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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Wildfire as a disturbance: ignition, burning, emissions and recovery

Wildfire as a disturbance: ignition, burning, emissions and recovery

How wildfires are ignited by people and lightning, how fuel and fire weather set burning, how much area and carbon burns each year, and how post-fire albedo and regrowth feed back on climate and the next fire.

Boundary: where this process starts

Starts with: Who starts wildfires? (United States record of 1.5 million fires, 1992-2012)

Boundary: where it ends

Ends after: Vegetation regrows after fire, rebuilding fuel and carbon stocks; fewer fires have increased the land carbon sink and cut aerosol loads

PARTICIPANTSRESOURCESFireVegetationHumansLightningAtmosphereBiomassCarbon dioxideAerosolsWaterSunlightImpact +4 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.84%Impact +4 of 5. Click for details and evidence.16%Impact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.↻ reinforces · weak · 0.3Impact +3 of 5. Click for details and evidence.Who starts wildfires? (United States record of 1.5 million fires, 1992-2012): uses BiomassHuman ignitions: 84% of wildfires and 44% of area burned, with a fire season three times longer than lightning's: uses BiomassLightning ignitions: 16% of fires but 56% of area burned, concentrated in remote summer fire seasons: uses BiomassFuel load, dryness and fire weather decide whether an ignition spreads; climate change is altering fire regimes faster than models capture: uses BiomassFuel load, dryness and fire weather decide whether an ignition spreads; climate change is altering fire regimes faster than models capture: uses WaterFires emit about 2.2 Pg C a year (3.0 in 1997, 1.8 in 2013), yet global burned area fell 24% in 18 years as farming replaced savanna fire: uses up Biomassuses upFires emit about 2.2 Pg C a year (3.0 in 1997, 1.8 in 2013), yet global burned area fell 24% in 18 years as farming replaced savanna fire: makes Carbon dioxidemakesFires emit about 2.2 Pg C a year (3.0 in 1997, 1.8 in 2013), yet global burned area fell 24% in 18 years as farming replaced savanna fire: makes AerosolsmakesA boreal fire warms in its first year (+34 W/m2 of burned area from gases, aerosols and soot on snow) but cools over an 80-year cycle (-2.3 W/m2) because the re: uses Carbon dioxideA boreal fire warms in its first year (+34 W/m2 of burned area from gases, aerosols and soot on snow) but cools over an 80-year cycle (-2.3 W/m2) because the re: uses AerosolsA boreal fire warms in its first year (+34 W/m2 of burned area from gases, aerosols and soot on snow) but cools over an 80-year cycle (-2.3 W/m2) because the re: uses SunlightVegetation regrows after fire, rebuilding fuel and carbon stocks; fewer fires have increased the land carbon sink and cut aerosol loads: makes BiomassmakesVegetation regrows after fire, rebuilding fuel and carbon stocks; fewer fires have increased the land carbon sink and cut aerosol loads: uses up Carbon dioxideuses upusesBiomass: usesusesBiomass: usesusesBiomass: usesusesBiomass: usesusesWater: usesuses upBiomass: uses upmakesCarbon dioxide: makesmakesAerosols: makesusesCarbon dioxide: usesusesAerosols: usesusesSunlight: usesmakesBiomass: makesuses upCarbon dioxide: uses upStart: Wildfire as adisturbance: ignition,burning, emissions a…STARTStart: Wildfire as a disturbance: ignition, burning, emissions and recoveryEnd: Wildfire as adisturbance: ignition,burning, emissions a…ENDEnd: Wildfire as a disturbance: ignition, burning, emissions and recoveryWho starts wildfires?(United States recordof 1.5 million fire…📄1Who starts wildfires? (United States record of 1.5 million fires, 1992-2012)Human ignitions: 84% ofwildfires and 44% ofarea burned, with…📄1Human ignitions: 84% of wildfires and 44% of area burned, with a fire season three times longer than lightning'sLightning ignitions:16% of fires but 56% ofarea burne…📄1Lightning ignitions: 16% of fires but 56% of area burned, concentrated in remote summer fire seasonsFuel load, dryness andfire weather decidewhether an igniti…📄2Fuel load, dryness and fire weather decide whether an ignition spreads; climate change is altering fire regimes faster than models captureFires emit about 2.2 PgC a year (3.0 in 1997,1.8 in 2013), y…📄2 ↗1Fires emit about 2.2 Pg C a year (3.0 in 1997, 1.8 in 2013), yet global burned area fell 24% in 18 years as farming replaced savanna fireA boreal fire warms inits first year (+34W/m2 of burned ar…📄1A boreal fire warms in its first year (+34 W/m2 of burned area from gases, aerosols and soot on snow) but cools over an 80-year cycle (-2.3 W/m2) because the reVegetation regrowsafter fire, rebuildingfuel and carbon stock…📄2Vegetation regrows after fire, rebuilding fuel and carbon stocks; fewer fires have increased the land carbon sink and cut aerosol loads
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

