Spring flowering response to climate change over 70 years in central Alberta, Canada
Extra seminar by Elisabeth Beaubien, founder of Plantwatch Canada
We evaluate long-term trends in phenology and spring climate risk environments over 70 years for seven plant species that bloom in succession from early April to mid June in the central parklands of Alberta, Canada. In documenting biological response to global climate change the IPCC has relied considerably on phenology studies but a comprehensive dataset from the high latitudes of North America is missing. We find a substantial warming signal that ranges from 5.5°C in February to 1.5°C in May over 70 years. The earliest blooming species (Populus tremuloides and Anemone patens) advance bloom dates by 15 days over this period, while the latest species advance their bloom date by 6 days. Interestingly, early blooming species are advancing faster than predicted by standard thermal time models, and they also exceed the rate of late spring frosts occurring earlier due to warmer temperatures. In other words, risks of frost damage from late spring frosts are increasing for these species under observed and predicted climate change. The database we analyze was assembled as a collaborative effort among university biologists, government researchers, and over 1,000 citizen scientists. This data comes from both rural and urban areas, but urban sites are warmer especially at night and in winter. This urban heat island effect can exaggerate the observed climate warming trend and associated phenology response. We find the effect is significant for early blooming species, accounting for up to 5 days of earlier flowering response (i.e. approximately 25% of the observed long-term response).
ELISABETH G. BEAUBIEN
Phenologist and PhD candidate
Dept. of Renewable Resources,
University of Alberta
Founder of Plantwatch Canada