Saved from goats, silversword succumbs to climate change

The impacts for Hawai`i of climate change are numerous and troubling.

They range from coral death due to warm waters, to coastal inundation from sea level rise, to changes in ecosystems due to weather pattern changes, to dramatic reductions of rainfall.

(Image: The impressive bloom of a Haleakala silversword, Argyroxyphium sandwicense, against a background of its volcanic Maui home. Credit: USGS; Paul Krushelnycky, UH-Manoa.)

Those are macro kinds of changes. At a micro level, looking at a single iconic plant, the issues come into focus.

The Haleakala silversword, that unearthly spiked globe that dots the high volcanic desert on Maui, is likely to be a victim of the changing environment. Indeed, it is already a victim, its numbers declining now for nearly a generation. Previous studies have shown that high-elevation Hawaiian rainfall has been reduced significantly in recent decades.

Not the first time the silversword has been threatened (goats were killing them off in the early to mid 1900s), but after a significant rescue effort, they now face a new problems that fences won’t solve.

“Despite the successful efforts of the National Park Service to protect this very special plant from local disturbance from humans and introduced species, we now fear that these actions alone may be insufficient to secure this plant's future,” said Marcia McNutt, director of the U.S. Geological Survey.

Researchers are finding that since the 1990s, they have once more begun to decline, due to more frequent drought conditions on the Maui mountaintop where they live. Silverswords are adapted to high elevation, and extreme solar radiation, and well-drained cinder. But heat and extreme dry periods are increasing the threats faster than they can adapt further.

They are dying from moisture stress, and that’s a caution for many other plants that might not be so well studied, and thus whose response to changing conditions haven’t been identified.

“The silversword example foreshadows trouble for diversity in other biological hotspots,” said University of Hawaii biologist Paul Krushelnycky, of the College of Tropical Agriculture and Human Resources.

“Even well-protected and relatively abundant species may succumb to climate-induced stresses,” he said.

A scientific paper on the research into climate impacts on the silversword is entitled “Climate-associated population declines reverse recovery and threaten future of an iconic high-elevation plant.” It is published in the scientific journal Global Change Biology. The authors are Krushelnycky, Lloyd Loope, Thomas Giambelluca, Forest Starr, Kim Starr, Donald Drake, Andrew Taylor and Robert Robichaux.

The continuing work is funded by the new U.S. Department of the Interior Pacific Islands Climate Science Center, one of eight such centers throughout the country.

The paper abstract is here. 

The USGS news release is here. 

© Jan TenBruggencate 2013