The Nature Conservancy. Protecting nature. Preserving life.™

The Nature Conservancy’s Kaiholena Preserve in Ka‘ū on Hawai‘i Island, recently marked its two-year anniversary of being pig-free. A six-mile, animal-proof fence, completed at the end of 2007, protects the 1,200-acre lowland forest preserve, which is now thriving with rarely seen native species.

“It’s amazing to see the abundance of new plant life,” said Shalan Crysdale, the Conservancy’s natural resources manager at Kaiholena. “Plants that haven’t been seen in years are popping up all over the preserve.”

Among the returning wildlife are lobelias: two species of koli‘i (Trematolobelia wimmeri and Trematolobelia grandifolia) and three species of ‘ōhā wai, including one named for Mauna Loa (Clermontia montis-loa).

Most impressive, however, has been a resurgence of the beautiful nuku ‘i‘iwi, a native vine traditionally found in Kaiholena.

“The flower of the nuku ‘i‘iwi, or ‘beak of the ‘i‘iwi,’ resembles the curved bill of the native honeycreeper it’s named after—and has the same bright reddish-orange color,” said Dr. Sam ‘Ohu Gon, the Conservancy’s senior scientist and cultural advisor.

On the Big Island, the nuku ‘i‘iwi is found only in Kaiholena and in Laupāhoehoe above Hilo. It is also found on Kaua‘i, O‘ahu, Maui and Moloka‘i but seldom seen except in high-quality native forest.

Gon credited the return of these species to the fence that was constructed in 2007 to keep pigs and mouflon sheep out of the preserve. Wild pigs and other feral animals wreak havoc in the islands’ native forests. Where they root and trample, they destroy native vegetation, accelerate erosion and pollute the water supply with eroded silt, feces and foreign diseases.

“The resurgence in plant life is a standard response of our native forest to protection from browsing animals,” Gon said. “If there isn’t a major weed problem, the natives often come roaring back.”

A local crew from the Sunshine Fence Co. built the six-foot-high enclosure, which is the state’s first mouflon-proof fence built in a forest. To do the job, crew members had to camp in the preserve during construction, clear fence lines by hand and have all fencing materials flown in by helicopter sling loads. On weekends, as many as 20 workers were part of the effort, which took eight months to complete.

It took another year to remove all the pigs. “We started removing pigs in early 2008,” said John Replogle, a senior member of the Conservancy’s Ka‘ū field crew. “Local community hunters took out 33 pigs the first month, but over the next few months were unsuccessful in getting the last ones out. We ended up catching the last five pigs ourselves doing staff hunts. They were all wise old boars.”

To maintain the pig-free status, the Conservancy’s field crew walks the fence line each week, checking for problems such as ingress, fallen trees or corrosion.

“Over time, as we do our fence checks, we have seen dramatic changes in the number of rare native seedlings popping up. I would not have thought pigs had such a destructive effect on these particular plants until I saw how many are now germinating and growing to maturity,” said Replogle. “There is moss on the ground now where it was just soil before. When you look along the fence, the ground level on the outside is three to four inches lower than inside the fence. This is erosion caused by the presence of pigs.”