Tamarisk, a feathery green Eurasian shrub with pink flowers, was brought to the West a century ago to control erosion. It quickly became a pest along desert rivers from California to Colorado, sucking up water and choking out native willows and cottonwood. To get rid of it, federal agencies use herbicides, backhoes and chainsaws. But those methods require maintenance and are too expensive to apply on a large scale, so several years ago, the government started using bugs. A leaf-eating beetle from Kazakhstan is the tree’s natural enemy, and scientists have released it near rivers in six Western states (see our story, Beetle Warfare).
But as the bugs munch their way south, their appetite threatens the Southwestern willow flycatcher, a rare songbird. The endangered bird once relied on native trees in Arizona and New Mexico, but as tamarisk displaced them it began to nest in the newcomer trees instead. Now, enviro groups are suing the Department of Agriculture to stop the beetle’s expansion into flycatcher habitat. Managing subprime securities is less complicated than managing wildlife, it seems.