Wildfires and wilderness life cycles
Wildfires are a natural and essential component of many ecosystems, playing a critical role in shaping wilderness life cycles. Fires can be ignited by natural occurrences, such as lightning, or by human activities, and they significantly influence the health and diversity of plant and animal life. Various types of fires, ranging from smoldering surface fires to high-intensity crown fires, affect different ecosystems uniquely. For instance, grasslands can recover within three years following surface fires, while forests may have longer intervals between fires, influencing the type of vegetation that thrives.
In northern ecosystems, fire is infrequent, promoting the germination of specific tree species like pine and spruce on fire-cleared soil. Chaparral regions require periodic fires to prevent overgrowth and maintain biodiversity. However, the increasing frequency and intensity of wildfires, exacerbated by climate change and human encroachment, pose significant risks to both natural habitats and human infrastructures. Wildfires are thus seen both as natural cycles in wilderness life and as challenges that require careful management to balance ecological health and safety for nearby communities.
Wildfires and wilderness life cycles
Wildfire is an integral part of wilderness life cycles, helping keep ecosystems healthy and diverse in plant and animal life. Controlled human-set fires aid farmers, ranchers, and foresters in making their lands more productive.
Background
Fire is both inevitable and necessary to most land ecosystems. Every day, lightning strikes the ground about eight million times globally, and one stroke in twenty-five can start a fire. Even so, lightning accounts for only about 10 percent of ignitions; humans are the leading agent in setting fires. Fire was one of the first tools humans used to shape their environment, and it has remained among the most common tools ever since. Add to lightning and humans as agents the molten from volcanoes and the sparks sometimes caused by rock slides, and not surprisingly millions of hectares of land burn worldwide every year.
Because fire is so prevalent, ecosystems have evolved tolerance to it or even a symbiotic dependence on it. Wildfires foster decomposition of dead material, recycle nutrients, control diseases by burning infected plants and trees, help determine which plant species flourish in a particular area, and in some cases even play a role in germinating seeds. Purposefully set fires, today called controlled burns, have flushed game for hunters since prehistoric times and are still put to work fertilizing fields and clearing them of unwanted plants, pruning forests, combating human and animal enemies, and eliminating dead, dry materials before they can support a destructive major fire.
Types of Fire
Not all fires are equal. Scientists distinguish five basic types in increasing order of intensity and destructive potential: those that smolder in deep layers of organic material; surface backfires, which burn against the wind; surface headfires, which burn with the wind; crown fires, which advance as a single front; and high-intensity spotting fires, during which winds loft burning fragments that ignite separate fires. Moreover, the intensity, likelihood, and range of fires for any locale depend upon the climate, season, terrain, (especially the wind), relative moisture, and time since a previous burn. The dominant species of plant also affects which type of fire an can support.
Tundra and Far-Northern Forests
Fires visit northern ecosystems infrequently because they retain a great deal of moisture even during the summer: There are intervals of sixty to more than one hundred years between fires for forests and several centuries for tundra. Caused primarily by lightning, light surface fires are most common. Crown fires are rare. The seeds of many northern tree species, such as pine and spruce, germinate well only on soil that a fire has bared. Fire does not occur in high Arctic tundra and plays only a minor role in the development of low Arctic tundra.
Grasslands
Grasslands of all kinds rebound from surface fires in about three years. In shortgrass and mixed-grass prairies, grass species, especially buffalo grass and blue grama, survive fires well, while small cacti and broadleaf plants succumb easily, assuring dominance of the grasses. For this reason, cattle ranchers frequently burn the prairies to remove litter and inedible species, thus improving the distribution of grazing fodder. In tallgrass prairies, big bluestem, Indian grass, and switchgrass increase after a fire, whereas cold-season grasses, such as Kentucky bluegrass, are devastated, and fires prevent invasions of trees and woody shrubs.
Semidesert and Desert Regions
Similarly, surface fires control shrubs in semidesert grass-shrub lands on mesas and foothills, while allowing the fire-resistant mesquite to flourish. Desert sagebrush areas in the intermountain West have a surface fire about every thirty-two to seventy years. A burned area takes about thirty years to recover fully, although horsebrush and rabbitbrush come back quickly.
Chaparral-Dominated Lands
The chaparral of temperate coastal climates, such as that in Southern California, ignites easily and is likely to burn from surface fires every ten to fifteen years. In fact, without fire, chaparral fields, which also support manzanita, scrub oak, and coyote brush, become choked, and many nonsprouting shrubs die. Light fires every twenty to thirty years are therefore necessary to species survival. Unburned for longer than that, the fields accumulate so much dead debris that the chances for a tremendously destructive fire soar.
Forest Fires
Great diversity in tree types and, accordingly, fire frequency and intensity, exists among evergreen and deciduous forests. Forests can fall prey to all types of fire; crown and high-intensity spotting fires are most common in Douglas fir-dominated areas, while mature stands of pure juniper are nearly impossible to burn. In general, fire helps maintain the dominance of pines by preventing hardwoods, which burn more readily (with the exception of some oak species), from invading. Several pine and spruce species, most notably ponderosa pine, require fire-cleared soil to germinate seeds. Wildfire intervals range from five to ten years for ponderosa pines and up to five hundred years for redwoods.
Beginning in the 1960s, government land managers used controlled burns and unopposed wildfires to clear away underbrush and dead trees in public forests. However, since such fires destroy public timber resources and sometimes, out of control, ravage private lands and human residential areas, the practice has been controversial, especially after the devastating Yellowstone National Park fire of 1988.
The political as well as economic infeasibility of controlling overgrowth may have contributed to Southern California’s “Station Fire” of 2009, which ravaged roughly two hundred square miles of the Angeles National Forest and adjacent residential interface areas (an area the size of San Francisco) during the largest forest fire in the history of Los Angeles County. The region, normally prone to fires driven by Santa Ana winds, instead underwent a fuel-driven fire that threatened lives and destroyed approximately one hundred homes as well as vast areas of wildlife habitat. Australia experienced similar massive fires during this period.
Such events, while part of a natural cycle, pose immediate threats not only to ecological and other natural resources but also to human infrastructure when development has encroached on the areas subject to burning. Combined with evidence of global warming and concomitant trends toward droughts and longer or unbroken “fire seasons,” such fires can be expected to increase the strain on economic and human resources.
In many biomes, global warming has caused a sharp increase in the number of annual wildfires. This has had a significant impact on local wilderness and ecosystems. In California alone, scientists estimate that global warming has caused a 172 percent increase in areas burned by wildfires since the 1970s. Scientists expect these incidents to increase over the coming decades.
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