Note the information and assessments made herein are those
of the author. Some statements of facts
and forecasts involve a degree of conjecture.
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
Plants: Carbon dioxide
+ water + light YIELDS glucose + oxygen + water
Humans and other mammals: Glucose
+ oxygen YIELDS carbon dioxide + water
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.
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.
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.
Redwood thunder is an uncommon but not rare event. It occurs when a large redwood tree falls to the forest floor, sometimes striking and taking other redwoods, firs, spruce, oaks, and maples with it. A cubic foot of redwood weighs 50 pounds, so if a moderately large 20,000 cubic foot redwood topples that is a million pounds, or 500 tons of wood crashing to the earth.
For redwood thunder to occur usually soaked soil and wind are required, though if the tree fractures on itself soaked soil is not an ingredient. Sometimes before redwood thunder occurs the tree will lean against an adjacent tree, with the trunks and branches rubbing with the wind and making screeching sounds like giant stringed instruments.
All redwood trees eventually topple, or at least break off down to a low point on the trunk. If a given old growth redwood has a one in a thousand chance of falling in any given year than that means, based on acres of old growth redwoods, the average annual tree fall count in the large redwood parks is about 300 trees, per park.
If there are multiple trees involved in a tree fall or if the tree falls across a creek, the tree fall is noticeable in Google Earth. If you hike the same trails over several years you will for sure see trees that have recently fallen. Their upper trunks are huge and their logs run sometimes more than a football field along the forest floor.
2 Examples of Tree Falls
Here are several examples of tree falls I ran across in 2016. Included are a picture I took of the tree fall accompanied by before and after Google Earth views of the tree fall areas (using Google Earth historical imagery).
In Humboldt redwoods a neighbor of the big Dyerville Giant log fell in the late spring 2016. Its trunk shattered and splintered into sections where it struck the Dyerville Giant log.
Another recent tree fall in Humboldt was in the area where a seasonal foot bridge is put in to link the Rockefeller Redwood area to the Giant Tree area on either side of Bull Creek in the upper Bull Creek Flats. The new big log is used a lot to cross the creek, though it would be a pretty tough eight foot or so fall from the log to the rocky creek bottom if your foot or the bark slipped.
A third fall in Humboldt occurred in Harper Flat. The tall north side of a twin trunk redwood fell in the last couple years.
The final example is in an area of tall hillside redwoods on the east side of Redwood Creek a little north of McArthur creek near the seasonal foot bridge. Here the tree fall took out a number of redwoods and the whole group of fallen trees is slowly sliding down toward Redwood Creek.
3 What Can Be Learned From Fallen Redwoods
A recently fallen redwood is a great opportunity for whole tree research once the soil in the fall area has stabilized. The root system and affixed soils can be studied without any digging, this is the big primary benefit. But also core samples can be extracted without having to climb and core living trees. The canopy structure can be measured and reviewed without climbing and an unlimited amount of destructive sampling can be done.
NASA maintains a global canopy height map on its website. This map is comprised of airplane based LIDAR mapping (2.4% of land mapped for canopy height) and satellite based “spectroradiometer” equipment (97.6% of land area mapped for canopy height). The canopy height is appropriately in shades of progressively darker green with the darkest green indicating at least eighty percent of the tree canopy in the area is over 70 meters (230 feet). All the dark green areas in northern California are old growth redwood stands. The average tree height in old growth stands in northern California is 250-300 feet, with maximum demonstrated individual tree height at 380 feet. To see more on this subject see my posting on “Distribution of Tree Height in an Old Growth Redwood Forest”.
Below is a portion of the Global Canopy Height map that includes the area from Fortuna to Klamath. The dark green (old growth redwood) forests have been noted from north to south. The old growth forests include Prairie Creek Redwoods and Redwood National Parks. No surprises there. However there are five additional areas with large enough tracts of old growth redwoods to be discernable on the global canopy height map.
You can click on the map to see a larger version.
