, rolled out the first program of this kind in California last year. Now they’re expanding it. Next month, a vector district covering a large swath of Los Angeles County will launch its own pilot, followed by Orange County in the near future. Other districts are considering using the sterile insect technique, as the method is known, or watching early adopters closely.
On the plus side, it’s an approach that doesn’t rely on pesticides, which mosquitoes become resistant to, but it requires significant resources and triggers conspiracy theories.
“People are complaining that they can’t go into their backyard or barbecue in the summer,” Birhanie said at his Ontario lab. “So we needed something to strengthen our Aedes control.” Of particular concern is the Aedes aegypti, which love to bite people — often multiple times in rapid succession.
Releasing sterilized male insects to combat pests is a proven scientific technique, but using it to control invasive mosquitoes is relatively new.
Vector control experts often point to the success of a decades-long effort in California to fight Mediterranean fruit flies by dropping enormous quantities of sterile males from small planes. That program, run by the U.S. Department of Agriculture and the California Department of Food and Agriculture, costs about $16 million a year. That’s nearly four times West Valley’s annual budget.
So rather than try to tackle every nook and cranny of the district, encompassing roughly 650,000 residents, West Valley decided to use a more targeted approach. If a problem area reaches a certain threshold — over 50 mosquitoes counted in an overnight trap — it becomes a candidate.
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1. Solomon Birhanie inspects a container of mosquito larvae in the lab at the West Valley Mosquito and Vector Control District in Ontario. 2. Birhanie and his team raise mosquitoes in the lab, separating them by sex, because only the males, which don’t bite humans, will eventually be released. 3. Mosquito eggs in the West Valley lab. 4. The lab can grow about 10,000 mosquitoes at a time. 5. Before the male mosquitoes are released, an X-ray machine sterilizes them. If the zapped males mate with a female, her eggs won’t hatch. (Allen J. Schaben / Los Angeles Times)
And it’s still a big lift. About 10,000 mosquitoes are reared at a time at West Valley’s facility, about half of which will be males. The males are separated out, packed into cups and placed into an X-ray machine that looks like a small refrigerator. The sterilizing process isn’t that different from microwaving a frozen dinner. Zap them on a particular setting for four to five minutes and they’re good to go.
Equipment purchased for the program costs roughly $200,000, said Brian Reisinger, spokesperson for the district. He said it was too early to pin down a cost estimate for the program, which is expanding.
Some districts serving more people are going bigger.
The Greater Los Angeles County Vector Control District plans to unleash up to 60,000 mosquitoes a week in two neighborhoods in Sunland-Tujunga from mid-May through November.
With the sterile-insect program, “the biggest hurdle we’re up against really is scalability,” said Susanne Kluh, general manager of the L.A. County district, which is responsible for nearly 6 million residents across 36 cities.
In part to save money, Kluh’s district has partnered with the Orange County Mosquito and Vector Control District. They’re sharing equipment and collaborating on studies, but L.A. County’s releases will move forward first, said Brian Brannon, spokesperson for the O.C. district. Orange County expects to release its “ankle biter fighters,” as Brannon called them, in Mission Viejo this fall or next spring.
So far, the L.A. County district has shelled out about $255,000 for its pilot, while O.C. has spent around $160,000. It’s a relatively small portion of their annual budgets: L.A. at nearly $25 million and O.C. at $17 million. But the area they’re targeting is modest.
Mosquito control experts tout sterilization for being environmentally friendly because it doesn’t involve spraying chemicals, and it may have a longer-lasting effectiveness than pesticides. It can also be done now. Other methods involving genetically modified mosquitoes and ones infected with bacteria are stuck in an approval process that spans federal and state agencies. One technique, involving the bacteria Wolbachia was recently approved by the Environmental Protection Agency and is now heading to the California Department of Pesticide Regulation to review, said Jeremy Wittie, general manager for the Coachella Valley Mosquito and Vector Control District.
“Using pesticides or insecticides, resistance crops up very quickly,” said Nathan Grubaugh, associate professor of epidemiology at the Yale School of Public Health.
Vector control experts hope the fact that the sterilization technique doesn’t involve genetic modification will tamp down conspiracy theories that have cropped up around mosquito releases. One erroneous claim is that a Bill Gates-backed effort to release mosquitoes was tied to malaria cases in Florida and Texas. Reputable outlets debunked the conspiracy theory, pointing out that Gates’ foundation didn’t fund the Florida project and that the type of mosquito released (Aedes) does not transmit malaria.
