Print Window Close Window Fire -- To Burn, or Not To Burn Forests are not static. When we talk about preserving a forest, or any ecosystem, we know that individuals within that system will die. New stands of trees will gradually replace old ones. Catastrophic natural disturbances may periodically affect much larger areas. Thus, what we are protecting is not an object, but a system. Like many forest types, most of the boreal forest is a fire-driven system. Started by lightning, fires typically burn any particular area every 50 to 150 years, although certain spots, such as the rich habitats along riverbanks, may burn less frequently and thus harbor older trees. For years, Smoky the Bear told Americans, “Only you can prevent forest fires.” Fire was prevented at all costs. But land managers were unwittingly setting themselves up for disaster, as year by year the potential for large, devastating fires increased. What happened in Yellowstone is a good example of the results. Clearly, prevention is not the answer. On the other side of the question, however, are those who feel that if the forest is going to burn anyhow, we might as well clear-cut it. If fires can occasionally decimate large areas, what makes their effects different from the effects of clear-cutting? First, fires are patchy, and highly variable in size. A fire can burn one area heavily, another area lightly, and skip over an intervening patch altogether. This creates a mosaic of habitats for species that prefer to spend part of their time in open areas and part of their time in the shelter of the forest. Second, cutting and burning have very different effects on the nutrient composition of the soil. Ash tends to be high in readily available minerals. If the trees are harvested, many of these minerals leave the site on logging trucks. Slash (pieces of trees too small to be of interest to loggers) can be left behind to return to the soil, but this decomposition process is slow, especially in northern climates, and large heaps of slash can obstruct regeneration for years. Third, tree species have adapted to fire-driven environments over millions of years of evolution. For example, black spruce keep their cones for several years. The cones remain sealed shut until opened by the heat of a fire. Seedlings sprout quickly in the mineral soil left in burned areas. Clear-cuts, on the other hand, often regenerate slowly, or have to be artificially replanted. There may be no seed trees left nearby, and no means of seed dispersal whereby seeds can reach the center of big cuts. In the boreal region, clear-cut areas previously dominated by white spruce tend to be overtaken by hardwoods (birch or aspen), since these trees can sprout quickly from their undamaged roots. Finally, the trees that burn are not always the trees that are logged. For example, in Interior Alaska, loggers are mainly interested in larger timber, particularly the white spruce that grow in areas that are relatively biologically rich, such as near streams or rivers. These trees may be three hundred years old, and they are not particularly susceptible to burning. On the other hand, the spindly stands of black spruce that grow in harsher or boggier spots are of little interest to the timber industry, and are more likely to burn in a forest fire. Fire may seem undesirable to humans, and burned areas are ugly—at least until vibrant purple fireweed takes over the site the following spring. But fires are a necessary part of the boreal ecosystem. Trying to mimic nature is a difficult game, although this doesn’t stop forest “managers” from trying to control highly complex systems. If the history of forestry in America has taught us anything, it should have taught us caution. |