It was several weeks after the Windy Fire burned through many of California’s giant sequoia groves in September 2021 that we were finally able to access Red Hill grove. Save the Redwoods League, where I am the director of science, owns this rugged 160 acres, home to more than 100 magnificent ancient giant sequoias. Firefighters were still fighting the fire miles away, and the smell of smoke hung in the air.

From the road, it was apparent that fire had burned through Red Hill grove, some of it at such a high intensity that it killed dozens of mature giant sequoias. In places, what was once a vibrant forest was bleak — blackened trunks and ashy ground, leached of all color. Giant sequoias can live up to 3,000 years. But unlike their cousin the coast redwood, which will resprout and recover from fire, once giant sequoias are dead, they’re gone.

This disaster, as Diana Leonard recently reported for The Post, is unfolding across the entire giant sequoia range. Between the 2020 Castle Fire and the 2021 KNP Complex and Windy fires, we lost up to 19 percent of these natural treasures in about 16 months. The continued loss of these trees is an emergency that we must address now.

We knew that Red Hill was vulnerable. Decades of fire suppression throughout the Sierra Nevada have allowed the dense ingrowth of smaller trees and undergrowth that, when ignited, can bring fire into the crowns of the giant sequoias. The League had planned a prescribed burn for fall 2020 to reduce the risk of catastrophic loss, but the crew was called off to fight a wildfire. In 2021, permits and contractors were in place and the control lines for the burn were ready, but circumstances beyond our control intervened again. The Windy Fire got there first.

Giant sequoias have evolved to thrive with frequent, low- to moderate-intensity fires. Their protective bark can be up to two feet thick, insulating them from fire damage. Cones actually rely on heat from fire to open and release seeds. But these new, more intense fires, fueled by unnaturally dense forests plus drought and climate change, have changed everything. Now large, mature giant sequoias are dying in wildfire like never before.

Decades of proactive forest management, including prescribed fire, to reduce overgrowth of small trees likely spared the popular Giant Forest grove and Trail of 100 Giants. But most groves haven’t had those treatments. Fortunately, there are actions forest managers and policymakers can take to help.

First, we must act immediately to reduce the unnatural buildup of vegetation in the highest-risk groves. The Giant Sequoia Lands Coalition of government agencies, tribes and nonprofit organizations, including the League, has set a goal of treating 2,000 acres of the highest-risk groves before the 2023 wildfire season. This would include prescribed burning and/or removal of dense understory vegetation.

Securing the long-term survival of the groves will require a substantial investment: $500 million over five years to treat at least 60,000 acres of vulnerable groves with buffer zones. And it will require far more personnel than we currently devote to the problem. Treating so many groves in such a short time will require a high-capacity, full-time, year-round workforce, as well as a more unified approach across agencies. We also need to return stewardship roles to tribal communities and nations, which have managed land for thousands of years and continue to do so.

Second, we need to get rid of the red tape that is delaying urgent work in the giant sequoias. Projects can be expedited through an emergency declaration as proposed in the bipartisan Save Our Sequoias Act, introduced this week in the House. The legislation will expedite this important work, while retaining the bedrock environmental protections of the National Environmental Policy and Endangered Species acts.

The League had worked for more than a year to line up treatment at Red Hill, and by the time we got everything in place, it was too late. Walking through Red Hill grove after the fire, seeing one blackened giant sequoia after another, dead but still standing, I felt cold regret. This loss was so unnecessary, because we know how to protect these trees and were prepared to do it — but could not before the wildfire arrived. It was heartbreaking to show up to do the work of land care and see that our ever-increasing wildfires got there first.

I told myself that while these trees couldn’t be saved, we would keep fighting for the ones that have survived. They have lasted thousands of years; now, it’s our responsibility to hand them off safely to the next millennium.