The Bull Creek groves in Humboldt Redwoods State Park run six kilometers east to west, starting at the confluence of Bull Creek and the South Fork Eel River and extending west to a short distance past the Mattole Road Bridge over Bull Creek. All the tall redwoods (those over 100 meters in height) in the Bull Creek groves are within 225 meters of Bull Creek itself. Therefore, the area with very tall redwoods encompasses about 2.7 million square meters / 270 hectares / 670 acres. The tall redwoods are more or less uniformly distributed throughout this area, which is known as the “Bull Creek Flats”.
Despite what a sign says, the Bull Creek Flats have NOT been a wilderness for thousands of years. This area was long used by Native Americans, especially in the winter when salmon were in the creek. In the present day Mattole Road runs through the entirety of the Bull Creek groves, and the area is well trailed, on both the north and south sides of Bull Creek. You can virtually drive Mattole Road through the Bull Creek Flats using Bing Maps (this area is not available on Google Earth Street View).
John D. Rockefeller Jr. donated $2 million in the late 1920’s to purchase the Bull Creek groves and a portion of the surrounding hillsides from the Pacific Lumber Company. That sum was matched by state of California taxpayers to complete the $4 million purchase of approximately 9,400 acres encompassing the Bull Creek Flats, Dyerville Flats, and some of the surrounding hillsides in 1931. This is why the area in the present day is called Rockefeller Forest, though John D. Rockefeller Jr. preferred the name Bull Creek – Dyerville Forest.
Coast Redwoods are the dominant canopy species in Bull Creek groves. The coast redwood is the only living tree species with more than a handful of individual trees over 100 meters in height. There are approximately 2,000 coast redwoods over 100 meters in height. Of these 2,000, about 800 are in the Bull Creek groves. About 25 of the approximately 45 trees in the world over 110 meters in height (all coast redwoods) are in Bull Creek groves.
Notable trees marked on older maps for this area include the Rockefeller Redwood (Tall Tree), Giant Tree, Flat Iron Tree (now fallen), and the Giant Braid.
Lower, Middle and Upper Bull Creek Flats
Although the Bull Creek groves (Bull Creek Flats) are continuous, sometimes the area is subdivided into the lower, middle, and upper Bull Creek Flats. Using 2018 LiDAR data, I have created three derivative maps detailing the crowns in each area color shaded by ten meter height increments, stopping at 100 meters. The crowns with white shading on top are over 100 meters, and there are about 800 such crowns along Bull Creek. The tallest tree in the Bull Creek groves is Stratosphere Giant, which is about 114 meters tall. Its specific location can be found through a standard web search.
A Photo Tour of the Bull Creek Groves
Below are photos I took from 2014 though 2019 of locations in the Bull Creek groves. They give a good overall idea of what can be found on the Bull Creek Flats, and some specific additional facts are included in the photo captions.
I have also created a three minute You Tube / Power Point on the Bull Creek groves. There is some background music, please forgive the middling skill of the piano player (me).
Coast redwood tree height is of great interest, as these are the tallest trees currently growing on our planet. There are about 2,000 trees over 100 meters in height, and all of them (except one or two) are coast redwoods. Then the tallest coast redwood is a little over 116 meters in height.
There are longitudinal studies of redwoods over their range, centering on eleven defined plots, each about 10 m x 1000 m in size, with two each in Jedediah, Prairie Creek, and Redwood National parks and one each in Humboldt Redwoods, Montgomery Woods, Samuel P. Taylor, Big Basin, and Big Creek Parks and Reserves. All the trees and vegetation in the plots are measured every three to five years and results are tracked over time.
The overall consensus is the redwoods in the northern plots are holding their own, and in fact growing faster than ever based on dendrochronology studies. Tan oaks, a companion species to old growth redwoods, are having difficulties due to a spreading root disease (SOD). Then hemlocks have become susceptible to invasive mistletoe spreading up trunks. A couple very tall hemlocks in Jedediah Smith upland have fallen or are standing dead. The largest tree that fell in the plots was a very large Douglas Fir in the Redwood National Park upland plot.
