10,000-Year-Old Clues Suggest Future Forest Changes

November 28, 1997

Some idyllic, alpine meadows and giant, red cedars in coastal rain forests may only be fond memories in B.C.'s not-too-distant future, according to Simon Fraser University biology professor Dr. Rolf Mathewes.

By studying the past in the form of pollen and other plant remains, Mathewes has gained valuable insights into what the future might hold. "We know that the climate was warmer in the past and how it affected forest cover, and we can use this information as an analog to predict the future," he explains.

Mathewes studied pollen to reconstruct vegetation - as old as 10,000 years - found in lake bottoms and wetlands. He has found that from 9,000 to 7,000 years ago in B.C. there was a warming trend similar to what is currently being predicted for the next century. His findings, confirmed by a serendipitous discovery on Castle Peak in the South Chilcotins near Lillooet, have serious implications for the province and its economy.

During the ancient warming period, forests on the south coast had more abundant Douglas fir, alder and bracken ferns than today. "All three species grow after a severe disturbance such as fire. We have found a large amount of charcoal in the lake bottoms dating to that period (7,000-9,000 years ago) indicating forest fires," Mathewes explains. He attributes the fires to a drier, warmer climate with prolonged droughts and possibly to an increase in the number of storms.

A chance discovery on Castle Peak helped confirm what Mathewes discovered in his lab. A surveyor from the Geological Survey of Canada, encamped on Castle Peak, went to collect water for his tea in a nearby stream. When he looked in the stream he found a log, even though he was 100 metres above the treeline.

Eventually Mathewes was called in and visited the site. "This serendipitous discovery helps confirm that the climate was warmer many years ago and helps confirm our theories of what happened in the past," he says. "The discovery was truly independent evidence that the climate was warmer than today. The treeline is determined largely by temperature and it was at least 100 metres higher at that time."

Mathewes also found fossil seeds and cones that indicate a thriving forest of whitebark pine and sub-alpine fir, radiocarbon dated at 9,000-8,000 years ago.

From this and other evidence, he can predict that, if our West Coast climate does warm, it will eliminate some current alpine and sub-alpine meadows as trees move up the mountains. "This has already been observed in some regions in the Pacific Northwest such as the Olympic Peninsula," he notes.

He says that a prolonged warming trend will have other implications for the forest industry and landscape as more drought-resistant Douglas fir trees begin to replace western red cedar and hemlock.

"We are likely to have more forest fires of increased severity. Cedar is especially susceptible to fire and drought. In fact there is evidence to show cedar is not regenerating well in some areas now," Mathewes says. He says the forest industry has already taken note of his findings in deciding what kind of seedlings to use in replanting clearcuts.

He also predicted that as a result of a warmer, drier climate, many small lakes and wetlands will dry up, threatening the survival of some species of birds, fish and other wildlife in B.C.

In the future, for those searching for flowering alpine meadows, it looks like their hikes will be higher and farther.
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Simon Fraser University

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