Tuesday, January 29, 2013

Forest Fires versus Forest Restoration

At ESA this year, one discussion turned to the elephant in the room of forest restoration thinning projects: the certainty that thinning will have some deleterious effects versus the probability that a thinned area would actually encounter a forest fire during the approximately 25-year window of restoration effectiveness.  Forest restoration typically involves thinning forests to lower stand densities to discourage the spread of stand-replacement crown fires in historically low-intensity fire regimes.  Yet,  absent the return to presettlement semi-annual burn patterns (i.e. an end to the total suppression paradigm), tree seedlings will recruit and form high density stands within a couple decades.  

What are the odds that a given patch of forest will encounter a mega-fire over a 25-year time span?  According to some participants in the discussion, the odds are quite low.  But that may depend on the forest.  Take, for example, the fire-prone semi-arid mountains of the southwest:

Representative map of burned areas in SE Arizona and SW New Mexico over the last decade.  The Wallow Fire (538,000 acres in the White Mtns) and the Horseshoe Two (223,000 acres in the Chiricahua Mtns) fire, are visible as large yellow areas.

Shaded areas indicate official MTBS 2000-2009 burned area polygons.  Yellow areas are provisional "fire detection" areas from MODIS.  This map was generated using the U.S. Forest Change Assessment Viewer (FCAV), which can map a large number of forest disturbance types, utilizing historical to contemporary GIS layers and current satellite imagery.

Perhaps the ESA discussion participants should read:

Rhodes, J.J. and Baker, W.L., 2008. Fire probability, fuel treatment effectiveness and ecological
tradeoffs in western U.S. public forests. Open Forest Science Journal, 1: 1-7.

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