To get ahead of concerns, districts carrying out the releases say they’ve engaged in extensive outreach and education campaigns. Residents’ desire to rid themselves of a scourge may overcome any anxieties.
“I think if you have the choice of getting eaten alive by ankle biters or having a DayGlo male X-rayed mosquito come by looking for a female to not have babies with, you’d probably go for the latter,” Brannon said. (“DayGlo” is a riff on the fluorescent pigment product of the same name — the sterilized mosquitoes were dusted with bright colors to help identify them.)
Sterilized male mosquitoes buzz around vector ecologist Jennifer Castellon as they are released in Rancho Cucamonga earlier this month.
(Myung J. Chun / Los Angeles Times)
Disease at our doorstep
As the climate warms and some regions become wetter, dengue is expanding to areas it’s never been seen before — and surging in areas where it’s established. Florida has seen alarming spikes in the viral infection in recent years, and Brazil and Puerto Rico are currently battling severe outbreaks. While most people infected with dengue have no symptoms, it can cause severe body aches and fever and, in rare cases, death. Its alias, “breakbone fever,” provides a grim glimpse into what it can feel like.
In October of last year, the city of Pasadena announced the Golden State’s first documented locally transmitted case of dengue, describing it as “extremely rare” in a news release. That same month, a second case was confirmed in Long Beach. Local transmission means the patient hadn’t traveled to a region where dengue is common; they may have been bitten by a mosquito carrying the disease in their own neighborhood.
Surging dengue abroad means there’s more opportunity for travelers to bring it home. However, Grubaugh said it doesn’t seem that California is imminently poised for a “Florida-like situation,” where there were nearly 1,000 cases in 2022, including 60 that were locally acquired. Southern California in particular lacks heavy rainfall that mosquitoes like, he said. But some vector experts believe more locally acquired cases are inevitable.
Ale Macias releases sterilized male mosquitoes in Upland this month.
(Myung J. Chun / Los Angeles Times)
Set them free
In mid-April, a caravan of staffers from the West Valley district traveled to five mosquito “hot spots” in Chino, Upland and Rancho Cucamonga — where data showed mosquito levels were particularly high — to release their first batches of sterilized male mosquitoes for the year. Peak Aedes season is months away, typically August to October in the district, and Birhanie said that’s the point. The goal is to force down the numbers to prevent an itchy tsunami later.
Males don’t bite, so the releases won’t lead to more inflamed welts. But residents might notice more insects in the air. Sterilized males released by West Valley will outnumber females in the wild by at least 100 to 1 to increase their chances of beating out unaltered males, spokeperson Reisinger said.
“They’re not going to be contributing to the biting pressure; they’re just going to be looking for love,” as Reisinger put it.
Eggs produced by a female after a romp with a sterile male don’t hatch. And female mosquitoes typically mate only once, meaning all her eggs are spoiled, so to speak. Vector experts say the process drives down the population over time.
Interestingly, the hot spots were fairly spread out across the district, indicative of the bloodsuckers’ widespread presence and adaptive nature. A picturesque foothills community in Upland was “especially interesting” because of its relatively high elevation, Birhanie said.
It was once inhabited primarily by another invasive mosquito that prefers colder, mountainous climates. Construction and deforestation in the area has literally paved the way for its humidity- and heat-loving brethren to move in.
Another neighborhood, in Rancho Cucamonga, posed a mystery. For the last two years, mosquito levels were consistently high. Door-to-door inspections, confoundingly, didn’t reveal the source.
“That’s one of the things about invasive Aedes mosquitoes — you can’t find them,” he said.
Next steps
Some vector control experts want to see a regional approach to sterile mosquito releases, similar to the state Medfly program.
Jason Farned, district manager for the San Gabriel Valley Mosquito and Vector Control District, believes a widespread effort “would be much more effective” and thinks that will come in time.
There are no talks underway to make it happen, and it’s not yet clear how it would work. Vector control agencies are set up to serve their local communities.
Fears of a bad mosquito year ahead are bubbling as the weather warms. Rain — which there was plenty of this spring — can quickly transform into real estate for mosquito reproduction.
