In this lesson, you'll learn about an idea that might seem strange at first--that is, that fires can actually be beneficial to forests.

Wildland fires play a very important role in many forests and other ecosystems. For many years, our firefighters have made sure they put out as many fires that burned on public lands as possible, with the goal of saving the land. However, what we didn't realize was that by doing this, we have disrupted the way nature handles fire on its own. Also, as more and more communities develop and grow in areas that are close to fire-prone lands (these areas are called the wildland/urban interface), wildland fires pose increasing threats to people and their property.

Many fires occur naturally and can have many positive effects on an ecosystem and help keep forests healthy. While this never means that we should start a fire, you may be surprised to learn that many ecosystems have already learned how to withstand--or even exploit--a wildfire.

PLANTS AND FIRE: Plants have many different adaptations to fire. In chaparral regions in Southern California, some plants have leaves coated in flammable oils that actually encourage an intense fire to burn! The heat will cause their fire-activated seeds to grow and to take advantage of the fact that there are no other plants to compete with in the newly-burned landscape.

Another example of this occurs in the Lodgepole pine. It is one of a number of plants that have smoke-activated seeds and/or fire-activated buds. Its cones are sealed with resin until fire melts it away and releases the seeds. Many plant species, including shade-intolerant giant sequoia (Sequoiadendron giganteum), require fire to make light gaps in the vegetation canopy. This allows their new seedlings to compete with more shade-tolerant seedlings of other species and establish themselves in a process known as "recruitment".

FIRE SUPPRESSION: Fire serves many important functions within fire-adapted ecosystems. It plays an important role in nutrient cycling--that is, ensuring that the soil is recharged with the nutrients needed by plants to grow. By putting out fires in forests, we have learned that this can lead to unexpected changes in ecosystems that often negatively affect plants, animals, and even humans.

But really, how can a fire be a good thing? Small, natural, "nomal" fires tend to burn in the forest UNDERSTORY, removing only small trees and shrubs. Only high-intensity fires burn into the CROWNS of the tallest trees. This means that fire naturally removes some of the fine fuels found in a forest, while leaving the heavy fuels--the fully-grown trees--alone. When these smaller files are prevented from burning, it leads to a build-up of fine fuels on the forest floor. Dry leaves, needles, and small brush build up in the forest, creating a dangerous situation. It means that if and when another fire starts, and it is not stopped, the forest has much more fine fuel in it, and can lead to generating enough heat to burn the heavy fuels too!

Forest health is affected in interesting ways when we allow trees to grow thick and untouched by natural forest fires:

• Diversity of plants, mammals, birds, and fish is likely to be low, since the dense forests inhibit diverse plant and animal populations.
• Trees often exhibit signs of plant stress as they grow larger and need increasing amounts of water and nutrients. Trees can be victimized insects or disease when deprived of nutrients. When this occurs, foresters often recommend that the stands be thinned so that the trees that are left have adequate light, moisture and nutrients for growth. Because the ones that need to be removed are the smaller, less valuable ones, however, such stands are often left untreated. They may stay this way until they fall victim to fire, wind, or pests.
• Reproduction and survival of new plants may change the character of the forest. As the larger, more dominant trees die for various reasons, they can be replaced by the shade-tolerant species that have grown in under them. This is how pine forests move toward fir or hardwoods, coastal Douglas-fir toward hemlock, and oak toward maple.

This is why prescribed fire is seen as a very healthy option by both foresters and fire professionals.

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