Drought years will contribute most to future burned areas
Burned forests in the Great Smoky Mountains National Park on the Roaring Fork Motor Nature Trail in Gatlinburg, Tennessee. Photo: iStock More droughts brought on by climate change could worsen the impact of wildfires in United States’ southern Appalachians, according to a new study.
Rising annual drought patterns and heightened drought variability may amplify the incidence of wildfires, leading to increased forest burning, a paper published in journal Fire Ecology, January 12, 2024 found.
The southern Appalachians is a unique section of the mountain range comprising Kentucky, Tennessee, Virginia, Maryland, West Virginia and North Carolina and features a wealth of forested land.
According to projections, drought years will be responsible for the majority of future burned areas. The results indicated that more area burned as the drought trend and variability increased, even when a high level of fire suppression was modelled.
Researchers, led by Zachary J Robbins of North Carolina State University, discovered that the most severe and frequent drought scenario would result in approximately 310 square miles (802.89 square kilometres) of forest in the southern Appalachians burning every year by the end of the century.
Thus, in the most extreme scenario of high drought intensity and year-to-year drought variability, the total area of forest burned would double within the next decade and increase by nearly 900 per cent, or nine times, by the end of the century. That would mean around 3,125 square miles (8093.71 sq km) of forests burning by 2100.
In 2016, around 231 square miles burned in the mountain region. According to a press release from North Carolina State University, this year was historic for wildfires in the southern Appalachians due to multiple acts of arson, accidental ignitions and downed power lines.
Short-term drought patterns also had a significant impact on the overall burned area. Other considerations include increased fuel loads as a result of rural abandonment and extended periods of fire suppression, as well as increased ignitions in previously remote areas due to increased access via fragmentation.
Failing to capture “exceptionally dry years will severely underestimate landscape-level wildfire activity, as these drought years account for a disproportionate amount of burned area,” the findings suggested.
The wildfires will also have an impact on the flora; results indicate that the species composition change has reached a tipping point and is unlikely to return to pre-fire suppression and exclusion composition in the southern Appalachians within the next century.
However, oak canopy dominance is likely to continue into the next century due to the current oak population's continued growth potential, but oak regeneration is less certain.
The spatial differences in fire return intervals (FRI) were influenced by landscape patterns of fire exclusion and suppression, according to the research. Future projections suggested varying fire regimes, with some areas having frequent fires per decade and others experiencing none.
Increased oak presence and decreased biomass of mesic hardwoods and maple were associated with more frequent fires. However, mesic hardwoods remained dominant in all fire intervals due to their current prevalence.
“The amount of area burned is unlikely to restore the majority of the landscape to more fire-adapted conditions, as even the most frequent FRI maintained near current levels of non-fire adapted mesic hardwoods,” said the study.
In other words, consistent reintroduction of fire, without additional land management restoration actions, may not restore the landscape to a more fire-adapted state.
“Our study shows that we’d be moving from fire years being anomalous among the southern Appalachians to there being a possibility of a major fire year, with greater than 195 square miles burned in wildfire, in your average year,” said Robbins.
The future fire dynamics in the southern Appalachians and other systems constrained by fuel moisture, could deviate from both past and current patterns, instead forming a distinctive ecosystem state influenced by climate and human activities, the study added.
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