The striking and rare Haleakalā silversword, found only on the high volcanic slopes of Maui, is on the decline, scientists report today (Jan. 15) in the journal Global Change Biology.

The culprit is shifting weather patterns, which have made the plant's environment too dry and warm for new seedlings to survive. Older plants are dying, too, said study co-author Paul Krushelnycky, a biologist at the University of Hawaii at Manoa.

The numbers tell the tale: From a low of 4,000 in the 1920s to a high of 61,000 in 1991, the plant population is now dropping. A sample census counted 28,492 in 2010 — but not all of them were alive. "It wasn't obvious at first, because when they die they remain in place for many years," Krushelnycky told OurAmazingPlanet.

Baby plants are also struggling to grow in the drier conditions. Even with population booms during wet years, the seedlings die within two to three years, the study found.