When the swarms come, mosquito haters can take typical precautions: dump standing water and wear repellent. And they can root for the sterile males to get lucky.
Science
A retired teacher found some seahorses off Long Beach. Then he built a secret world for them
Rog Hanson emerges from the coastal waters, pulls a diving regulator out of his mouth and pushes a scuba mask down around his neck.
“Did you see her?” he says. “Did you see Bathsheba?”
On this quiet Wednesday morning, a paddle boarder glides silently through the surf off Long Beach. Two stick-legged whimbrels plunge their long curved beaks into the sand, hunting for crabs.
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But Hanson, 68, is enchanted by what lies hidden beneath the water. Today he took a visitor on a tour of the secret world he built from palm fronds and pine branches at the bottom of the bay: his very own seahorse city.
The visitor confirms that she did see Bathsheba, an 11-inch-long orange Pacific seahorse, and a grin spreads across Hanson’s broad face.
“Isn’t she beautiful?” he says. “She’s our supermodel.”
If you get Hanson talking about his seahorses, he’ll tell you exactly how many times he’s seen them (997), who is dating whom, and describe their personalities with intimate familiarity. Bathsheba is stoic, Daphne a runner. Deep Blue is chill.
He will also tell you that getting to know these strange, almost mythical beings has profoundly affected his life.
“I swear, it has made me a better human being,” he says. “On land I’m very C-minus, but underwater, I’m Mensa.”
Hanson is a retired schoolteacher, not a scientist, but experts say he probably has spent more time with Pacific seahorses, also known as Hippocampus ingens, than anyone on Earth.
“To my knowledge, he is the only person tracking ingens directly,” says Amanda Vincent, a professor at the University of British Columbia and director of the marine conservation group Project Seahorse. “Many people love seahorses, but Roger’s absorption with them is definitely distinctive. There’s a degree of warm obsession there, perhaps.”
Rog Hanson keeps watch over a small colony of Pacific seahorses.
(Carolyn Cole / Los Angeles Times)
Over the last three years, Hanson has made the two-hour trek from his home in Moreno Valley to the industrial shoreline of Long Beach to visit his “kids” about every five days. To avoid traffic, he often leaves at 2 a.m. and then sleeps in his car when he arrives.
He keeps three tanks of air and his scuba gear in the trunk of his 2009 Kia Rio. A toothbrush and a pair of pink leopard print reading glasses rest on the dash.
Hanson makes careful notes after all his dives in a colorful handmade log book he stores in a three-ring binder. On this Wednesday he dutifully records the water temperature (62 degrees), the length of the dive (58 minutes), the greatest depth (15 feet) and visibility (3 feet), as well as the precise location of each seahorse. His notes also include phase of the moon, the tidal currents and the strength of the UV rays.
“Scientists will tell you that sunlight is an important statistic to keep down,” he says.
He has given each of his four seahorses a unique logo that he draws with markers in his log book. Bathsheba’s is a purple star outlined in red, Daphne’s is a brown striped star in a yellow circle.
Rog Hanson makes careful notes after all his dives. He has given each of his four seahorses a unique logo.
(Carolyn Cole / Los Angeles Times)
He’s learned that the seahorses don’t like it when he hovers nearby for too long. Now he limits his interactions with them to 15 to 30 seconds at a time.
“At first I bugged them too much,” he says. “I was the paparazzi swimming around.”
Hanson traces the origins of his seahorse story back nearly two decades to the early morning of Dec. 30, 2000.
He was diving solo off Shaw’s Cove in Laguna Beach when a slow-moving giant emerged from the abyss. It was a gray whale whose 40-foot frame cast Hanson in shadow.
The whale could have killed him with a flick of its tail, Hanson says, but he felt no fear. The two made eye contact and, as Hanson tells it, he felt the whale’s gaze peering directly into his soul.
It was all over in 10 seconds, but Hanson was altered. He had always wanted to live at the beach, but after this encounter, he vowed to make it happen. It took years —15, in fact — but he finally got a job as a special education teacher in the Long Beach public school system. He bought a van and parked it on Ocean Boulevard. He lived at the beach and dived every day for 3½ months before moving to Moreno Valley.
To amuse himself while he lived at the beach, he built an underwater city he called Littleville out of discarded toys he found at the bottom of the bay.