2 Lesser Known Areas With Old Growth Redwood Forests
From north to south here are some comments on the lesser known areas with old growth redwoods forests.
Six Rivers National Forest High Prairie Creek Section and Yurok Redwood Experimental Forest
This area is low elevation and is protected from the ocean by a large ridge and has riparian zones along High Prairie Creek. These are perfect conditions for large and tall redwoods and indeed there are many large tree crowns in this area as seen on Google Earth.
This area does not have any public access and most requests for special access will be declined.
This could be the best area for old growth redwoods between Prairie Creek Redwoods State Park and Jedediah Smith Redwoods State Park and the trees in this forest are representative of the redwoods found in those parks.
Private Holdings – GDRC and HRC
The GDRC dominates timber holdings north of Eureka while HRC has extensive holdings around Eureka and south. Both these companies provide detailed publicly available management plans and holdings maps. Most of their holdings are managed second growth but they do have some old growth forests. Any old growth areas of three acres or more are voluntarily and permanently protected from harvesting and road construction by both of these companies.
I am not familiar with the access requirements for these areas but certainly written permission would be required from the respective company.
Some folks call this the “mysterious Headwaters Reserve”. It was the scene of some famous forest protection protests in the 1990’s and culminated in 1999 with a $380 million purchase of 7,000 acres from the owning lumber company, of which 3,000 acres are old growth redwoods. The purchase was 100% taxpayer funded, $250 million from the Federal government and $130 million from the state of California. The Reserve is managed by the Bureau of Land Management.
The Reserve does have public access though it is limited. There is a north approach which requires a five mile hike or bike from a parking area to reach the heart of the reserve. Then there is a south approach from near Fortuna that requires a reservation and meeting up with a representative of the reserve.
This reserve contains a few redwoods in the 360 feet height range. This is exceptionally tall, there are less than sixty redwoods throughout their range that are over 360 feet in height. Undoubtedly there are exceptionally large diameter and volume trees in this reserve as well.
3 Record Breaking Redwoods Outside the Redwood State and National Parks?
Any of the lesser known areas highlighted above could hold a record breaking tall redwood tree. It is not likely but there is a chance. As one well known redwood explorer writes – “chance has potential”.
Based on the existing information on tallest redwoods, a super tall redwood can grow anywhere from near sea level to around 900 feet in elevation. That covers a lot of ground. As long as the soil is good, there is some protection from wind from surrounding trees and hills, and there are year round water sources (nearby creeks, springs, and fog drip) a very tall redwood is a possibility.
Then to increase the possibility there needs to be a forest of trees growing in conditions for super tall redwoods. Each of the lesser known areas outlined above contains such a forest, as confirmed by the NASA global canopy height map.
For the same reasons there could also be very large (over 20,000 cubic feet) redwoods in these areas as well.
Old growth redwoods – that phrase invokes a lot of different feelings in people. Certainly in the present the phrase describes the large never cut forests in the redwood parks. Forests full of giant trees, some by rivers or streams and others along hillsides. Forests covered with needles and sorrel and forests covered with ferns. Forests with deer moving through them to reach the creeks, all the while shadowed by mountain lions. Forests with black bear dens. Remote and rugged but never more than a few miles from a highway.
Two parks with many acres of old growth redwoods as well as the ten tallest trees in the world are Humboldt Redwoods State Park and Redwood National Park. Each parks contains hundreds of thousands of old growth redwood trees. Here is the math:
Acres Old Growth Redwoods
# Redwood Trees > 100 cm per Hectare
# Acres per Hectare
# Old Growth Redwood Trees
The redwood density figure is a general rounding of the findings in a redwood plots study underway at Humboldt State University.
If that number seems too high, well…. Here are two pictures. These are from the Redwood Creek Overlook on Bald Hills Road in Redwood National Park. The old growth forests and patches are very distinctive. If you go to that overlook and put a strong pair of binoculars on those forests it is an impressive site. Many big and tall trees all growing along Redwood Creek and the surrounding feeder creeks and hillsides. I can’t imagine a more spectacular forest. It is kind of intimidating.
