Safe haven or ecological island?
For wildlife in the Cascades, things are getting smaller. What can we do to better connect Cascades habitat for wildlife like lynx, wolves, and grizzly bears?
by Jasmine Minbashian, communications director. From the July 2009 Conservation NW newsletter)
Nestled in the foothills of the Cascade Mountains, on the edge of the Snoqualmie River Valley, you’ll find Camp Don Bosco. When my mom told me I could attend horse camp there in the summer of 1982, I thought I had won the lottery! Nothing could compare to a week in a small village nestled in a vast stretch of wild country. With a daily routine of horseback riding, archery, and campfires, I felt like a young brave preparing for a life of survival in the wild.
Since then, I’ve explored much more of the Cascade Range, and despite the clearcuts and logging roads on its flanks, I still think of these mountains as one of the wilder places on earth. All one has to do is look at a map of unroaded areas of the United States to see that the North Cascades is one the largest remaining chunks of wilderness left in the lower 48 states that can still host wide-ranging animals like lynx, wolves, and wolverines. The North Cascades is also home to a small, struggling population of grizzly bears—one of four remnant populations left within the contiguous states.
Rapid change for wildlife
But it wasn’t until fairly recently that I began to see that this wild place that I loved since childhood is being rapidly and aggressively fragmented and isolated by urban expansion and development.
Today, my idyllic Camp Don Bosco is located in a valley that is now considered a Seattle suburb, with a population that has more than doubled since my days as a camper. To put this growth in perspective, consider a recent study by the United States Geological Survey. They found that when compared with other regions that have been studied, the Puget Lowlands had the highest percentage of change of any region in the West.
This development trend is not limited to areas west of the Cascades. Growth rates in eastern Washington rival those along the I-5 corridor. The city of Wenatchee, touted as the next Bend, is expected to grow by up to 50% over the next 20 years.
As the Cascades become increasingly surrounded by development, getting cut off from other large ecosystems, the fewer number of species they will be able to support, as disconnected “islands” of habitat. I learned this basic ecological rule known as “island biogeography” in college, but I had never thought about it in the context of the Cascades—until now. For some species (many of them at the top of the food chain) roads and development pose as great a challenge to migration as a large body of water.
I now find myself asking: Are the Cascades becoming an ecological island?
But I am far from the first person to ask this question. In a seminal paper published in the journal Nature in 1989, William Newmark shared the results of his study of carnivores, hoofed animals, and rabbits in 14 national parks in the western United States and Canada. He discovered that 43% of his study species—29 species of mammals—had been lost or become extinct in the areas he surveyed.
“Only the largest North American park assemblage, the Kootenay-Banff-Jasper-Yoho park assemblage, still contains an intact historical mammalian assemblage,” he wrote.
Newmark found that the older and smaller a park is, the more species it loses. Small park size speeds the rate of extinction because smaller parks start with smaller, more vulnerable wildlife populations. Moreover, if wildlife populations on lands surrounding parks die off, park animals become isolated from others of their kind.
Connectivity = Suitable for animals to move through
Bill Gaines, a US Forest Service biologist, is building on these findings by studying the concept of “wildlife connectivity” (just a fancy term for an environment suitable for animals to move through). He has teamed up with other scientists to conduct large landscape analyses on the least risky routes wide-ranging animals could use to move into and around Washington.
Map: Shades of green indicate best pathways for wolves to move between secure habitats, food, and shelter. From “Landscape Permeability for Large Carnivores in Washington” by Peter Singleton, William Gains, and John Lehmkuhl (2002)
Gaines’ work reveals that if the North Cascades are to avoid becoming an ecological island, there are at least three major areas that need attention. The first is the north-south connection from the southern British Columbia’s Cascades to the North Cascades of Washington. The second is an east-west connection through the Kootenays of southeastern BC, into northeast Washington’s Kettle and Selkirk Ranges, and over the Okanogan Valley. The last is the north-south connection over the barrier to wildlife movement that is posed by Interstate 90 near Snoqualmie Pass. “Identifying and prioritizing the areas important to wildlife connectivity are positive steps in the right direction,” Gaines comments.
Conservation Northwest has relied on Gaines’ work to help identify our organization’s conservation priorities. It is why we are working so hard to protect the wild places left in the Columbia Highlands and why building a wildlife overpass at Rock Knob along I-90 has implications well beyond the freeway corridor. It is why the fate of the mountain caribou’s old-growth habitat in British Columbia should matter to a hiker in Seattle who wonders why he doesn’t see as much wildlife as he used to in the Cascades. The future of the North Cascades is inevitably tied to fate of lands in British Columbia and the Rockies.
John Muir, the grandfather of the conservation movement, wrote in 1911, “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” And today we know that is certainly true for ecosystems, too.