Raiders of the lost park

One foreign species in the Great Basin is being used to control the invasion of another, and the results have been water conservation, according to a new study.

UC Santa Barbara researchers went to Northern Nevada’s Humboldt and Walker rivers to study the Asian beetle, or tamarisk leaf beetle, as it devoured the leaves of tamarisk. Also known as saltcedar, tamarisk is a particularly thirsty and invasive tree from Eurasia that covers more than a million acres in western North America. In Nevada, it edges out native vegetation like wildrye grasses, cottonwoods and willows.

The study, published in the journal Oecologia, showed a water savings of 2,500 acre-feet in the Humboldt River Basin during the first year of large-scale tamarisk defoliation by the beetle. That’s enough to irrigate about 1,000 agricultural acres a year, or provide for the annual water needs of 5,000 to 10,000 homes, according to UCSB researcher Tom Dudley. The researchers said these savings could be even more important in drier desert regions of the U.S. Southwest.

Tamarisk is notoriously hard to eradicate. Chemical controls, if used, have to be repeated year after year. And even with the beetles munching away, it can resprout within weeks of a single defoliation. However, researcher and first author of the study Robert Pattison said the tamarisk leaf beetle had a dramatic effect on the trees. “Entire stands were defoliated within a few years of release,” he said.

Previous studies have found that the Asian beetle has the potential to suppress, though not eradicate, tamarisk by 75 to 85 percent. A USDA program to release the tamarisk leaf beetle in 13 northwestern states was discontinued in 2010 over concern for the federally endangered southwestern willow flycatcher, which nests in tamarisk. Other states, such as Colorado, that have continued to use the beetles as a biological control have seen the return of native plants to some areas, which also provides nesting habitat for birds and other species.