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The effects of climate change are complex, . As we seek to better understand human-driven climate changes, long-term baselines for environmental data are essential.

However, records of past environmental conditions are too short to give us a robust understanding of how these systems have changed over time. One solution is to look at natural archives.

There are many natural processes that leave behind records of past environmental conditions, .

Trees form a ring of wood every year, and the width of that ring can have a significant relationship with climate. We can then create a model based on the time period for which there is both recorded climate data and tree-ring widths. That model can be applied to the rings that formed before climate records began to reconstruct past conditions.

The challenge is to find forests with both strong climate-growth relationships and trees over a century old—substantially older than the length of climate data. This is especially difficult in southeastern Canada, .

Sensitive old growth forests

In the Appalachian Mountains of the Gaspé Peninsula, Québec, we studied a rare old-growth cedar grove tucked into the valley between the base of Mont-Albert and the Sainte-Anne River, known for its Atlantic salmon fisheries.

The average hiker passing this eastern white cedar grove would probably not guess that some of these relatively small-diameter cedars are more than 500 years old, an age that is still relatively young .

The strong competition for light in this closed-canopy forest causes trees here to grow very slowly. We found they grow especially slowly during years where the winter snow remained on the ground late into the spring. effectively shortens the trees' growing season and leads to a thinner tree ring that same year.

We went on to sample hundreds of trees in the valley and on the slopes at sites that had never been logged. We repeatedly found a strong relationship with snowpack and a related relationship with spring river flow. With these two closely related connections, we were able to .

Modern climate change records

Our recent study reconstructed spring and early summer river flow from 1822 for the Sainte-Anne River, a major river , the second-largest provincial park in southern Québec.

Analysis of this tree ring/snowpack/river relationship—which was previously undocumented in eastern North America—suggests that the region was affected quite early by modern climate change. A significant shift occurred in 1937, after which individual years of extremely high river flows and high snowpacks declined. Newspaper reports of floods in the greater region matched the years of high flow in our reconstruction as far back as the year 1872, further validating the results.

The reconstruction also reveals that the short river flow records for the Gaspésie mountains under-represent the region's susceptibility to prolonged periods of drought-like conditions. Local river flow records kept since 1968 show that the region experienced an equal number of decade-long dry springs and wet springs. However, our reconstruction suggests that during the 1822-1968 period, long bouts of dry spring climate were substantially more frequent and prolonged than wet ones.

Conservation impacts

The insights from this reconstruction could have implications for wildlife and hydropower. First, .

Second, alpine snowpack serves as a refuge for the threatened woodland caribou populations, which used to be spread . Today, the caribou are in sharp decline, with less than 40 remaining south of the St. Lawrence River, all within the Gaspé Peninsula.

The primary threat to these caribou is the extensive . Younger forests provide less food for caribou and lead to an increased abundance of moose and deer, along with their predators—mainly coyotes and black bears—.

Changing mountain snowpack conditions add to their peril as the snowpack has important effects on .

Given this, a better understanding of the implications of reduced snowpack on caribou urgently requires further study.

Lastly, Québec's billion-dollar hydroelectric industry might also benefit from a better understanding of past moisture in the region, .

Documented histories

Our study improves our understanding of past moisture patterns across the east coast of North America. It fills a large gap in climate research based on tree rings between New York and northern Québec.

When comparing the past 200 years of these East Coast reconstructions, important climate connections arise. The comparison suggests that the complex Atlantic climate system can synchronize, leading large portions of the coast to collectively lock into periods of very wet or very dry conditions.

This is important for water resource managers, who often rely on help from other managers in neighboring basins, which may not be available given this common synchrony.

The insights from the tree rings of these forests are another reminder of . As we try to better understand the context of human-induced environmental change, our search continues for old forests with a story to tell.

Our ongoing research includes analyzing dead cedars preserved for almost 800 years at the bottom of lakes. The resulting tree ring chronology will extend our work with trees in the region so far, helping us further examine the environmental history of our rapidly changing planet.