When immortals die

Giant sequoias come as close to immortality as living organisms can. Many live over a thousand years despite nature’s challenges. So it comes as a shock to read that over 10% of all the giant sequoias on Earth — thousands of trees — were killed in last year’s Castle Fire in the Sierra Nevada Mountains. 

When the immortals die, we can’t deny that we have entered a time of ecological disaster. The landscapes of the West have been shifting before our eyes. Driven by climate change, familiar ecosystems are becoming … something else. The dead sequoias ask: What will that “something else” be?

It’s tempting to imagine that ecosystems will simply adapt, relocating to stay within their preferred climatic conditions. Where I live in southern Oregon, there is a well-defined succession of plant communities from the hot, dry valleys to the cool, wet mountain peaks. So, predictions about responses to climate change are often expressed in relation to elevation. For example, we might expect higher temperatures to cause pine forests to “move up the mountainsides,” making room for expanding oak woodlands.

To see if that’s realistic, let’s look at California’s Sierra National Forest, between Yosemite and Kings Canyon national parks. Following a severe drought and resulting pine beetle outbreak, a staggering 58% of the trees in the Sierra National Forest died between 2014-2017.

Forest Service biologists determined that mortality was especially high among the largest ponderosa pines. New seedlings were mostly incense-cedar and oak species, “representing a potential long-term shift in composition from forests that were dominated by P.ponderosa.” 

So, will these Sierra pine forests discreetly withdraw to cooler and wetter higher elevations? Will oaks move in to replace them? Given a century or two, maybe. 

But in the time frame of the next few decades, the answer is almost certainly no.  Human-caused climate change is occurring with such unprecedented speed that ecological transitions will not be orderly or gradual. They will be often violent, and in forest ecosystems will be driven by that agent of chaos — wildfire.

Individual trees don’t move; if conditions become unsuitable, they die, and dead trees are fuel.

In 2017, the Railroad Fire burned over 12,000 acres in the Sierra National Forest. In 2018, this was followed by the 96,000-acre Ferguson Fire. In 2020, the Creek Fire burned a staggering 375,000 acres of the same national forest. And just south of the Sierra National Forest, 2020’s Castle Fire burned almost 175,00 acres in the Sequoia National Forest and Giant Sequoia National Monument. 

Fueled by huge numbers of beetle-killed dead trees, these mega-fires consumed normally fire-resistant mature pines and giant sequoias, and of course, burned all the seedlings of oaks, incense-cedar, and other plants beginning to establish a new forest. 

Unfortunately, the situation in the Sierra National Forest is not unusual.  California — and the West — is burning everywhere.  Seventeen of the 20 largest wildfires ever recorded in California have occurred since 2003, and five of the six very largest all happened last year.

Repeated intense wildfires destroy the seedbank of trees, leaving behind a scabland of weeds and invasive grasses.  

I know many federal and private land managers. They do their best to reduce fuel loads and help communities of plants adapt to the new conditions. Managers of the Sierra National Forest also tried, but In the face of relentless warming and drought, it made little difference.

I fear that by unleashing incredibly rapid climate change, humanity has hit a hard reboot for the biosphere. The planet is resilient, and life will eventually stabilize, but it may take centuries.  

In the meantime, is there anything can we do?

First, of course, we must drastically cut CO² and methane emissions. Next, we need to preserve habitat linkages, to give plants and animals “escape routes” as they seek the conditions they need to survive. We may also need to take an active hand, moving key species to newly suitable areas as their former habitat is lost. For some species, like the giant sequoia, that may be the only hope. I hope we have the ecological wisdom to do what’s needed.

Welcome to chaos, it’s where we live now.

Pepper Trail is a contributor to Writers on the Range, writersontherange.org, a nonprofit dedicated to spurring lively conversation about the West. He is a biologist and writes in Oregon.