The Archie Carr National Wildlife Refuge is a 20-mile stretch of coastline running from Melbourne Beach to Wabasso Beach in southern Brevard County, Florida. It’s also one of the most important breeding sites for threatened loggerhead and green turtles.

Unfortunately, the dune erosion that came from Hurricane Irma took what scientists are calling a devastating toll on this year’s nesting sites. It swept away some sea turtles’ nests and exposed the eggs of others. The damage is made even worse because 2017 was a record year for green turtle nesting along the refuge’s beaches. Researchers from the University of Central Florida estimate that of the nests laid through the end of September, more than half of the season’s green turtle nests and a quarter of loggerhead nests were lost.

“Last year with Hurricane Matthew, we lucked out because it was a low green turtle year,” said UCF Assistant Professor Kate Mansfield, director of the UCF Marine Turtle Research Group. “This year was an extraordinarily exciting year for green turtle nesting, breaking all previous records within the refuge and continuing the conservation success story for the species. Unfortunately, we had another big hurricane this year, highlighting the need for continued conservation efforts in this area.” Mansfield noted that green turtles typically alternate between high and low nesting years.

Green turtles laid a record 15,744 nests in the 13-mile portion of the refuge monitored by UCF. An estimated 8,830 of those were lost in the storm. Since green turtles nest later in the season than other species, so many of their eggs hadn’t hatched by the time Irma hit. Fifty-six percent of total green turtle nests were lost, and an estimated 81 percent of those still had incubating eggs in them.

Loggerhead turtles also laid nests—9,690 of them in 2017—but most had already hatched when Hurricane Irma hit. Nonetheless, about 2,290 loggerhead nests, 24 percent of the total, were lost. Worse, 91 percent of the nests that were lost were still incubating when Irma’s storm surge came ashore.

UCF also monitors 16.4 miles of beach at Patrick Air Force Base. Although many fewer sea turtles lay nests there, the numbers are still high compared to other parts of the country. On those beaches, about 642 of 2,251 green turtle nests and 831 of 6,220 loggerhead nests were lost due to Hurricane Irma.

However, some sea turtles have come ashore to lay new nests. Researchers counted 466 new green turtle nests and eight new loggerhead nests that were created after Irma came through.

“Green turtles are still nesting, but recent extremely high tides have likely wiped out many of those new nests, too,” said UCF Assistant Research Scientist Erin Seney. “The good news is that the nesting habits of sea turtles do protect them from large-scale nest loss and make them more resilient to this kind of event. They lay multiple nests per nesting season, roughly every other year for 30 years or more.”