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| SMU fire scientist Christopher Roos Photo Credit: Courtesy of Southern Methodist University |
Scientific Frontline: Extended "At a Glance" Summary: Pacific Island Wildfires
The Core Concept: The interdependent relationship between human land-use practices and natural climate variations, specifically El Niño-driven droughts, in driving historical and modern wildfire activity on Pacific islands.
Key Distinction/Mechanism: While previous ecological models primarily attributed Pacific island deforestation and wildfire susceptibility to human agricultural practices, recent isotopic evidence demonstrates that natural climate variations independently caused significant fire activity millennia before human settlement.
Origin/History: In 2013, researchers excavated deep soil cores from Fiji's Sigatoka River valley, utilizing charcoal and stable carbon isotopes to reconstruct an environmental history that predates human habitation.
Major Frameworks/Components:
- Isotopic Analysis: The extraction of stable carbon isotopes from deep soil cores to identify historical plant communities and reconstruct past environmental conditions.
- El Niño Southern Oscillation (ENSO): A recurring climate pattern that periodically induces severe droughts in the Pacific, creating optimal conditions for natural wildfires ignited by lightning strikes.
- The Grass-Fire Cycle: An ecological feedback loop wherein invasive or fire-adapted grasses increase fuel loads, leading to more frequent fires that further promote grass expansion at the expense of native forests.
- Human-Climate Synergy: The compounded effect wherein human land modification increases ecological vulnerability to climate shifts, and shifting climate patterns exacerbate the impacts of anthropogenic land use.
Branch of Science: Environmental Archaeology, Anthropology, Climatology, and Ecology.
Future Application: Utilizing historical, traditional land-management techniques alongside modern climate models to predict, prepare for, and mitigate the increasing severity of the grass-fire cycle under ongoing climate change.
Why It Matters: Understanding the dual drivers of wildfire frequency is critical for developing effective disaster mitigation strategies, particularly as global climate change is projected to intensify the frequency and severity of future El Niño events.
It’s long been understood that human settlement contributes to conditions that make Pacific Islands more susceptible to wildfires, such as the devastating Aug. 8 event that destroyed the Maui community of Lahaina. But a new study from SMU fire scientist Christopher Roos published in the journal Nature Ecology & Evolution shows that climate is an undervalued part of the equation.
Roos, SMU environmental archaeologist and professor of anthropology, traveled with his team to the Sigatoka River valley in southwestern Fiji in 2013, where they collected charcoal and stable carbon isotopes from deep soil cores to understand historic patterns of fire activity in the area. Different plants have distinct carbon isotopic signatures, which can provide information about past plant communities.
The team found fires and fire-created grassy areas that predate human settlement by millennia and actively corresponded to droughts likely driven by a regularly occurring weather pattern known as El Niño. El Niño events can alter precipitation patterns worldwide, making environmental conditions more favorable for wildfires. The National Oceanic and Atmospheric Administration issued an El Niño advisory in June, announcing the latest arrival of the climate event that continues to influence weather worldwide.
Lightning strikes also act as a natural cause of wildfires, igniting plant material that acts as fuel.
The impact of human settlement, farming activity (particularly the clearing and burning of land) and resulting deforestation of remote Pacific islands is well established in the scientific record, and research from the Roos team only confirms what Roos calls “a modern environmental parable.” But the impact of climate must be considered, too, the study finds.
“It struck me that these fires are not exclusively human-driven, because when I looked at earlier pre-human spikes in fire activity, those lined up with El Niños,” said Roos. “The combination of climate and human activity drives island deforestation and increases wildfire activity. It may be that human activity is making the landscape more sensitive to those climate variations. But it could also be that the climate is making the landscape more sensitive to human activity.”
In the past, Roos said, research often focused more on human activity harming Pacific Islands' land without considering climate's role in the damage. He believes an approach that considers both causes is necessary, especially with catastrophic wildfire events occurring more regularly.
Roos also points out that the Pacific Islands are natural laboratories to study the grass-fire cycle, which is prevalent in areas where wildfire is occurring with the spread of invasive grasses. Traditional farmers have practiced successful techniques for clearing and burning land for centuries, and past lessons could offer ways to prepare and cope with future wildfire events. Roos stresses that we must adapt to the new environment climate and humans have created.
“Droughts triggered by El Niño events appear to have played a role in intensifying the grass-fire cycle and contributing to deforestation in the past," he said. "And looking forward, climate models indicate that the Pacific Islands could experience conditions similar to El Niño events more frequently due to ongoing climate change. We need to reflect on what we’re doing and whether or not those actions make places more or less vulnerable to future wildfire events.”
Research team members included Julie S. Field, from Ohio State University and John V. Dudgeon, Idaho State University and the Center for Archaeology, Materials, and Applied Spectroscopy at Idaho State University.
Reference material: What Is: El Niño, La Niña, and a Climate in Flux
Published in journal: Nature Ecology & Evolution
Authors: Christopher I. Roos, Julie S. Field, and John V. Dudgeon
Source/Credit: Southern Methodist University
Edited by: Scientific Frontline
Reference Number: es100223_01