Unintended consequences: Tamarisk leaf beetle is extending range into Flycatcher habitat

From The Arizona Republic (Brandon Loomis):

Exotic beetles released by the U.S. government to kill exotic trees along the upper Colorado River have munched a destructive path into central Arizona, officials have confirmed, proving to be more mobile and resilient than predicted.

The tamarisk leaf beetle now threatens the endangered southwestern willow flycatcher and other birds that have adapted to the non-native tamarisk that grows so thick along some of the region’s rivers. The beetles can strip a tree of its leaves, ruining it as a home for the birds.

Arizona environmentalists and biologists worry the beetle’s June 8 discovery in Wickenburg dooms many of the remaining flycatchers. Salt River Project has invested millions of dollars and 2,400 acres in mandated habitat protections throughout the Gila River drainage as a condition of raising Lake Roosevelt and displacing old nesting areas.

Some people, like suburban Buckeye’s mayor, are cheering the prospect of a natural thinner for the shrubby tamarisks crowding the Gila River, where thickets of the trees are blamed for flood and fire risks.

But no one knows how much farther the beetles will spread if they find new paths into the Gila River drainage area, which stretches north and east on the Verde and Salt Rivers and south on the Santa Cruz and San Pedro rivers.

An Arizona biologist found beetles and their larvae living in tamarisks on the Hassayampa River, a Gila tributary west of metro Phoenix. The insects had previously moved south from Utah’s Virgin River to Lake Mead and then down the lower Colorado. From there they moved east along the Bill Williams River and its tributaries.

Now they’re within striking distance of the heart of what remains of flycatcher country.

Gila River watershed.

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