By Jeff Holmquist, White Mountain Research Center, Institute of the Environment and Sustainability, UC Los Angeles
The Nüümü, one of several “Paiute” Peoples, have lived in what is now eastern California since time immemorial. To survive, Nüümü People developed unique methods to harvest the bounty of plants and animals found in the region. Among those foodways is a practice of harvesting the nutritious caterpillars of a moth native to Western pine forests. Ongoing work by Tribal Members and scientists now suggests that caterpillar harvesting may help protect the region’s forests from wildfires that are increasing in size and intensity due in part to our changing climate.
Caterpillars of the Pandora moth (Coloradia pandora) voraciously consume pine needles and have been widely viewed as forest pests. Yet the presence of these caterpillars (known to Nüümü People as piyuga) may have historically reduced wildfire damage. How might this be? A team composed of Nüümü Tribal Members, US Forest Service land managers and researchers, and UC Los Angeles scientists based at the UC UC Nature’s White Mountain Research Center in the eastern Sierra Nevada has been collaborating in an effort to find out.
One of the larger forest insects in North America, the Pandora moth has a two-year life cycle. Every other summer, the caterpillars, packed with fat from feasting on pine needles, descend the tree trunks to pupate in the ground through the following year. The Nüümü and other indigenous peoples living in and around these dry, montane forests long ago developed an ingenious method to harvest piyuga. They found that digging shallow trenches around the base of trees enabled them to corral large numbers of the rather bumbly piyuga as the caterpillars reached the ground. Decisions about which trees to trench were traditionally made based upon the amount of caterpillar poop found beneath a tree; the more poop present, the more caterpillars could be harvested.An extended Nüümü family could collect hundreds of pounds of piyuga in a week. The fatty caterpillars were a calorie-rich seasonal food resource. It’s no wonder piyuga were so sought after: the caterpillars are tasty when cooked, with a flavor similar to scrambled eggs.
Before a piyuga trench can be dug, needles, duff, and dead branches must be cleared around a tree, leaving only bare soil. The removal of flammable vegetation inspired the study team to wonder whether the clearing and digging of piyuga trenches created “defensible space” around individual trees, in the same manner that clearing vegetation and plant debris around a house helps protect the building from fire. Might clearing for piyuga trenches have historically reduced wildfire damage to trees? Might it still?
The team planned to examine these questions using an experiment. First, historically trenched trees would be cleared and retrenched. The trenched trees then would be compared with two types of control trees nearby: untrenched trees and historically trenched trees that were not cleared and retrenched. After a large number of these three-tree replicates were created across the forest landscape, prescribed fire would be used to test wildfire damage while also reducing fuels in the overgrown forest. The retrenching effort began in 2015.
Young people from the Bishop Paiute Tribal Youth program were a key part of the effort. While learning about Tribal language, culture, environmental science, and stewardship, the Youth also help care for land on the reservation and in surrounding areas. In our piyuga collaboration, the Youth learned about traditional foodways and harvesting and practiced trench construction. At the same time, the young people learned how to assess forest health and survey insect populations. The Youth participants proved eager learners, teachers, and enthusiastic contributors.
However, nature and chance foiled our best laid plans for a uniform, lower-temperature prescribed burn. Before we were able to construct all of the planned trenches, a lightning strike sparked a very non-prescribed wildfire that tore through the study area. The 2016 Clark Fire burned at low-intensity in some areas, as planned, but escalated into a high-intensity blaze that completely torched trees in other areas. Despite the nature of the unplanned fire, and the fact that we completed fewer trenches than we had planned, the team was still able to detect differences in wildfire damage between trenched and untrenched trees. Our post-fire analysis revealed there was indeed less damage to the cleared and trenched trees. A resurvey seven years later showed that trenched trees were also more likely to survive over the long term.
Our group concludes that the Nüümü practice of piyuga trenching seems to reduce wildfire damage, at least at the scale of individual trees and clusters of historically trenched trees. Further, even though piyuga trenching causes caterpillar losses due to harvesting, the practice may ultimately benefit the Pandora moth as well. That’s because trenching reduces damage to pines, and pines are the only food this insect eats. Many of our results appear in two papers that include Tribal authors.
The team continues to use a productive mix of Traditional Ecological Knowledge and Western science to uncover more about these complex forest interactions. Current work includes investigating the natural history of the moths and caterpillars, focusing on their activity and movements, and the role of insect parasites; and examining how climate change and increasing wildfire severity might create “ecological traps” for the species. The group is also making detailed, large-scale maps of historic trenches to learn more about the cultural legacy of this practice. The map data should help reveal the extent of benefits trenching might provide at the forest scale. The close teamwork seen in this endeavor is an excellent example of science co-production, a highly positive way in which Reserves and their scientists can engage with Tribes.
Collaborators
Bishop Paiute Tribe:Tom Gustie, Raymond Andrews, James Denver; US Forest Service: Michèle Slaton, Jacquie Beidl, Marc Meyer; WMRC: Jutta Schmidt-Gengenbach
Related papers
Holmquist, J.G., J.M. Schmidt-Gengenbach, M.R. Slaton, and T.E. Gustie. In press. A race to the bottom: Observations on Pandora moth larvae during the hour of tree descent, dispersal, and prepupal burrowing. Western North American Naturalist.
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