Posts

bark beetle tree

California Tree Mortality At An Unprecedented Level

Tree Mortality Overview

According to U.S. Forest Service study done in the summer of 2017, about 6.3 billion dead trees are still standing in 11 Western states, an increase of half a billion from five years ago. 103 million trees have died in California alone since 2010. So what’s happening to the trees? Well, established trees are normally fairly resilient to seasonal changes in their environment, but the last five years of drought in CA coupled with climate change impacts have imposed several stressors acting on the trees at the same time. Most native California trees are fairly resilient to drought, but a prolonged drought weakens the trees and exposes them to pests and disease that a healthier tree could normally fight off. A recent story by the CBS San Francisco discussed the situation in the Sierra National Forest with two Forestry experts there. They stated that there are more dead trees than live ones and will be dealing with the tree mortality there for many years to come.

Tree Mortality Danger

When a tree dies, its wood dries out and becomes very flammable.  When building a campfire, there’s a reason we use downed wood instead of chopping down live trees. Healthy, living trees have a relatively high moisture content.  This helps trees survive a wildfire and slows the progress of that wildfire. When tree death occurs from old age or other reasons, standing dead or fallen trees provide a large amount of dry fuel for wildfires, encouraging fire growth and hindering efforts to put it out. Not only are decomposing trees more flammable, they can also present a safety hazard to firefighters. Specifically, dead trees can fall during fires (which have resulted in deaths), and fallen trees can be an obstacle preventing vehicles and firefighters from reaching or escaping a wildfire.

bark beetle-caused tree mortality

Bark Beetle impact from 2012 US Forest Service report

What’s Happening to the Trees?

Established trees are fairly resilient to seasonal changes in their environment, so it is difficult to understand exactly what is causing so much tree death in California. Perhaps not surprisingly, several stressors have been acting on the trees at the same time.

Drought:

California saw a five-year historic drought that only just ended this last year. Most native California trees are fairly resilient to drought, but this prolonged drought weakened the trees and made them more susceptible to beetles and disease. Two deadly invaders that a healthier tree could normally fight off.

tree mortality in Julian

Tree death (brown trees) near Julian in San Diego County

Pests:

Tree bark is the main defense for trees against pests, disease, and fires. Bark beetles burrow into the bark and expose the trees to other pests or diseases, and can reduce their fire resiliency. Different types of bark beetles act as pests to different types of trees. The Pines and Conifers in the Sierra Nevada Mountains have been decimated by these beetles. Beetle-kill trees have been blamed for prolonging the firefight on the Beaver Creek Fire in Northern Colorado and also the Cedar Fire in California’s Southern Sierra Nevada Range. Tree deaths due to these beetles have been attributed to several major campaign fires across the west over the past few summers. The map above shows hard-hit beetle kill timber forests across the west (in red), which includes both the Cedar and Beaver Creek fire areas.

Disease:

The coast live oak trees have been exposed to Sudden Oak Death, which is caused by a non-native tree fungus. This fungus and other non-native diseases are responsible for an estimated 5 – 10 million oak tree deaths. Many dead trees were identified in the areas where the Soberanes fire near Big Sur is currently burning and have likely contributed (along with major drought) to its acreage eclipsing 100,000 this week.

Plans for Tree Death Prevention

Drought, pests, and disease all put stress on otherwise healthy trees.  When these stresses are combined, we can expect to see continued tree death at unprecedented scales. California has programs to both reduce the amount of tree death and to remove dead trees as a means of reducing fire danger.  Lately, resources have been too scarce to keep up with the levels of tree deaths plaguing the state. Learn more about the epidemic and what is being done to prevent further problems here.


Sources:

www.fs.fed.us

www.fire.ca.gov

www.yale.edu

The Denver Post

Editor’s Note: This article was originally published in September 2016 and was updated in September 2017

Aerial photo over Kynsna area (Source: South African Red Cross)

Wildfires Rage Across South Africa’s Cape After Massive Winter Storm

Hundreds are left homeless and thousands remain evacuated after the strongest winter storm in decades assaulted Cape Town, South Africa, and continued across the southern region of South Africa known as the Western Cape. Numerous lightning strikes associated with the massive storm ignited wildfires that raged across hillsides, fueled by gusting and strong winds, even as nearby areas began to flood and were drenched by rain. Tuesday evening, June 6th, the storm began to impact the Western Cape. By Wednesday, thousands of residents along the major roadway N2, famously known as the “Garden Route”, were evacuated as wildfires blazed toward nearby neighborhoods. As of June 8th, 4pm PDT, nine deaths are attributed to the storm, home collapses, and wildfires.

Storm Impact & Wildfires in Area around Cape Town and Knysna (Source: Google Earth)

Storm & Wildfire Impacted Area around Cape Town and Knysna (Source: Google Earth)

Current Situation

The local media is referring to this as the “mother of all storms”. A compounding factor to the devastating impact to the region is the already poor housing covering much of the area. Shanty towns burn quickly and can also collapse simply due to the strength of the winds. Flood waters also washed away several communities due to non-permanent construction. Part of the evacuation process included a local hospital in Knysna had to move all personnel and patients due to the approaching wildfires. The rain now falling on the Knysna area will assist firefighting efforts to get the wildfires under control; however, the additional rains will increase the possibilities for mudslides in the area.