⑂ Who starts wildfires? (United States record of 1.5 million fires, 1992-2012)
HumansLightningFireBiomass
Evidence (1) · added by Briangold-Claude
  • Balch et al. 2017, Human-started wildfires expand the fire niche across the United States, PNAS 114:2946-2951, https://doi.org/10.1073/pnas.1617394114: Over 1.5 million agency fire records from 1992-2012 were classified by human versus lightning ignition. (confidence 0.9)
Human ignitions: 84% of wildfires and 44% of area burned, with a fire season three times longer than lightning's
HumansFireBiomass
Evidence (1) · added by Briangold-Claude
  • Balch et al. 2017, Human-started wildfires expand the fire niche across the United States, PNAS 114:2946-2951, https://doi.org/10.1073/pnas.1617394114: Humans accounted for 84% of all wildfires and 44% of total area burned; the human-caused fire season was three times longer and added about 40,000 fires a year. (confidence 0.9)
Lightning ignitions: 16% of fires but 56% of area burned, concentrated in remote summer fire seasons
LightningFireBiomass
Evidence (1) · added by Briangold-Claude
  • Balch et al. 2017, Human-started wildfires expand the fire niche across the United States, PNAS 114:2946-2951, https://doi.org/10.1073/pnas.1617394114: Lightning-ignited fires are the remainder: 16% of fires and 56% of area burned (100 minus the human shares). (confidence 0.85)
Fuel load, dryness and fire weather decide whether an ignition spreads; climate change is altering fire regimes faster than models capture
VegetationAtmosphereFireBiomassWater
Evidence (2) · added by Briangold-Claude
  • Bowman et al. 2009, Fire in the Earth system, Science 324:481-484, https://doi.org/10.1126/science.1163886: Climate change alters fire regimes and fires are still poorly represented in global models. (confidence 0.8)
  • Andela et al. 2017, A human-driven decline in global burned area, Science 356:1356-1362, https://doi.org/10.1126/science.aal4108: Fire models could not reproduce the pattern and magnitude of observed burned-area declines. (confidence 0.8)
Fires emit about 2.2 Pg C a year (3.0 in 1997, 1.8 in 2013), yet global burned area fell 24% in 18 years as farming replaced savanna fire
FireVegetationHumansCarbon dioxideAerosolsBiomass
Evidence (2) · added by Briangold-Claude
  • van der Werf et al. 2017, Global fire emissions estimates during 1997-2016 (GFED4s), Earth Syst. Sci. Data 9:697-720, https://essd.copernicus.org/articles/9/697/2017/: Global mean fire carbon emissions were 2.2 Pg C per year during 1997-2016, with a maximum of 3.0 in 1997 and minimum of 1.8 in 2013. (confidence 0.9)
  • Andela et al. 2017, A human-driven decline in global burned area, Science 356:1356-1362, https://doi.org/10.1126/science.aal4108: Global burned area declined by 24.3 +/- 8.8% over 18 years, most in savannas, driven by agricultural expansion and intensification. (confidence 0.9)
A boreal fire warms in its first year (+34 W/m2 of burned area from gases, aerosols and soot on snow) but cools over an 80-year cycle (-2.3 W/m2) because the re
FireBoreal forestSnow and iceCarbon dioxideAerosolsSunlight
Evidence (1) · added by Briangold-Claude
  • Randerson et al. 2006, The impact of boreal forest fire on climate warming, Science 314:1130-1132, https://doi.org/10.1126/science.1132075: The net effect of a boreal forest fire was +34 +/- 31 W/m2 of burned area in the first year but -2.3 +/- 2.2 W/m2 averaged over an 80-year fire cycle, because multidecadal albedo increases outweighed fire-emitted greenhouse gases. (confidence 0.9)
Vegetation regrows after fire, rebuilding fuel and carbon stocks; fewer fires have increased the land carbon sink and cut aerosol loads
VegetationFireBiomassCarbon dioxide
Evidence (2) · added by Briangold-Claude
  • Andela et al. 2017, A human-driven decline in global burned area, Science 356:1356-1362, https://doi.org/10.1126/science.aal4108: Fewer and smaller fires reduced aerosol concentrations, modified vegetation structure and increased the terrestrial carbon sink. (confidence 0.85)
  • Bowman et al. 2009, Fire in the Earth system, Science 324:481-484, https://doi.org/10.1126/science.1163886: Fire shapes vegetation distribution and structure. (confidence 0.8)