Forest fires, like those currently burning in many parts of British Columbia, are consistently growing larger and have been happening more often as our planet warms. However, while the loss and sadness often associated with wildfires cannot be overemphasized, it is important to recognize that fire plays an important, and in some cases necessary, role in the health of our forests.
In order to properly understand the role a forest fire has in an ecosystem we must first put on our ecologist hats and talk a little about the concept of succession. Ecologists talk about two similar, but very different types of succession. The first, primary succession, describes the process whereby plants and animals move into a previously unoccupied area and slowly populate it, changing the environment as they grow and compete for space. The first organisms to move into a new area are referred to as the pioneer species. The repopulation of a chaste area, for example following the retreat of a glacier, could be described as primary succession. Secondary succession, like primary succession, describes the repopulation of an area, however it describes the repopulation of an area which has had an existing ecosystem wiped out, for example by fire.
Secondary succession can take place much faster than primary succession mainly because, following an event such as a forest fire, root systems and soil seed banks are still intact. Furthermore, the area’s soil does not need to be conditioned for plant growth, an important step that was performed by former residents.
In years gone by, ecologists would sometimes talk of the eventual outcome of succession as a climax community, or an optimal ecosystem where plants and animals would reach equilibrium with one another, creating a stable ecosystem. However, as ecologists’ understanding of ecosystems evolved, the concept of a naturally existing climax community began to seem unrealistic. Today many ecologists feel that natural ecosystems never reach a climax situation as they are in a state of constant flux.
In Canada, forest fires represent perhaps the best and most dramatic examples of ecological flux, to the point where there are now people who call themselves fire ecologists. Their job is to study forest fires as a natural and essential part of the forest.
Fire prevention programs
Traditionally, governments have considered forest fires ecological disasters. As such, millions of dollars were spent trying to prevent and contain them. At the time it was thought that these fire prevention policies were in the best interest of the plants and animals of the ecosystem, as well as industries which relied on them for business. We now know that this is not always the case.
In the first half of the twentieth century, fire prevention programs, aimed at preserving the giant sequoias — one of, if not the largest species of tree on the planet — were in place in the northwestern United States. What the organizers of these programs did not know was that the sequoias actually depended on fire for reproduction, and their efforts were actively preventing the trees from thriving.
Dendrochronologists, scientists who study the natural history of forests, estimate that prior to the adoption of fire prevention programs small fires would move through the sequoia groves every five to 15 years. This played an important role in the growth of sequoia saplings since, unlike many of the tree species they compete for space with, the young trees are shade-intolerant, meaning that they need an abundance of light to thrive and grow. The regular fires in the sequoia groves would clear away faster-growing, shade-tolerant species and create holes in the canopy, allowing light to filter through to the forest floor and provide an ideal habitat for sequoia saplings to act as pioneer species in a secondary succession scenario. Furthermore, sequoia seeds are actually encouraged to germinate through exposure to fire.
The relationship between the giant sequoia and fire, while fascinating, is not unique. We now know that many species of conifer rely on fire for their reproduction. Jack pine, for example, develop seed cones sealed with a waxy resin. Upon exposure to the high temperatures of fire the resin melts away, releasing the seeds onto the newly cleared ground. Some tree species, such as the larch, have developed thick woody bark allowing them to survive fires, while others actively encourage forest fires, either by shedding extreme amounts of dry branches onto the forest floor, or even by excreting flammable oils.
Forest fires and climate change
While forest fires are an important part of many ecosystems, its still possible have too much of a good thing. The Scripps Institution of Oceanography, in association with the University of Arizona, has found that of the 1,166 forest fires reported in the western United States between 1970 and 2003, 932, or 80 per cent, have occurred after 1987, the first year that spring and summer average temperatures began to rise in those areas. This trend has lead to predictions that we could see as much as a 118 per cent increase in forest fires by the year 2100.
Despite these observations, there is little to no quantitative evidence suggesting that climate change is having a direct effect on forest fires. But experts do point out that springs which start earlier and winters which start later mean that there are more days every year when snow is not covering the ground — extending the current forest fire season in some areas by as much as a month.
As the climate warms and communities grow into the forests of Canada, forest fires will no doubt continue to fill our consciousnesses. While it is difficult to tout their nurturing qualities in the face of so much human tragedy and destruction, it is undeniable that fire plays an important and irreplaceable role in the forest ecosystem. Without it Canada’s parks and wild places would probably look unrecognizably different. As a destroyer and creator it is truly a double-edged sword, and perhaps one of the most obvious reminders of how little we know about the wilder parts of this country.