Final answer:
Seawalls can lead to greater storm impact on shorelines and damage beach ecosystems, threatening local fisheries, tourism, and the local economy.
Step-by-step explanation:
One problem with constructing seawalls to protect buildings from flooding or erosion is that they can lead to greater storm impact on shorelines and damage to beach ecosystems. Dredging projects associated with seawall construction can damage reefs, sea grass beds, and shorelines, which in turn can kill off marine life and threaten local fisheries, tourism, and the local economy.