Forest Thinning Will Increase Wildfire Risk

- by Charles Thomas, The Ore­gon­ian

As fires again rage across the West, sen­a­tors from John McCain, R‑Ariz., to Ron Wyden, D‑Ore., echo the refrain “thin the forests” to pre­vent wild­fires. Unfor­tu­nate­ly, most of the advo­cat­ed thin­ning will actu­al­ly stoke the wild­fires of the future rather than lessen their occur­rence and impacts.

Thin­ning pre­scrip­tions pro­posed in Wyden’s O&C leg­is­la­tion, designed by emi­nent foresters Jer­ry Franklin and Norm John­son, will stim­u­late hot­ter, faster-grow­ing wild­fires that are more haz­ardous to fight. These pre­scrip­tions dras­ti­cal­ly thin for­est canopies through tim­ber sales designed pri­mar­i­ly to gen­er­ate tim­ber vol­ume, often leav­ing the slash and small­er shrubs and trees for non-com­mer­cial fire haz­ard reduc­tion projects that are usu­al­ly under­fund­ed, unable to match the pace of canopy thin­ning projects and clear-cuts across the landscape.

Thin­ning for­est canopies opens the stands to more sun­light, which encour­ages growth of fine fuels, includ­ing shrubs, small trees and grass­es. Pen­e­tra­tion of sun­light and dry sum­mer winds effec­tive­ly increas­es the active fire sea­son by dry­ing this new growth and left­over log­ging slash much faster than in adja­cent unlogged for­est stands, where greater canopy clo­sure with tall shade columns retains mois­ture in soils and vegetation.

Active fire sea­son begins weeks ear­li­er in thinned forests and lasts weeks lat­er, dras­ti­cal­ly increas­ing the time span dur­ing which dry for­est con­di­tions con­tribute to rapid fire spread. These dry, thinned forests often burn hot­ter and more errat­i­cal­ly than unthinned stands, even caus­ing retreat of fire­fight­ers when con­di­tions become too dan­ger­ous to main­tain fire lines.

Even worse than canopy thin­ning is clear-cut­ting, preva­lent on pri­vate indus­tri­al forest­lands, which often cre­ates dense brush fields of fire-prone veg­e­ta­tion. Where refor­esta­tion is suc­cess­ful, dense plan­ta­tions over­stocked with young trees grow into future fire-bombs of fine fuels with no nat­ur­al resilience to wildfire.

Exam­i­na­tions of for­est fires, par­tic­u­lar­ly in the dri­er regions of south­ern and east­ern Ore­gon, reveal where young stands of dense brush and small trees, often choked with untreat­ed log­ging slash, explode into errat­ic fires, forc­ing fire crews off the lines for their own safe­ty. Often these fires lie down and under-burn when they reach resid­ual stands of old­er forests with closed canopies and a greater lev­el of mois­ture reten­tion, pro­vid­ing safer zones for fire fighters.

Clear-cut­ting is wide­ly pro­posed in both the Sen­ate and House ver­sions of O&C leg­is­la­tion. When added to the dom­i­nant prac­tice of clear-cut­ting on pri­vate tim­ber­lands, Ore­gon is being stoked for mas­sive fires beyond any­thing expe­ri­enced his­tor­i­cal­ly. Canopy thin­ning is icing on the cake — baked by replac­ing old­er forests nat­u­ral­ly resis­tant to wild­fires with degrad­ed forests and plan­ta­tions poised to become con­fla­gra­tions of the future.

Ore­gon needs eth­i­cal approach­es to the onset of cli­mate change, which threat­ens increased for­est fires from high­er tem­per­a­tures and extend­ed fire sea­sons. It is uneth­i­cal to place Ore­gon’s rur­al com­mu­ni­ties and brave fire­fight­ers at risk to gar­ner high­er prof­its for the tim­ber indus­try. An eth­i­cal approach would be to focus on under­sto­ry and plan­ta­tion thin­ning to reduce fire haz­ards, espe­cial­ly along roads and around rur­al com­mu­ni­ties, while retain­ing mois­ture con­serv­ing canopy clo­sure in old­er stands nat­u­ral­ly resis­tant to wildfire.

Charles Thomas, of Jack­sonville, has a mas­ter’s degree in envi­ron­men­tal edu­ca­tion and has worked for 40 years in sev­er­al capac­i­ties in the forests of south­west Oregon.


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