UH Mānoa Pavel Professor of Oceanography David Karl, study co-author, found vital clue to the puzzle.
While the iconic Haleakalā silversword plant made a strong recovery from early 20th-century threats, it has now entered a period of substantial climate-related decline. New research, “Climate-Associated Population Declines Reverse Recovery and Threaten Future of an Iconic High-Elevation Plant,” published in the scientific journal Global Change Biology warns that global warming may have severe consequences for the silversword in its native habitat.
Known for its striking rosette, the silversword grows for 20–90 years before the single reproductive event at the end of its life, at which time it produces a large (up to six feet tall) inflorescence with as many as 600 flower heads.
The plant was in jeopardy in the early 1900s due to animals eating the plants and visitors gathering them. With successful management, including legal protection and the physical exclusion of hoofed animals, the species made a strong recovery, but since the mid-1990s it has entered a period of substantial decline.
A strong association of annual population growth rates with patterns of precipitation suggests the plants are undergoing increasingly frequent and lethal water stress. Local climate data confirm trends towards warmer and drier conditions on the mountain, which the researchers warn will create a bleak outlook for the threatened silverswords if climate trends continue.
“The silversword example foreshadows trouble for diversity in other biological hotspots,” said Paul Krushelnycky, a biologist with the University of Hawaiʻi at Mānoa’s College of Tropical Agriculture and Human Resources, and principal investigator for the project. “It also illustrates how even well-protected and relatively abundant species may succumb to climate-induced stresses.”
Krushelnycky co-authored the paper along with Lloyd Loope, scientist emeritus with the U.S. Geological Survey, and University of Hawaiʻi at Mānoa’s Thomas Giambelluca, Forest Starr, Kim Starr, Donald R Drake, Andrew Taylor and University of Arizona’s Robert H. Robichaux. They explain that although climate change is predicted to place mountaintop and other narrowly endemic species such as the silversword at severe risk of extinction, the ecological processes involved in such extinctions are still poorly understood, and they are hoping to increase this understanding.
’Adapted from a UH Mānoa news release