Study Says Loss of Wolves Damaging Olympic National Park's Forest Ecosystem
To many, the heart and soul of Olympic National Park is the temperate rainforest. There so much moisture falls that places such as the Hoh Rainforest and the Queets valley feel spongy, the air heavy with humidity.
Indeed, when the park was set aside in 1938, it was done so "to preserve the finest sample of primeval forests in the entire United States."
But there's trouble in this paradise, according to a study from Oregon State University. The loss of wolves from the park's ecosystem is causing a decline in those forests, for the predators are not around to keep Olympic's elk herds in check. As a result, the ungulates are over-grazing the forests.
This recently released study maintains that "the extermination of wolves in the early 1900s set off a 'trophic cascade' of changes that appear to have affected forest vegetation and stream dynamics, with possible impacts on everything from fisheries to birds and insects."
Published in the journal Ecohydrology, the report cites information gathered by the Press Expedition during its exploration of the Olympic peninsula in 1890. That expedition found the banks of the upper Quinault River “so dense with underbrush as to be almost impenetrable,” according to the OSU report. "Logs jammed the rivers, dense tree canopies shaded and cooled the streams, and trout and salmon thrived along with hundreds of species of plants and animals."
Such a scene is hard, if not impossible, to find today.
“Today, you go through the same area and instead of dense vegetation that you have to fight through, it’s a park-like stand of predominantly big trees,” says Bill Ripple, a co-author of the study and forestry professor at Oregon State University. “It’s just a different world.”
Elk, he says, are transforming Olympic's landscape as streamside ecosystems are losing young trees to the voracious animals.
Compounding the problem of wolf eradication was the creation of the national park in that it offered protection to the elk from hunters. As a result, their numbers soared and vegetation tumbled.
“Our study shows that there has been almost no recruitment of new cottonwood and bigleaf maple trees since the wolves disappeared, and also likely impacts on streamside shrubs, which are very important for river stability,” said Robert Beschta, lead author of the study and professor emeritus of forest hydrology at OSU. “Decreases in woody plant communities allow river banks to rapidly erode and river channels to widen.
“Tree and shrub species along stream banks and floodplains started crashing first,” Professor Beschta explains. “Then, apparently, the rivers began to unravel. Now we have large areas where the forest understory vegetation is mostly just grasses and ferns.”
The report notes that streams that once flowed in tight channels held in check by thick vegetation have broadened and become braided. Too, the scientists note that the water is open to the warming sun and less enriched by plants and insects. Nearly half of the terraces along the Queets River have disappeared because of accelerated erosion over a period of multiple decades.
“We’ve seen the impact of wolves on the ecosystem in Yellowstone, the effect of cougars in Yosemite National Park, the same basic story about the importance of key predators being played out in many different places,” Professor Ripple says. “What’s so surprising here is that it’s happening in a temperate rainforest, which is hugely productive and has such high levels of vegetation growth. But even there, when the ecosystem gets overwhelmed with many large herbivores, the vegetation just can’t keep up.”
An effort was considered to restore wolves to the park ecosystem in recent years, but no decision or actions have been undertaken to accomplish that.