Listen to the Trees!

Guest post by Jim Steele

What’s Natural?

Published in Pacifica. Tribune August 20,2019

This summer I taught a class on the Natural History of the Sierra Nevada for San Francisco State University’s Sierra Nevada Field Campus. The first day we taught students how to identify the trees. Once students know their trees, they can easily see how tree species vary with elevation, temperature, moisture, and snow pack. They can see which species colonize open sunny areas and which trees need shade before they can invade. Old time naturalists used trees to identify “life-zones” where different species of mammals, birds, insects and other plants can be found. Furthermore, when you listen to the trees, you can see change.

The class explored forests along the North Yuba River. Free from politics, trees tell us about changes in fire frequency, logging, climate change and ecosystem resilience. Photographs taken during the late 1800s during California’s gold rush days, revealed the total devastation of local forests. Gold miners needed wood for heating and cooking, for their metal forges, and for timbers to reinforce their mines. They needed wood to build flume boxes that altered river courses to expose riverbeds. Flume boxes also carried water from high to low elevations where giant water cannons completely washed away hillsides in their search for gold.

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Still, by comparing catastrophic photos of forests during the gold miners’ days to our current forest conditions, I was filled with optimism. The forests had totally recovered and again are quite dense. So dense, that local inhabitants fear there’s too much fuel on the forest floor that could feed catastrophic fires. Nevertheless, the lush re-growth is testimony to our forest’s amazing resilience.

We counted tree rings and determined a majority of trees were no more than 170 years old. Those trees began their lives shortly after the gold miners had cut down all their older relatives. Occasionally we found a few larger trees, 300 years or older, that fortuitously avoided the miners’ ravenous saw blades.

Scientists determine the natural frequency of fires by reading tree rings and fire scars. Low elevation trees like Ponderosa Pines naturally endured wildfires about every 25 years. At higher elevations, where temperatures are colder and the snow pack lingers, fire scars suggest wildfires naturally happen about every 100 years. In contrast to media hype, fire scars in living and fossil trees suggest wildfires were far more common during the cool Little Ice Age.

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Tree stumps tell us that trees once bordered Arctic shores 9000 years ago. Since then, cooler temperatures have pushed trees to lower latitudes and warmer elevations. Hikers in the Sierra Nevada often encounter dead trees several hundred feet above our current tree line. Accordingly, researchers determined that for the last 3 thousand years, tree line was mostly higher than today because temperatures were much warmer. However, during the Little Ice Age, between 1300 AD and 1850 AD, it got so cold, tree line dropped and tree seedlings in the Ural Mountains couldn’t germinate for hundreds of years. Ancient tree lines suggest if temperatures increase over the next century, it will not be a crisis. Trees will simply reclaim their former habitats.

Trees reveal past rainfall patterns. California’s Blue Oaks are very sensitive to changes in precipitation. In drought years they generate narrow rings contrasting with wider rings during wet years. A recent tree ring study of Blue Oaks finds no rainfall trend over the past 700 years, but it suggests Californians can expect extreme droughts and extreme rainfall 3 to 4 times a century. More concerning, tree stumps at the bottom of Lake Tahoe dating back 6000 years ago, suggest Californians can naturally expect far more extreme droughts than living humans have yet to experience.

Trees tell us how climate has changed. Fossil trees indicate Antarctica once experienced subtropical temperatures 40 million years ago. Similarly, trees tell us about recent temperature changes. Tree rings have correlated accurately with instrumental temperatures for over 100 years. However, since the 1960s, tree ring temperatures suggest a much cooler global climate in contrast to thermometers and models.

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Tree rings indicate the warmest decades of the 20th century were the 1930s and 40s, and temperatures have yet to surpass those decades. This divergence between thermometers and trees is best explained by the fact that instrumental temperatures are biased upwards when taken at hot airports or in areas recently suffering from growing urban heat island effects. In contrast, trees measure temperatures in natural habitat.

There are too many fear mongering politicians pushing an “existential climate crisis”. I find the climate history told by the trees far more trustworthy, and the trees are whispering there is no crisis.

Jim Steele is director emeritus of the Sierra Nevada Field Campus, SFSU and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

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60 thoughts on “Listen to the Trees!

  1. Thanks Jim. I taught the equivalent in sand dune succession in NSW, Australia. I enjoyed reading very much.

    • As always, Jim in a mine of useful facts presented in a scientific and objective way. A true scientist. Always informative and a pleasure to read.

      If only there were more like him.

