Life After Fire

Forrest M. Mims III

In 2007 drought plagued much of the Western and Southeastern US. In early 2008, drought conditions across Texas contributed to numerous grass fires sparked by fireworks, discarded cigarettes and trash fires. A downed power line or the hot catalytic converter of a car or truck can also ignite dried grass.

Recently I photographed a raging grass fire that burned more than 20 acres and came perilously close to a row of mobile homes. Before the fire fighters arrived to control the flames, some of the residents used garden hoses and shovels to fight the advancing line of fire.

Forest fires are terrifying, but even lowly grass fires can ignite vehicles, buildings and homes. They can also kill livestock and wild animals.

Forest fires can become so hot that they literally bake the ground beneath them. Even the roots and seeds of plants are often destroyed. Yet some plants are specifically designed to survive fires, for their seeds germinate only when heated by flame.

Figure 1. This grass spike emerged from a blackened field only days after a grass fire. Photograph by Forrest M. Mims III.

Grass fires leave behind a blackened landscape seemingly devoid of plant life. But a grass fire doesn't heat the ground nearly as much as a major forest fire. While stubble may be entirely consumed, some green sprigs may survive. And if roots are undamaged, new life will soon emerge from the devastation.

Several weeks ago a grass fire started on the south side of an Interstate highway directly across from a gas station in a small Texas city. A strong north wind quickly whipped the flames across the frontage road, where they ignited the grass in front of the gas station. Meanwhile, the fire moved west along the margin of the highway and crossed the frontage road into a 9-acre field that borders the west side of the gas station. The entire field was quickly consumed.

The fire was over fairly quickly, and it left behind what appeared to be a blackened field with no obvious sign of life. But all that changed in the following days.

The brush trucks that tried to suppress the fire sprayed water over portions of the field and the highway margin. That water provided more moisture than the rain the area had received over the past several months. Tiny points of green were sprinkled across the landscape.

A few days later, the green points had become spikes of grass nourished by the ashes and the moisture left behind by the fire fighters (Fig. 1). Bright spring sunshine did the rest.

Today that field is a solid green blanket of grass. It's a fascinating reminder of how quickly grass can recover from a fire. Would that homes and buildings destroyed by grass fires could also be replaced so quickly.

Forrest M. Mims III and his science are featured online at www.forrestmims.org and www.sunandsky.org. "World of Science" columns are selected and sometimes revised from columns published in the San Antonio Express-News or the Seguin Gazette-Enterprise. The columns are intended for a general audience.