While firefighters are "aggressively attacking" the fires to help suppress them, the blazes have the potential to affect the park's infrastructure and resources, the park's website said. Giant sequoias -- which can reach heights of 300 feet -- have already been hit hard by fires in the state in recent years: "Two-thirds of all giant sequoia grove acreage across the Sierra Nevada has burned in wildfires between 2015 and 2020," the National Park Service says. Sequoias that were killed during last year's Castle Fire could have ranged from hundreds to 3,000 years old, the service added.
In this Sunday, September 12 photo released by the KNP Complex Fire Incident Command, smoke plumes rise from the Paradise Fire in Sequoia National Park, California.
KNP Complex Fire Incident Command/AP
The park is being threatened by the KNP Complex Fire, which was started by lightning last week and comprises the Colony and Paradise Fires. It has burned nearly 6,000 acres within the park's footprint, according to the National Wildfire Coordination Group. Containment information for the blaze was not available.
The Paradise Fire raced out of control Monday night, crossing the Generals Highway and the middle fork of the Kaweah River, prompting evacuations of park employees.
All facilities and services in the Sequoia National Park, including campgrounds, visitor centers and park stores, are closed until the fire threat is diminished, the park said.
"Due to wildfire activity in the area, we are closing all trailheads that enter into Sequoia National Park to backpacking and day use hiking. All existing permit reservation holders will be issued a full refund," an alert on the park's website added. "Beginning September 12, backpackers will not be able to get overnight wilderness permits that start from the Mineral King Valley, Lodgepole or Giant Forest area, or Ash Mountain (foothills)."
Other areas in the wilderness are open, the park said, but are "heavily affected" by smoke and dangerous air quality.
Sequoias only naturally grow across the western slopes of the southern Sierra Nevada mountain range. Somewhere between 7,500 to 10,600 mature giant sequoias were destroyed by last year's fire, according to a report by the National Park Service.
That's about 10-14% of the entire world's population of mature sequoias.
While the trees rely on fire to crack open their cones and release seeds to reproduce, those fires historically burned naturally at lower temperatures, killing small trees and thinning the forest. But fire suppression efforts have allowed the forest to grow denser, which, when combined with a yearslong drought, has allowed many of those trees to die out. That has created more fuels that burned hotter and more intensely than in previous fires.
"The unprecedented number of giant sequoias lost to fire last year serves as a call to action," Clay Jordan, the superintendent of the Sequoia and Kings Canyon National Parks, said in a July statement. "We know that climate change is increasing the length and severity of our fire seasons due to hotter temperatures and drought. To combat these emerging threats to our forests, we must come together across agencies. Actions that are good for protecting our forests are also good for protecting our communities."