Tundra fires are wildfires that occur in the Arctic and sub-Arctic regions. These fires consume vegetation and organic soil layers in ecosystems where trees are scarce or absent. Tundra fires have specific characteristics that set them apart, making their increasing frequency a growing concern for these delicate polar landscapes.
Unique Nature of Tundra Fires
Tundra fires differ from other wildfires because their primary fuel source extends beyond surface vegetation. They burn through low-lying plants like mosses, lichens, and dwarf shrubs, and significantly into deep organic soil layers, known as peat. This organic mat, formed from decomposing plant material, can be quite thick and acts as an insulating blanket for the permafrost below.
Fires in the tundra often smolder deep underground within this organic layer, making them difficult to detect and extinguish. This smoldering can persist for weeks or even months, sometimes overwintering beneath the snow and re-emerging later. The presence of permafrost plays a unique role, as these fires can burn through the organic layer, exposing the frozen soil to warmer temperatures and initiating thaw.
How Tundra Fires Start
Tundra fires can be ignited by both natural causes and human activities. Lightning strikes are the primary natural ignition source, especially during dry weather. Hot lightning, characterized by longer duration currents, accounts for most natural fires. Periods of above-normal summer temperatures can lead to increased convection, fostering more thunderstorms and a greater number of lightning strikes.
Human-caused ignitions also contribute to tundra fires. These can result from accidental campfires left unattended, carelessly discarded cigarettes, or sparks from infrastructure. Dry vegetation and drought create conditions susceptible to ignition and rapid fire spread. While human activity accounts for many ignitions, lightning-caused wildfires are responsible for burning the largest areas in high latitudes.
Impacts on the Environment
Tundra fires have profound impacts on the Arctic environment, affecting ecological systems and influencing global climate. These fires damage slow-growing tundra vegetation, which can take decades to recover, and disrupt wildlife habitats.
A major consequence of tundra fires is their impact on permafrost. When fires remove the organic layer, the underlying permafrost is exposed to warmer temperatures, leading to its thaw. This thawing can cause ground subsidence, known as thermokarst, characterized by the melting of ground ice and the formation of irregular topography, including new lakes or dried-up hollowed areas.
Permafrost thaw releases vast amounts of ancient carbon, stored for hundreds to thousands of years, into the atmosphere. Microbes in the thawed soil convert this carbon into greenhouse gases, primarily carbon dioxide and methane, which contribute to further climate change. Carbon emissions from Arctic wildfires can be among the highest on Earth per unit area, comparable to tropical peatland fires.
Why Tundra Fires Are Increasing
The observed increase in the frequency and intensity of tundra fires is directly linked to climate change and rising Arctic temperatures. The Arctic is warming at a rate two to four times faster than the rest of the planet, leading to longer and drier fire seasons.
Warmer temperatures encourage more thunderstorms, which bring an increased risk of lightning. Studies project that lightning strikes could increase by 12% for every degree Celsius of warming, potentially leading to a 50% increase by the end of the century. This increase in dry lightning activity, coupled with drier fuel conditions, is a factor in the growing number of tundra fires.