Scientists have made the first-ever map of how tamarisk beetles have spread into the Grand Canyon from other states. The leaf-eating beetles were introduced to control the invasive trees. But as KNAU’s Melissa Sevigny reports, they weren’t supposed to survive as far south as Arizona.
The map shows tamarisk makes up about a third of the riverside vegetation along the Colorado River in the Grand Canyon. Fifteen percent of those trees have been affected by the beetles.
Teki Sankey of Northern Arizona University is one of the study’s authors. "Some areas are very heavily impacted, whereas others are not so much," she says. "The range of impacts we found was anywhere from 1 percent to 86 percent reduction in the healthy, green leaves of tamarisk after the beetle arrival."
It’s not clear if the affected trees will die or recover. Tamarisk trees can crowd out desirable native species, but also provide habitat for birds and shade for river runners. Coauthor Joel Sankey of the U.S. Geological Survey says the study can help land managers plan restoration projects.
He says, "For example, if you’re working at a particular site you’d want to know, if we’re going to remove all the tamarisk, how much tamarisk is actually there? That’s one of the great things about this type of science and work; a map will tell you that."
High resolution images were collected from piloted aircraft in 2009, before the beetles arrived, and again in 2013. Tamarisk trees were identified by their unique “spectral signature.”
The study appears in the journal Ecological Indicators.