If you think there’s not much beach space left in Waikiki right now, chances are it’s going to be a lot worse in 35 years.

Scientists at the University of Hawaii’s School of Ocean and Earth Sciences and Technology (SOEST) studied data from 10 retreating beaches on Oahu, Maui and Kauai islands and found that beaches will erode as much as 20 feet by 2050 and 40 feet by 2100.

The study, titled “Doubling Of Coastal Erosion Under Rising Sea Level By Mid-Century In Hawaii,” was published this week in the journal “Natural Hazards.”