Dams reduce the creation of natural sandbars, which is bad news for birds that depend on them for nesting habitat. More than 200 hectares of engineered sandbars have been built along the Missouri River to address this problem — but how does this compare to the real thing? A new study takes advantage of a natural experiment created by the region’s 2011 floods, demonstrating that engineered habitat doesn’t provide the benefits of sandbars created by nature.