This presentation was part of A Century of Design in the Parks Symposium, Santa Fe, New Mexico, June 21-23, 2016.
By Suzana Radivojevic
Wood is one of the most common materials featured in the built environment in U.S. and even more prominent in National and State parks’ structures. The longevity and integrity of wooden structures depends on the susceptibility of wood to degradation caused by biological organisms, among which true wood-decay fungi and wood-boring insects are known to cause the largest damage. Wood degradation risks and rates are correlated to the environmental exposure conditions of the building element in service. Corresponding relationships between environmental variables and the durability of wooden structures have been adequately understood and incorporated throughout the history into building practices, codes and standards. At present, it is evident that the climate change will significantly alter the environmental conditions that control wood degradation in exterior settings, with potentially dramatic consequences on heritage wooden structures worldwide. This paper intends to synthesize the current scientific knowledge on the effects of projected climate parameters on the deterioration of wood, to review recent advances in modeling the long-term deterioration risks, and to discuss the future preservation priorities for the wood-built structures in National and State Parks specifically.
The main objective of this research is to evaluate how long-term changes in temperature and precipitation will affect the deterioration risks by common decay fungi and wood-boring insects typical for the U.S. Wood decay rates depend directly on the moisture content of wood, which depends on the temperature, precipitation and duration of wetting. The average historic precipitation and temperature data have been used to model above ground wood decay hazards for in the U.S. climate regions with high accuracy and more recently, similar approach has been used to model future decay hazards using temperature and precipitation projections and to produce risk maps corresponding to the climate change in European Union. Although detailed predictive models have not been developed for the U.S., it can be expected that the incidence of fungal decay will decrease in regions experiencing warmer and dryer climate, and increase in regions with increased annual precipitation. Wood-boring insect species are biologically more diverse and can have a wider range of optimum growth requirements in comparison to decay fungi. There is sufficient scientific evidence that the insect caused damage to wood in built structures can be expected to follow temperature change trends, with increased insect population dynamics, infestation spreading rates, and larger damage to wood in regions experiencing increased annual and summer temperature averages. Indirectly, many of the wood deteriorating species such as wood boring beetles and termites have the potential to alter or extend their natural geographic range in response to regional temperatures changes. A comprehensive review of the pertinent scientific literature, government and intergovernmental reports and other publications will be used to summarize current knowledge and identify major long-term deterioration risks to wooden structures and deterioration potentials specific to U.S. geographical regions, and identify knowledge gaps and future research needs.
Dr. Suzana Radivojevic holds a Ph.D. in Wood Science from the University of Toronto, Canada, and a B.Sc.F.E. from the University of Belgrade, Serbia. She teaches at the University of Oregon, in the Historic Preservation Program, in the Department of Architecture, and at the UO Historic Preservation Pacific Northwest Field School. Her research interests are related to wood preservation technologies, wood building pathology, wood identification and dendrochronology. She has published her work in peer-reviewed journals and presented internationally. She serves as a referee for journals APT Bulletin and Studies in Conservation. She also works as an independent consulting researcher.