According to Molly Melius, program manager at Stanford University’s Environmental and Natural Resources Law and Policy Program, seawalls can reduce beach width, decrease sand replenishment of beaches, and also accelerate erosion at the ends of seawalls. In some cases, seawalls are inadvertently accelerating the problem they were designed to solve. Coastal armor can also degrade ecosystems that might naturally protect the shoreline from erosion. “Previously, before a lot of development, there was a lot of room for shoreline migration,” said Nichols, meaning that coastal ecosystems could migrate along with the coastline. The development of concrete structures like seawalls and other kinds of armor produces an effect called “coastal squeeze,”  meaning that these ecosystems are not able to migrate. “You can lose whole coastal habitats” this way, says Melius.