REGINA, Sask. — There are various ways to study climate change’s impact on the Earth, but one method may be less familiar to the public.
At the University of Regina (U of R), the Prairie Adaptation Research Collaborative (PARC) uses tree rings to understand climate change and how it has affected the environment over time.
“We collect tree rings at lower elevations to understand the growth over time and what it experienced over its lifetime,” explained David Sauchyn, director of PARC.
Tree rings show the life of a tree each year it lives, with each ring containing a lighter and darker section.
“The lighter part is called the early wood, and it grows early in the growing season, when there’s usually decent soil moisture and longer days. Throughout the summer, as the soil dries out and the days become shorter, the tree slows down, and the wood becomes denser and darker,” said Sauchyn.
PARC measures a tree’s annual growth while also comparing how its growth changes from year to year. Tree rings that are closer together over several years indicate limited growth, while rings that are farther apart indicate greater growth.
Through its research, PARC has found a “whiplash” effect in tree rings over the past few decades, with significant swings between wet and dry conditions.
“We’re swinging dramatically from very wet to very dry from year to year, or decade to decade. So, it’s this amplification or intensification of the natural variability. We can only detect that because we have 1,000 years of tree-ring data,” said Sauchyn.
He emphasized that having 1,000 years of data is crucial for climate change research, particularly when most weather records in the area only date back about 120 years.
By comparing tree-ring data with existing weather records, researchers can better understand how climate conditions have changed over a much longer period.
“We’re able to reconstruct temperature, heat and soil moisture over 1,000 years, when we only have about 100 years of recorded measurements for soil moisture, precipitation and temperature,” said Sauchyn.
However, one challenge presented by the research is determining whether trees are adapting to climate change.
“Trees might be adapting to a changing climate. If there’s enough human-caused climate change, it could actually cause the forest to change and individual trees to adapt to things like a longer growing season or warmer winters,” he said.
“Once that adaptation occurs, of course, it complicates our work because we’ve always assumed we can produce a mathematical model that predicts, for example, soil moisture based on tree growth, and that the model remains valid over time. If there’s enough human-caused climate change, that may not be the case, and our model may not be quite as effective.”
Sauchyn also said the climate of the Prairies can obscure long-term trends associated with climate change because of the region’s significant year-to-year variability.
“We’re so far removed from the oceans that we have this incredible variation from year to year in precipitation and soil moisture. So, when we look at tree growth, it’s largely dominated by that year-to-year variation.”
But while some tree rings show significant year-to-year variations, others reveal longer-term trends.
Sauchyn said tree rings have shown decades of drought with limited growth, providing an indication of conditions people should prepare for in the future.
“We should be preparing for a point in the future, in a warming climate, when we could have a lack of water for consecutive years. Four, five, six or even up to 10 consecutive years, because it has happened in the past.”
While society is better prepared to manage droughts, Sauchyn said there are still limitations.
“If drought persists for more than a few years, our toolbox is pretty limited in terms of what we can do about it. We know it happens because it happened in the 1930s and again in the 1980s, with devastating consequences.”
As PARC’s research continues, Sauchyn and his team plan to further examine the long-term impacts of climate change and what historical tree-ring data can reveal about future conditions.
