BBNP Superintendent Bill Wellman is working to implement natural methods to clear the intrusions and help claim what is left of this once great river.
Projecting slides on the screen during his lecture to the Sierra Club last week, Wellman compared a 1955 photograph of a vegetation free and clearly channeled Rio Grande at the mouth of the Santa Helena Canyon to a recent shot of the same place, where a small green forest of non-native salt cedar and giant cane grew over and around an easy sloped, slightly trickling Rio Grande.
“The Rio Grande is flowing at one sixth of historical levels,” Wellman said. “The river is unable to move the silt, sand and sediment. We’ve had an 8 1/2 foot buildup of silt since 1991.”
Salt cedar, also known as Tamarisk and giant cane, are non-native exotic plants that act as sediment traps.
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“We can chop down the salt cedar and the giant cane but it’s expensive and takes a long time,” Wellman said.
The new attack plan for the salt cedar is to release the salt cedar beetle, an insect found in Kazakhstan and the surrounding Central Asian region.
They hope to obtain an 85- percent control factor on the tree, utilizing the beetle’s healthy appetite for the tree’s leaves.
“These beetles grow exponentially and once they eat most of the trees, most will die,” Wellman said. “They will almost starve to death before they’ll eat anything else.”
The Park Service presently has the beetles in cages along release sites on the river. They expect to release them into the wild in early fall.
Controlling the giant cane is almost a bigger problem according to Wellman.
In the past, burning the giant cane and then treating the reduced biomass with herbicide was one way of getting rid of the cane.
An old fashion method, recently done at a national heritage site near Yuma, AZ, produced “excellent results,” Wellman said, but the labor-intensive, shovel-dig operation was very expensive.
Bulldozing is another option but Wellman said that is “more manipulative than we like to do in a national park. Ideally, we want to use the river as our bulldozer.
“Giant reed doesn’t have the roots that the Tamarisk has,” Wellman said. “If we can get the flow higher, cave in the banks, we can get it down river.”
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