Burned Area and Carbon Emissions Across Northwestern Boreal North America from 2001–2019

Abstract

Abstract. Fire is the dominant disturbance agent in Alaskan and Canadian boreal ecosystems and releases large amounts of carbon into the atmosphere. Burned area and carbon emissions have been increasing with climate change, which have the potential to alter the carbon balance and shift the region from a historic sink to a source. It is therefore critically important to track the spatiotemporal changes in burned area and fire carbon emissions over time. Here we developed a new burned area detection algorithm between 2001–2019 across Alaska and Canada at 500 meters (m) resolution that utilizes finer-scale 30 m Landsat imagery to account for land cover unsuitable for burning. This method strictly balances omission and commission errors at 500 m to derive accurate landscape- and regional-scale burned area estimates. Using this new burned area product, we developed statistical models to predict burn depth and carbon combustion for the same period within the NASA Arctic-Boreal Vulnerability Experiment (ABoVE) core and extended domain. Statistical models were constrained using a database of field observations across the domain and were related to a variety of response variables including remotely-sensed indicators of fire severity, fire weather indices, local climate, soils, and topographic indicators. The burn depth and aboveground combustion models performed best, with poorer performance for belowground combustion. We estimate 2.37 million hectares (Mha) burned annually between 2001–2019 over the ABoVE domain (2.87 Mha across all of Alaska and Canada), emitting 79.3 +/- 27.96 (+/- 1 standard deviation) Teragrams of carbon (C) per year, with a mean combustion rate of 3.13 +/- 1.17 kilograms C m-2. Mean combustion and burn depth displayed a general gradient of higher severity in the northwestern portion of the domain to lower severity in the south and east. We also found larger fire years and later season burning were generally associated with greater mean combustion. Our estimates are generally consistent with previous efforts to quantify burned area, fire carbon emissions, and their drivers in regions within boreal North America; however, we generally estimate higher burned area and carbon emissions due to our use of Landsat imagery, greater availability of field observations, and improvements in modeling. The burned area and combustion data sets described here (the ABoVE Fire Emissions Database, or ABoVE-FED) can be used for local to continental-scale applications of boreal fire science.

The net GHG balance and budget of the permafrost region (2000-2020) from ecosystem flux upscaling

“…Our fire carbon emission estimate for boreal ecosystems (CO 2 and CH 4 , 113.2 TgC yr -1 ) is slightly lower than the one of 142 Tg CO 2 -C yr -1 previously reported by Veraverbeke et al (2021). Using GFED4s data, our budget might underestimate fire CO 2 emissions as shown in Potter et al (2022), where GFED4s emissions were 36% lower than the ones obtained using the ABoVE-FED data-driven product.…”

The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling

“…Using GFED4s data, our estimate might underestimate fire CO 2 emissions, as shown in Potter et al. (2022), where GFED4s emissions were 36% lower than those obtained using the ABoVE‐FED data‐driven product.…”

Wildfire‐induced increases in photosynthesis in boreal forest ecosystems of North America

“…Carbon storage within boreal forest ecosystems can be reduced if high‐carbon ecosystems are replaced with low‐carbon storage ecosystems (Koven, 2013) or if losses from harvest and fire are not balanced by gains in recovering forests (Wang et al., 2021). For example, organic carbon storage declines when thick moss and organic soil layers that are often present in black spruce stands are removed by fire (Potter et al., 2023; Walker et al., 2019). Build‐up of organic soil layers is often slower in aspen and birch stands because of more rapid leaf decomposition and pulse of leaf litter that may impede moss growth (Johnstone, Chapin, et al., 2010; Van Cleve & Viereck, 1981).…”