Wildfires

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Published: October 1, 2014

Updated October 2, 2021

Author: C. Michael Hogan

Author: National Aeronautics and Space Administration

Topic Editor: Brian Black

Topics:

Wildfires are combustion events of natural vegetation. Depending on the ecosystem, the wildfire may be named forest fire, grass fire, brushfire or any number of regional names. The earliest wildfire has been dated in Wales to 420 million years before present based upon charcoal records.

Ancient and Historical Wildfires

Ancient wildfires mostly originated from lightning strikes or volcanic lava contact with terrestrial vegetation; however, man made events have caused increasing numbers of wildfires, ever since man's discovery of fire. Human caused fires since ancient time consisted of intentional fires for enhancement of agriculture, but also used in warfare. In modern times increased man caused fires are occurring due to control burns and arson.

Proxy paleoclimate data for terrestrial lands in the Molucca Sea demonstrate that greatest wildfire frequencies occurred in the Early Holocene, rather than in Industrial Era or modern time. (Haberle et al, 2010)

Modern Era

A meta-analysis found 17 times more wildfires annually in California prior to 1800 compared to recent decades (1,800,000 hectares/year compared to 102,000 hectares/year). (Stephens, 2007) Natural and human-caused wildfires diminished by 24.3% from 1998 to 2015. (NASA, 2017) According to NASA: "Fire models were unable to reproduce the pattern and magnitude of observed declines, suggesting they may overestimate fire emissions in future projections." This decline comes in spite of an increase in conifer plantations, since it is known that highly combustible monoculture forests are more susceptible to wildfire spread.
USA wildfire time history since 1900 showing annual acreage burned. Chart shows significant decline since peak in 1928. Source: US Forest Service.
The decrease in wildfires since 1800 is also surprising since aggressive fire suppression has been used in the modern era, which suppression is known to cause increased risks of wildfire (Kimmerer, 2001); furthermore, the lack of forest management in modern times is a conspicuous ingredient of added fuel in wildlands. This lack of forest management and reduced timber harvests are particularly notable in California and the entire western USA in recent decades. In 2018, California set a goal of treating (slashing, burning, sawing or thinning trees) of 500,000 acres of wildland per year, yet as of 2021 California remains far from meeting that target.

Prevention

Chief means of wildfire prevention are forest management techniques. These include forest fuel reduction (e.g. timber harvesting, removal of dead wood, prescribed burning (Kolden, 2019), creation of fire breaks), discouraging arson, and removal of homeless encampments in forests.

Maintenance of components of the electric grid, especially clearing transmission lines from vegetation, is an voiimportant preventative step to avoid starting wildfires from downed transmission line and tranformers on poles. Furthermore, it is valuable to keep an adequate baseload on the electric grid, to avoid bad decision making by electric utilities; for example in the Napa, Sonoma and Butte County California wildfires of the last four years, PGE was found responsible for these fires, caused in part by management decisions to keep the grid working in marginal base load conditions.

Other important prevention measures include rapid response of fire crews and sufficient aerial combat resources, which is critical in rugged terrain. Both of tthese factors can greatly decrease the risk of extensive spread of wildfire. Finally, consistent penalties for wildfire arson need to be applied; California and Oregon, particularly have had numerous major wildfires set by arsonists. In many cases serial arsonists are released, often to set seven to twelve other fires, while out on bail (or without any bail).

Worldwide Perspective

Flannigan et al. made projections of wildfire in circumpolar boreal forests in response to scenarios of hypothetical future climate scenarios. Simulations were based on GCM outputs for doubled atmospheric CO2 concentrations. The simulation and fire history results suggest that the impact of carbon dioxide increase on northern forests on forest fires is not as severe as previously suggested, and that there may be large regions of the Northern Hemisphere with a reduced fire frequency. These simulation results are attributed to a switch from using finer grained output than previous researchers. (International Arctic Science Committee (2012) The scenarios produced areas where the interval between fires is likely to decrease (i.e., more frequent fires), but they also produced regions of no change or with greater probability of an increasing interval (i.e., less frequent fires).

