But it was a wildfire four years ago that posed the greatest risk to Simpson's home. The 2018 Klamathon Fire burned uncontained for 16 days, sending giant flames toward Simpson's property.
"The fire just came right up over that ridge," Simpson tells NPR during a visit to his property. "[It] burned all the trees and destroyed all that conifer forest up there."
Yet Simpson's land and much of the local community remained safe. He credits the community's Wild Horse Fire Brigade.
"It started getting into the area where our local herd of wild horses had reduced the fuel...large areas that were grazed open became safe zones for Cal Fire personnel and equipment that were stationed in front of the fire," Simpson says. "These horses helped mitigate the Klamathon Fire."
This local herd is the collective poster child for Simpson's proposal to re-wild horses rounded up by the Bureau of Land Management (BLM) and placed in government holding facilities.
The Wild and Free-Roaming Horses and Burros Act
The BLM is charged with managing the nation's wild horses under the Wild and Free-Roaming Horses and Burros Act of 1971. Congress passed it to protect America's wild horses and burros that had been hunted to near extinction. Whenever the BLM determines there are too many horses in a given area, it can order helicopter roundups.
But the roundup is controversial. BLM helicopters sometimes swoop down above frightened wild horses, chasing them, sometimes for miles, until they're funneled into traps on the range.
"After this marathon of terror, they're then put into the corrals and these animals have never been in any kind of confinement," says Kelsey Stangebye, a lawyer who in 2017 authored a law review article critical of the BLM's roundup practices and management program.
Once trapped, the horses can panic. Videos show them striking out at fencing and at other horses as they try to escape.
"They're all piled in there together and they're fighting the fence lines; they're jumping the fence lines," Stangebye says. "It's dramatic, visually, horrific for the animal." Horses get injured, some fatally.
The BLM calls the situation unfortunate and says those numbers are small and unavoidable. The agency then ships the captured horses to BLM holding facilities. Some get new homes through the agency's adoption program.
However, some of those horses turn up in auction houses frequented by kill buyers who send them to slaughter. Thousands of others live out their lives in BLM holding facilities. As of May 2022, BLM statistics show they held 58,314 horses in captivity at a cost of about $90 million for the year for feed and care and nearly $50 million more to conduct the roundups and operate the program.
Simpson says holding wild horses captive makes no sense, especially with today's hotter-burning megafires now killing off entire swaths of forest and incinerating towns.
"Keeping wild horses out of the wilderness and in confinement is like putting the fire department in jail during fire season," he says.
The Horses and the Environment
Simpson lives on the edge of the Soda Mountain Wilderness area with his partner Michelle Gough. This is arid country, where clumps of juniper, oak, pine and fir trees dot the land that's home to about 90 free-roaming horses. In the middle of it, at the top of a steep dirt driveway overlooking a large reservoir, sits Simpson's cabin.
He describes the vista, first pointing west toward Six Rivers National Forest.
"If we look to the south, you can see the top of Mt. Shasta right there," Simpson says, gesturing at the 14,179-foot-high peak of the volcano . "Then to the North we have Oregon just two miles away."
Simpson lives among and studies these horses, a herd made up of about 20 family bands, using an embedded observation method similar to primatologist Jane Goodall's study of chimpanzees in Africa. Simpson is completely familiar with all his study subjects - their personalities and their all-important status within the herd.
"Hey, Baby, you going to come over and see us?" he says to a yearling that watches as we move our interview into a pasture below the cabin where the horses often congregate.
"This guy down here," Simpson says pointing to a beefy white horse standing a few yards away. "That's a stallion. We named him Mystic."
He then motions toward a chestnut-colored horse. "Here comes Candyman, who thinks he's a tough boy."
"This morning they were way up there by those rocks grazing," he said pointing to the mountains above. "From here they can be in Oregon in an hour."
The horses tread lightly in this environment, Simpson says. They use the same game trails deer and elk created, trimming flammable grass and brush along the way — about five-and-a-half tons of it, per horse, per year.
Today, that grazing happens largely on mixed-use public range lands - alongside livestock operations where ranchers and others have hunted out the predators to protect their animals. Without mountain lions, bears and wolves, wild horse herds grow unchecked. That leads to resource competition with cattle and resource depletion on the ranges, which can trigger roundups.
Natural Wildfire Abatement and Forest Protection Plan
Simpson says his proposal, called the Natural Wildfire Abatement and Forest Protection Plan, would help fix that problem. It calls for rewilding and humanely relocating intact families of wild horses away from areas of contention with livestock and other land users and placing them instead onto some of the nation's 110 million acres of designated wilderness.
"These are highly protected areas that contain endangered and threatened flora and co-evolved fauna and are at great risk and are burning right now - catastrophically," Simpson says. "Putting horses in there helps to protect those trees and those ecosystems."
Among the advantages of grazing horses in wilderness areas, Simpson says, is their ability to reseed plants, including native and endangered species. Unlike non-native cows and other ruminants that thoroughly digest their food, horses pass live, whole seeds through their droppings.
Simpson picks up a piece of dry horse manure and breaks it in half.
"You can see they're like little compost balls with seeds in it. This is a product of millions of years of coevolution with the local flora," he says.
