What Hap­pens to Trees Af­ter Wildfires?

Any per­son who keeps up with the news knows that Cana­da is go­ing through one of its worst wild­fires ever. The city of Fort Mc­Mur­ray is in ru­ins with over 1600 homes and build­ings burned in the fire, and more than 90,000 peo­ple evac­u­at­ed from the area. Luck­i­ly no lives have been lost, yet the com­mu­ni­ty mourns the loss of their homes, pos­ses­sions, and an im­age of a place burned to the ground.

While build­ings can be re­con­struct­ed, and things bought again, one thing that caught my at­ten­tion was the trees. What hap­pens to forests af­ter a wild­fire? Well that de­pends on a cou­ple of things.

Dry­ness

A study by Phil van Mant­gem, a re­search ecol­o­gist, sur­veyed thou­sands of trees in more than a dozen west­ern parks, and found that those trees burned in dry con­di­tions was more like­ly to die than a tree sim­i­lar­ly burned in wet con­di­tions. Trees in ar­eas which were go­ing through a drought were more like­ly to burn completely.

In­ten­si­ty of the Fire

The high­er the in­ten­si­ty of the fire, the more dam­ag­ing its ef­fects. Sur­pris­ing­ly, low-in­ten­si­ty fires are ac­tu­al­ly ben­e­fi­cial to main­tain­ing a healthy for­est in the long run. Trees can al­so re­cov­er from mod­er­ate-in­ten­si­ty fires, as the strongest and most health­i­est trees sur­vive leav­ing some for­est cov­er. But stronger fires are dam­ag­ing in the long run as they lose pro­tec­tion from rain­fall and ero­sion caused by the re­sult­ing white, grey ash from the fire.

Pri­or Treatment

For­est Ecol­o­gy and Man­age­ment pub­lished a study on tree sur­vival af­ter a wild­fire, on ar­eas treat­ed with thin­ning and pre­scribed fire. The re­sults showed “prob­a­bil­i­ty of sur­vival was great­est in those ar­eas that had both thin­ning and pre­scribed fire pri­or to the wild­fire event. Sur­vival was near ze­ro for the un­treat­ed ar­eas. Sur­vival in thinned-on­ly ar­eas was greater than un­treat­ed ar­eas but sub­stan­tial­ly less than the ar­eas with both treatments.”

Un­der­stand­ing how cer­tain trees sur­vive in a wild­fire, is cru­cial to pre­vent­ing their dam­age and lim­it­ing the spread of the fire. While it is cer­tain­ly a large task, it’s ef­fects would be sub­stan­tial on peo­ple liv­ing in wild­fire-prone ar­eas and the wildlife liv­ing there.