In Russia, wildfires have been generally diminishing on a decadal basis from a local high in the year 1950. (FAO, 2001) Finland, Sweden, and Norway account for a very small percentage of total area burned in the boreal forest and generally have not experienced large fires in modern times. In addition, lightning fires are not a major factor, accounting for less than 10% of all fires. (Stocks, 1991; FAO, 2001)

Data Sources

Using the 30 yr Landsat period from 1975 to 2005, data can be used to examine changes in land cover, abundance of vegetation in the summer (peak abundance) and relate changes to climate conditions. Each Landsat scene covers an area approximately 185 km x 185 km and the data is provided in a digital format. Data consisted of an image from 1975, and one each from 1990, 2000 and 2005. Summer images were selected to acquire data near the time of maximum vegetation cover. CAVEAT: data was not acquired on the exact same date each year due to cloud cover or other data problems however, all images were collected within the same very small time frame. Landsat 1975 data was acquired by a Multispectral Scanner (MSS).

References

  • Cole, Brendan (7 January 2020). "What Caused the Wildfires in Australia? Amid Worst Blazes for a Decade, 24 People are Charged with Arson ". Newsweek. Archived from the original on 14 February 2020. In 1974, 117 million hectares of land was burnt in wildfires in central Australia.
  • FAO, 2001. Global Forest Resources Assessment 2000. Main Report.
  • Stocks, B.J., 1991. The extent and impact of fires in northern circumpolar countries. In: J.S. Levine (ed.). Global Biomass Burning: Atmospheric, Climatic, and Biospheric Implications, pp. 197–202.
  • Flannigan, M.D. and C.E. Van Wagner, 1991. Climate change and wildfire in Canada. Canadian Journal of Forest Research, 21(1):66–72.
  • International Arctic Science Committee (2012). Climate change and fire in the Arctic. Encyclopedia of Earth. National Council for Science and Environment. Washington DC. Retrieved from http://editors.eol.org/eoearth/wiki/Climate_change_and_fire_in_the_Arctic
  • Simon Haberle, ‎Janelle Stevenson, ‎Matthew Prebble (2010) Altered Ecologies: Fire, Climate and Human Influence on Terrestrial Landscapes
  • Kimmerer, R. W.; Lake, F. K. (2001). The Role of Indigenous Burning in Land Management. Journal of Forestry. 99(11): 36–41. doi:10.1093/jof/99.11.36. ISSN 0022-1201
  • Kolden, Crystal A. (2019). "We're Not Doing Enough Prescribed Fire in the Western United States to Mitigate Wildfire Risk". Fire. 2 (2): 30. doi:10.3390/fire2020030
  • Meyer, G.A.; Wells, S.G.; Jull, A.J.T. (1995). "Fire and alluvial chronology in Yellowstone National Park: Climatic and intrinsic controls on Holocene geomorphic processes". GSA Bulletin. 107 (10): 1211–1230. Bibcode:1995GSAB..107.1211M. doi:10.1130/0016-7606 107<1211:FAACIY>2.3.CO;2
  • National Aeronautics and Space Administration (2017) Researchers Detect a Global Drop in Fires NASA Earth Observatory. 30 June 2017. 
  • Rackham, Oliver (2003). "Fire in the European Mediterranean: History". Arid Lands Newsletter. 54.
  • Scott, Andrew C.; Glasspool, Ian J. (18 July 2006). "The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration". Proceedings of the National Academy of Sciences. 103 (29): 10861–10865. Bibcode:2006PNAS..10310861S. doi:10.1073/pnas.0604090103. ISSN 0027-8424. PMC 1544139. PMID 16832054.
  • Michael Shellenberger (2020) Apocalypse Never: Why Environmental Alarmism Hurts Us All. Harper Collins Publishers
  • Stephens, Scott L.; Martin, Robert E.; Clinton, Nicholas E. (2007). "Prehistoric fire area and emissions from California's forests, woodlands, shrublands, and grasslands". Forest Ecology and Management. 251 (3): 205–216. doi:10.1016/j.foreco.2007.06.005
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