By: Mike Wulder, Senior Research Scientist with the Canadian Forest Service

Map of harvest and wildfire forest changes in Canada

(A) A 2010 composite image of Canada created using Landsat data and the Best Available Pixel (BAP) approach (Landsat TM/ETM + bands 5,4,3) superimposed with the boundaries of the forested ecozones analyzed in this study.
(B) Map of the area disturbed by wildfire and harvest (1985–2010), as identified using the Composite to Change (C2C) approach.
Image credit: White et al., 2017

Apr 10, 2017 • In a recently published paper, Joanne White (Research Scientist, Canadian Forest Service) and co-authors communicate their findings characterizing 25 years of forest disturbance and recovery for Canada using satellite data. Using open data from the Landsat series of satellites and high performance computing opportunities, White and co-authors use tens-of-thousands of images representing billions of pixels, to map forest wildfire and harvesting on an annual basis and to then characterize the return of forest vegetation following the disturbance. Forest disturbance is captured and mapped to type (such as wildfire or harvest). Using the measurements from the post-disturbance satellite data, it is found that given time forests return following disturbance. As Joanne indicates,

“The capacity to distinguish recovery trends by disturbance type provides insights on forest dynamics that are both spatially detailed and national in scope.”

What are the major findings of this research?

  • 57.5 Mha or 10.75% of Canada’s net forested ecosystems (exclusive of water) were disturbed by either wildfire or harvest, representing an annual rate of disturbance of approximately 0.43% per year.
  • Wildfire accounted for 2.5 times more area disturbed than harvest. On average, wildfire impacted 1.5 Mha annually, compared to 0.65 Mha impacted by harvesting. Moreover, the amount of area impacted by wildfire was much more variable annually (σ = 1.5 Mha) when compared to harvest (σ= 0.1 Mha).
  • Regionally, boreal ecozones had the greatest absolute area of disturbance from both wildfire (Boreal Shield West) and harvest (Boreal Shield East).
  • Spectral recovery metrics indicate that vegetation returns following disturbance.
  • Areas impacted by harvest exhibited more rapid spectral recovery rates.
  • 78.6% of areas impacted by harvest having a mean recovery time ≤ 10 years, compared to 35.5% of areas impacted by wildfire
  • Overall, less than 1% of the areas disturbed by wildfire and harvest were identified as non-recovering by all three spectral measures of recovery used in our analysis.

Citation and open access:

White, J.C., Wulder, M.A., Hermosilla, T., Coops, N.C., Hobart, G.W. (2017). "A nationwide annual characterization of 25 years of forest disturbance and recovery for Canada using Landsat time series.." Remote Sensing of Environment, pp. 194: 303-321 DOI: 10.1016/j.rse.2017.03.035

Get it here: https://authors.elsevier.com/sd/article/S0034425717301360