      “This divergence between thermometers and trees is best explained by the fact that instrumental temperatures are biased upwards” … by constant manipulation by climatologists with an agenda, having no trouble with Schneider’s “dilemma” of whether to be honest or “effective”.

  2. As always, it is such pleasure reading Jim Steele’s articles. He is my favourite environmentalist. “The trees are whispering, there is no crisis”.

  3. Do you know where the second photo in the article, showing the bristlecones at tree line, was taken?
    Looks like White Mtns. In CA?

    • More likely in the Northern Sierra. I suspect the North Yuba given the inroductory remarks. There simply aren’t any streams in the White Mountains that would match the river in the image. Essentially every Gold Rush town in the Sierras looked like that during the Gold Rush. The best match I can find is Downieville: https://westernmininghistory.com/towns/california/downieville/. The image on the web site appears to be a crop of the large one in the article.

  4. The tree I find amazing is the ubiquitous Lodgepole Pine. They appear at a casual glance as several different species, depending on the habitat. I grew up among ones in moderate elevations in N. Idaho that were literally lodgepoles – tall, straight, skinny, bereft of branches except near the very tops, in groves “like hair on a dog’s back.” But in the Sierra around Tahoe I couldn’t recognize them as stunted, dense shrubbery. Only the cones and needles were diagnostic.

    • They also differ greatly with age. Young lodgepoles are relatively straight and straight grained.
      As they get older they begin to twist until many older ones look like barber poles, which makes them pretty much useless for anything other than aesthetics.

  5. “Trees reveal past rainfall patterns. California’s Blue Oaks are very sensitive to changes in precipitation. In drought years they generate narrow rings contrasting with wider rings during wet years. A recent tree ring study of Blue Oaks finds no rainfall trend over the past 700 years, but it suggests Californians can expect extreme droughts and extreme rainfall 3 to 4 times a century. ”

    here is what they said

    ‘For the past three years (2012–2014), California has experienced the most severe drought conditions in its last century. But how unusual is this event? Here we use two paleoclimate reconstructions of drought and precipitation for Central and Southern California to place this current event in the context of the last millennium. We demonstrate that while 3 year periods of persistent below‐average soil moisture are not uncommon, the current event is the most severe drought in the last 1200 years, with single year (2014) and accumulated moisture deficits worse than any previous continuous span of dry years. Tree ring chronologies extended through the 2014 growing season reveal that precipitation during the drought has been anomalously low but not outside the range of natural variability. The current California drought is exceptionally severe in the context of at least the last millennium and is driven by reduced though not unprecedented precipitation and record high temperatures.”

    “Based on our NOAA‐NADA composite PDSI record, we estimate that 2014 is the worst single drought year of at least the last ∼1200 years in California (Figure 1). Taking into account the uncertainties in scaling the NADA tree ring data to the instrumental PDSI, 6 years were possibly similar to or drier than 2014, (including 1580, 1782, 1829, and 1841 CE) at the 1σ level, while 36 years out of the last 1215 years include the 2014 value within 2σ uncertainty. Three year droughts are not unusual over the last millennium in California and they can occur with as little as a single year between negative moisture anomalies (Figure 3a). Over the last 1200 years, we estimate that there are 37 occurrences of 3 year droughts and a total of 66 uninterrupted dry periods (e.g., every year below the 800 to 2014 mean) lasting between 3 and 9 years. We estimate that ∼44% of 3 year droughts go on to last 4 years or longer. However, the 2012–2014 drought stands out in the context of the last millennium. In terms of cumulative severity, it is the worst drought on record (−14.55 cumulative PDSI), more extreme than longer (4 to 9 year) droughts. Considering only drought episodes defined by at least three consecutive years all lower than −2 PDSI, only three such events occur in the last 1200 years, and 2012–2014 is the most severe of these.”

    • I note that the referenced Blue Oaks paper was published in 2014 and, fortunately for the people of California, rainfall since has returned their reservoirs to a much fuller state. Although the recent drought was severe, the “no rainfall trend” statement seems correct.

      • I do remember seeing a paleoclimate reconstruction for California using tree rings that indicated several multi-decade droughts early in the Little Ice Age. ~`=1400’s or so, which would have been rather more severe than the most recent multi-year drought.
        The remarkable thing from that reconstruction was how even and relatively drought free California had been since ~1850, and the start of instrumental weather records in the state. The point of the record was just how unusual “normal” weather had been, in a historical sense.