2 Height Distribution for the Tallest Trees
Thorough ground based searches combined with LiDAR technology have given a pretty complete picture of tree height in all parks with the exception of the Headwaters Reserve. The tallest redwoods, those over 365 feet, are all in Humboldt Redwoods State Park and Redwood National Park, with the exception of two trees in the exceptional Montgomery Woods Reserve. Then all the trees over 370 feet (there are only ten or so) are in Humboldt Redwoods State Park and Redwood National Park.
There are two things that are apparent when viewing these graphs. First, the distribution patterns are very similar between the parks. And second, there are a lot more tall trees in HRSP than in RNP. Based on this data paired with the history of each park the explanation is certainly this: In Humboldt most of the forests with the tallest trees are intact. In Redwood National Park most of the forests with the tallest trees have been thinned or removed.
3 Height Distribution for Old Growth Redwood Trees
Noting the steepness of the curve on the tall trees graph it is evident there is some type of “bell shaped” distribution where there are many trees of a certain height, say 350 feet, then the trees get fewer and fewer at 360 feet and even more scarce at 370 feet.
Using this information and the total number of old growth redwoods we can infer the number of trees of certain heights:
Expected Pct of Trees Less Than
HRSP Expected Trees
RNP Expected Trees
HRSP + RNP Expected Trees
Looking at the results of expected trees versus actual tree populations, it is evident four standard deviations describes 368 feet or so redwoods, while 4.5 standard deviations describes the very tallest redwoods (380 feet).
Then with some calculations and interpolation, we can arrive at three standard deviations corresponding to a 338 foot redwood tree. This then results with the following very approximate distribution of tree height in old growth redwood forests in Humboldt Redwoods State Park and Redwood National Park.
So the average old growth redwood in Humboldt and Redwood NP is 250 feet tall. Remember this covers all old growth trees at all elevations that are at least 3.28 feet in diameter.
Then there are 1,000 trees over 338 feet in height.
What do you think?
4 Old Growth Redwood Groves Close Ups
For some closer in views of old growth, here are pictures from two of my favorite areas in the redwood parks. There are views like this all over the redwood parks.
Montgomery Woods State Natural Reserve is a very scenic spot with a high concentration of very tall redwood trees. The tall trees list shows 17 trees in this reserve over 350 feet in height. The tallest redwood in the reserve (Mendocino Redwood) is about 368 feet tall and is the 11th or so tallest tree in the world. The tall trees over 350 feet are found throughout the reserve – in the lower, middle, and upper flats. But that is a small area – a long stretched oval about 1.5 miles around and only 150 or so yards wide.
I had the fortune to recently hike through this reserve with Jerry Beranek. Jerry is a noted redwood photographer and writer who has published several books. His book “Coast Redwood – Tree of Dreams and Fortune” is a must have for any redwood enthusiast. It contains many great pictures of redwood trees as well as lots of information on the trees, plants, and animals that coexist with redwoods.
Jerry points out Montgomery Reserve may have been a lake at one time. A landslide could have backed up the creek for several centuries or thousands of years, allowing the shallow lake to form. Then the natural dam let go, the lake drained, and the rich soil was populated by redwoods which grew tall in the protected valley on the north side of a coast range mountain. As he mentions the redwoods needed to “stretch” to get up above the rim of the bowl and get more sunlight.
This picture is from the area at the start of the grove after hiking up the hill from the parking lot. You can see the evidence for a long ago earthen dam (I am standing on it) as well as the beauty of the grove. Montgomery Creek winds through the flat area with tall redwoods uniformly distributed throughout.
