As Venice was deluged this week with the highest tide in 50 years, images of the historic floods stunned the world and captured the scale of the floods:

Residents and tourists wading through knee-high water in popular spots. And the mayor blaming climate change, in an indication that worse things may lie ahead.

On coastlines across Europe and the world, low-lying cities like Venice are facing rising sea levels that could make vast stretches of land uninhabitable. A recent study suggested about 300 million people may be living in low-lying areas that are expected to flood by 2050.