A NASA research scientist analyzing satellite images of the earth’s surface has detected a marked increase in wildfire fuel across former ranchlands at the Point Reyes National Seashore, offering the first quantitative evidence of how quickly the landscape is changing after cattle were removed from most of the peninsula.
Christopher Potter, an earth scientist at NASA’s Ames Research Center, found that dense vegetation—the readiest combustible fuel for wildfires—was, on average, 62 percent greater in March 2026 compared to the same month in 2024, when cattle were still grazing the land. In some pastures, the increase reached 150 percent.
“Without cattle, you’re going to have an encroachment of burnable fuels very rapidly,” Dr. Potter told the Light. “When you take most of the ranches out, things are going to change quickly, and that’s what we’re seeing now.”
The findings arrive as large swathes of Point Reyes undergo one of the most sweeping land-use transformations in the park’s history. Following a 2025 settlement brokered by the Nature Conservancy, 12 of the park’s 14 ranches have shut down operations on more than 17,000 acres of open grassland.
The National Park Service has entered into a long-term cooperative agreement with the Nature Conservancy to manage the former ranchlands, replacing the roughly 4,700 cattle that once grazed there with a conservation grazing regime expected to average about 600 animals.
The future of that footprint, however, is far from settled. As the Light reported last month, officials in the Trump administration’s Interior Department are exploring whether to restore livestock levels closer to those in place before the buyouts.
Together, NASA’s satellite data and the park’s own planning documents point to a growing mismatch between the pace of ecological change on the ground and the government’s effort to manage it. Left ungrazed, grasslands can give way to scrub and eventually to timber, building heavier fuel loads and increasing the risk of more intense fires.
Grazing has long functioned as a primary tool for reducing fire fuels, yet a comprehensive replacement plan for the vacated lands has yet to be seen, even as vegetation accumulates across thousands of acres.
The park service did not respond to questions about wildfire risk on the vacated ranchlands.
The NASA satellite data comes amid record warm winter temperatures in California that have heightened concern about a blazing wildfire season. Northern California is expected to face an above-normal wildfire threat this summer, according to the National Interagency Coordination Center, the federal agency that coordinates wildland firefighting resources.
To track vegetation changes across the park, Dr. Potter analyzed imagery from Landsat 8, a joint NASA and United States Geological Survey satellite that has monitored the earth’s surface for decades. Every two weeks, it passes over the Point Reyes peninsula, capturing images in wavelengths of light invisible to the human eye.
By comparing two of those wavelengths—red light, which plants absorb, and near-infrared light, which plants reflect—scientists calculate what is known as the Normalized Difference Vegetation Index, or N.D.V.I., a standard measure of how much live green vegetation is present in any given location. Widely used by federal land agencies, the index allows researchers to track shifts across large landscapes over time, including the effects of wildfire, climate change, urbanization and deforestation.
The results suggest not only more vegetation growth, but a shift in its seasonal pattern. “With the ranches, what we saw was that the fuel load went up in the winter and then was grazed right back down during the summer,” Dr. Potter said. “The satellite imagery clearly shows there is a year-round presence of fuel to burn.”
Wildfire requires both a spark and fuel. The spark can come from lightning, power lines, campfires, cigarettes, cars or arson. An abundance of dried fuel acts as kindling.
Fire ecologists have long understood that grasslands and scrublands—like those that dominate the former ranch areas—play a central role in wildfire spread. Research by the University of Wisconsin-Madison and the U.S. Forest Service has found that grassland and scrubland fires burn more land and destroy more homes across the United States than do forest fires.
Although forests tend to burn more intensely because of heavier fuel loads, grass fires can move more rapidly across a landscape when wind picks up, giving communities less time to respond, said Mark Brown, executive director of the Marin Wildfire Prevention Authority.
“Without cattle grazing, the immediate concern is increased grass crops,” he said. “And eventually there will be a transition from grass to brush, and eventually from brush to timber.”
The connection between grazing and reduced fire risk at Point Reyes has been documented for decades in the park’s planning records. A 2006 operational strategy amendment to the seashore’s 2004 fire management plan identified grazing as a fuel-reduction tool and noted that in several areas in the Olema Valley where cattle had been removed, Douglas firs were already encroaching into open grasslands.