Activity of Wildfires in last 48 hours, centered on Knysna (Source: Advanced Fire Information System Viewer – AFIS)

Wildfire activity in last 48 hours, centered on Knysna (Source: Advanced Fire Information System Viewer – AFIS)

Recovery & Outlook

So far, reports indicate more than 150 structures were destroyed throughout 20 suburbs. Cape Town, fortunately, has restored approximately 90% of its power. Across the impacted area, staff are opening shelters and resource centers to assist those displaced. The rains received may help with a fraction of the drought situation, but Level 3 water restrictions remain in place. Wetting rains over a longer duration are needed to truly have an impact. Local volunteers are collecting donations of items such as food, water, blankets, and other basic necessities for those affected by this disaster.

Aerial photo over Kynsna area of wildfires (Source: South African Red Cross)

Aerial photo over Kynsna area (Source: South African Red Cross)

Read further

Live update stream: http://www.news24.com/SouthAfrica/News/live-knysna-evacuation-underway-20170607

http://www.bbc.com/news/world-africa-40199270

http://www.accuweather.com/en/weather-news/powerful-winter-storm-kills-at-least-eight-in-cape-town/70001884

http://www.cnn.com/2017/06/08/world/south-africa-fires/

http://www.aljazeera.com/news/2017/06/storm-kills-displaces-thousands-cape-town-170608052748704.html

California in Severe Drought!… Or is it?

It’s no secret that California has been in a major drought for the last five years.  This has resulted in larger and more aggressive wildfires during that time, keeping firefighters busy and resulting in increased levels of acreage burned.  However, the California drought conditions are actually better than some experts predicted, and metrics other than rain and snowfall levels may indicate impending recovery.

California drought 2015 vs 2016

2015 vs 2016 conditions, Source: U.S. Drought Monitor

Complex Water Resources

Most of California has a naturally dry climate, and it relies on a complex system of aqueducts, aquifers, and reservoirs to transport and store water resources. As such, the state of the drought from a human-use perspective can be gauged by how full the reservoirs are compared to historical averages.

California drought measured by Reservoir Levels

California Reservoir Levels, Source: California Department of Water Resources

As the map depicts, many California reservoirs are at or near historical average levels. Also, these levels do not yet take into account the snowpack melts during the spring season, which should increase the reservoir levels even further. While California is far from having a comfortable amount of water to survive future potential droughts, this wet season should provide at least a temporary reprieve from the drought conditions and restrictions.

La Niña Less Severe than Anticipated

The El Niño event in 2015 which was expected to be one of the strongest on record resulted in little rainfall to ease the dry conditions. An El Niño event is marked by warmer-than-usual waters in the mid-latitudes of the Pacific Ocean, and often leads to excess rainfall across the West Coast. El Niño events are often followed by La Niña events, which are very dry and lead to drought. Fortunately, 2016 is proving to be much wetter than a typical La Niña event and is even producing moisture that is helping to mitigate drought conditions rather than worsen them.

Why the California Drought Matters

The ongoing California drought has caused major ecological damage, led to severe water use restrictions, and contributed to major fire seasons. While this may seem like an issue specific only to Californians, the drought has ripple effects on the entire country.

California produces a majority of the fresh produce consumed nationwide. Seventy percent of total fruit and tree nut production and 55 percent of vegetables come from the state. Agriculture consumes 80 percent of California’s water resources on an average year, and a lack of water has led to lower crop yields and higher-priced produce nationwide.

Sources:

California’s Drought Could Upend America’s Entire Food System

California Sees Largest Drought-Free Patch Since 2013

California Drought Farm and Food Impacts

 

Wildfire 101: Dead Fuel Moisture

What is Dead Fuel Moisture?

A recent lack of significant rainfall has kept Southern California in extreme drought, which means there is increased potential for significant wildfire due to dangerous levels of dead fuel moisture. As explained by NOAA, fuel moisture is a measure of the amount of water in a potential fuel, and is expressed as a percentage of the dry weight of that fuel.  So if leaves and downed trees were completely dry in a given area, the fuel moisture level would be 0%.

When fuel moisture content is high, fires do not ignite readily, or at all, because most of the fire’s heat energy is used up trying to evaporate and drive water from the plant in order for it to burn. When the fuel moisture content is low (like in drought-stricken Southern California), fires start more easily and can spread rapidly as all of the heat energy goes directly into the burning flame itself. When drought is extreme and the fuel moisture content is less than 30%, that fuel is considered to be dead, giving us the “dead fuel moisture” designation.

The United States Forest Service which manages a nationwide fuel moisture index, classifies fuel moisture based on two metrics:  fuel size and time lag.

