Increased Atmospheric CO2 Is Increasing the Maximum Height of Old Growth Redwood Trees in Northern California

Note the information and assessments made herein are those of the author.  Some statements of facts and forecasts involve a degree of conjecture.

1       Increase in Atmospheric CO2 Since 1900

Atmospheric carbon dioxide (CO2) has increased since 1900 at an increasing rate.   This is due to the burning of fossil fuels to support industrialization, transportation, and home comfort.  Before 1900 the concentration of atmospheric CO2 was about 285 ppm and holding steady.  Now it is 415 ppm, increasing at an increasing rate, and will likely be around 500 ppm by 2050. 

For plants, CO2 provides energy for photosynthesis.  For humans, CO2 is a product of cellular respiration and must be released by breathing.  Increasing CO2 from the background level of 285 ppm up to about 1,000 ppm enables faster plant growth.  This is commonly done in indoor green houses.

However we humans have evolved over the past 200,000 years with CO2 at 285 ppm, now it is much higher.  In the same way increased CO2 supports increased plant growth, it is possible increased CO2 creates adverse issues for human cellular functioning.  Indoor CO2 levels over 1,000 ppm cause people to start to feel drowsy, an indicator of impeded brain function.

Plants:  Carbon dioxide + water + light YIELDS glucose + oxygen + water

Humans and other mammals:    Glucose + oxygen YIELDS carbon dioxide + water

2       Increase in Redwood Tree Growth Rates Since 1950

Studies of tree rings have shown redwood trees in the northern redwood parks have increased their growth rates markedly, especially since 1950.  Tree ring width since 1950 can average 50% per year more than what was experienced on average in the tree’s 1,000 to 2,000 years of life before 1950.

The northern redwood parks have not experienced adverse climate change like the southern redwood parks.  The recent droughts in the Humboldt and Del Norte county redwood parks were not as severe as those further south and there were no major fire events within these parks.   The increased CO2 has not led to substantial adverse climate events in the northern redwood parks and the redwood trees are increasing their growth rates in response to the CO2 increase.

3       Height Changes in very Tall Redwood Trees Since 2000

The increased growth rate in redwood trees is also expressed in increased crown growth, leading to increased tree height. It is documented theoretical tree height is limited to 425 feet or so due to how far ground nutrients can be pulled upward by adhesion versus the effect of gravity. For tall redwood trees this is partially offset by fog absorption but the demonstrated current height limit is 381 feet, with an historic height limit of maybe 400 feet. But for most of their lifespans the tallest redwood trees dealt with CO2 at 285 ppm, now it is 415 and going to 500.  So they may be able to get taller, all other things being equal.

To assess this, here are height changes in the tallest redwood trees by park that were measured somewhere around 2000 and then again somewhere around 2013.  So the height changes are over a 13 year period on average.

If redwood trees were experiencing their maximum heights then it would be expected the tallest trees in 2000 would grow less in the next thirteen years than trees that were a bit shorter. 

For RNP and HRSP this is not the case, the tallest trees grew just as much as other slightly shorter trees during the thirteen year period.   For MWP the tallest trees were suppressed, this is in line with the drought and fire conditions experienced by that redwoods reserve.

Humboldt redwoods 25 tallest trees measured in 2000 and 2013. Ordered left to right by descending height. Note tallest trees continued to grow at rate of less tall trees.

Humboldt Redwoods 93 tallest trees measured in both 2000 and 2013. Ordered left to right by descending height. Note tallest trees continued to grow at rate similar to less tall trees.

Redwood National Park tallest trees mesured in both 2000 and 2013. Ordered left to right by descending height Note tallest trees continued to grow at rate of less tall trees. Also note many current RNP tall trees were unknown in 2000.

Montgomery Woods Reserve tallest trees measured in both 2000 and 2013, ordered left to right by descending height. Note max height has been reached as tallest trees grew less than less tall trees. Park was subject to drought and fire during the 2000-2013 time period.

4       Tallest trees in 2050

It is likely the tallest redwood trees in the northern redwood parks will continue to grow, at an increasing rate, at least to the year 2050.  By 2050 the tallest trees, and the entire redwood canopy, are likely to be six or more feet higher than they are now.

So at least in part of their range, the redwood trees are benefitting from increased CO2.  As for people, the benefits are less certain.

Thanks for reading.

3 thoughts on “Increased Atmospheric CO2 Is Increasing the Maximum Height of Old Growth Redwood Trees in Northern California”

  1. Hi Mark. Related to #2 … there was drought-like conditions for a growing season or two the past 6 years or so. I still recall the ferns in Humboldt Redwoods withering so small as to wonder about them. But most seem to have pulled-through as well as the odd increase in yearly height growth rate among some tallest redwoods around Redwood National. There were some fire events, but not unconstrained or spreading. Apparently a few small strikes were contained to areas as small as an acre or less. I can’t recall a single lightning strike in the past 10 years that’s been allowed to run its own course in Redwood National and State Parks. Since I don’t know the answer about something else, it would be a pure guess other species are putting on bulk too. But if the redwoods are putting on bulk and enjoying the CO2, seems likewise the maples, red alder, hemlock, etc., could also.

    1. Hi Mario

      Would make sense everything with a leaf is benefitting from increased CO2, all other things being equal.

      If plants can store more carbon through increased growth this should mitigate the rate of increase in atmospheric CO2.

      Thanks for the correction on the level of drought in the northern redwood parks.

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