CONTRA COSTA COUNTY RESIDENTS love their trees — that’s probably why the county has an ordinance in place to protect and preserve them. But trees here are being killed by latent pathogens, and climate change is making things worse.
A study funded in part by the East Bay Regional Parks Foundation shows just how climate change-driven drought is affecting trees across the county and the rest of the state.
Matteo Garbelotto, co-author of the study and a forest pathology specialist in the Department of Environmental Science, Policy and Management at UC Berkeley, compares the rise in such die-offs to virulent viruses spread among people in its scope and impact.
According to the study, almost every major variety of tree in Contra Costa County has been impacted: oaks, manzanitas, tanoaks, eucalyptus, bay laurels and acacias.
The most common latent pathogens in Contra Costa County are fungal, which spread through spores. These spores can stick to water, bugs, and even gardening tools. If any object with spores on it touches a healthy tree, that tree is exposed to the disease.
Dormant pathogens awakened by climate change
Contagious pathogens are nothing new in plant species, but specialists have long held that latent ones — those that lie dormant and may not show any effects — don’t play a role in their spread. The UC Berkeley study shows data that these sleeping microbes actually can be triggered by climate change.
“This has been a long conversation in professional circles and some people still do not believe these latent pathogens really play a role,” said Garbelotto in a news release after the study was published. “But our data show and prove they do. We now provide evidence that in areas affected by climate change these often-native latent pathogens can be as problematic as non-native and invasive introduced pathogens.”
Drought caused by climate change reduces the amount of total energy these trees have. The trees cannot effectively fight these diseases, so more trees are dying or at risk of dying.
“We now provide evidence that in areas affected by climate change these often-native latent pathogens can be as problematic as non-native and invasive introduced pathogens.”
Matteo Garbelotto, study co-author
Though climate change is driving the drought that is exacerbating the problem, ironically, wet weather is what really gets some tree diseases to spread. The more water and rain, the more these pathogens spread, Garbelotto said. This comes as we move into the rainy season, meaning come summer, we could see more trees impacted by these pathogens next year.
Between 2019 and 2024, researchers at UC Berkeley explored woodlands, collecting samples from trees. They discovered 10 woody plant species in six regions of the state that had been attacked by nine fungal species, all latent pathogens.
The impact of these fungal pathogens killing local woodlands runs deep into California’s and Contra Costa County’s ecosystem. These dead trees also pose an enormous fire risk.
Upsetting natural fire defenses
Garbelotto gave the sobering example of California’s famously fire-resistant redwoods being harmed by trees killed by latent pathogens — trees impacted by these pathogens burned so hot that they were able to kill redwoods.
Since the tree pathogens seem to be triggered by drought, water is the best medicine during the dry season for landscape trees, Garbelotto said, though he added that California’s water supplies are also something important to consider. At the very least, many of the trees that blanket Contra Costa County and its parks are living in climates they are not accustomed to, he said.
“It is like ‘Chronicle of a Death Foretold’,” said Garbelotto of the pathogen problem. “All of the tree and shrub species affected are growing at the ecological edge of where they would be comfortable. As they cross that edge, they become susceptible to latent pathogens.”
Garbelotto suggests planting more drought-tolerant native species that are better adapted to the environment — not just the current climate, but for a hotter one in the future — and prioritizing watering at-risk trees in landscape settings.
Though these trees’ deaths may be “foretold,” awareness around climate change’s impacts on pathogens is a way to address the issue.
“Understanding why this is happening can help direct land managers and landowners in the right direction, avoiding waste of resources by focusing on what really matters,” Garbelotto said.
Westley Burnham is a 10th grader at El Cerrito High School in El Cerrito and a CCYJ reporter.
This story originally appeared in CCSpin.
The post Fungal forests: New study reveals the fatal impacts of climate change on East Bay trees appeared first on Local News Matters.