KNP COMPLEX FIRE OVERVIEW
- Ignited by lightning on September 9th, 2021.
- Burned 88,307 acres mostly within Sequoia and Kings Canyon National Parks.
- Around 46.6% of the fire burned at a moderate to high severity.
KNP COMPLEX FIRE Sequoia Grove OVERVIEW
- An open-source NPS data set was used for the grove shapefiles and subsequent calculations. There is inherent uncertainty present in defining the range of the species and the project was unable to use the more exact grove shapefile compiled by the USFS.
- 5,082 acres burned in 16 sequoia groves which is 9.77% of ALL giant sequoia grove extent.
- 1,241 acres are classified as unburned within the fire perimeter, there are 6,323 acres of sequoia groves included in this image.
- This value is 16% greater than the 4,374 grove acres burned reported by the NPS, suggesting that the following statistics may overestimate sequoia mortality in the KNP Complex Fire.
- This discrepancy is due to the inclusion of USFS acreage, a less accurate grove shapefile, and the hand-digitization of the KNP Complex perimeter.
SEQUOIA MORTALITY IN THE KNP COMPLEX FIRE
- 68.7% of grove area in the perimeter was unchanged or experienced low intensity fire.
- Low intensity fire is beneficial for sequoia health and regeneration (Stephenson, 2020).
- 31.3% of the the grove area burned at moderate to high severity, which is very similar the NPS value of 31% for moderate to high burn severity in groves for the KNP Complex Fire (“2021 fire season impacts” – NPS).
- Values were calculated on an estimate of 2.61 sequoias per acre in groves (Stephenson, 2020).
- Using an estimate of 20% mortality in moderate severity zones and 80% mortality in high severity zones based upon previous fires (Stephenson, 2020)
- 987 acres moderate severity ≈ 515 sequoias
- 994 acres high severity ≈ 2,075 sequoias
- We estimate around 2,590 Giant Sequoias have died or will die in the next 5 years as a result of the KNP Complex Fire
- The NPS estimates 1,330 to 2,380 sequoias have died or will die from the KNP Complex Fire. These estimates are likely more accurate due to increased knowledge and surveying of sequoia groves along with individual sequoia stem map data which was not available for this study (“2021 fire season impacts” – NPS).
- Further studies are required to fully understand the impacts of these fires, particularly in the form of field survey.
REDWOOD MOUNTAIN GROVE
- Redwood Mountain is the world’s largest old growth Giant Sequoia grove and 97% of the grove’s 3,946 acres burned in the KNP Complex Fire (3,830 acres inside fire perimeter).
- The Redwood Mountain Grove accounted for 85% of high severity burns in sequoia groves in the KNP Complex Fire.
- 38.96% of the grove burned at moderate to high severity with 22.00% of the grove burning at high severity.
- As a result of these values, we estimate that 1,760 Giant Sequoias have died or will die in the next 5 years in the Redwood Mountain Grove.
- A crosshatch fill overlay illustrates the extent of past prescribed burns in the Redwood Mountain Grove, illustrating how areas treated in the past are less likely to experience high severity fire.
- Our analysis found that 22.0% of the grove burned at high severity, which matches the National Park Service value of 22% high severity burn in the Redwood Mountain Grove (“2021 fire season impacts” – NPS). The other fire severity classes show some discrepancy likely due to the use of different burn indices and analyses.
- The shocking mortality statistics for this grove may somewhat overestimate the damage done. However, a 2021 study focused on mapping sequoia vulnerability based primarily upon canopy water content (CWC) and elevation found that 74% of the most vulnerable sequoias in the parks were found in the Redwood Mountain Grove (Baeza, 2021). This correlated to 18% of the Redwood Mountain Grove being classified as high-risk for sequoia mortality because of consistent downward trends in canopy water content in trees over a three year period (Baeza, 2021).
- The amount of high risk areas (18%) for sequoia mortality is very similar to the amount of the grove that burned at high severity (22%) and it is likely that there is significant overlap between these two variables as lower-elevation parts of the grove were more likely to experience high severity fire.
- In comparison, the Giant Forest only had a high risk vulnerability of 0.1% of the grove area, which is consistent with the majority of this grove not burning or experiencing low intensity fire.
REDWOOD MOUNTAIN GROVE: BEFORE AND AFTER
The two images below provide a comparison of the Redwood Mountain Grove two weeks before the start of the fire and a month after fire ignition. Note that the before image contains visible particulate matter from fires burning in the Southern Sierra. At the time the before image was taken, conditions were extremely dry and Redwood Creek was completely dry.
HOW MANY SEQUOIAS BURNED?
First, let’s figure out impacted areas from these colored NDVI images
Before Windy Fire (8/7/2021)
After Windy Fire (10/10/2021)
Windy Fire mainly impact the left side of Sequoia National Park and close to Kings Canyon National Park
Before the Windy Fire (8/7/2021)
After the Windy Fire (10/10/2021)
- Change Detection Statistics show ~ 7136100 m2 (≈1763 acres) impacted area
- close to prior data estimating ~ 1723 acres of impacted areas in Windy Fire (Shive, Brigham, Caprio, & Hardwick, 2021)
- Of the 2,312 acres of largest grove in the park, 1763 acres were impacted
- ~ 76% sequoias suffered degrees of burn during Windy Fire in Sequoia National Park
Difference between the images
Change Detection Statistics Analysis
ARE THE FIRES ALL COMING UP TO THE BOUNDARIES OF OTHER FIRES?
We can notice that except the left side of Windy Fire impacted area, there are also another huge part of low NDVI area in the middle and top, and these areas are very close; they are all coming up to the boundaries of other fires
After the Windy Fire (10/10/2021)