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What Drives Fire Frequency, Intensity, and Spread (focused on the Rocky Mountains)

What Drives Fire Frequency, Intensity, and Spread (focused on the Rocky Mountains). Aka: Fuels vs. Climate Bottom up or Top down Local vs Regional. The Facts. Both area and intensity of fires appears to be increasing. The Political Rhetoric.

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What Drives Fire Frequency, Intensity, and Spread (focused on the Rocky Mountains)

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  1. What Drives Fire Frequency, Intensity, and Spread(focused on the Rocky Mountains) Aka: Fuels vs. Climate Bottom up or Top down Local vs Regional

  2. The Facts Both area and intensity of fires appears to be increasing

  3. The Political Rhetoric “Healthy Forests Restoration Act of 2003… reduces the threat of destructive wildfires while upholding environmental standards and encouraging early public input during review and planning processes. The legislation is based on sound science and helps further the President.s Healthy Forests Initiative pledge…..” “The Need for Common-Sense Forest Legislation” Source: www.whitehouse.gov/infocus/healthyforests/

  4. Where Do We Go From Here? • Stephens 1998 • Modeling of effect of fuels treatment on fire behavior • Schoennagel et al. 2004 • Synthesis of geographical patterns in historical fire regimes and 20th century changes in these • Stephens and Ruth 2005 • Review of federal forest-fire policy

  5. Questions to Address(Schoennagel et al. 2004) • Where, and in what ecosystem forest types have fuels increased? • How will fire respond to fuel reduction in different forest types? • Where and when will climate override fuels in determining fire behavior?

  6. Methods High elevation, subalpine forests (spruce-fir to lodgepole to limber and bristlecone) High severity fires Mid elevation Mixed conifers Mixed severity fires Low elevation ponderosa pine Low severity fires

  7. Typical sub-alpine forest Spruce-fir abundant live ladder fuels Lodgepole stand, sparse understory fuels high tree densities

  8. High Intensity fires • Climate governs fire behavior • regional synchronicity • fire interval>suppression interval • No consis. relation: time since fire and fuel abund. • Fires are infrequent and historically intense. • Fire suppression has had little effect on fire frequency, intensity, or size.

  9. High Intensity Fires continued • Fuels treatments ineffective. • Abundant ladder fuels and dense trees are natural • Mechanical fuel reduction not restoration, but departure from natural range of stand structure.

  10. Dry ponderosa pine stand from Jemez Mtns, NM

  11. Recruitment rate over time in the same forest(this and preceding slide from Allen et al. 1988) Year

  12. Low Severity Fires • Fine fuels govern fire behavior • But climate plays a role too (El Nino/Nina) • Fires were historically frequent and low-intensity. • Fire suppression has significantly increased tree density and ladder fuels thereby increasing fire severity. • Fuels reduction treatments can mitigate extreme fire behavior

  13. Proportion pre-fire fuels treatments burned in Rodeo-Chediski fire

  14. Mixed Severity Fires • Historical fire regime is complex. • Fuels and climate are both major influences on frequency, size, intensity. • Suppression has had variable effects. • Occurrence of high-severity fires is not outside historical range but size/frequency may be increasing. • Supression has probably significantly affected only sites at lower elev., drier aspects, and adj. to grasslands.

  15. Mixed Severity Fires continued • Extreme climate and weather can override stand structure and fuels. • Fuel treatments may reduce severity under moderate conditions but may not under extreme weather conditions. • Stephens 1998 • Fuel treatments may not restore historical stand complexity or structure.

  16. Summary • High intensity fires systems climate driven • Low intensity fire systems fuels driven • Mixed intensity fires systems are a bit of both.

  17. Policy implications? • One-size fits all approach won’t work • Is that what is happening with the HFI? • WHO KNOWS?? • Bushies say NO (local imput) • Enviros say YES (excuse for logging) • Scientists say ??

  18. How can either side know?(Stephens and Ruth 2005) • Federal policy has focused on fuels reduction, not fire behavior and effects. • Assumption that forests that have missed more fire intervals will have higher hazards. • Policies attempt to maximize acres treated. • Most fuel treatments do not measure before and after fuel loads!

  19. Where do we go from here? • Who’s telling the truth? • bushy or the enviros • What are our goals/priorities? • Restoration (and to what state)? • Community protection? • Protect all structures?

  20. More Research is Needed! • Into the complexities of of mixed-severity fires and forests. • Ground-truth evaluation of fuels treatments. • Study and address the urban-wildland interface issue.

  21. More Research is Needed! • Stand, NF, and regional mapping of forest types and likely fire types to help prioritize fuels treatments • Extend fire/fuels models to other community types and regions. • Effects of Climate change?

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