UBC Graduate Research

Preparing for the Future : Climate Change and Western Red Cedards at the David C. Lam Asian Garden, University of British Columbia Botanical Garden Hang, Virginia


For the University of British Columbia Botanical Garden (UBCBG), species such as western redcedar (Thuja plicata Donn ex D. Don) are predicted to be maladapted to their current environment by 2071 under a medium emissions scenario and by 2041 under a high emissions scenario. This report addresses several physiological and ecological traits of western redcedar and identifies several themes of management challenges that the University of British Columbia Botanical Garden will need to address. Changes in soil moisture, shifts in temperature and precipitation, and vulnerability to diseases and pests can influence the decline of western redcedar. Actions to enhance the future conservation of western redcedar include the development of an adaptive management program, assisted seed migration (seed provenance strategies), and a monitoring program that engages citizen scientists. Furthermore, future planting lists of species that are more suitable to the predicted future climates are explored to help facilitate the transition of the UBCBG to one that is better matched to the climates modelled for 2071 to 2100. Botanic gardens conserve plant diversity through in-situ and ex-situ conservation and are responsible for maintaining living plant collections for science and education. While plant collections change over time, climate change impacts to existing plant species require strategic approaches and adaptation planning to ensure a botanical garden’s ongoing role in plant conservation. The following key findings in this report describes both management challenges and opportunities for western redcedar: 1. The Asian Garden in the UBCBG is expected to transition from a highly suitable location for western redcedars to one that has very low to no climate suitability to facilitate the growth of the species. Based on the results of the climate modelling projections and western redcedar distribution models, this species is not expected to survive in 2071 under both RCP 4.5 and 8.5 scenarios. The potential extirpation of this iconic species highlights the need to develop an adaptive management strategy to mitigate the loss of species involving seed migration and planting of species that are likely to succeed in future climates, monitor changes through longitudinal data management, and to design programs to engage the public in conservation. 2. Based on SSP2-4.5 and SSP5-8.5 scenarios, the key stressors that are considered important for western redcedar include abiotic and biotic factors. Abiotic factors include drier sites and moisture deficits due to warming temperatures and less precipitation during the summer growing season. Biotic factors include indirect damaging agents such as insect outbreaks linked to warming temperatures favouring the reproduction and proliferation of pests. 3. Western redcedar has an inability to occupy very dry sites and has better growth on moist sites in humid environments. It is expected that specific irrigation and water retention methods may be necessary as a climate adaptive measure to ensure that western redcedar will not be susceptible to water-deficit conditions. 4. An opportunity arises to plant western redcedar seeds from southern climates via assisted seed migration. Freeze and thaw damage to new seedlings from southern provenances may be minimized in the future as the frost-free period extends, the number of frost-free days increases, and minimum mean temperatures in the winter increase. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”

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