Fire ecology studies the role of wildland fire and how it relates to the living and non-living environment. All living components in the environment eventually die and are in a continuous process of being built up or reduced and recycled. This ebb and flow makes life possible by seeking a balance between all components, living and non-living. Fire is studied as a natural process operating as a component of an ecosystem. To understand an ecosystem requires looking beyond the ecosystem's present state.

A full understanding includes an investigation of the ecosystem's origin, the cycles the system progresses through, and possible future stages. Fire is one of many natural events that promote change in an ecosystem. Prior to 1930, most researchers believed all wildland fire was bad. In the years following many began to challenge the negative notions about wildland fire, and this new thinking prevails today. They argued that fire was essential to many plant and animal communities. It is the common belief today that fire is required in some ecosystems to help in the decay of dead plants, breaking down and recycling the nutrients, and in preparing seedbeds for some fire dependent species.

Acadia's Fire History
The history of wildland fire in Acadia National Park extends back thousands of years. Park researchers have used several methods to determine when and why fires occurred in both pre-and post-European settlement periods. By analyzing pollen grains captured in the sediment of some lakes and ponds within the park, the researchers have determined that the forest composition has changed over time. Prior to 2,000 Before Present (BP), northern hardwoods and hemlocks predominated. Over time the area climate cooled and red spruce began to increase. As Native Americans used the area, fire occurrence increased allowing other species to appear. Some scholars suggest that Native Americans may have started periodic fires to encourage the growth of paper birch for their own use. After Europeans settled the area, the evidence shows a much higher incidence of fire. At present much of the area within the park is forested with a spruce/fir forest mixture.

Natural fire ignitions (lightning) are, and most likely were, of little importance in accounting for less than 2% of all wildfire in the park between 1936 and 2005. The moist, humid climate of coastal Maine does not encourage natural ignitions. This lack of fire causes large amounts of dead woody fuels to accumulate on the forest floor. Fuels can also include foliage or grass. They may be fine, such as twigs or needles, or heavy such as logs, branches, or whole trees. They may also be living such as understory layer of tree regeneration or a layer of shrubs. If the fuel load is light a fire may burn through the forest with a very low intensity, typically consuming only the litter on the very top of the ground. If the fuel load is heavy the fire intensity may become very high. As the forest ages the canopy breaks up, allowing younger trees to sprout and grow. This understory layer forms a "ladder" of fuel that may allow an intense fire to ascend in the tops of the trees, creating what we know as a highly destructive "crown fire."

For an ignition to take place, the fuels must be dry. As summer advances the moisture content in the fuels may go down in a dry year. If conditions are right, the park may experience periods of elevated fire danger. There is evidence that periodically, at intervals of a few hundred years, fires have burned portions of Mount Desert Island (see The Year Maine Burned - pdf - 99kb).

Fire has naturally occurred for thousands of years prior to settlement. For many ecosystems fire is a natural catalyst for species diversity and a healthy forest. Without periodic fire, the land can become an overstocked monoculture, plagued with excessive fuel accumulation, stagnation, and below-normal reproduction, which ultimately encourages widespread disease and insect infestations.

Fire is a natural part of the ecosystem at Acadia National Park, helping to renew and recycle the forest at periodic intervals. However, the area of Acadia National Park and the neighboring towns and villages are in such close proximity to the forest themselves that allowing a fire to burn in a natural state is not an option. It has often been said that we really don't prevent wildfires, we just defer them. Wildfire will always present a risk to homes built in the wildland. The park is attempting address this issue by making its neighbors aware of the problems inherent in living in the wildland/urban interface.

Indeed as the park moves into the new millennium it faces questions on how the ecology of the park might benefit from the effects of wildland fire. Prescribed fires are used in some areas of the park to maintain scenic vistas and cultural landscapes.