“Scientists have relied on stories from oral tradition to piece together the three-thousand-year history of a vast Californian forest that frequently burns,” reports Nature. Their results, published in Proceedings of the National Academy of Sciences, suggest that parts of the forest, established in the Californian part of the Klamath Mountains, are denser than ever. Therefore, a high risk of destructive fires threatens these areas.
“This work is part of a growing practice of combining indigenous knowledge with scientific data to improve our understanding of the history of ecosystems.”, specifies the scientific journal, which also specifies that “the principle of the study was first approved by the Karuk Tribal Council [l’une des plus grandes tribus de Californie]”. Frank Lake, a co-author who has worked extensively with the Karuk, Yurok, and Hoopa Valley tribes, points out:
“It helps in a way to decolonize the research model, which has so far left little room for the history of indigenous peoples.”
The researchers analyzed the sediments of the lakes of the region, in particular the pollens, markers of the nature of the trees and the evolution of their density. The measurement of the charcoal contained in the sedimentary layers combined with the examination of tree rings and burn scars on the stumps of the trees allowed them to map the fluctuations in the number of fires in the region.
Controlled cultural burning has stabilized forests
These data were combined with stories from environmental knowledge and traditions shared by Indigenous peoples. Together, they show that cultural burning practiced by these tribes – small, controlled fires that keep biomass low and reduce the risk of more widespread burning – has promoted stability in the forests of the Klamath Mountains for at least a thousand years.
With her team, Clarke Knight, researcher at the American Geological Service, first author of the study, showed that the density of trees in this region of the Klamath Mountains had started to increase when the area was colonized, “in part because European settlers prevented indigenous peoples from practicing cultural burning”, precise Nature.
The findings of this study could be extrapolated to other low-altitude lake sites that have similar vegetation types, the researcher believes. Dominick DellaSala, chief scientist at the Wild Heritage forest conservation organization in Oregon, points out that the results suggesting record tree densities cannot be applied to the entire Klamath region. . Other work involving indigenous peoples could make it possible to decide.