  • Fuel size refers to the actual physical dimensions of the fuel (i.e. the diameter of downed logs or branches).
  • A fuel’s time lag classification is proportional to its diameter and is loosely defined as the time it would take for 2/3 of the dead fuel to respond to atmospheric moisture.  For example, if a fuel had a “1-hour” time lag, one could expect its wildfire susceptibility to change after only 1 hour of humid weather.  Fuels with 100- or 1000-hour time lags would be expected to be much less resistant to humidity.

Fuel moisture is dependent upon both environmental conditions (such as weather, local topography, and length of day) and vegetation characteristics.  The smallest fuels most often take the least time to respond to atmospheric moisture, whereas larger fuels lose or gain moisture slowly over time.

The classifications of the Forest Services’s index (also known as NFDRS) are as follows:

Dead Fuel Moisture

The Dead Fuel Moisture Time Lag Classes as defined by the United States Forest Service

Drought Conditions Improving in California

According to the weather almanac, San Diego–home to RedZone’s intelligence team–had received a minuscule .7 inches of rain since June 1st.  Luckily, a significant rain event entered the southern California region on Thursday evening, adding wetness to the low fuel moisture readings around the region.

Since late Thursday night (12/15), significant rains have finally fallen across the area. The gusty winds and showers are expected to begin tapering off late Friday as the moisture exits to the east, but a long-awaited significant wetting event has been left behind. Early reports on Friday (12/16) have measured up to 3.3 inches in the East County Mountains and greater than 1 inch along the San Diego Coast, far exceeding the cumulative totals since June.

As we discussed a few weeks ago, the drought situation in Northern California had already improved earlier this year, and now the dry weather in Southern California appears to be coming to an end.


Source(s):

http://patch.com/california/ranchobernardo-4sranch/storm-moves-through-san-diego-region

https://www.ncdc.noaa.gov/monitoring-references/dyk/deadfuelmoisture

http://www.nwcg.gov/glossary/a-z

http://www.wfas.net/index.php/dead-fuel-moisture-moisture–drought-38

Tree Death Fuels California Wildfires

Tree Death Adds Fuel to the Fire

A record 66 million trees have died in California since 2010, adding a huge fuel threat to an already dangerous fire landscape.  Not only are decomposing trees more flammable, they can also present a safety hazard to firefighters. Specifically, dead trees can fall during fires (which have resulted in deaths), and fallen trees can be an obstacle preventing vehicles and firefighters from reaching the fire.

Dead Wood Danger

When a tree dies, its wood dries out and becomes very flammable.  When building a campfire, there’s a reason we use downed wood instead of chopping down live trees. Healthy, living trees have a relatively high moisture content.  This helps trees survive a wildfire and slows the progress of that wildfire. When tree death occurs from old age or other reasons, standing dead or fallen trees provide a large amount of dry fuel for wildfires, encouraging fire growth and hindering efforts to put it out.

Bark Beetle impact from 2012 US Forest Service report

Bark Beetle impact from 2012 US Forest Service report

What’s Happening to the Trees?

Established trees are fairly resilient to seasonal changes in their environment, so it is difficult to understand exactly what is causing so much tree death in California. Perhaps not surprisingly, several stressors have been acting on the trees at the same time.

 

Drought:

California has been in an historic drought for the past five years. Most native California trees are fairly resilient to drought, but a prolonged drought weakens the trees and exposes them to pests and disease that a healthier tree could normally fight off.

Tree death (brown trees) near Julian in San Diego County

Tree death (brown trees) near Julian in San Diego County

Pests:

Tree bark is the main defense for trees against pests, disease, and fires. Bark beetles burrow into the bark and expose the trees to other pests or diseases, and can reduce their fire resiliency. Different types of bark beetles act as pests to different types of trees. The Pines and Conifers in the Sierra Nevada Mountains have been decimated by these beetles. Beetle-kill trees have been blamed for prolonging the firefight on the Beaver Creek Fire in Northern Colorado and also the Cedar Fire in California’s Southern Sierra Nevada Range. Tree deaths due to these beetles have been attributed to several major campaign fires across the west over the past few summers. The map above shows hard-hit beetle kill timber forests across the west (in red), which includes both the Cedar and Beaver Creek fire areas.

Disease:

The coast live oak trees have been exposed to Sudden Oak Death, which is caused by a non-native tree fungus. This fungus and other non-native diseases are responsible for an estimated 5 – 10 million oak tree deaths. Many dead trees were identified in the areas where the Soberanes fire near Big Sur is currently burning and have likely contributed (along with major drought) to its acreage eclipsing 100,000 this week.

Plans for Tree Death Prevention

Drought, pests, and disease all put stress on otherwise healthy trees.  When these stresses are combined, we can expect to see continued tree death at unprecedented scales. California has programs to both reduce the amount of tree death and to remove dead trees as a means of reducing fire danger.  Lately, resources have been too scarce to keep up with the levels of tree deaths plaguing the state. Learn more about the epidemic and what is being done to prevent further problems here.


Sources:

www.fs.fed.us

www.fire.ca.gov