High-severity Wildfires in California’s Sierra Nevada Forests Have Risen Dramatically Since the Euro-American Settlement

According to a study conducted by the Safford Lab at the University of California, Davis, and its collaborators, high-severity wildfires are increasing in the Sierra Nevada and Southern Cascade forests and are burning at unprecedented rates compared to the years before the Euro-American settlement.

These rates have risen dramatically in the last decade.

The Euro-American Settlement

European nations came to the Americas to increase their wealth and influence in global affairs.

The Spanish were among the first Europeans to explore and settle in what is now the United States, as per America's Library.

However, by 1650, England had established a commanding presence on the Atlantic coast. In 1607, the first colony was established in Jamestown, Virginia.

Many of those who immigrated to the New World did so to escape religious persecution. In 1620, the Pilgrims, the founders of Plymouth, Massachusetts, arrived.

The colonists flourished with some help from Native Americans in both Virginia and Massachusetts.

New World grains, such as corn kept the colonists from going hungry, while tobacco provided a valuable cash crop in Virginia.

Enslaved Africans made up a growing proportion of the colonial population by the early 1700s. More than 2 million people lived and worked in Britain's 13 North American colonies by 1770.

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Good fire, bad fire

(Photo : JAVIER TORRES/AFP via Getty Images)

Scientists analyzed fire severity data from the United States for the study, which was published in the journal Ecosphere, as per ScienceDaily.

Across seven major forest types, the Forest Service and Google Earth Engine collaborated.

They discovered that the average annual area burned at low-to-moderate severity in low- and middle-elevation forest types have decreased from more than 90% before 1850 to 60% to 70% today.

Simultaneously, the annual area burned in high severity has nearly quintupled, rising from less than 10% to 43% today.

Many fire ecologists discuss the need to burn more acreage while preventing "bad fire" by putting "good fire" on the ground, such as through prescribed burning.

In forests such as oak woodland, yellow pine, and mixed conifer, good fire refers to the low-to-moderate severity burning that the dominant species are adapted to.

They are usually sparked by lightning or by humans in order to enrich and restore the land.

Before the mid-nineteenth century, many such fires were started by Native Americans as part of their cultural burning practice.

In California prior to 1850, much more land burned each year than it does today.

According to the study, the gap is beginning to close. Unfortunately, the majority of what is burning is dangerous, high-severity fire.

As per the authors, this is the most concerning finding: the average area of high-severity burning in the region is now greater than the best estimates of high-severity burning prior to Euro-American settlement, despite the fact that overall burning in the modern era is still much lower.

Nine of California's ten largest wildfires have occurred in the last decade.

The state's record-breaking fire year of 2020, in which nearly 9,900 fires burned 4.3 million acres, was the only year in which the annual area burned exceeded historical levels, but much of that burned at high severity.

The authors said that this trend is especially concerning because the majority of the affected low- to middle-elevation forest types are adapted to low-to-moderate severity burning.

Fires that are too severe in these forests can harm landscapes as well as the habitat and ecosystem services they provide.

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