Rising sea levels may change our coastlines and give some home owners new beachfront property, but among the myriad of real problems the world will experience, we can add one more: internet outages.

New research mapped out the U.S.’s internet infrastructure and overlaid that patchwork of cables, power stations, and data transfer stations with a map of proposed sea level rise, National Geographic reports. The result was not pretty. In the next 15 years, thousands of miles of fiber optic cables will be flooded with rising ocean waters. While some of this hardware can deal with water from time to time, none of it was built to withstand the rigors of being permanently submerged.

“So much of the infrastructure that’s been deployed is right next to the coast, so it doesn’t take much more than a few inches or a foot of sea level rise for it to be underwater,” said Paul Barford, study co-author and University of Wisconsin-Madison computer scientist.

According to data from the National Ocean Service, the sea level is rising at approximately an eighth of an inch per year, but that rate is increasing. The causes are thermal expansion (water expands as it warms) and melting land-based ice from ice sheets and glaciers. Rocks are not the cause of rising sea levels, as one Republican lawmaker inaccurately posited.

Cities such as Miami, New York City, and Seattle could see up to a foot of sea level rise by 2030, according to National Geographic. At that point, 20 percent of the country’s key internet infrastructure could be flooded. Roadways, power lines, and sewage networks will be affected, as well.

As most of us know quite well, even temporary internet outages can cause serious disruptions to our connected way of life. They affect not just our ability to get online, but the functionality of street lights and operations of airports, too. If actions aren’t taken to replace, relocate, or otherwise shore up coastal internet lines, rising sea levels could prove increasingly problematic.

H/T National Geographic