23 July 2004

Season of fire and smoke

Forrest M. Mims III

The arrival of summer signals the prospect of wild fires across large expanses of the United States.

This season, major fires are burning in Alaska and the American West. On 19 July, smoke from these fires crossed the central US and reached South Texas.

These fires are detected 24 hours a day by infrared sensors on various NASA and NOAA satellites.

Larger fires that produce dense smoke plumes can be seen in daylight satellite images when clouds don't block the view.

The fire season begins as early as May in the Southwest U.S. Forest fires often occur first in New Mexico and Arizona. As summer approaches, fires occur farther West and North.

July brings the summer monsoon rains to the Southwest. Powerful lightning storms can ignite fires. But the accompanying rain often extinguishes them.

Outside the monsoonal Southwest, major fires may consume more than 100,000 acres before being extinguished by a thousand or more fire fighters and millions of dollars. Or they may burn until cool temperatures and rain arrive in the fall.

Scientists who study the role of fire in the environment point out that fire is a natural force. The traditional policy of putting out all forest fires has left the floors of our forests littered with thick layers of fuel ready to be ignited by a single spark.

Putting out fires has also allowed forests to become densely crowded. In many areas, thousands of spindly trees grow where fewer than 100 formerly grew. This has led to stunted, unhealthy trees that compete for limited soil moisture and become targets for massive beetle invasions.

It took a century for our forests to arrive where they are today. It will be some time before they can be restored.

Some land managers believe that fire is the solution. They point out that certain plants and trees require fire to release their seeds.

Others believe an intensive program of thinning is necessary to restore the forests. They point out the unpredictable nature of intentionally ignited forest fires and the hazards of smoke pollution that accompany them.

The Federal government is pressing ahead by trying both approaches.

Meanwhile, old habits need changing. The goal of 100 percent fire suppression is no longer as practical or achievable as in the past. People must take more responsibility for their own safety when they build homes in fire-prone forests.


Forrest M. Mims III and his science are featured online at http://www.forrestmims.org/.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.