On the south-eastern corner of Santa Rosa Island lies a grove of a few thousand Torrey pine trees, some of them more than 250 years old. The only other place on earth where these gnarled pines exist is in San Diego county, but biologists classify the two groves as different subspecies. So when a rare wildfire broke out on Santa Rosa Island late last week, firefighters raced to keep it from spreading into the grove, where it threatened to consign the island’s Torrey pines to extinction.

So far, they appear to be succeeding – even as the 18,000-acre fire has torched nearly one-third of the island’s surface. But biologists who have studied Santa Rosa Island’s unique ecology are watching anxiously as the fire continues to burn a part of the island that is home to six plants found nowhere else on the planet.

“We’re all watching this with a little bit of trepidation,” said Dr Heather Schneider, Santa Barbara Botanic Garden’s director of research and conservation.“Are these plants going to recover on their own?”

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Biologists widely view Channel Islands national park as a unique success story, where rare native plants made a resounding comeback in recent decades after more than a century of pummeling by non-native livestock and imported wild game animals. Today, the Channel Islands are home to dozens of “endemic” plants – species that grow only there. Six of them, including the Torrey pines, grow on Santa Rosa Island alone. Ten per cent of the island’s plants are considered rare, according to Schneider.

The Santa Rosa Island fire is threatening that comeback. Wildfires rarely occur on the Channel Islands, raising questions among conservationists about whether the rare species found there have the evolutionary adaptations needed to withstand a severe burn.

The threat to species found nowhere else on earth

Santa Rosa Island’s Torrey pine grove has attracted the most attention. But the fire threatens all six of the island’s endemics.

Steve Junak, a biologist who has studied the Channel Island’s flora for nearly four decades, found reasons to remain hopeful about the future of some of the plants. The Santa Rosa Island manzanita belongs to a genus of plants that tends to thrive after fires. The Santa Rosa Island live-forever grows in open areas with sparse vegetation, while the Hoffman’s slender-flowered gilia is found in sandy areas – habitats that offer less fuel to sustain wildfires.

But Junak worries about the Torrey pine grove and the East Point dwarf dudleya, a succulent whose range has already been torched by the fire.

“Their response to fire is not known at all,” Junak said of the dudleya. “They’re only found on a very small area just on the east end of Santa Rosa Island, where this fire has been concentrated. I hope they survive this event.”

It’s also unclear how fire will impact the soft-leaved Indian paintbrush, a yellowflowering herb. The federally endangered plant’s range, however, extends to the north of the island, which has yet to burn.

A rare island fire

Wildfires historically occurred on the Channel Islands only after a rare lightning strike. The one currently raging on Santa Rosa Island appears to be human-caused.

A 67-year-old sailor crashed his boat into the rocks on the island’s shore last week, according to the US Coast Guard. The man fired at least two flares in order to catch the attention of passing vessels, prompting speculation that the shots first set the blaze. Coast Guard officers rescued the man, who did not appear to suffer any injuries.

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Footage obtained by SFGate, however, showed a burning sailboat on the shore of Santa Rosa Island – presumably the same boat crashed by the marooned sailor. It was unclear whether the boat exploded on its own or the sailor set fire to it.

Authorities are “aware of the multimedia related to this incident, and the fire remains under investigation”, Sierra Frisbie, a fire information officer assigned to the Santa Rosa Island fire, said in an email.

A helping hand

Drone footage captured this week appeared to show that firefighters have so far managed to shield the Torrey pine grove from the worst of the damage.

“Initial video from the area offers cautious optimism because some green canopy remains visible,” Frisbie wrote. “However, scientists say it is still too early to determine the long-term survival of many trees. Delayed mortality can occur months or even years later, especially in species that are not well adapted to wildfire.”

Biologists will have to wait until the fire is controlled to learn the full scope of the damage to the rest of the island’s rare flora. That damage may have consequences that will take time to understand, Junak said.

“When we think about the effects of this fire on the special plants on the island, we need to consider how the endemic insects and animals that interact with them are being affected,” Junak wrote in an email. “The island’s plants provide nectar, pollen, food, and shelter for them.”

“Another adverse effect of this fire will be the damage caused to the soil crusts that cover the ground around some of these plants,” Junak added. “These soil crusts – composed of lichens, algae, mosses, and liverworts – reduce the spread of invasive, non-native plants, and also reduce soil erosion, especially in heavy rainfall years.”

If the fire does wreck a cataclysmic impact on Santa Rosa Island’s rare plants, the Santa Barbara Botanic Garden may be able to help. The institution has spent several decades building a seedbank that biologists can use to help restore the lost plants, including a conservation grove of 40 Torrey pines.

“This is why we do what we do,” Schneider said. “There’s always the hope that nature will recover on its own. But if it doesn’t, we have been gathering the seeds we need to help.”