Louisiana’s crumbling coast would suffer devastating flooding and dramatic land loss, leading to mass evacuations within a few decades, if president-elect Donald Trump carries through with his pledge to pull the U.S. out of a global agreement to reduce greenhouse gas emissions. That...

For several years, people in the coastal restoration community have debated whether the state should rebuild its sinking, crumbling wetlands with massive river diversions or by pumping mud from the river into the marsh. People in favor of diversions contend they’re the...