California Wildfire Threatens Yosemite and Sends San Francisco Into a State of Emergency


Home / California Wildfire Threatens Yosemite and Sends San Francisco Into a State of Emergency

The Northern California wildfire known as the Rim Fire is huge – and only 7% contained as of August 25th. Image of the California Fire Map by Decoded Science

Last week’s Rim Fire began in the remote Stanislaus National Forest, but its force and size is moving it into more populated and notable areas, including Yosemite National Park.

On the weekend, the Northern California fire was 150 miles outside San Francisco, posing a potential threat to the city’s power and water supply. Due to the concerns about the city’s utilities, city officials declared a state of emergency and continue to monitor the water quality in the Hetch Hetchy watershed, which supplies 85 percent of San Francisco’s water supply. The water from the reservoir also powers two hydro-electric generators that supply electricity to San Francisco, including the San Francisco General Hospital.

Northern California Fire: Forest is Dry Fuel Source

As of Sunday, August 25th, nearly 3000 firefighters were working to quell the blaze, which was burning in very challenging terrain. The oak and pine ecosystem has seen very little rain this year, so the forest makes an ideal dry fuel source. The fire is burning with enough force to create its own internal weather patterns, which makes it hard to predict which way it will move. As of this morning, the fire has consumed over 130,000 acres of forest and is only 7% contained, according to the US Active Fire Mapping Program.

Rim Wildfire Threatens Giant Sequoias

In addition to the over 5000 structures that are threatened by the wildfire, the Rim fire also threatens certain iconic areas of Yosemite National Park. The park is known for its groves of giant trees, the famous giant sequoias (Sequoiadendron giganteum).

The most famous grove of sequoias is the Mariposa grove, and it is the most easily accessible. The Tuolumne and Merced groves in Yosemite are the closest giant sequoia groves to the wildfire.

The Rim Fire threatens the sequoia in the Merced grove. Image by Schick

The Tuolumne is home to 25 giant trees, including one sequoia with a tunnel through it. The tunnel was cut in the 1870s to attract tourists to the area.

The Merced grove contains 20 giant trees. Over the weekend, park officials have been clearing brush from around the trees and setting sprinklers to discourage the wildfire from spreading to the trees, should it reach the area.

Ecologically, fire does have a role in the sequoia ecosystem, since it helps moves nutrients from the trees into the soil and helps create new soil conditions where seeds can grow. Fire opens up gaps in the forest canopy, allowing light to move into the system. While fire brings devastation, it can also bring new life. However, it takes many thousands of years to grow a giant sequoia, so the burning of these giants would mean that Yosemite would lose its most illustrious residents for many, many generations.

Rim Fire in Northern California

The Rim fire is large, and presents challenging conditions to firefighters. This wildfire also has internal variability and momentum, so it’s difficult to tell whether the trees of Yosemite and the structures within the blaze will make it through this fire season unscathed.


Active Fire Mapping Program. Current Large Incidents. (2013). Accessed August 25, 2013.

Kilgore, Bruce M. Fire’s Role in a Sequoia Forest. Accessed August 25, 2013.

NBC News. Harsh, Dry Winds Hamper Moves to Douse Massive California Wildfire. (2013). Accessed August 25, 2013.

USA Today. High Winds Likely To Push Flames Further Into Yosemite. (2013). Accessed August 25, 2013.

Google. California Fire Map. (2013). Accessed August 25, 2013.

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