IT’S LIKE CHEMO FOR THE FOREST

On March 10, the Eastern Sierra Climate and Communities Resilience Project (ESCCRP) held its 10th meeting since November 2020 regarding how the region plans to protect its forests from wildfire and other climate-change related threats.   

“Though we’ve come a long way, we have a long way to go before we’re in any position to actually be celebrating” said Janet Hatfield, Project Manager. 

The meeting opened with ecologist Marc Meyer presenting general climate change data and why the ESCCRP is an important, timely goal for the region. 

According to Meyer’s data, the Eastern Sierra has seen temperatures increase 3.5-5.8 degrees Fahrenheit since the 1890s. Droughts have generally become more common. Snowmelt now occurs about 10-15 days earlier when compared to the early 1900s. 

Scientists anticipate that temperatures will increase significantly in the Sierra Nevada by 2100; winter temperatures will most likely increase by 2-4 degrees Fahrenheit, while summer temperatures will most likely go up by 4-8 degrees Fahrenheit. Mid-elevation snowpack is predicted to decline 30-65% by the end of the century. 

To put this in context, the last time global temperatures changed by 4-5 degrees Fahrenheit was 20,000 years ago when much of the Southern Sierra Upper Montane was covered in hundreds of feet of ice and Death Valley was a 600-foot deep lake.

Following the national trend, the Sierra Nevada has also seen an increase in annual burn area, burn size and burn time among forest fires, making wildfires larger, more frequent, and greater in severity. According to Meyer, this is mainly driven by fuel aridity, decreased snow cover, and increased temperature. 

Projected vegetation changes in the Eastern Sierra that will result from these patterns include loss of yellow-pine and mixed conifer, red fir and subalpine forests, as well as loss of alpine vegetation. There is predicted to be an initial increase in shrublands, but then a decrease and a conversion to grasslands. 

With all of this in mind, the question became, “what can we do about it?” 

Ecologist Malcolm North responded with his data on tree resilience, advocating for trimming down roughly 80% of the trees in the region in order to prevent total dissemination from fire.  

According to North, a forest’s resilience from fire is determined by the stand density index (SDI) of the forest. This is defined as a measure that combines the number of trees per acre and the diameter of those trees in order to assess the total biomass of the forest. North uses a “relative SDI” to measure how crowded or open a forest is, which directly correlates with how resilient it is against effects of climate change.

During his presentation, North responded to a Fresno Bee Op-Ed criticizing his work, which was summarized in the February 25 edition of The Sheet titled, “Thinner Might Not Be Better”. 

He refuted the arguments made in the Op-Ed, originally written by his former student Chad Hanson, that stated that denser forests burn at lower intensity, logging increases fire intensity by changing the microclimate, and that removing trees will not curb fire intensity. 

North replied, “All of this ‘research’, all authored by Hanson, DellaSala and Baker, has been widely discredited, including in a recent systematic review of these claims authored by more than 50 of the leading forest and fire researchers … you can only get this amount of scientists to agree on something when you really piss them off.”  

He also objected to the statement that the study “promotes removing 80% of the trees through commercial logging” by saying that, “small trees would be removed with thinning and/or fire costing agencies.” 

According to North’s research, in open stands that have little competition, trees grow more rapidly. This growth vigor is their best defense against stresses such as fire, drought, bark beetles, and climate change, because it promotes large increases in ring width. In crowded forests, this rapid growth of ring width does not happen and therefore the trees are less resilient. 

North explained that he used data from 2011 to test this idea, as it was exactly 100 years after timber inventories were taken in the Stanislaus and Sequoia National Forests in 1911. In 1911, the forests showed 73-85% of trees were free of/or in partial competition. By 2011, 82-95% of them were in full competition to the point of imminent mortality.  

In order to sustain tree growth and preserve trees with a large enough diameter/ring width to withstand outside forces such as fire, drought, and invasive species, North argued that the trees need to have less competition among each other; i.e., the density of the forest must be thinned. 

And according to North, the amount that needs to be thinned is not small. He advocated for a maximum SDI of 35%, meaning that at least 65% (though more like 80% would be preferable) of trees must be removed if the remaining ones are to grow strong enough to be resilient. 

He advocated for creating a complex spatial pattern between the trees, including combining individual trees to make clumps of trees as well as leaving openings, as he believes this is the best way to keep the forest resistant from fire spread and drought.   

North’s argument is similar to the strategy of chemotherapy: when a cancer is invading all the cells of an area in the body, killing almost all of them, including healthy ones, and allowing new ones to regenerate is the best we can do currently to treat the cancer. 

Sometimes chemotherapy still isn’t enough. But is it worth it to still try?  

By spring of 2023, ESCCRP hopes to have an analysis of the project completely finalized.