Then there are lists of the tallest redwoods (those over about 105 meters or otherwise locally tall for their area) where these trees are measured every so often, some every year and others perhaps once a decade.
The tree heights for redwoods in the plots and on the tall tree lists are very accurately measured by Laser Range Finders or by crown tape drop (with measuring pole for the tip). Obviously only so many redwood trees can be assessed in this way.
However, there is another way to track canopy height. Not exact height, but pretty close. It is LiDAR.
LiDAR data is available for many of the areas with tall redwoods. Availability and download tools are available on the National Map, NOAA Elevation Data, and Open Topography LiDAR Portal. For certain areas, LiDAR data is available starting from 2007 (though typically private and not available for download) all the way through 2020 (later years are typically public and available for download). Be sure to download all points and to work in meters.
I would be remiss not to lobby for public availability of LiDAR data captured for public lands, especially if the LiDAR acquisition was partially or fully publicly funded.
Using LiDAR Data to Measure Canopy Height Over Time
In order to use LiDAR data longitudinally, it is necessary to create LiDAR derivatives for individual surveys, export the height above ground rasters created from these surveys, then compare the height above ground rasters between surveys done at different dates.
To use LiDAR point cloud data to create height above ground, there are several sources with detailed steps. Let me briefly summarize a method I find works well:
Software – ArcGIS Pro
Filter point cloud to ground points, use Geoprocessing Tool “LAS Dataset to Raster” to create a dem layer. Within Tool use Interpolation type “Binning”, Cell Assignment “Average”, Void Fill Method “Natural Neighbor”, Sampling Value “1”, Z Factor “1”.
Next filter point cloud to first return points, use Geoprocessing Tool “LAS Dataset to Raster” to create a dsm layer. Within Tool use Interpolation type “Binning, Cell Assignment “Maximum”, Void Fill Method “Natural Neighbor”, Sampling Value “1”, Z Factor “1”.
Now that dem and dsm layers have been created, use Geoprocessing Tool “Minus” and subtract the dem layer from the dsm layer. The resultant layer is the tree height. A map can be created to show colors by height band. However, at this point, to access forest height over time, we are interested in exporting this information to a table.
This height layer to table process is a little involved, there is a paper on it, link is here:
Since a raster height layer has already been created, we can skip steps 1 and 2 and start with step 3.
Run Geoprocessing Tool “Raster to Point”. Here the input file is the height above ground layer, the field is “Value”, and an output file will be named and created. Let’s call this result RasterT_FoundersGrove.
Run Geoprocessing Tool “Add Geometry Attributes”. Input features are “RasterT_FoundersGrove”, Geometry Properties are “Point x,y,z and m coordinates”, Length Units are “Meters”, Area Units are “Square Meters”, and Coordinate System is “Current Map”. These attributes are then added to “RasterT_FoundersGrove”.
Run Geoprocessing Tool “Add Surface Information”. Input features are again “RasterT_FoundersGrove”. The input surface is the height above ground layer, for Output Property “Z” is checked (this is height above ground), the Method is forced to “Bilinear” (don’t worry the information behind this Method on point averaging and sampling, it will not be done due to how the height above ground layer was created), and leave Sampling Distance blank. This adds surface information to RasterT_FoundersGrove.
Run Geoprocessing Conversion Tool “Table to Table”. Input Rows are again “RasterT_FoundersGrove”. The output location will default to the project database but can specify any available folder. The Output Name can be anything but the .csv extension must be explicitly included. For this example, we can call it FoundersGrove.csv.
The output CSV file will look like this:
Both grid_code and Z are height above ground in meters. Then POINT_X and POINT_Y are meters east and north in the Universal Transverse Mercator coordinate system.
In a general sense, the 2007 Private LiDAR covers all the northern redwood parks. Then there is 2017 and 2018 public LiDAR for northern redwood parks south of Eureka. There is also updated LiDAR, from about 2016, for redwood parks north of Eureka but for now it is private.