Hanson saw his first seahorse in January 2016 while checking on Littleville. It was bright orange, just 4.5 inches long, and Hanson, who had logged over a thousand dives in the area, knew it didn’t belong there.
Daphne is one of the seahorses that Rog Hanson is studying in Alamitos Bay.
(Carolyn Cole / Los Angeles Times)
The range of the Pacific seahorse is generally thought to extend from Peru to as far north as San Diego. This seahorse ended up about 100 miles north of that.
Scientists said the seahorse and others that joined her had probably ridden an unusual pulse of warm water up the coast, along with other animals generally found in southern waters.
“We were getting a lot of weird sightings in the fall of 2015,” says Sandy Trautwein, vice president of husbandry at the Aquarium of the Pacific. “There was a yellow-bellied sea snake, bluefin tuna, marlin, whale sharks — a lot of animals associated with warm water.”
Most of these animals eventually left after ocean temperatures returned to normal, but Hanson’s seahorses stayed.
That may be because Hanson had built them a home.
It happened like this: In June 2016 he watched in horror as more than 100 high school football players splashed in the shallow waters, right where his seahorses usually hung out.
“I thought, I gotta do something, I gotta do something,” he says.
“On land I’m very C-minus, but underwater, I’m Mensa.”
— Rog Hanson
Then he remembered that, back in the Midwest where he grew up, he used to help the city park service make “fish cribs.” In early spring they would use brush and twigs to build what looked like a miniature log cabin with no roof on an ice-covered lake. When the ice melted, the cribs would fall to the bottom, creating a habitat for fish and other animals.
“So I said to myself, build them a city that’s deeper, where feet can’t get to it even at low tide,” Hanson says.
And he did.
By July 2016 two pairs of seahorses had moved into the new habitat. Daphne, the runner, was named after the nymph from Greek mythology who flees Apollo, Kenny’s name came from the proprietor of a local kayaking company. “Bathsheba” was inspired by a Bible story, and her mate, Deep Blue, named after a dive shop that has helped sponsor Hanson’s work since he launched his seahorse study.
He’s seen Kenny’s and Deep Blue’s bellies swell with pregnancy and noted how their partners check in on them daily, frequently standing sentinel nearby. He’s visited the fish at odd hours to see how their behavior changes from morning to night. And he mourned when Kenny disappeared in January. He still hasn’t come back. (A new member, CD Street, arrived June 29.)
“It feels like I’m reading a book, the book of their life, and I can’t put it down,” he says.
He’s also reached out to seahorse scientists across the globe to compare notes. “I won’t say I know the most about seahorses in the world, but I know the people who do,” he says.
Amanda Vincent, the director of Project Seahorse, says that seahorses spark an emotional reaction in almost everyone.
Daphne is one of the seahorses that Rog Hanson is studying in Alamitos Bay. Hanson and Ashley Arnold keep watch over a small colony of Pacific seahorses.
(Carolyn Cole / Los Angeles Times)
“Remember those books with three flaps where you can mix the head of a giraffe with the body of a snake and the tail of a monkey? That’s what we’ve got here,” she says. “They appeal to the sense of fancy and wonder in us.”
When Mark Showalter, a planetary astronomer at the SETI Institute, recently discovered a moon orbiting Neptune, he named it Hippocamp in part because of his love of seahorses.
“I’ve seen them in the wild and they are marvelously strange and interesting,” he says. “It’s a fish, but it doesn’t look anything like a fish.”
Pacific seahorses are among the largest members of the seahorse family. Males can grow up to 14 inches long, while females generally top out at about 11. They come in a variety of colors, including orange, maroon, brown and yellow. They are talented camouflagers that can alter the color of their exoskeleton to blend into their environment.
“I won’t say I know the most about seahorses in the world, but I know the people who do.”
But perhaps their most distinguishing characteristic is that they are the only known species in the animal kingdom to exhibit a true male pregnancy. Females deposit up to 1,500 eggs in the male’s pouch. The males incubate the eggs, providing nutrition and oxygen for the growing embryos. When the larval seahorses are ready to be released, he goes into labor — scientists call it “jackknifing” — pushing his trunk toward his tail.
After three years of observation, Hanson has collected new evidence about seahorse mating practices. His research suggests that although most seahorses are monogamous, a female will mate with two males if there are no other female seahorses around.
