pollen records raise questions about pristine

Erling Friis-Baastad We tend to throw around the words "pristine" and "wilderness" readily in the Yukon.

Erling Friis-Baastad

We tend to throw around the words “pristine” and “wilderness” readily in the Yukon. For most of us, the terms conjure visions of boreal forest untouched by human activity, a landscape that appears much as it did a couple million years ago – minus the camels and mammoths.

However the hypothesis approached by a paper recently published by Quaternary Science Reviews suggests that our territory might not be as pristine as we like to believe and that what constitutes human impact could stand some serious reimagining.

Anthropologist Charles Schweger, professor emeritus with the University of Alberta, Edmonton, is a co-author, along with three other earth scientists, of “Pre-glacial and interglacial pollen records of the last 3 Ma from northwest Canada: Why do Holocene forests differ from those of previous interglacials?” While the paper was released only last year, the research behind it has been underway much longer, says Schweger, who began looking at Quaternary biology in the North in Alaska in the 1960s and in the Yukon in the 1970s.

The Quaternary Period, which began roughly two and a half million years ago, and contains the Pleistocene and the Holocene epochs, has been a time of repeated glaciations, ice ages, and interglacials, or warmer periods. In fact, our own “scene,” the Holocene – the last 10,000 years – is an interglacial.

Schweger and his colleagues collected data over four to five decades. Science usually arrives at its “eureka” moments only after the bits and pieces are gathered over time and by a number of scientists, he says. “You collect a little bit of data and you don’t quite know what it means so it you set aside, and a couple years later you’ve got more data, and … you set it aide.” Then one day, you look at all those little pieces and patterns begin to emerge, “relationships you couldn’t have foreseen.”

While we tend to think of the Quaternary in terms of its ice ages – mammoths trumpeting across frozen steppes – the period was punctured repeatedly by interglacials and not much work has yet been done on these. “The warm periods are almost easier to work with because they are easier to find in the field,” says Schweger. “You can easily recognize them when you’re doing geology because you’ll find buried peat deposits, evidence of trees … and that sort of thing. This indicates the climate was much warmer.”

The scientists who had turned their attention to the interglacials stumbled into a timely piece of research, an analogue for what the North might come to look like under climate change: “The kind of thing we might anticipate with global warming as northern latitudes warm up with the high CO2 concentrations in the atmosphere,” says Schweger.

“They want to know what the impact would be on vegetation, its composition and distribution, etc.” It’s a “predictive application,” with which scientists can try to link the past and present with the future, he says.

As with so many other Quaternary science projects, Schweger’s research took him into the Klondike gold fields, where miners had unearthed ancient sediments while digging for gold, and down to river valleys where moving water had cut away layers of earth. The exposed sediments contain fossilized pollens, among other treasures. With a microscope researchers can identify the species of vegetation that launched the pollens.

“For almost 3 million years we had forests that were dominated by spruce and fir and we know that the fir was so much, much more widespread in the Yukon and extended well up into the Old Crow Basin,” says Schweger. In our own time, however, fir has appeared over a much more limited range: the subalpine zones of mountains (such as Mt. Sima) to the south and central Yukon. The last 10,000 years have tended to exclude fir while favouring pine.

What happened? Well, one factor would have been the elimination of some ice age fauna, the extinction of the mammoths and other hungry beasts. These creatures grazed and browsed, ate some plants, trampled or tore down some plants, and fertilized others with nutrient-rich manure. “When the animals became extinct, the vegetation should have responded in some way.” But there was a glitch in this otherwise comfortable theory. “The problem,” says Schweger, “is we began to see pine appearing in the Yukon several thousand years after those animals became extinct.”

However, another creature was proliferating across the landscape, one who had mastered fire, and used it for cooking and preserving food, preparing hides, keeping warm, protection, signalling, bending wood for snowshoes and many other tasks, including, possibly, changing vegetation cover to favour moose, a major food source.

Fir is not a fire-adapted species. Pine is. In fact, it thrives in fire-cleared landscapes. By 2,000 to 1,500 years ago, pine had begun extending further north after the fir retreated. Schweger warns that the conclusion is actually a hypothesis, that more work remains to be done, especially on remnant charcoal, but it appears likely that human use of fire may have greatly changed the landscape.

Europeans showed up and suppressed wildfires, not understanding their importance in rejuvenating forests … a reason why we have so much “senile” old tree cover, prey to spruce beetles and then the massive forest fires of today, says Schweger.

“When we talk about vegetation across the North, it is so easy to say we have true wilderness,” he says. It’s easy to declare, “‘If you go to the Yukon, you will experience true wilderness. A landscape that’s been untouched by humans over a large area….’”

But the current research suggests that such preconceptions are wrong. People have been part of the Yukon landscape for thousands of years and have been capable of altering vegetation. “And it really makes us have to rethink this whole idea of what constitutes wildness and wilderness,” says the scientist.

This column is co-ordinated by the Northern Research Institute at Yukon College with major financial support from Environment Yukon and Yukon College/ The articles are archived at www.taiga.net/yourYukon.

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