SHERIDAN, Wyo. (AP) — An archaeologist says organic artifacts preserved by ice patches in Yellowstone National Park are being lost to research because warmer temperatures are melting the ice.

Staffan Peterson was park archaeologist at Yellowstone for four years. He is now leading the cultural and natural resources program at Little Bighorn Battlefield National Monument in Montana.

Peterson says archaeologists seek to collect pollen, pine needles, sticks, dung, bones and other artifacts preserved in the ice patches. They help provide clues of the human past.

But they decay quickly when exposed to the open air.

While he said this isn't just a problem in the world's first national park, he said there's only about a dozen ice patches left in Yellowstone.