Friday, May 24, 2013

The Role of Fire

Generally when people hear the word "fire" all they think of is devastation. However, in nature fire is a complex thing that brings many changes to the environment, not all of which are negative.

Fire can be a great source of good in environments. It cuts back on plant growth, clearing out underbrush. This provides open space for young plants to receive enough sun to grow. Some young plants are even fire resistant and will thrive after others burn. In addition, fire is actually a requirement for certain plants to reproduce. The cone of the jack pine (Pinus banksiana), for example, will only open after they have been exposed to the heat only a fire can provide. There is a natural fire cycle, with the fire clearing out space that plants will then quickly colonize. This is why some plants reproduce only after a fire sweeps through an area: it gives their offspring a better chance of survival.

New life sprouting after a controlled burn
For a very long time the prevailing view concerning fire was that all fire was bad and must immediately be extinguished. This led to some very costly lessons being learned nearly twenty-five years ago.

The fairly recent history of Yellowstone National Park tells how blanket fire suppression can be a very dangerous policy. Many years of suppression combined with a drought in the summer of 1988 turned the park into a tinderbox. The forest ignited and by the time an early September snowfall finally brought the fires down enough to be controlled over one million acres had been touched by flames. Hundreds of large animals died, including over three hundred elk. Dozens of buildings had been destroyed and all told there was approximately $3 million in property damage. $120 million had been spent fighting the fires. Up to nine thousand firefighters at a time had battled the flames.

Perhaps the most tragic aspect to the devastation that hit such a large part of the National Park is the fact that it was largely preventable. Fire management policies have changed significantly since the Yellowstone "Summer of Fire" and for very good reason. The natural fire cycle cuts back on underbrush, preventing it from building up too much. A great many tree species have fire-resistant trunks, so if underbrush is fairly sparse and low to the ground flames can never reach high enough to kill the life that makes a forest a forest: the trees.  If there is a large amount of underbrush, on the other hand, the flames can burn hotter and higher, potentially reaching all the way up to the crown of a tree. Crown fires are far more devastating than fires that stay low to the ground as they can jump from one crown of a tree to the next. This is especially true in areas where the trees grow very close together.  Crown fires can lead to the complete devastation of a forest.

Many small fires will keep a huge, terrible fire from happening in the future.

I have concentrated on forests here, but any environment can be affected by flames. In the future I plan to discuss the link between fire and mudslides in California.

Sources are the Florida Forest Service, National Park Service, and PBS NOVA Online. Image was taken by me.

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