Earth Notes - Tamarisk Beetles

Flagstaff, AZ – Earth Notes: Tamarisk Beetles

For decades people have worried about invasive tamarisk trees in the Grand Canyon and along other southwestern waterways. But now an invasive beetle is knocking the trees back at unexpected speed.

Tamarisk trees from Europe and Asia were first planted here in the 19th century, partly to stabilize soil along rivers. They took off, and now dominate more than a million and a half acres of mostly riverside habitat throughout the Southwest, where they've crowded out natives like cottonwoods and willows.

Starting in 2001, biologists began importing tamarisk-killing beetles from Khazakhstan and releasing them into the upper Southwest. The beetles were never expected to survive below the 38th parallel, about the level of Lake Powell. But in late 2009 Grand Canyon biologists got a surprise when they found a few about 12 miles downstream from Lees Ferry.

Surveys last year revealed that the beetles are now defoliating trees between Lees Ferry and Redwall Cavern, about 33 miles downstream. Another population of beetles apparently has migrated into the canyon from southwest Utah, and set up shop about 50 miles downriver from Phantom Ranch.

Without native trees to fill in the gaps, a rapid tamarisk die-off could make for wide swaths of denuded beach, increased erosion, and trouble for some wildlife species. Biologists are keeping close watch on the beetles and their effects and they're telling Grand Canyon boaters and hikers not to be surprised to see brown where green reigned only a year or two ago.

-Anne Minard