With water, nutrients, and space divided among many more individuals, the overall health of the forest has declined. These forests are more susceptible to disease and insects, and in some cases, to more intense burns than in the past. Catastrophic fires are not abnormal, but rather, are ecologically important parts of the landscape. Indeed, while hundreds of small fires reduce fuels over many parts of the landscape, most of the acreage burned in forest fires occurs in a few very large fires. These might only visit a particular site once every couple of hundred years, when conditions of prolonged drought, wind, fuel loading, and ignition all unite to set the stage for significant fires.
Frequent fires have many ecological benefits for soil and plant fertility.
Over much of the Pacific Northwest, wet winters are followed by predictable summer drought. Thus, the time of year when it's warmest and most conducive to bacterial and fungal decomposition, moisture is limited, and rapid decomposition of litter is precluded. There is usually only a short period of the year during the spring months when soils are both moist enough and warm enough to provide decomposing organisms the proper environment for composting litter. Without fires, dead material accumulates, locking up essential nutrients necessary for plant growth. Fires release these nutrients, and enhance the production of nitrogen- fixing plants that often revegetate recently burned areas.