For Founders Grove, there is 2014 and 2018 LiDAR available. I followed the process noted above and used a max function against the final csv files to find the tallest point within each of 430,000 square meters downloaded for both 2014 and 2018. I then did these height comparisons:
For points in same square meter where the height was over 70 meters in both 2014 and 2018:
Crown Sq Meters
Avg Hgt 2014
Avg Hgt 2018
Std Dev of Chg
Median of Chg
Height Changes in Same Square Meter Canopy Location in Founders Grove, Canopy Over 70 Meters
Then for points in same square meter where the height was over 90 meters in both 2014 and 2018:
Crown Sq Meters
Avg Hgt 2014
Avg Hgt 2018
Std Dev of Chg
Median of Chg
Height Changes in Same Square Meter Canopy Location in Founders Grove, Canopy Over 90 Meters
In Founders Grove, the trend is increasing height, of about 0.14 meters per year from 2014 to 2018. The median height change was an increase of 5.5 inches per year, with 70% of crowns gaining height.
From this information Founders Grove growth can be assessed as increasing in height, and this is a favorable condition in relation to forest health.
This same comparison can be done over longer periods for many redwood park areas as LiDAR data exists in both the 2007-2010 time frame as well as the 2016-2020 time frame.
Redwood trees are noted for reaching exceptional heights. This is the only species of tree that currently has numerous individual trees over 100 meters in height. But even for redwoods, 100-meter trees are relatively uncommon, with about 1,900 individual trees exceeding this height. Then there are only 40 or so redwoods over 110 meters in height, with the current demonstrated maximum height about 116 meters.
This table recaps the counts for tall redwood trees by Park
Tree Height vs Age In Old Growth Forests
In 2009 and 2010 redwood research plots were established in
old growth forests across the current redwood range, sixteen in all. Each plot is one hectare (10,000 square
meters) and is shaped in a long narrow 10-meter X 100-meter rectangle, with two
tall redwoods near each end. These plots were put in to monitor redwood
tree and redwood tree forest health over time.
As part of this research, the tree heights are measured every so often,
and the tree ages were established by core samples up the trunk to allow the
thin increment borer to reach the center of the trunk if possible. A few redwoods outside the plots are also
included in the longitudinal study.
All of this is detailed in the fine research paper:
Carroll AL, Sillett SC, Kramer RD (2014) Millennium-Scale
Crossdating and Inter-Annual Climate Sensitivities of Standing California
Redwoods. PLoS ONE 9(7): e102545. doi:10.1371/journal.pone.0102545
From Appendix F in the research paper, the tree heights and ages can be plotted. I have generated this plot and table from the information in Appendix F.
From this graph we can see the youngest 100-meter redwood is
about 500 years old. Then the tallest
redwoods cover a broad age range, from about 700 years old to about 2,000 years
old. The growth structure of these trees
is covered in Appendix K of the same paper.
Some of the older trees lost some height but then grew tall again, this
is termed reiterated growth. Then other trees have continued to grow
without much crown breakage. The very
oldest trees tend to be a little shorter and include many reiterations. So, if you happen to measure a redwood tree as
100 meters in height, it is almost certainly over 500 years old.
Tree Height vs Age in Second Growth Forests
Redwood tree forests were timbered starting around 1850. After timber operations left an area the redwoods
began to grow again from the ground up, either as new growth from stump roots
or growth from seedling sprouts. These
second growth forests are in both managed timber lands and in parks and
reserves. In parks and reserves the second
growth redwoods have been thinned over time to help the forests more quickly
mature. The tallest second growth
redwoods are about 285 feet tall and about 160 years old. How long will it be before these trees reach
100 meters in height? It is likely much
sooner than 500 years.
For example, in Navarro Redwoods the tallest trees are
250-275 feet tall and growing on average eight inches per year. These trees are definitely ahead of the
growth versus age curve in old growth forests, where 80-meter trees are between
190 and 400 years old. Then the 80-meter redwoods in Navarro are increasing
height at more than double the rate of 80-meter old growth redwoods.
