Proposed forest thinning will sabotage natural forest climate adaptation, resistance to drought, fire, insect outbreaks

Proposed Forest Thinning Will Sabotage Natural Forest Climate Adaptation and Resistance to Drought, Fire, and Insect Outbreaks
Thinning logging in Arizona. Thinning sabotages natural forest adaptation to climate change. Credit: USDA Forest Service

The USDA Forest Service is proposing widespread forest thinning on our public lands across the West in a misguided attempt to reduce the impact of drought, fire, and insects (see National Forest Restoration Projects, Sierra Nevada National Forest Land Management Plan Revisions, news articles). These logging schemes are the latest in a series of Forest Service attempts to chainsaw their way out of a perceived problem. However, forests in the western United States have evolved to naturally self-thin uncompetitive trees through forest fires, insects, or disease. Forest fires and other disturbances are natural elements of healthy, dynamic forest ecosystems, and have been for millennia. These processes cull the weak and make room for the continued growth and reproduction of stronger, climate-adapted trees. Remaining live trees are genetically adapted to survive the new climate conditions and their offspring are also more climate-adapted, resistant, and resilient than the trees that perished. Without genetic testing of every tree in the forest, indiscriminate thinning will remove many of the trees that are intrinsically the best-adapted to naturally survive drought, fire, and insects.

Recent studies have demonstrated that genetic variation is high within populations of forest trees, with especially high diversity found at the lower latitudes and altitudes that form the edges of a species' distribution. Local genetic and epigenetic variation makes some individuals naturally more likely to survive drought, fire, and insect outbreaks. This is because ecotones, or transitional areas, are where each species experiences the most extreme climate conditions that it can survive, the lowest elevation and latitude boundary. These natural edges are where trees with the most resistant and resilient adaptations are found. It is also where significant mortality is to be expected as part of the process where the distribution of tree species shifts north and uphill in our warming climate.

After forest fire or insect-caused mortality, green forest naturally regenerates without any need for expensive human interventions. Locally climate-adapted tree seedlings sprout and grow, and nitrogen-fixing shrubs and forbs replenish the soil and curb erosion. In the meantime, standing dead trees, snags, and logs provide critical food and shelter for many types of wildlife. Seedlings used in most Forest Service replanting efforts are bred for timber production, and although breeding programs are now looking for drought and temperature tolerance, there is a natural breeding program already underway that costs nothing and ensures the most locally adapted individuals will resist and persist as the climate warms.

Weather and climate data are painting a clear picture of warmer, drier summers across most of the western United States. Forest fires are strongly correlated with the Palmer Drought Severity Index where drier years make bigger fires, so people living in fire-prone areas need to be prepared for wildfire as an inevitable occurrence, and take all precautions to protect their homes with defensible space and ember-stopping attic vent screens. Thinning the forest within a hundred yards from structures and some minor fireproof retrofitting are the only practices proven to protect homes and communities from wildfire.

The West is getting drier than it was in the recent past, and that will require some adaptation, particularly in light of the significant recent human population growth in rural areas. We must also understand that recent fires are not unprecedented in size or severity as is often claimed by people who make money cutting our trees. The early 20th century sometimes saw 30 million acres of burn, and that was before widespread fire suppression, so fuel buildup is not the looming fire monster some folks who profit from logging have made it out to be. The world is an inherently dynamic and changeable environment, and generally the cost of fighting change is much more expensive than adapting to it.

Explore further

Dead trees don't fuel megafires

More information: Kolb, T.E., Grady, K.C., McEttrick, M.P. and Herrero, A., 2016. Local-scale drought adaptation of ponderosa pine seedlings at habitat ecotones. Forest Science, 62(6), pp.641-651.

Prunier, J., Verta, J.P. and MacKay, J.J., 2016. Conifer genomics and adaptation: at the crossroads of genetic diversity and genome function. New Phytologist, 209(1), pp.44-62.

Pinnell, S., 2016. Resin duct defenses in ponderosa pine during a mountain pine beetle outbreak: genetic effects, mortality, and relationships with growth. PhD Thesis, University of Montana, Missoula.

Journal information: New Phytologist

Citation: Proposed forest thinning will sabotage natural forest climate adaptation, resistance to drought, fire, insect outbreaks (2017, January 16) retrieved 17 October 2019 from
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Jan 16, 2017
"I will terminate spending on all of NASA's climate change programs until they say their CO2 end of the world is as real as they say the planet isn't flat and those news editors responsible for abusing science and fear mongering our children will have their day in court."

So why doesn't NASA just say it before it's too late to say it and end this debate to; "save the planet"?

Jan 16, 2017
The West is getting drier than it was in the recent past

Hmmm...the recent past couldn't possibly be the 1930s, when it was hotter and drier.
The fact is, the intense fires and outbreaks of insects and diseases are a direct consequence of the indiscriminate fighting of forest fires.

Jan 16, 2017
I don't buy your argument that the small-scale selective harvesting that is taking place in fuel reduction treatments will eliminate the genetic variation of fire dependent species from the landscape. Some counter points:
1.) Fire intolerant (i.e. Grand/white fir) are often targeted during silvicultural prescriptions that are implemented in fuel reduction treatments. Leaving most of the fire tolerant/dependent trees right where they are.
2.) No one is getting rich from fuel reduction treatments. Most prescriptions are limited to max diameters of 21" or less and after processing and removing the large quantity of non-merchantable material treatments barely break even.
3.) Wildfires are getting bigger and more severe - Look at the MTBS datasets
4.) Fuel treatments represent a fraction of the acreage that burn up every year in wildfires.
5.) Fuel treatments will not stop wildfires but can create refugia that will protect genetic diversity and prevent critical wildlife habitat loss

Jan 17, 2017
pfkety, you are misinformed.

The USDA Forest Service is implementing hundreds of thousands of acres of 'thinning' and pushing for vastly more acreage. That is not small scale. It is hundreds of millions of dollars in taxpayer-funded budget stuffing for an ecologically damaging and ineffective method of fire safety. If the Forest Service wants to protect communities, they should work there, not in the vast landscape they want to thin. Go read the documents I linked in the story and you will see what I am talking about.

WIldfires are not getting bigger and more severe over the longer term scale of centuries. MTBS data only go back to 1984, so you are spreading misleading info extrapolating trends from a few decades of recent satellite data.

Thinning treatments do not stop the biggest, hottest wildfires, The USFS own scientists have said their treatments did nothing to slow or stop the Rim and King Fires. Many other studies from real fires and real treatments confirms this.

Jan 17, 2017

The fact is, the intense fires and outbreaks of insects and diseases are a direct consequence of the indiscriminate fighting of forest fires.

WRONG antigoracle. Our warming and drying climate is driving recent trends in fires and insects. Long-term studies, going back thousands of years, shows climate is the ultimate driver of fires. The narrative of 'fire suppression creates more intense fires' is spread by people who want to profit from logging our publicly-owned national forests. Timber companies and the USDA Forest Service increase their profits and budgets when they sell our timber, and they use any excuse to do so. The story keeps changing as to why our forests should be logged, but for a century, the solution proposed has always always been logging.
Follow the money and you will see a pattern.

Jan 24, 2017
The forest service have their own Ph.Ds and apparently disagree.

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