Fragile sand dunes of Moʻomomi on Molokaʻi, once overrun with alien kiawe thickets, are blooming with new native growth.
(Image: Native vegetation restored to a Mo`omomi, Moloka`i sand dune. Credit: The Nature Conservancy of Hawai`i.)
A 14-year passive restoration program by The Nature Conservancy and the Molokaʻi Land Trust is letting the blue blossoms of
paʻu o Hiʻiaka and the yellow flowers of
ʻilima bloom amid the spiky native ʻaki ʻaki and shimmering hinahina.
That’s on dunes that once held single-species thickets of the introduced legume, kiawe (Prosopis pallida), which was brought to Hawai`i to support cattle ranching.
“Kiawe transforms
the ecosystem. It forms dense thickets. If there’s a fire, it burns hot
and hard. Since it’s a legume and fixes nitrogen, it changes the soil,”said Russell Kallstrom, graphical information system coordinator for the Conservancy's Molokaʻi Program.
Kiawe removal
combined with predator and weed control benefits not only native plants,
some of them rare, but also the uaʻu kani or wedge-tailed shearwater. The number of wedge-tailed shearwater burrows has increased from 3 nests in 1999 to 704 nests in 2012.
“It seems like the
shearwaters were trying to recolonize before 1999, but feral cats used
the safety of kiawe thickets as staging areas for raids on the nests,”said Wailana Moses,
the Conservancy's Moloka'i weed coordinator. “When we removed some of
the kiawe clumps near the bird colony, we would find piles of shearwater
wings.”
The shearwaters face
a three-pronged mammal threat: mongooses would prey primarily on eggs,
cats would take birds one at a time, and dogs would occasionallywipe out dozens at a time. In 2009, a single dog killed 60 shearwaters in one night.
The Nature
Conservancy began kiawe control at its 921-acre Moʻomomi Preserve in
1998, under the direction of its Molokaʻi Program manager, Ed Misaki.
“The idea of passive
restoration was to focus on removing invasive species and let the
natives naturally regenerate—removing the threats and allowing thenative system to heal itself, basically,” Misaki said.
The conservation
crews learned as they went along. One key strategy was to remove kiawe
next to intact native sand dune habitat so the natives could reclaimthe open area naturally.
Another technique
was to quickly paint a small amount of herbicide on the cut kiawe stump,
to prevent it from re-sprouting. Still another was to use a chipper to
grind up kiawe branches,
creating mulch that helped the native crawling plants and inhibited weeds.
“We learned that if
we took out too much kiawe, we would have a hard time keeping up with
removing weeds coming into the area—primarily buffel grass, foxtail,
golden crownbeard,
Australian saltbush and a non-native goosefoot,” Moses said.
The ʻakiʻaki grass
was generally the first species to move in after kiawe removal. “The
chips slowed the weeds down a little and helped the ʻakiʻaki grow into
the area,” she said.“Little by little,
the other species came in like ʻenaʻena, kaunaoa and ʻakoko, even the
rare Solanum nelsonii (popolo),” Moses said.
Kallstrom said the
native plants do better on some of the land you’d think was the worst
habitat for them—the northeast sides of dunes, which are blasted by the
trade winds and regularly doused with salt spray. Most of the weeds can’t handle the salt; the coastal natives by contrast are adapted to it.
“It’s really an
amazing thing to see. After the kiawe is removed and the chips cover the
open area, the natives just crawl in from the outside. The ʻakiʻaki
turns fluorescent green when it hits the nitrogen left by the kiawe chips," he said.
The kiawe occurs in
patches across the Moʻomomi dunes, and the removal process, since
increments must be small, has cleared a little over 9 acres in the
program’s 14 years. For most of that period, it was done
by Conservancy staff and volunteers, but since 2010, some of the work
has been contracted to the Molokaʻi Land Trust, which also does weed
control.
The results are remarkable. Some of the cleared areas, originally bare sand, now support dense mats of Hawaiian coastal species.
The Nature
Conservancy is a leading conservation organization working around the
world to protect ecologically important lands and waters for nature and
people.
The Conservancy
and its more than 1 million members have protected nearly 120 million
acres worldwide. Visit The Nature Conservancy on the Web at www.nature.org.
