A new report on climate change finds the number of wild reindeer in the Arctic has dropped a startling 56% in the past two decades. The study, compiled by the U.S. National Oceanographic and Atmospheric Administration and released at an American Geophysical Research Union meeting, found the population has dropped to roughly 2.1 million from 5 million, with some herds shrinking more than 90%.

Reindeer, referred to as caribou in some areas, are affected by higher temperatures, resulting in changes in vegetation and drought in some areas, according to scientists. Other locales are seeing increased rain, which freezes and prevents reindeer from reaching their food.

The rise in temperatures is also causing more insects in the Arctic, making reindeer expend more energy when swatting them off their bodies.

Scientists warn their concerns continue.

“As a result of atmosphere and ocean warming, the Arctic is no longer returning to the extensively frozen region of recent past decades,” the study reads. “In 2018 Arctic sea ice remained younger, thinner, and covered less area than in the past. The wintertime maximum sea ice extent measured in March of 2018 was the second lowest in the 39-year record, following only 2017.”