Southeast Alaska is renowned for its rich biodiversity, boasting over 850 species of native trees, shrubs, and wildflowers.
This incredible variety constitutes more than half of all plant species found in Alaska, flourishing in just a fraction of the state’s territory—approximately 6%.
This vibrant tapestry of plant life raises the question: when did these species first emerge in an area previously covered by glacial ice?
A significant piece of the puzzle lies in Hummingbird Lake, a small yet intriguing body of water nestled between steep ridges of hemlock and cedar trees on the southwest coast of Baranof Island.
Geosciences and Environmental Change Science Center scientist Tom Ager, now retired, visited Hummingbird Lake 25 years ago to study the sediment settled on the lake’s bottom.
Ager’s interest in the “muck” at the lake bottom stemmed from his belief that it contained crucial evidence of a “lost world” dating back thousands of years.
By examining pollen and spores preserved in the lake’s sediment, Ager sought to unravel a history of the region that had survived the ice ages.
He selected Hummingbird Lake as his research site because it appeared to have escaped burial by glaciers during a critical timeframe between 14,000 and 29,000 years ago, a period marked by the dominance of massive glaciers across much of Alaska and Canada.
Intriguing signs of this “glacial refugia” have prevailed in the area, with researchers discovering genetically distinct ancient populations of brown bears whose bones were found in caves scattered throughout Southeast Alaska.
These bears were isolated from other populations for millennia, likely due to the ice sheets that enveloped the region.
On a summer day, Ager reached Hummingbird Lake via a U.S. Forest Service ship, which took him to a lake unmarked on maps but alive with the sound of hummingbirds.
After inflating his raft, he rowed to the center of the lake and inserted a tube into the lakebed, extracting 14 feet of sediment deposits that recorded 16,000 years of ecological history.
With careful analysis of the pollen grains, fern spores, and bits of moss he collected, Ager was able to reconstruct the environmental timeline of Southeast Alaska.
Layers of pinkish-gray ash within the sediment hinted at the aftermath of two monumental volcanic eruptions, the most recent occurring approximately 13,760 years ago from the Mount Edgecumbe volcanic field near Sitka, while the older eruption likely came from a volcano on the Alaska Peninsula.
Notably, the study revealed that pine trees were releasing pollen in the region as early as 15,000 years ago, hinting that these resilient trees likely survived the peak of North America’s glaciation.
Spruce, mountain hemlock, alder, and ferns gradually appeared next, with western hemlock establishing itself approximately 10,000 years ago.
These early trees likely played a vital role in supporting the first people to migrate into the Americas from Asia along the North Pacific coast, providing necessary resources such as fuel, shelter, resin, and construction materials for boats.
However, life was not without adversity for these early Americans, as Ager notes.
They faced a tumultuous environment marked by major earthquakes, tsunamis, and repetitive volcanic eruptions.
Evidence of these early inhabitants is scarce, but some significant discoveries have been made along the coastal routes used by the First Americans.
In 1996, parts of a 10,300-year-old human skeleton were unearthed in a cave on Prince of Wales Island, while dated human footprints have been found preserved in buried beach sands in central coastal British Columbia.
These footprints, belonging to seafaring individuals, are estimated to have been made approximately 13,000 years ago, suggesting that these early people may have thrived on the abundant resources of the ocean while navigating the landscape dotted with “pine parklands.”
Much of this historical evidence has been lost to time or submerged beneath rising sea levels, yet a few remnants remain, locked within the sediment layers of Hummingbird Lake, waiting to reveal more about the early inhabitants of Southeast Alaska.
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