Fire Severity and Vegetation Recovery in Yellowstone National Park, Wyoming, USA
Introduction
In August 1988, Yellowstone National Park had a series of devastating wild
fires that were considered the largest forest fire burn event in the recorded
history of the national park. (Scullery, 1989). The fire started as a series of
smaller fires which were exacerbated by increasing winds and drought which
burned for several months. Thousands of firefighters and military personal
fought the fire but it was not until early October that the fire was brought
under control by cool and moist weather conditions. This project aims to
evaluate burn severity following the forest fire along with the vegetation re-
covery response 23 years later. This process was done through the use of re-
mote sensing technology which has been proven to be an accurate tool to
evaluate forest fires and ecological recovery.
Natural-like Rendition of Yellowstone National park After the Fire on October 10, 1988
Figure 1. This image was created with the band combination of 7,4,2 which provides a natural-like ren-
dition while also penetrating smoke and atmospheric particles. Red indicates a recent forest fire,
bright green areas indicate healthy vegetation, pink represents barren soil, and blue areas represent
water.
Burn Severity Assessment Using Normalized Burn Ratio in 1988
NDVI Change
No Change
Increase (Moderate)
Increase (High)
NDVI Change and Vegetation Recovery of Severe Burned areas as of 2011
No
Change
Increase
(Moderate)
Increase
(High)
Percent of
High severity
Area
0.24% 53.60% 46.16%
Table 2. NDVI Change between 2011 and
the days after the fire in 1988
Methodology
Three images for Yellowstone National Park were acquired from Landsat
5. The first image was acquired for September 22, 1987, which was a year
before the wild fire started. The second image was acquired for October 10,
1988 which was eight days directly after the fire. The third image was ac-
quired for September 24, 2011 which was 23 years after the fire. The dates
were chosen as close to the day and month of each other as possible to
avoid any spectral variances due to the time of year.
To analyze the severity of the forest fire, Normalized Burn Ratio (NBR)
was used. NBR utilizes the short-wave infrared bands which are not affected
by dust, smoke and atmospheric particles (Avery & Berlin, 1998; Eva & Lamb-
in, 1998). Cocke et al. (2005) states that several studies have concluded that
using this band combination provides the highest accuracy for burn severity
analysis. The NBR algorithm was applied on the pre-fire and post-fire images
and then a change in NBR was calculated through an image differencing al-
gorithm. The unsupervised classification was then combined with the
change in the NBR map in a GIS software to create a fire severity index seen
in Figure 3.
To analyze the restoration of the damaged forest, change detection using
normalized vegetation index (NDVI) was used. NDVI gives an indication of
the amount of green vegetation and is effective in detecting vegetation re-
covery after a fire event (Delgado et al., 2003). Change in NDVI values were
examined in high severity burned areas since those areas experienced com-
plete vegetation loss.
Results and discussion
Burned area was classified based on how much damage the forest canopy
sustained and was characterized by four categories: low severity, moderate-
low severity, moderate-high severity and high severity (Figure 3). With a rela-
tively even distribution of percent burned areas in each category (Table 1), it
becomes clear that certain areas of forest were affected by the fire to a
different degree. Further ground based research could indicate what tree
species or environmental factors contribute to each severity category.
Within the high severity burned areas, NDVI change detection revealed
that 53.6% of this area experienced a moderate increase in vegetation while
46.16% experienced a high increase in vegetation. This indicates, without a
doubt, that the forest within high severity category is recovering to some de-
gree.
Low
Severity
Moderate-
Low
Severity
Moderate-
High Severity
High Severity
Percent of
Burned
Area
21.61% 22.46% 32.77% 23.16%
Table 1. Fire Severity Established Through Normalized Burn Ratio
References
Avery T. E, Berlin G. L .(1992) ‘Fundamentals of remote sensing and air photo interpretation.’ (Prentice Hall: Upper Saddle River, NJ) 472 pp.
Cocke, A. E, Fule, P. Z, & Crouse, J. E. (2005). Comparison of burn severity assessments using differenced Normalized Burn Ratio and ground
data. International Journal of Wildland Fire Vol 14, 198-198.
Delgado, D, Lloret, F, & Pons, X. (2003). Influence of fire severity on plant regeneration by means of remote sensing imagery. International
Journal of Remote Sensing Vol 24, No. 8, 1751-1763.
Eva H, Lambin E. F. (1998) Burnt area mapping in Central Africa using ATSR data. International Journal of Remote Sensing 19, 3473–3497.
Schullery, P. 1989. The fires and fire policy. Bioscience 39: 686-695.
1988-2011 NDVI Composite
Figure 2. This image combines both NDVI images from October 10, 1988 and September 24, 2011 to
a show change in NDVI values . Bright cyan indicates an increase in vegetation, bright red indicates a
decrease in vegetation, black represents water, grey indicates barren soil, light red indicates forests
that have no change and light cyan indicates grassland that have not increased in vegetation values.
Fire Severity
High Severity
Moderate-high Severity
Moderate-low Severity
Low Severity
0 30 6015 Km
0 30 6015 Km 0 30 6015 Km
0 30 6015 KmFigure 3. Figure 4.
More Information
Data source: Landsat 5
Adriano Nicolucci -Poster presented for partial fulfillment of The Professional Geographer (GEO871).