    • Would this be the same NOAA that told us the year after Katrina would be even worse? Why yes, it is! 😄

    • Mosher,

      You confuse the tree evidence with a manufactured index.

      The trees did not show any evidence of a change in precipitation. As they reported “Tree ring chronologies extended through the 2014 growing season reveal that precipitation during the drought has been anomalously low but not outside the range of natural variability.”

      The climate guys then mashed the tree evidence with their Palmer Drought Index they that is notorious for certain biases. It assumed that heat causes more evaporation and thus more drought when just the opposite was the case. The lack of precipitation caused more heat. Using the Palmer index amplified the drought only I virtual statistical reality

      Listen to the Trees Mosher!

    • RE: “the current event is the most severe drought in the last 1200 years … is exceptionally severe in the context of at least the last millennium and is driven by reduced though not unprecedented precipitation and record high temperatures.”

      1200 years? Is that all? As Jim says, “Listen to the Trees!” There are living Sequoia trees in California that have lived through several such periods. They were already healthy adults when Pythagoras was sorting out the secrets of right triangles, and still young when a certain rabbi was wandering around the hills of Judea starting a new religion 500 years later. They have seen it hotter than now (Roman Warm Period, Medieval Warm period) and colder than now (Dark Ages, Little Ice Age) and have endured countless generations of mayfly creatures like field mice and humans tromping about under foot. Now in their golden years, if they take any notice of humans at all it would only be to notice that the frenetic activity of these annoying little animals has made it a little easier to breathe in the carbon they need to stay healthy.

    • “Taking into account the uncertainties in scaling the NADA tree ring data to the instrumental PDSI, 6 years were possibly similar to or drier than 2014, (including 1580, 1782, 1829, and 1841 CE) at the 1σ level, while 36 years out of the last 1215 years include the 2014 value within 2σ uncertainty. Three year droughts are not unusual over the last millennium in California and they can occur with as little as a single year between negative moisture anomalies…”

  6. Jim,
    When you talk about tree recovery after the gold mining ended, you might also note that the land has also mostly recovered.
    Mining has been given a bad name by people who do not understand it – or want to understand it. Most people have little idea of the tiny area of land globally that has been affected by mining, let alone the even more minuscule area remaining after both natural and man-made rehabilitation.
    Not surprisingly, geologists are among the more prevalent users of the knowledge of trees. There are even specialists in geobotany and biogeochemistry. In the 1970s we did an exercise with bow and arrows to sample new leaf growth from tall trees over uranium ores hidden under mile after mile of monotonous, signal-lacking laterite soils. Chemical analysis of the leaves gave signals that easily helped map the concealed bedrock geology.
    It is all a matter of Science progressing by measurement, observation, logical deduction. No place whatever for consensus beliefs. No place for adjusting measurements for a better fit to vague preconceptions.
    What it more, good Science done well is great fun and intellectually rewarding. Jim, your essays convey this too. They are most welcomed. Geoff S

  7. “In contrast to media hype, fire scars in living and fossil trees suggest wildfires were far more common during the cool Little Ice Age.” – article.

    That won’t make the ecohippies happy, any more than describing changing weather patterns as what they are (reality) instead of what they are not (imaginary).

    Good article, and I’m glad to see facts being presented to students instead of fluffy bunny fantasies.

  8. Trees tell us how climate has changed.

    Trees record weather. Heat, humidity, cloudiness, etc. Those are not climate, those are conditions.

  9. From the article: “Tree rings indicate the warmest decades of the 20th century were the 1930s and 40s, and temperatures have yet to surpass those decades.”

    This caught my attention. All the *real* evidence says the same thing. 🙂

    Great article, Jim.

  10. A very interesting article
    Our oaks have two flushes of growth, the main spring flush and then depending on the amount of rainfall, a late summer flush.
    Rainfall and sunlight seem to be the two main instigators of growth, then pest attack and crowding by other trees are the main factors responsible for reduced growth.
    Temperature seems to be less important apart from its effect as a byproduct of a late spring and early autumn.

  11. Great information and so easy to understand. Intelligence I can easily pass on to my grand-children to debunk the lies they get at school.
    Thank you

  12. Hikers in the Sierra Nevada often encounter dead trees several hundred feet above our current tree line. Same as the Colorado Rockies. Thanks for another great post Jim.

  13. Jim – as a retired forester I very much appreciated your essay.

    Another observation: ~14,000 years ago, there were boreal elements (black spruce, balsam fir, e.g.) on the US Gulf of Mexico coast.

    Trees move in response to climate, slowly, but they do move.