He also found that males, who are in an almost constant state of pregnancy, tend to stick to an area about the size of a king-size mattress, while the females roam up to 150 feet from their home during a typical day.
Eventually, he may be able to help scientists answer another long-standing question: What is the lifespan of Pacific seahorses in the wild? Some researchers say about five years; others think it could be up to 12.
“It will be interesting to see what Roger finds out,” Vincent says.
In June 2017, about one year after Hanson began formally tracking the seahorses, he took on a partner: a young scuba instructor named Ashley Arnold.
Arnold, who has short red hair and a jocular vibe, is a former Army staff sergeant who served in Iraq and Afghanistan. She learned to dive as part of a program the Salt Lake City Veterans Affairs hospital offered to female veterans suffering from post-traumatic stress disorder and military sexual trauma. Arnold suffered from both. Diving became her salvation.
Dive instructor Ashley Arnold is a former Army staff sergeant who says that diving at least twice a week helps her deal with PTSD and MST.
(Carolyn Cole / Los Angeles Times)
“All the irritation on the surface disappears when you go under the water,” she says. “It’s like, ‘What was I concerned about?’ You forget about everything else. Nothing else matters.”
She used her GI Bill to pay for a scuba instructor course and to set up her own business. Now, she finds that if she dives at least twice a week and has a dog, she does not need to take medication.
“All the irritation on the surface disappears when you go under the water.”
— Ashley Arnold
“That’s a pretty big statement in my opinion,” she says.
Arnold and Hanson met in June 2016 on a dive trip to Catalina. Hanson mentioned his seahorses. Arnold was intrigued, but still lived in Salt Lake City.
One year later, Arnold moved to Huntington Beach and gave Hanson a call.
“I said, ‘Hey Roger, let’s chat. Any chance I could join you at the seahorses you talked about?’” she says. “And he decided I was acceptable.”
Now, Arnold and her boyfriend, Jake Fitzgerald, check in on the seahorses about once a week and help Roger rebuild the city he created for them.
Rog Hanson, 68, teamed up with dive instructor Ashley Arnold two years ago to keep watch over a small colony of Pacific seahorses.
(Carolyn Cole / Los Angeles Times)
“We call them our kids because we love them so much,” Arnold says.
Hanson and Arnold are very protective of their seahorse family. They tell visitors to remove GPS tags from their photos. They swear them to secrecy.
There is little chance anyone would find Hanson’s seahorses without a guide. Also, diving in these waters off Long Beach can be a challenge.
The water is shallow. It’s hard to get your buoyancy right. A misplaced flipper kick can stir up blinding sand and silt.
But if Hanson wants to show you his underwater world, nothing will stop him. He will hold you firmly by the hand and guide you down to the forest he built at the bottom of the bay.
Ashley Arnold, right, gets rinsed off with a hose by Rog Hanson after a dive Alamitos Bay.
(Carolyn Cole / Los Angeles Times)
He will use a plastic tent stake, jabbing it into the bottom to propel himself — and you holding on — across the ocean floor. When he spots a seahorse he will use the stake as a pointer. Through the murky water you strain to see. Then it appears.
Orange and rigid. Thin snout. Bony plates. Stripes down the torso. Totally still.
And if you’ve never seen a seahorse in the wild before, you will feel honored and awed, as if you’ve just seen a unicorn beneath the sea.
Science
California’s summer COVID wave shows signs of waning. What are the numbers in your community?
There are some encouraging signs that California’s summer COVID wave might be leveling off.
That’s not to say the seasonal spike is in the rearview mirror just yet, however. Coronavirus levels in California’s wastewater remain “very high,” according to the U.S. Centers for Disease Control and Prevention, as they are in much of the country.
But while some COVID indicators are rising in the Golden State, others are starting to fall — a hint that the summer wave may soon start to decline.
Statewide, the rate at which coronavirus lab tests are coming back positive was 11.72% for the week that ended Sept. 6, the highest so far this season, and up from 10.8% the prior week. Still, viral levels in wastewater are significantly lower than during last summer’s peak.
The latest COVID hospital admission rate was 3.9 hospitalizations for every 100,000 residents. That’s a slight decline from 4.14 the prior week. Overall, COVID hospitalizations remain low statewide, particularly compared with earlier surges.
