Zombie Forests: 20% of Trees in California Sierra Nevada Is No Longer Compatible With the Climate They Live

A "vegetation climate mismatch" is putting some trees in California's Sierra Nevada mountain range in a vulnerable state.

Some Conifers Are Living in Zombie Forests

Ponderosa pines, sugar pines, and Douglas firs stand tall in the Sierra Nevada mountain range. However, they are already living in borrowed time because, according to researchers, they can disappear with just one wildfire, extreme drought, or logging event, Smithsonian Magazine reported.

Avery Hill, an ecologist and a plant biologist at Stanford University and lead author of the study, said in a video that they are cheating death because a disturbance event could shake things up. When it happens, they are unlikely to survive.

The team examined 90-year vegetation data from the 1930s, showing how the conifer's elevation grew from nearly 112 feet upslope to 600 feet.

The zombie forests are found in lower elevations of the mountain range below 7,730 feet. However, humans have been moving into the foothills of the Sierra Nevada.

Chris Field, a biologist at Stanford focusing on climate change and a co-author of the study, said in a statement that they should look for serious options to protect and enhance the ecosystem for the said trees.

According to the researchers, the climate factors include annual precipitation and winter temperatures as the main reasons for the changes in suitable conditions. Additionally, numerous decades of aggressive fire suppression strategies also left the forest vulnerable to high-intensity wildfires.

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More About the Study

According to NPR, the team studied 30-year data from the 1930s when all Sierra Nevada conifers grew inappropriate climate conditions. They learned that the change is due to higher temperatures, less rainfall in the lower-elevation areas, and human activities like logging and an uptick in wildfires.

The average elevation has also increased. According to Hill, the elevation of trees increased because lower-elevation conifers died while conifers at higher elevations where the air is cooler grow.

However, the conifer's uphill trick hasn't been enough to keep pace with the dramatic temperature increase. The researchers predicted that conifers incompatible with their environment would double in 77 years.

Hill and his colleagues developed a map predicting the zombie forests' future state and were hopeful that it would help people understand the effects of climate change.

Hill said conservationists and scientists know that the ecosystems are changing and more changes are expected, and the people are grappling with the changes.

He added that the maps are unique because one can point to a certain area expected to transition due to climate change. However, it also forces us to answer some difficult questions, including how to manage them while resisting impending changes.