This is an estimate of growth curves for second growth redwoods in optimal habitats. It is predicted 160 year old second growth redwoods in optimal growing areas will on average reach 100 meters in height at age 400 years (240 years from now). There will likely be a few very fast-growing second growth trees that reach 300 feet in 30 years and 328 feet (100 meters) in 100 years.
Redwood tree height measurement came into its own in the 1990’s. Skilled researchers and naturalists combined laser rangefinder technology, LiDAR height estimation, hiking and climbing skill, and direct tape drop from the canopy to create a nearly complete inventory of tall redwood trees throughout their range (with the exceptions of Six Rivers National Forest and Headwaters Reserve, which have not been thoroughly assessed). From this it was determined redwoods over 100 meters (328 feet) in height were uncommon, totaling about 2,000 trees. And redwoods over 350 feet (106.7 meters) in height were very uncommon, totaling about 230 trees. Each tall tree is remeasured every five years or so, with the tallest trees having more frequent measurements.
I don’t have direct access to the 15-25 years of longitudinal height data for tall redwoods but through research I was able to find height information for the tallest known trees in the year 2000 as well as their remeasured heights as of 2015. There were 129 trees over 350 feet on the 2000 list, indicating many more 350-foot redwoods were yet to be identified, particularly in Redwood National Park. Here are the height changes for these 129 trees in inches growth per year (parks with smaller tree counts are excluded) on the left axis and 2015 height on the right axis (line).
On the chart the trees are grouped by Bull Creek (Humboldt
Redwoods along Bull Creek), Eel River (Humboldt Redwoods along Eel River
including Rockefeller Loop), Montgomery (Montgomery Woods State Natural Reserve)
and Redwood (Redwood National Park).
It is evident in all four areas most trees had height
increases over fifteen years. Nine trees
lost height, a few in each area. Median
height growth was about three inches per year.
Over the past few years two of the trees in the data have fallen.
The chart also includes tree height in 2015. Correlation between 2015 height and height
change is 0.53, correlation between 2000 height and height change is 0.02. So height change was not related to initial
Here is summary data related to the chart.
This data indicates the canopy of very tall redwood trees increased three feet from 2000 to 2015. The canopy in 2000 was the result of several thousand years of forest development. Then why did the tallest existing redwood trees increase on average another three feet in height from 2000 to 2015? Some potential contributing factors:
More sun reaching the leaves of edge habitat trees due to cutting of nearby trees from 1860-1979.
Increased atmospheric CO2 providing more energy for photosynthesis
Future of These Tall Trees
Based on plot information, 350-foot tall redwoods are between
700 and 2000 years old, with the median age 1180 years. It is very likely almost all of the current
350-foot tall redwoods will fall over the next 1000 years, being replaced by
grow in from trees currently under 350 feet and trees yet to sprout.
Let’s test this against the known 350-foot trees to fall in
the last 30 years in Humboldt Redwoods State Park.
It can be expected about ten percent of the tallest redwoods
will fall every 100 years, with 3-4 trees falling each decade.
Before falling many trees will lose and regain height over
time. About two thirds of the 350-foot
redwoods in study plots have reiterated tops.
is the Maximum Height for Redwoods
The current tallest tree is about 381 feet tall. There are four trees around 375 feet tall or
taller, and all four are gaining height.
Then the data shows the canopy for very tall trees in general is
increasing by about one foot every five years.
So will there be 385-foot redwoods in 20 years? Could be.
Will there be 390-foot redwoods in 50 years, and 400-foot
redwoods in 100 years? Maybe. The theoretical maximum height based on tree
structure and physics has been calculated to be 425 feet. There is no reliable historic record for a redwood
tree over 400 feet in height. One was
measured right at 400 feet about fifty years ago along Wilson Creek by an
expert timber cruiser.
Will some second growth Douglas Fir beat all the redwoods
and get to 400 feet first? Maybe, but
then again the reliable historic maximum height for Douglas Fir is 393 feet.
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.