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‘Zombie forests’: Why trees in the Sierra Nevada are in the wrong place

By Marcela Chavez,


FRESNO, Calif. ( KSEE/KGPE ) – A study from Stanford warns that California’s Sierra Nevada conifer forests are likely to become stranded in habitats that are becoming too warm for them to survive.

Researchers have determined that the conifer trees native to lower elevations in California’s Sierra Nevada mountain range it’s in what they called an ‘unrecognizable climate.’

The study revealed that about a fifth of all Sierra Nevada conifer forests are considered a mismatch for their regions’ warming weather.

The paper, published last month, highlights how so-called “zombie forests” are temporarily cheating death and are likely to be replaced with tree species that will adapt to new conditions following one of California’s increasingly frequent catastrophic wildfires.

This study provides a strong foundation for understanding where forest transitions are likely to occur, and how that will affect future ecosystem processes like wildfire regimes.

Avery Hill, study lead author.

Avery Hill, a graduate student in biology at Stanford led a related study in November that showed how wildfires have accelerated the shifting of Western trees’ ranges.

The Stanford Woods Institute for the Environment defines zombie forests as once-thriving ecosystems that now struggle to adapt to climate change representing a high-risk factor for catastrophic wildfire.

Researchers say Sierra Nevada conifers, such as the ponderosa pine, sugar pine, and Douglas Fir are among Earth’s tallest and most massive living things. They have stood watch as temperatures around them have gotten warmer by an average of two degrees Fahrenheit since the 1930s.

Additionally, experts say in recent years the area has seen a giant wave of new human residents drawn to the lower elevations of the Sierra Nevada by spectacular scenery, relaxed lifestyles, and relative affordability.

Given the large number of people who live in these ecosystems and the wide range of ecosystem services they confer, we should be looking seriously at options for protecting and enhancing the features that are most important

Chris Field, study co-author.

The study states that the combination of hotter weather, more construction, and a history of fire suppression have fueled increasingly destructive wildfires, “making the communities like Paradise and Caldor synonymous with Mother Nature’s fury.”

Experts say the speed of the temperature change has outpaced the ability of many conifers to adapt or shift their range, making the highly vulnerable to a replacement, especially after stand-clearing wildfires.

According to the study, 20% of all Sierra Nevada conifers are mismatched with the climate around them. Most of those trees are found below an elevation of 2,356 meters or 7,730 feet.

The expectation is that the number of Sierra Nevada conifers that are no longer suited to the climate will double within the next 77 years.

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