2 Fire Event in 2008
There was a large fire in this reserve in 2008 that burned the undercover (it has since fully recovered) and some of the hardwoods on the slopes above the flat (they didn’t make it). This fire was part of a group of wildfires that occurred in July that were very destructive to Mendocino County. Most of the redwoods came out ok as one of their specialties is fire survival given their thick bark. However a few of the hollow redwood trees sustained significant damage including one really big one that burned for days like a giant smokestack and then collapsed. As part of the collapse event one huge branch splintered into three sections as it crashed to earth. Each of the three sections entered the ground at about the same angle. These branch sections are still buried in the earth – three big widow makers. They are pictured below.
3 A Big Tree and a Tall Tree
The biggest and fourth tallest tree in the reserve is the Montgomery Giant, with a diameter of 17 feet and a height of 361 feet. Jerry and his buddies did some climbing in this reserve in the 1980’s. In 1981 Jerry climbed the Montgomery Giant and measured its height via tape drop at 357 feet. While at the top an even taller tree in the distance was noted as the tallest tree in the reserve. This tree was assigned the name Mendocino Redwood in the 1990’s and for a few years it was the tallest known tree (before the Stratosphere Giant was identified).
Here are two pics of the Montgomery Giant. The first is a mid to upper trunk view. Then the second is of Jerry and I having a discussion on how to get a fish line over the lowest branch in the tree.
4 Finishing Up the Hike
Jerry, like some other redwood enthusiasts, hikes with a tripod and camera. Here he is checking light while setting up for a photo.
Recently eight of so interpretive information signs have been put up along the trail. They are well done. Here is one of them.
Montgomery Redwoods Reserve is a great hike. This was my second hike there and both times I was lucky to hike with someone knowledgeable about the reserve. Jerry’s knowledge of and experiences in the redwood forests are impressive, interesting, and entertaining.
Over the past twenty years the redwood groves on public lands have been systemically surveyed for tree height using both ground based rangefinders as well as airplane based LiDAR pulse measurements. The resulting point in time data has identified 220 individual trees at or over 350 feet in height on public lands. It is possible there are a few other trees over 350 feet on private lands (half the remaining old growth redwood forest is on private land but the public lands generally have the better redwood habitat).
This is a graph of the distribution of height for these trees.
As you can see redwoods over 360 feet are rare, just 51 trees. And redwoods over 370 feet are exceedingly rare, just 8 trees. Then the two tallest trees are about 377 and 380 feet in height.
There apparently are factors in play that are limiting tree height. From the demonstrated heights the trees have a hard time obtaining 370 feet. There are several studies on theoretical redwood maximum height that have come up with heights a little over 400 feet. These studies take into account the energy required to draw water up to the top of the tree as well as the water which can be extracted from atmospheric fog. However there are no trees now in excess of 380 feet.
While it is true what remains is just five percent of the original redwood old growth the parks themselves are in some of the best areas for big and tall trees. Also many of the parks have been around for quite some time now, and in some cases there is a fifty year growth record that can be referenced for some of the tallest trees. For example in 1964 National Geographic published research on very tall trees along Redwood Creek in the area that became Redwood National Park. At that time the three tallest trees in that area were 364 – 368 feet in height. In the fifty years since 1964 none of these three trees have reached 370 feet in height. There is a physiological limiter on tree height that seems to be around the 370 foot mark.
As another example, the Humboldt Rockefeller forest is noted as having many of the tallest redwoods. This forest has been protected for over eighty years. At this point in time no tree has reached 375 feet in that old growth forest. There are dozens of trees over 360 feet in the Rockefeller forest area but none have reached 375 feet. Again some type of physiological maximum appears to exist for tree height around the 370 foot mark.
2 Example – Humboldt State Park 373 ft Redwood
To review a specific tree, let’s take a look at this 373 foot redwood. This is a magnificent tree in the Humboldt Rockefeller forest whose most recent published height measurement is 372.73 feet. As you can see it also has a large diameter – over 17 feet. Based on lists of the largest redwoods, this is the largest volume redwood of those over 370 feet.
When I found this tree in the forest I immediately knew what tree it was and it just took my breath away. It is an impressive tree in an incredible forest setting.