The manure provides a rich microbiome full of nutrients that protects the seeds.
"So, when this gets wet, it's like a little potted plant," he says. "It just starts growing and it had actually a significant survival advantage over other native seeds on the landscape."
The horses also help fireproof the trees they use for cover by trimming tree limbs five to six feet above the ground, the same amount of vertical clearance fire officials recommend to homeowners who want to protect their properties.
"They hang around these trees...and they scratch and then they break off the limbs. You can see that one down there a lot of limbs are busted off," Simpson says, pointing to a nearby Juniper shading some of the horses.
In a majority of western fires, grass and brush and forest understory are key fuels that allow flames to climb from the forest floor into fragile tree canopies. Once there, they can rapidly spread, killing trees and destroying entire swaths of forest.
But where animals trim these fuels, fire burns low and slow. Deer help make that happen but habitat loss, disease and other factors have in recent years pummeled western deer populations. Wildlife data from California show their numbers down by 80 percent since the 1960s.
"Those deer were grazing three million tons of annual grass and brush," Simpson says. "That's a lot of fire fuel."
He calls catastrophic fire in North America a "brand-new paradigm since we lost large body herbivores that control grass and brush."
A paradigm made worse by warmer temperatures, lower humidity and drier brush.
For wild horses to help fill the grazing void left by the depleted deer population requires their relocation – and in the case of captive horses, their rewilding – into remote wilderness areas most threatened by destructive wildfires.
Simpson says the ideal areas are too rugged for ranchers to run cattle, which studies show extract a heavy toll on the lands they graze. That's partly because of their propensity to stay in one area and graze it thoroughly. Free-roaming horses move constantly as they graze, logging as many as 10 to 20 miles a day. "Predators are the key driver in this movement," Simpson wrote in his study.
Cows also affect the soil far differently than horses, due to a distinctly different hoof anatomy.
Both animals weigh about the same, but a cow has a much smaller, double-toe hoof, Simpson explains. In wet and riparian areas especially, cow hooves sink into the soil like a stiletto heel on a soft lawn. Horses' hooves are comparatively wide and rounded, which distributes the animal's weight over a larger area, limiting hoof penetration and soil damage.
Simpson's study contains photographs that catalog these and other aspects of horse life in the wild – including death by predators.
"Not many babies survive out here," he says. "Packs of coyotes will take them. And the lions and bears will take the [old and sick] adults. We don't see the herd growth that they see on BLM lands."
Documenting these losses are the toughest part of his work, he says. But at the same time, he understands it's nature's way of culling herd numbers and preserving genetic vigor in a way artificial birth control can't do.
"We've got all these horses held off range at great cost – basically warehousing and feeding these horses — when all we need to do is locate them in the wilderness...where they evolved and where they have their co-evolved predators," Simpson says. "And suddenly, we change the whole wildfire regime."
Instead of costing taxpayers, he says each horse would provide $72,000 of grass-and-brush-clearing-work over its lifetime. Simpson bases that on the cost of prescriptive burns or hand-clearing the same amount of fuel a wild horse eats over its average 15-year lifespan.
What's more, if fewer or less destructive fires result, he says, that value goes way up. The Klamathon Fire was among 8,500 fires that burned through California in 2018, causing nearly $150 billion in economic losses, according to researchers at the University of California, Irvine.
"If we affected that just by 2 or 3 percent," he says, "we're talking hundreds of millions of dollars in additional savings on top of the $72,000."
The BLM doesn't share Simpson's enthusiasm.
In an email to NPR, the agency says it has concerns about horses in wilderness areas. Among them: that despite the existence of predators, re-wilded horses in wilderness areas nevertheless might overpopulate and cause harm to the ecosystem.
Still, Simpson's plan — which is based on federal law that allows for the humane transfer of captured wild horses to government agencies for use as work horses — is gaining traction among fire-weary elected officials on both sides of the California-Oregon border.
Some scientists, too, are intrigued. Julie Murphree is an Arizona State University professor of wildlife management and biological ethics.
"To me that seems like a win-win solution," says Murphree, who studies wild horses and now volunteers as a board member for Simpson's non-profit Wild Horse Fire Brigade organization.
Murphree points to fossil evidence, anthropological evidence and new DNA sequencing that links the modern horse to those that originated in North America about 1.7 million years ago.
"We now know horses have evolved on the North American continent," she says. "They should be considered native."
Simpson says there's a growing body of evidence that contradicts those who claim the horse is an invasive species harmful to the land.
Murphree agrees and says the evidence further supports the notion that wild horses would prove ecologically symbiotic in wilderness areas and thus well-suited to provide grass and brush abatement in these rugged regions of the West. Yet she also acknowledges unintended consequences can happen even when a species is reintroduced onto lands it once roamed.
For instance, Murphree says, wild horses in the wilderness might attract more mountain lions that might go after more of that depleted deer population.
"So, there is a concern there," she says, adding there's also a way to mediate those concerns.
In the wildlife conservation field, she says, scientists often employ an "adaptive management strategy," which relies on rigorous monitoring and real-time adjustments in the field.
With such safeguards in place, Murphree says, she supports William Simpson's push for a pilot program to test whether America's wild horses can provide part of a much-needed wildfire solution in the American West.