Fire was used as a management tool by indigenous people in southern California for thousands of years before Eutopean settlement: careful burning promoted food species (both plants and animals) and otherwise shaped the environment for human habitation. As a result, most ecological communities of the region consist largely of fire-adapted species.
After European settlement, fires were much more often accidental. The frequency of fires was likely reduced, and their extent increased. Add to this the fire suppression associated with development, the magnified effects of fire in fragmented habitats, and the interactions of fire with invasive species, and it is apparent that the role of fire in modern habitats is complex.
There have been two major fires in the undeveloped areas of Cal Poly Pomona. The first was in August, 1981. A car fire on the I-10 freeway burned up the hill between Cal Poly Pomona and Forest Lawn Covina Hills, and into Box Canyon behind Building 1. All of Box Canyon was burned, but the fire was stopped before burning the canyons to the south and west. This provided more or less comparable burned and unburned areas for future studies.
The second was on July 28, 1989. Sparks from contruction on a new housing development southwest of the undeveloped canyons spread across all the area, and was stopped when it reached the plantings around the Kellogg Mansion (now Kellogg House Pomona). The lack of unburned areas was a hindrance to future studies, but inventories taken after the 1981 fire and before the 1989 fire were useful for comparison.
The species diversity of birds decreased markedly in the burned areas after both fires, and took a number of years to recover. Invasive plants increased in some areas after the 1989 fire. Other studies are ongoing.
Respones to fire can directly increase invasive species. Following the 1989 fire (and despite protests from biologists), the California Department of Forestry aerially seeded the burned areas. We have not obtained a list of the species that they used, but four species showed up afterwards that are common in such seeding mixtures. Two were natives: purple needlegrass (Stipa pulchra), that in much earlier times would have grown in the Quad, but not in the hills, and doveweed (Croton setigerus), which is an indicator of overgrazing (and which has since largely disappeared). The other two were invasive weeds: ryegrass (Festuca perenne, commonly—and mistakenly—used to prevent erosion), and tree tobacco (Nicotiana glauca). The purpose of aerial reseeding is to prevent erosion. Scientific studies show that it is ineffective, and that it can increase the flammability of the areas seeded. At Cal Poly Pomona, most germination took place after the winter rains.