Tree Mortality & Falling Hazards

Dead and dying trees in the Tahoe National Forest and Nevada County is a fact of contemporary life. Being aware of hazards that dead trees cause and hyperconscious of fire starting activities will help keep families and neighbors safer.


From 66 million dead trees in 2010 to 129 million in 2017, the State of California is losing trees at a rate that no one has previously seen.

An effective response is beyond what the US Forest Service and CalFire can handle.

Keeping populated areas safe from wildfires and falling trees, as well as aiding in forest recovery will take cooperation between homeowners, PG&E, NID, recreation facility managers, environmental, nonprofit, and government agencies.”

“Though California received record-breaking rains in the winter of 2016-2017, the effects of five consecutive years of severe drought, a dramatic rise in bark beetle infestation, and rising temperatures have led to historic levels of tree die-off. ” – Tree Mortality Task Force – News Release 12/12/17

“The Tree Mortality Taskforce has provided an essential venue for coordination of response efforts, exchange of ideas, reporting, and accountability for the ongoing statewide response to this incident,” says Supervisor Nathan Magsig of Fresno County. – News Release 12/12/17 Tree Mortality Taskforce. 

In Executive Order B-42-17, Governor Brown relaxed regulations so that anyone licensed for timber and tree service operations can perform tree removal in high-risk areas.

California’s ‘New Normal’ Fire Safety Strategies

“Approximately 95% of all wildfires in California are caused by people,” says the California Wildland Fire Coordinating Group (CWCG).

Roadway, Burn Pile, and Camping Safety

Sparks Along Roadways

Burn Pile Safety

Putting out Campfires

Falling Trees

  • stay clear of large stands of dead trees, especially if it is windy
  • look up and around before parking near dead trees, don’t park in the potential path of a tree fall
  • if traveling to remote areas, keep a chainsaw or ax in your vehicle in case a tree fall blocks the road
  • Tree Mortality – Watch Out – PDF

Defensible Space Around Homes

“The importance of removing dead and diseased trees cannot be overstated. Addressing widespread tree mortality is a crucial first step to not only safeguarding our forest communities but also in creating a healthier and more resilient Sierra Nevada forest – which provides more than 60 percent of the state’s water supply.” – Tom Berryhill, Tree Mortality Update – 3/2016

  •  Remove dead trees
  • Create defensible space around your home
  • Call PG&E (1-800-743-5000) if you have a dead tree threatening a power line
  • Create a home evacuation plan and ‘go-kit.’ Check kit supplies monthly

After the McCourtney and Lobo fires in October 2017, Nevada County residents were harshly reminded about how quickly wildfires can move through communities.

We also have an opportunity to witness the adaptations that nature makes in response to drought, global warming, and pest infestations.


If you liked this post, check out Native Plants for Healing the Land after Fire or bark Miniscule Mountain Beetle Turning Forests Red


Forest Research and Outreach – University of California

Homeowner Responsibilities – USDA

Nevada County FireSafe Council – 2018-2019 Fire Season Guide + Emergency Preparedness and Evacuation Guide

One Less Spark – One Less Wildfire – fire prevention

Ongoing hazards from trees affected by drought – PG&E

Our Forests are Changing  – USDA

Prepare for Bark Beetle – CalFire

USDA Forest Service – Aerial Detection Survey Results

With California Drought Over, Fewer Sierra Pines Dying –  10/24/17 – 

Miniscule Mountain Beetle Turning Forests Red

“It’s about the size of a mouse turd,” says Diana Six, Professor of Forest Entomology/Pathology at University of Montana, when describing the Mountain Pine Beetle.

Historically, the Mountain Pine Beetle contributed to a healthy forest by eliminating weakened trees, making room for new growth. Cold temperatures kept populations in check, only 20% of larvae would survive a winter.

Beetle Lifespan

At higher altitudes, Pine Beetles may live for up to two years; however, most beetles complete a life cycle within one year. They go through egg, larva and pupa stages beneath the bark of a tree. When summer temperatures warmed sufficiently, adults emerged in search of a new host. Females lead the charge, emitting pheromones that beckon males to follow.

Carrying a fungus in mouth pockets, it is released inside the tree when the beetles begin boring into it. The fungus grows, gathering nitrogen that supplies the beetles with needed food. A female will lay approximately 60 eggs. The fungus supplies nutrients to the growing offspring.

Fungus Kills the Tree

The fungus invades the sapwood, preventing the tree from using pitch to repel beetles.  It also blocks water and nutrient transport inside the tree.

Pine Beetles are opportunists. When conditions are right, they colonize and reproduce. Now might be the beetle’s greatest moment in history.

Contributing Factors to Widespread Beetle Success

  • Managed forest landscapes – the practice of replanting only a single species
  • Years of fire suppression procedures
  • Climate change – low night temperatures at night don’t drop enough to kill larvae
  • Forest trees weakened by years of drought 2014 – 2017

Mountain Pine Beetles have been devastating forests in Canada, trees at higher altitudes with no natural resistance.  The insects aren’t picky when food source areas are depleted, they move on to another one. Ponderosa and other pines in Nevada County, stressed and weakened by drought, are feeling the bite.

It may be the largest forest insect blight
ever seen in North America. – Wikipedia

Unfortunately, by the time tree needles turn red, the beetles have already settled in another host. A single besieged tree will nourish enough beetles to infect seven more. With numbers like that, they cut a wide swath through a forest quickly. Aside from keeping dead trees from becoming a hazard to humans or buildings, there is no effective method to halt or control the infestation…

Infestation Evidence

  • Reddish dust and “boreholes”
  • “Pitch tubes” resing globules the tree produced in an attempt to protect itself
  • Leaves / needles turning yellow, then red
  • Horizontal larvae egg galleries under the bark
  • A blue-gray color in sapwood, caused by beetle introduced fungus

As disturbing as it is to see huge areas of forest turning red, a bright spot may be the survivors – genetic adaptors. These are trees that struggled in cooler, wetter conditions. The beetle blight is giving them an opportunity to flourish. Mountain Pine Beetles don’t ‘see’ those trees as food.

It is too soon to tell the effects that these species will have on animal habitats, water retention, and snow packs.

“Insects are expected to be one of the first indicators of climate change in terrestrial ecosystems because they are cold blooded.  Everything they do – everything – is dependent on temperature.”  -Andrew Nikiforuk, author of Empire of the Beetle

 Sound as Pest Control





click on image to see more Life on the Creek art



If you liked this post, check out Tree Mortality State of Emergency


Bark and Wood Boring Beetles of the World

Mercury News – Why tiny insects are tearing up Sierra forests

National Geographic 4/2015 – Pine Beetle Epidemic

Nature of Things with David Suzuki 8/2014 – The Beetles are Coming

San Francisco Chronicle – Bark beetles ravaging droughtstricken forests in California

University of Montana – Diana Six, Professor of Forest Entomology / Pathology

USDA – Bark Beetle Management

YubaNet – Tree Mortality in Nevada County 9/9/16

Wikipedia –  Dendroctonus ponderosae

(beetle discussion with Diana Six 0-14:33)

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