October 4, 2009

Boise River’s cottonwoods in decline

The black cottonwood trees that hold the banks of the Boise River together and shade its water are in decline, officials say.

Dams constructed on the river have reduced the flooding that scours the river banks and creates seed beds for new trees. Today's trees grow from root suckers rather than seeds and are not as vigorous or healthy, the Idaho Statesman reported.

They don't have the stature or vigor of trees that grow from seeds, Rob Tiedemann, an ecologist and wetland scientist, said. We now have a genetically similar forest, with every tree a clone of the one next to it. They're less resistant to drought, insects, climate change. They're wimps.

Should the black cottonwoods die off and be replaced by smaller species of trees that cast less shade, the fish population will change.

Cottonwoods provide large, woody debris fish need and places for cavity-nesting birds like falcons, woodpeckers and bluebirds, John Heimer, retired Idaho Department of Fish & Game fisheries biologist and a river outfitter, said.

The trees are les Bois, named by French trappers who saw them after crossing the desert, give the Idaho city and the river their names.

The trees could be saved if the river is allowed to run higher, but that would mean less water is available for irrigation and authorities have not come up with a specific solution. They are asking anyone with suggestions or who wants to be part of the river dialogue to contact Liz Paul of Idaho Rivers United at [email protected]