Army Corps to California: Trees on levees have to go

If a tree grows on a levee, is it bad? According to a recent scientific review, there's no way to tell by reading federal policy.

In 2007, in the wake of Hurricane Katrina in New Orleans, the U.S. Army Corps of Engineers began enforcing national levee maintenance policy in California for the first time. The policy allows only grass on levees; trees and shrubs are banned.

The corps' rules have caused alarm in the Central Valley ever since, where trees and shrubs growing on levees provide the only remaining riverside habitat. Critics say removing that vegetation poses not only huge fiscal and environmental burdens, but would also drastically change the region's iconic scenery.

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