Monday, November 14, 2005

Salmon, the Aboriginal Habitat

Here is a very informative article about salmon, in their aboriginal habitat, from Open Space magazine.

Salmon and the Northwest
by Roy Hemmingway

Here in the Lower Forty-Eight, and in much of western Canada, natural habitat has almost vanished... Much that civilization demands for its sustenance has had a consequence in the fate of the salmon.

There is not much of it left. Of untouched salmon habitat there is almost none. Although salmon once occupied almost every ocean-seeking stream in the Pacific Northwest, the map where salmon go has been shrinking for the last hundred years, sometimes gradually as human forces slowly worsened the habitat, sometimes suddenly when millions of acres of habitat were blocked by dams.

Now to see the headwater-to-the-sea habitat where the salmon thrive in abundance, one must go to Alaska. Here in the Lower Forty-eight, and in much of western Canada, it has almost vanished. A century and a half of logging, farming, ranching, mining, damming, road building, and urbanizing activity has taken its toll. Much that civilization demands for its sustenance has had a consequence in the fate of the salmon.

The Aboriginal Habitat

Only in a handful of small pockets, miniature and isolated ecosystems, can there still be found habitat as it once was. On the Oregon coast, just south of the town of Yachats, is a little untouched watershed, barely eight miles from the headwaters to the ocean. Cummins Creek winds through a narrow, steep-sided valley. There, free from the ax and chainsaw, and now protected under the federal Wilderness Act, trees many feet thick rise to the sky, almost blocking out the sun.

Over years, as trees have died, they have fallen or been blown into the creek. Although the creek is small and shallow in many places, even in the low water of summer it is a struggle for humans to walk the streambed. Tree trunks are everywhere in the creek, creating dams over which the water must plunge, digging out pools that could soak a person up to the neck. Gravel bars have built up where the creek slows. The fallen trees push the creek from bank to bank, undercutting, and causing more trees, rootwads and all, to end up in the creek bed. All this adds up to stream "complexity,"a diverse set of stream conditions that create the habitat needed for healthy salmon.

In other streams, where the trees have not been allowed to mature and die and end up in the creek, what we see is a far more simplified stream. What most of us now envision as the pristine natural stream, bubbling along at a uniform pace smoothly to the sea, is not what the pioneers saw in many of the Northwest watersheds. Instead, west of the Cascades, they found creeks so choked with trees that in places they could not reach the water for the many layers of criss-crossing trunks over the streambed. On the larger rivers, log jams were common barriers to navigation, which had to be blown up or painstakingly picked apart by men who risked their lives not knowing when the jam would give way.

Whether for aesthetics or practicalities, man in the American West has systematically rid both large and small streams of the logs, boulders, and other "debris"that shape the stream and give life to salmon. Abundant beaver built dams on the smaller streams. The ponds behind the dams gave refuge to juvenile salmon from the high currents of winter floods and the warm waters of summer droughts. Now trapped and driven from much of their previous range, beaver once were as ubiquitous in the Northwest as salmon.

The simplified stream channels now seen everywhere and which have such dire consequences for salmon are in no small part due to the absence of beaver. Before the effects of man, creeks and streams and rivers moved across their floodplains, changing positions as high water cut new channels and dammed up old ones. Floods spread out into multiple channels, where the over-wintering juvenile salmon could find refuge from the fast water. In summer, these streams, slowed and directed by logs and boulders near the banks, dug deep channels, keeping the water cool throughout the hot days. It was into these conditions that the salmon evolved. They are a product of this particular landscape.

Although the salmon were home throughout the Columbia River and Pacific Coast states, from the coastal rain forests to the high deserts, the streams in which they began and ended their lives all shared these attributes. Vegetation along stream banks provided shade and engineered the variety that salmon need during the freshwater phases of their life cycle. The rivers "interacted"with their flood plains by changing channels as flows increased and decreased. Small spawning streams were narrow, deep, and cool, with lots of riffles, pools and gravel bars. In the arid areas east of the Cascades, where fewer firs and pines grow, willows, aspens, locusts, and cottonwoods provided stream complexity.

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