The first published height for this tree, shortly after it was identified as one of the tallest trees, was 368.6 feet in 2000. Then the most recent published height was 372.7 feet in 2013. So that is a growth rate of 4.1 inches per year or one foot every three years. So does that mean this tree can get to 380 feet in twenty years and 400 feet in eighty years? I would say 380 feet is a good possibility but 400 feet is a stretch.
3 Example – Redwood National Park 371 Ft Redwood
This beautiful tall redwood grows on a bench along Redwood Creek. It is another one of the extremely rare 370 footers – the latest published height I have found is 371 feet from 2013.
This tree could not be in a more pleasant setting.
Published measurements over time indicate this tree has grown about eight feet in the last fifty years. This works out to be two inches per year. In recent years the height gain per year has been more than the fifty year average. Does that mean this tree will be a 380 footer in a few years and a 400 footer in thirty years? Again 380 seems possible, even probable, and 400 would be a stretch. There is no confirmed record of a current or historic 400 foot redwood tree.
It is possible factors could be in play to increase or decrease redwood growth rates. For example the increase in atmospheric carbon could be helping the forest get taller as there is more energy provided for photosynthesis. Or if there is a decrease in foggy summer mornings that might have a negative effect. These types of changes are being evaluated and quantified by current redwoods researchers.
Also any tree that gets high above its neighbors has a top that is less protected from wind. All the tallest trees will eventually lose part of their crown to wind. However they could still keep on adding wood to their surface area over time, allowing them to become the largest volume redwoods. And it is possible their crowns could “reiterate” (grow back) after breaking off.
So how tall can a redwood tree grow? My guesstimate is 400 feet.
4 Maximum Volume of Redwood Trees
It is more difficult to assess the volume of a redwood tree than to measure its height. Trees have different shapes at the bottom and then taper off at different rates as height increases. Then the volume of the branches and limbs needs to be taken into account as well.
As a rule of thumb the volume of a redwood can be estimated using the formula for the volume of a perfect cone. It works pretty well for some of the big volume redwoods:
In the last five years no new tallest redwoods have been identified. But there have been some new top ten largest redwoods found and preliminarily measured. There are areas of the redwood parks that have not been fully explored for the largest redwoods. Generally these are off trail hillside areas in the northern redwood parks.
There are also some differences of opinion on what to include for volume when a redwood tree has a complex trunk with partial fusions. This is particularly true for the two largest trees listed above.
This is a point in time distribution of the thirty largest by volume redwoods. It is incomplete because not all the redwood range has been surveyed for volume and new discoveries are being made.
As you can see there are very few redwoods over 35,000 cubic feet. It is possible a few historic redwood trees may have exceeded 45,000 cubic feet and rivaled the 52,500 cubic feet in the largest known living tree – the General Sherman sequoia. Possibilities are the Crannell Creek Giant and Lindsey Creek tree. There is more unknown out there for tree volume, the current profile of top redwood trees by volume is not as complete as the profile of top redwood trees by height. It’s just harder to come up with a volume measure for a redwood, although if diameter and height are known a volume range can be inferred.
5 Humboldt Largest Redwood
The largest known volume redwood in Humboldt is about number ten on the list of the largest redwoods by volume. It is a powerful presence in the forest.
It sits in a forest growing on an alluvial flood plain. This tree lost maybe thirty feet from its top decades or centuries ago. At one time it was probably one of the tallest trees but now has aged into one of the largest ones.
A large volume redwood probably adds more wood per year than a tallest redwood since it has more surface area to cover. I am sure attempts are being made to measure redwood volume over time. A new technology I have noticed here and there are ground based LiDAR sensors tied into remote power generation stations. This would be an effective way to use technology to measure something that is difficult to measure.
So how large can a redwood tree become? The current maximum is around 45,000 cubic feet, there may have been a few larger than that in the past. And in the future there could again be 50,000 cubic foot redwoods. No doubt.