(Credit: Forest Service, USDA/Flickr)
The severity of wildfires in the Sierra Nevada region of California has been sensitive to changes in climate over the past 1,400 years, according to new research.
The findings suggest that future climate change is likely to drive increased fire activity in the Sierras.
“Our data show that climate has been the main driver of fire on a regional scale,” says lead author Richard Vachula, a PhD student in earth, environmental, and planetary sciences department at Brown University. “We find that warm and dry conditions promote fire, which in light of climate model predictions suggests that future fires may be more extensive than we have observed in the last century.”
The researchers based their findings on sediment cores from the bottom of Swamp Lake, located toward the northern edge of Yosemite National Park. As fires have burned in the region over the years, charcoal from smoke plumes falls into the lake, eventually sinking to the bottom and embedding itself in sediment. By tracking changes in charcoal content with depth, Vachula and his colleagues created a sequential record of how much area had burned around the lake over the past 1,400 years up to 2007, when researchers took the cores.
The sizes of the charcoal particles enabled the team to track both local and regional fire activity. Smaller particles, which can travel farther in the air, record regional fire in a roughly 90-mile radius of the lake. Larger particles, which don’t carry as far, represent local activity within about 15 miles.
By synchronizing the charcoal data with existing climate records measuring temperature and rainfall, the team could measure correlations between climate and fire over time. The researchers also included data aimed at measuring the effects of direct human forest management, either by indigenous populations or the US government.
The study found that the regional trends track closely with climate trends, with warmer and dryer periods correlating to periods of increased fire activity. Fire activity peaked during what’s known as the Medieval Climate Anomaly, a period of unusual heat and drought lasting from about 950 to 1,250 CE.
The effect of human activity was largely confined to the local scale for most of the study period, the research found. The team used archeological records to track the size of Miwok Native American populations over time. The Miwok, whose dietary staple was acorns, used fire to control underbrush in order to promote the growth of acorn-producing oaks.
The study showed that when the Miwok population was large, burning increased at the local level even when climate was adverse to burning. At the regional level, however, the influence of climate remained dominant.
The only time human activity seemed to supplant climate as a regional influence on fire was from 1900 to 1970, when the National Parks Service systematically suppressed fire throughout Yosemite. That intervention seemed to reduce fire even when climate conditions favored increased activity.
Taken together, the findings underscore the importance of climate in driving fire activity in the Sierras, the researchers say.
“Our results are significant because they clarify the relative roles of human management and climate as controls of fire regimes in California, and they highlight the need to prepare for future fire activity,” Vachula says.
The research appears in Environmental Research Letters.
Source: Brown University
Climate Change: What Everyone Needs to Know
by Joseph Romm
The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon
Climate Change: The Science of Global Warming and Our Energy Future second edition Edition
by Jason Smerdon
This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena. Available On Amazon
The Science of Climate Change: A Hands-On Course
by Blair Lee, Alina Bachmann
The Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon
From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.