The number of newly admitted COVID hospital patients has declined slightly in Los Angeles County and Santa Clara County, but ticked up slightly up in Orange County. In San Francisco, some doctors believe the summer COVID wave is cresting.
“There are a few more people in the hospitals, but I think it’s less than last summer,” said Dr. Peter Chin-Hong, a UC San Francisco infectious diseases expert. “I feel like we are at a plateau.”
Those who are being hospitalized tend to be older people who didn’t get immunized against COVID within the last year, Chin-Hong said, and some have a secondary infection known as superimposed bacterial pneumonia.
Los Angeles County
In L.A. County, there are hints that COVID activity is either peaking or starting to decline. Viral levels in local wastewater are still rising, but the test positivity rate is declining.
For the week that ended Sept. 6, 12.2% of wastewater samples tested for COVID in the county were positive, down from 15.9% the prior week.
“Many indicators of COVID-19 activity in L.A. County declined in this week’s data,” the L.A. County Department of Public Health told The Times on Friday. “While it’s too early to know if we have passed the summer peak of COVID-19 activity this season, this suggests community transmission is slowing.”
Orange County
In Orange County, “we appear to be in the middle of a wave right now,” said Dr. Christopher Zimmerman, deputy medical director of the county’s Communicable Disease Control Division.
The test positivity rate has plateaued in recent weeks — it was 15.3% for the week that ended Sept. 6, up from 12.9% the prior week, but down from 17.9% the week before that.
COVID is still prompting people to seek urgent medical care, however. Countywide, 2.9% of emergency room visits were for COVID-like illness for the week that ended Sept. 6, the highest level this year, and up from 2.6% for the week that ended Aug. 30.
San Diego County
For the week that ended Sept. 6, 14.1% of coronavirus lab tests in San Diego County were positive for infection. That’s down from 15.5% the prior week, and 16.1% for the week that ended Aug. 23.
Ventura County
COVID is also still sending people to the emergency room in Ventura County. Countywide, 1.73% of ER patients for the week that ended Sept. 12 were there to seek treatment for COVID, up from 1.46% the prior week.
San Francisco
In San Francisco, the test positivity rate was 7.5% for the week that ended Sept. 7, down from 8.4% for the week that ended Aug. 31.
“COVID-19 activity in San Francisco remains elevated, but not as high as the previous summer’s peaks,” the local Department of Public Health said.
Silicon Valley
In Santa Clara County, the coronavirus remains at a “high” level in the sewershed of San José and Palo Alto.
Roughly 1.3% of ER visits for the week that ended Sunday were attributed to COVID in Santa Clara County, down from the prior week’s figure of 2%.
Science
Early adopters of ‘zone zero’ fared better in L.A. County fires, insurance-backed investigation finds
As the Eaton and Palisades fires rapidly jumped between tightly packed houses, the proactive steps some residents took to retrofit their homes with fire-resistant building materials and to clear flammable brush became a significant indicator of a home’s fate.
Early adopters who cleared vegetation and flammable materials within the first five feet of their houses’ walls — in line with draft rules for the state’s hotly debated “zone zero” regulations — fared better than those who didn’t, an on-the-ground investigation from the Insurance Institute for Business and Home Safety published Wednesday found.
Over a week in January, while the fires were still burning, the insurance team inspected more than 250 damaged, destroyed and unscathed homes in Altadena and Pacific Palisades.
On properties where the majority of zone zero land was covered in vegetation and flammable materials, the fires destroyed 27% of homes; On properties with less than a quarter of zone zero covered, only 9% were destroyed.
The Insurance Institute for Business and Home Safety, an independent research nonprofit funded by the insurance industry, performed similar investigations for Colorado’s 2012 Waldo Canyon fire, Hawaii’s 2023 Lahaina fire and California’s Tubbs, Camp and Woolsey fires of 2017 and 2018.
While a handful of recent studies have found homes with sparse vegetation in zone zero were more likely to survive fires, skeptics say it does not yet amount to a scientific consensus.
Travis Longcore, senior associate director and an adjunct professor at the UCLA Institute of the Environment and Sustainability, cautioned that the insurance nonprofit’s results are only exploratory: The team did not analyze whether other factors, such as the age of the homes, were influencing their zone zero analysis, and how the nonprofit characterizes zone zero for its report, he noted, does not exactly mirror California’s draft regulations.