    • Yes, trees indicate climate.
      https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification

      Animals respond to weather. Plants can’t move, so must adapt to climate.
      Classical ecology. That’s why biologists understand climate better than physicists.
      Any biologist will say there has been no significant climate change in the last 8000 years.
      We are in a minor climate recovery from the little ice age. Which is mostly just random meandering since the end of the last glacial collapse. CO2 follows climate.

  14. Great article. Give us more.

    This does illustrate one thing that has continually bothered me. There must be a plethora of historic records that can give some indication of weather and climate throughout the world. Diaries, paintings, tax collections, harvest volumes, river flows, tree rings, tree lines, etc. have been kept for millennia all over the world. I know they are not as precise or as easy to gather and analyze, however, they can provide information like this article.

    Too many climate scientists want to deal with precise temperature readings, statistics, computer coding and mathematics rather than do the tedious and hard work of deciphering all of the different recorded information from the past and then developing a coherent view of climate from the past to the present. It’s more fun to computer model what might happen rather than deal with what has already happened.

    • Sure, the average grape grower in Roman times knew more about climate than any physicist will ever know. His life depended on his crop.
      History records climate changes, it shows minor shifts in local climates over century time scales.
      http://academic.emporia.edu/aberjame/ice/lec19/holocene.htm
      or
      https://en.wikipedia.org/wiki/Phenology

      The ego of the modern eco-fascist can’t admit that regional climates can shift slightly over centuries.
      At the same time, the major global climate has not changed significantly in 8000 years. The definitions of the major Koeppen climates show this clearly.
      Read the detailed observations of Lewis and Clark from their notes. Then follow their track today.
      No climatic changes since 1805.

  15. Tree ring data are probably not a good proxy for temperature, but rather rainfall. A wide tree ring indicates that the tree has grown more in that year than in a year with a narrow ring, but trees need both above-freezing temperatures and rainfall to grow. A relatively warm early spring or late fall might prolong the growing season, but if the summer is hot and dry, trees will not grow much.

    Interestingly enough, in the Wasatch mountains of northern Utah (which have snowy winters and rainy weather in April and May, but very dry summers), the south-facing slopes have very little vegetation (mostly grass and scrub brush) while the north-facing slopes have tall conifers up to about 10,000 feet elevation, even though those slopes receive less sunlight and are somewhat cooler than the south-facing slopes.

    This is probably due to the fact that on south-facing slopes, most of the snow melts by late March or early April, and there is not enough soil moisture to sustain a tree through the hot, dry summer. On the north-facing slopes, snow-cover can remain through May or early June, so that there is enough soil moisture to sustain trees through the dry months of July and August, and the tree roots help trap this moisture against erosion.

    This tends to indicate that tree growth rates are more sensitive to rainfall and humidity than to temperature.

    • Steve, You are right that tree rings could be more sensitive to rainfall and humidity, but those factors are being minimized.

      First, choice of tree location becomes important. Tree growth stops at high elevations due mostly to temperature. So temperature proxies are taken at treeline. In contrast Black Oaks in the California foothills are more sensitive to rain.

      Second the tree ring width is separated into early and latewood. Early wood cells expand according to the availability of moisture. The latewood develops smaller denser cells and is more sensitive to temperature, so MXD measurements, maximum density of latewood is used for temperature trends

    • Trees grow on the north slope of valleys in western North Dakota for the same reason. The snow melt off and drains away to early on the south facing slopes.

      • Mark A Luhman
        Similarly in California. Most of the rivers coming down off the Sierra Nevada are flowing west. This means that the north side of river canyons get more sun than the south side, and it is reflected in the vegetation to be found on opposite sides of the river, with trees and brush usually denser on the south (north facing) side and grass being more abundant on the north side. Although, there are some anomalous areas such as “Serpentine Canyon” east of Richbar on the Feather River, where both sides have sparse vegetation because of the bedrock.

  16. Thanks for the links to the report.

    My area (2400 ft el) is at the Northeast boundary of the Blue Oak zone- see supplemental info of the report. It doesn’t look as if any oaks from our area made it into the report. Our rainfall was about 24″ during the latest drought years and we had 88″ of rain during the drought buster a few years back.

    This years late rains/snows (7″ during the first couple weeks of May) meant our seasonal creeks and culverts were flowing until the second week of June. I still have some black berry bushes growing at the wettest part of our parcel.

    Our biggest oak, either a blue or red variety, is 18 and a half feet in circumference. It’s closest neighbor is up a grassy knoll. It passed away about a year and a half ago. That Black oak, we think, is just over 10 feet in circumference.