A 2020 environmental impact statement prepared as part of the update to the seashore’s general management plan warned that without grazing, coastal prairie could convert to coyote brush-dominated scrub within 15 to 25 years. That transition, the document found, would “substantially increase vegetative fuels and the probability of large, intense wildfires.” It cited research showing that coyote brush shrubland carries more than 12 times the biomass of grassland.
The park’s prescribed burn program has conducted few burns in recent years, though its 2004 fire management plan set a target of up to 3,500 acres burned annually.
The 2020 environmental impact statement envisioned prescribed burns for some parts of the park but noted that they were not planned for ranchlands because “the existing grazing regime reduces fire risk in those areas.”
The park updated its fire management plan last June, but it only shared pieces of it publicly after concerned residents inquired about it. The plan acknowledged the ranch closures but said that a multi-year fuels treatment plan for the affected lands was still in development. The fuels plan will outline which areas will be treated, by what methods and on what timeline.
Most of the former ranchlands fall within what is designated a “minimum management” zone, a 68,455-acre section of the 71,046-acre national seashore where prescribed fire is not currently used, and where mechanical treatment is largely limited to clearing vegetation near roads and buildings. That designation has not changed, even as land use on the peninsula has shifted dramatically.
“In the 2004 fire plan, while there was still all of that grazing, the park service said there was a moderate fire risk,” said Judy Teichman, a Point Reyes Station resident who has raised concerns about fire risk in the park for years. “So what happens when there is little to no grazing?”
The park service anticipates that tule elk, now free to roam the former ranchlands, will help maintain grassland habitats as their population expands.
Yet Dr. Potter said evidence from Tomales Point, where a herd has grazed for decades, suggests that won’t be enough.
“Did they ever keep the fuels down up at Tomales Point? No, never,” he said. “Even when the herd was packed into small areas, the area still had one of the highest fuel loads on the peninsula. There’s no scientific basis for the idea that elk can control this.”
The Marin County Fire Department, which serves as the primary response agency for the seashore, does not expect the change in land use to significantly alter how it responds to fires on the peninsula.
The most destructive “fires historically on the seashore have been in heavier
fuels—timber and dense brush—rather than grasses,” Fire Chief Jason Weber said.
Grassland fires, he added, are generally easier to contain. “Helicopters, air tankers, engines with hoses are very effective,” he said. “From a response standpoint, it’s really no change for us.”
Point Reyes has experienced two major fires in the past 30 years, both of which started in forested areas. The 1995 Mount Vision fire, begun by an unattended campfire, burned 12,354 acres in three days and destroyed 48 homes along the Inverness Ridge. The 2020 Woodward fire burned nearly 5,000 acres of park wilderness, ignited by an August lightning storm.
In West Marin, many homes occupy what is known as the wildland-urban interface, the places where housing and open spaces meet in an extremely flammable mix. Few residential neighborhoods border the former ranchlands directly, though some private inholdings and the Seahaven community lie nearby.
Fire behavior modeling included in the park’s newly updated fire management plan identified the wildland-urban interface along the ridge as an area of particular concern. Dense vegetation, narrow roads and limited defensible space combine to heighten the risk. Under severe weather conditions, the plan found, nearly a quarter of the park’s landscape has the potential to burn with very high or extreme intensity.
Chief Weber said prescribed burns would likely become an increasingly important tool in the park service’s wildfire strategy. “With this change in use, I know they are working on plans to use prescribed fire in the park more and we will certainly support them in that effort,” he said.
Before settlers began suppressing wildfire in the 19th century, the Coast Miwok had long used fire to manage the land and promote seed production. Prescribed burns, which clear away excess vegetation and reduce the risk of uncontrollable wildfire, are now increasingly used by land managers across the western states.
That history underscores a broader ecological point: grasslands cannot simply be left alone, said Maria Fernandez-Gimenez, a professor of rangeland ecology at Colorado State University.
“A healthy system is one that has an intact disturbance regime,” Dr. Fernandez-Gimenez said. “That could be grazing. It could be fire at appropriate return intervals. The biodiversity is highest with some level of moderate disturbance.”
Absent that, the system will eventually correct itself. “If we do nothing about it, nature will correct the situation,” Dr. Potter said. “In California, that correction is almost always a massive wildfire.”