Meanwhile, Michael Gollner, an associate professor of mechanical engineering at UC Berkeley who studies how wildfires destroy and damage homes, noted that the nonprofit’s sample does not perfectly represent the entire burn areas, since the group focused specifically on damaged properties and were constrained by the active firefight.
Nonetheless, the nonprofit’s findings help tie together growing evidence of zone zero’s effectiveness from tests in the lab — aimed at identifying the pathways fire can use to enter a home — with the real-world analyses of which measures protected homes in wildfires, Gollner said.
A recent study from Gollner looking at more than 47,000 structures in five major California fires (which did not include the Eaton and Palisades fires) found that of the properties that removed vegetation from zone zero, 37% survived, compared with 20% that did not.
Once a fire spills from the wildlands into an urban area, homes become the primary fuel. When a home catches fire, it increases the chance nearby homes burn, too. That is especially true when homes are tightly packed.
When looking at California Department of Forestry and Fire Protection data for the entirety of the two fires, the insurance team found that “hardened” homes in Altadena and the Palisades that had noncombustable roofs, fire-resistant siding, double-pane windows and closed eaves survived undamaged at least 66% of the time, if they were at least 20 feet away from other structures.
But when the distance was less than 10 feet, only 45% of the hardened homes escaped with no damage.
“The spacing between structures, it’s the most definitive way to differentiate what survives and what doesn’t,” said Roy Wright, president and chief executive of the Insurance Institute for Business and Home Safety. At the same time, said Wright, “it’s not feasible to change that.”
Looking at steps that residents are more likely to be able to take, the insurance nonprofit found that the best approach is for homeowners to apply however many home hardening and defensible space measures that they can. Each one can shave a few percentage points off the risk of a home burning, and combined, the effect can be significant.
As for zone zero, the insurance team found a number of examples of how vegetation and flammable materials near a home could aid the destruction of a property.
At one home, embers appeared to have ignited some hedges a few feet away from the structure. That heat was enough to shatter a single pane window, creating the perfect opportunity for embers to enter and burn the house from the inside out. It miraculously survived.
At others, embers from the blazes landed on trash and recycling bins close to the houses, sometimes burning holes through the plastic lids and igniting the material inside. In one instance, the fire in the bin spread to a nearby garage door, but the house was spared.
Wooden decks and fences were also common accomplices that helped embers ignite a structure.
California’s current zone zero draft regulations take some of those risks into account. They prohibit wooden fences within the first five feet of a home; the state’s zone zero committee is also considering whether to prohibit virtually all vegetation in the zone or to just limit it (regardless, well-maintained trees are allowed).
On the other hand, the draft regulations do not prohibit keeping trash bins in the zone, which the committee determined would be difficult to enforce. They also do not mandate homeowners replace wooden decks.
The controversy around the draft regulations center around the proposal to remove virtually all healthy vegetation, including shrubs and grasses, from the zone.
Critics argue that, given the financial burden zone zero would place on homeowners, the state should instead focus on measures with lower costs and a significant proven benefit.
“A focus on vegetation is misguided,” said David Lefkowith, president of the Mandeville Canyon Assn.
At its most recent zone zero meeting, the Board of Forestry and Fire Protection directed staff to further research the draft regulations’ affordability.
“As the Board and subcommittee consider which set of options best balance safety, urgency, and public feasibility, we are also shifting our focus to implementation and looking to state leaders to identify resources for delivering on this first-in-the-nation regulation,” Tony Andersen, executive officer of the board, said in a statement. “The need is urgent, but we also want to invest the time necessary to get this right.”
Home hardening and defensible space are just two of many strategies used to protect lives and property. The insurance team suspects that many of the close calls they studied in the field — homes that almost burned but didn’t — ultimately survived thanks to firefighters who stepped in. Wildfire experts also recommend programs to prevent ignitions in the first place and to manage wildlands to prevent intense spread of a fire that does ignite.
For Wright, the report is a reminder of the importance of community. The fate of any individual home is tied to that of those nearby — it takes a whole neighborhood hardening their homes and maintaining their lawns to reach herd immunity protection against fire’s contagious spread.
“When there is collective action, it changes the outcomes,” Wright said. “Wildfire is insidious. It doesn’t stop at the fence line.”
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