  17. I was always fascinated with the world around me. My parents had a weekender in the country and I spent formative time there from infancy to recently. My family had it declared a wildlife refuge. I went to uni and studied botany and zoology. I watched the world around me. I loved the trees, they are beautiful and such a great resource and so useful. I listened to what was being said about “The Environment”. I saw what had happened over my life. Things were not adding up. What I was told about landscapes and forests did not play out in what I could see happening. The forests were NOT disappearing. They were growing back thick and fast in just my short life span. I went to work in CSIRO. I saw that research was political and faddish, you had to put the right thing in your research grant proposal or you didnt get your mortgage paid. They had that Rio earth summit and our council enacted it. My parents property was sterilized from use and use of trees by the Agenda 21. We lost out greatly, the local mills shut, we could not use our own trees that had grown (really big ) in my lifetime. It is in a very good tree growing area. Land was worth less with trees on it! I saw all these fads in science, I wondered what the next one would be. Along came “global warming”. I tried that idea out for a bit then decided it was the next fad. So I was sceptical of global warming before I heard of it. Then the Australian government enacted Native Vegetation laws to meet UN carbon standards, effectively making farmers pay for the UN bs. If you have land with trees on it, it really is not yours any more and effectively belongs to the government. From my background I should be a classic greenie, but I have learned the hate the environmental movement with a passion, pack of lying frauds obscessed with power and money. By this time I was in the farming sector, and paying again for the fads in science. People dont realise its illegal to plough in NSW if you have not for 10 years because of the Narive Veg laws which apply to grasses. It is illegal to cut native grass in NSW. I have watched the trees (and grass) and try not to listen to the bs any more (I cant bear TV news) and they say such a different story than what we get told. I do trust the trees.

    • The big change in all Australian states has been the influence of the city based Green Party.
      These without listening to the trees have convinced the various levels of government to confiscate the trees from landholders. No compensation provided.
      Effectively the Green Party has pushed through punishment for anyone keeping and growing trees.
      The real environmentalists live on the land and observe (and hope to survive all the green regulation, taxes and compliance costs).

  18. Great article Jim. Just one observation about the comment that fossil trees indicate that Antarctica once experienced sub tropical temperatures 40 million years ago. Given the migration of the Continental plates it is probably more accurate to say that what is now the antarctic was positioned to experience subtropical temperatures 40 million years ago.

    • There is that, but geologists say that even with that taken into account, nearly the whole earth was tropical or sub-tropical with the mean global temperature 85℉ (currently at 57-58℉)

    • nw, The Antarctic reference was only intended to show that trees tell about pat climates, not what caused those climates.

      That said, I would argue that the evolution of the Antarctic polar climate was not because tectonics changed Antarctica’s position over the pole, but that tectonics broke up the land masses allowing the formation of the Antarctic Circumpolar Current which then insulated Antarctica from poleward transport of warm tropical waters.

  19. ‘Photographs taken during the late 1800s during California’s gold rush days’

    Uhh . . . no. The Gold Rush ended in 1855.

    In line with what Steve Z said, tree growth and distribution is significantly affected by both temperature and rainfall. Attributing historical growth or distribution to one or the other is questionable without actual data of the conditions at the time.

    • Gamecock
      I’m not sure what the point of your ‘correction’ is. While the bulk of the human migration took place took place in the early-1850s, the impacts on the environment resulting from placer and later, hydraulic mining, continued until 1884. As hardrock mining supplanted the original placer/hydraulic mining, the demand for mine timbers also put a strain on the forests. Hardrock mining basically continued up until WWII. And, indeed, from the earliest Argonauts on, the demands for lumber to rebuild the mining towns every time they burned, contributed to over-harvesting of the forests. I see no substantive problem with the statement “‘Photographs taken during the late 1800s during California’s gold rush days’

      https://www.goldrushnuggets.com/hymi1.html

      • Precisely Clyde,

        Gamecock seems desperate to just snipe and denigrate skeptic viewpoints. Although wikipedia might define “Gold Rush Days” as ending by 1855, the effects of gold mining in California existed throughout the late 1800s. The early gold rush simply found nuggets in the stream banks and the easy picking ended n 1855. However after tracing those gold nuggets to their source, minders began hydraulic mining and hard rock mining throughout the late 1800s. Gold fever continued to destroy ecosystems well past 1855.

        I have simply added Gamecock to my list of no-nothing internet snipers.

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