Recent years have been marked by multiple droughts and temperature increases around the world. Under these conditions, massive bushfires occurred in 2019 and early 2020, particularly in southeastern Australia where temperate forests have very high biomass. At that time, 4 million hectares were burned, which is 20% of Australia’s forests.
During these fires, the forest was burned from the ground up. Satellite images captured by the SMOS satellite, which allow biomass estimation before and after, show a rapid recovery of vegetation. Since the end of 2020, less than a year after the fires passed, weeds, bushes, and scorched eucalyptus are already starting to grow there. Under these conditions, how can losses and gains of carbon stocks be estimated?
To answer this question, INRAE scientists and their partners evaluated two parameters for the first time:
- loss of vegetation and biomass in forested areas of Australia (due to the simultaneous effects of drought, higher temperatures, and fires in 2019);
- The ability of vegetation to recover one year after such damage, thanks to the relatively humid weather conditions in 2020 (especially in the forested regions of southeastern Australia).
In addition to satellite imagery, the researchers used a full arsenal of analytical techniques and predictive models for carbon stocks. Thus they were able to assess changes in vegetation structure and function using specific parameters such as leaf surface or aerobic biomass.
The images collected show significant biomass losses in 2019, under the influence of fires, drought and high temperatures. The forest area lost the equivalent of 200 million tons of carbon, or 15% of the atmospheric biomass. Of the 200 million tons of carbon lost, 90 million are attributable to fires, and 110 million to the cumulative effects of drought and temperature extremes.
2020 saw twice as much precipitation as in 2019. The result: significant biomass gains in the same forest areas, which account for a total of more than 260 million tons of stored carbon in 2020. Of those 260 million, comes 220 million from the burned area and 40 million from the unburned area.
Several species of eucalyptus known for their ability to regenerate after fire and their adaptation to drought dominate Australian forests. Above-average precipitation in 2020 may have encouraged strong and rapid growth of forests and other vegetation components (grass and shrubs) in March, April, August and December 2020, and thus lead to a full recovery of lost carbon stocks by early 2021.
Chen Wai. Xiao X. Wengner c. et al. (2022). Significant loss and rapid recovery of above-ground vegetation and biomass over forest areas in Australia during the 2019-2020 period. Remote Environment Sensing, 278, 113087, https://doi.org/10.1016/j.rse.2022.113087.
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