Saturday, January 10, 2015

Ancient Karst Reef Sinkholes On The Ewa Plain Hold Secrets To Oahu’s Earliest Residents

Looking Back by Looking Down 

By Chad Pata, August 22, 2014  Go Kapolei Magazine


In general, sinkholes are created over centuries as the acidity of rainwater eats away at the limestone, causing underground caverns to form and eventually give way to the weight of the earth above them.

Here in Kapolei, anyone who has ever put a shovel in the ground knows that the entire plain is made up of an ancient reef that dried up as ocean waters receded 120,000 years ago. This weathered karst, as it is known, is a limestone substrate that through the centuries was eaten away by the rains creating thousands of vertical bell-shaped caves or sinkholes.

While they are—geologically speaking—of some interest, their true value comes from their unintended ability to serve as a trap for animals. Due to their vertical nature, once a creature found itself in such a place, there was little chance of escape as scaling the walls was impossible and rare is the bird that can hover straight up like a helicopter to escape these narrow confines.

So what we had was a perfect repository to collect fossils of the wildlife that occupied these islands long before the Polynesians ever set foot on this volcanic chain.

Unfortunately, 99 percent of these “fossil tombs” have either been bulldozed for agricultural lands, lain over with concrete for development or simply lost to the ever-shifting sands of time, which brings us back to our little six-acre plot in Kapolei.

They were first discovered in the 1970s by Jennie Peterson, an archaeologist with Bishop Museum, as she was doing an environmental impact study on the once-proposed Deep Draft Harbor, but the history of the sinkholes would be written by local zoologist Dr. Alan Ziegler who spent decades exploring, documenting and teaching others about the wonders to be found out here on the Plain.

Eventually, the Smithsonian got involved with the project and the preeminent avian paleontologists Storrs Olson and Helen James came in to examine the remains.

What they found was astounding. More than 40 extinct species were interned in the sinkholes and of whose existence no one had known until they were discovered here.

There were remains of sea eagles and hawks, flightless rails and finches, and most shocking of all the moa nalo, which in Hawaiian means “lost fowl.” It was a three-foot tall flightless goose-like duck with a head like a tortoise. Many of the remains were in articulated form, as they had most likely died in the sinkhole after having fallen in, giving scientists an unadulterated look into our distant past.

“Back in the day, with all these birds, it must have been quite a raucous place!” says Marjorie Ziegler, daughter of Alan and executive director for the Conservation Council for Hawai‘i who hopes to oversee the care of the preserve one day.

Many of these remains now reside in Washington, D.C. at the Smithsonian and while the important artifacts have been removed, there is still much for future generations to learn at this holdover from pre-human contact Hawai‘i.

For years the CCH and Hawai‘i Nature Center led tours to the sinkholes, allowing children a chance to play archaeologists for a day. Ladders would be set up, many of the holes are 8-feet deep, and the kids would descend into the depths to use trawls, scoop sand and bring buckets of it to the surface.


Here they would use screens to discover the bones of Hawaiian petryls, the ‘ua‘u, that is only found on neighbor islands now and the beaks of long-gone crows who used to call O‘ahu home. They would always return the remains to the sinkhole to allow the next group to discover them.

But in recent years, invasive species of plants have overgrown the property, the holes are obscured by weeds making it difficult to find them or, even worse, hard to see their openings until you are falling into one.

The sea air and vandals have ravaged the fencing; and while still protected on paper, Ziegler is concerned about what could happen to this valuable natural resource.
“I worry less about homeless people setting up camp in there than about the accidental bulldozer collapsing them,” says Ziegler.

The holdup on the turnover of the land to the DLNR is a modern-world one.

The property cannot be conveyed until the surrounding land is subdivided and the subdivision cannot happen until there is improved road access to the surrounding industrial park development. This development, named Kapolei Harborside is planned to happen over the next decade, so while the plan is still to turn the land over to the DLNR, it may be some time before the public gets to visit this important bit of our area’s history.

When this lot at the corner of Malakole and Hanua streets is officially turned over, Ziegler and her team at CCH have big plans for the sinkholes starting with clearing the land of all the invasive species, including many large kiawe trees, and marking the sinks so that the visitors can be safe when visiting.

Next will be to build an educational area where kupuna can talk about these extinct species before kids go visit the sinkholes. And here, Ziegler’s visions can finally be realized, as amongst the remains our ancient past, the minds of our future can grow.

For more on the Conservation Council for Hawai‘i, log on to www.conservehi.org





SINKHOLE BIRDS THAT ARE EXTINCT

Extinct species of birds from sinkholes on the 'Ewa Plain:

Pterodroma jugabilis, a medium-sized petrel
Thambetochen xanion, a large flightless species of waterfowl (moa nalo)
Branta (uncertain species), a weak-flying goose, closely related to the nene
Porzana ziegleri, a small flightless rail
Porzana ralphorum, a large flightless rail
Circus dossenus, a small harrier, apparently adapted to feed on forest birds
Grallistrix geleches, a long-legged, bird-eating owl
Corvus impluviatus, a raven-sized crow with a deep, arched bill
Corvus viriosus, a raven-sized crow with a long, straight bill
Myadestes oahuensis, the O'ahu thrush
Moho apicalis, the O'ahu 'o'o (a honeyeater)
Chaetoptila (related to) angustipluma, a large honeyeater
Telespiza persecutrix, a small finch similar to the Laysan and Nihoa finches
Chloridops wahi, a grosbeak finch similar to the extinct Kona finch of the Big Island.
Chloridops regiskongi, a grosbeak finch with a really large bill, nicknamed King Kong finch.
Rhodacanthis litotes, similar to the extinct koa-finches of the Big Island.
Xestospiza fastigialis, a finch with a conical bill that was once common on O'ahu, Moloka'i and Maui.
Hemignathus upupirostris, an 'akialoa (Hawaiian honeycreeper with a long, thin, decurved bill)
Aidemedia chascax, a Hawaiian honeycreeper with a long, straight bill
Aidemedia zanclops, a Hawaiian honeycreeper with a sickle-shaped bill
Ciridops (uncertain species), a short-billed, strong-legged Hawaiian honeycreeper of a type previously known only from the Big Island.

SINKHOLE BIRDS STILL THRIVING

Sinkhole birds that are not extinct:

Pterodroma sandwichensis, the Hawaiian petrel; not previously known from O'ahu but bones are abundant in the sinkholes, showing that the region once had a major colony.
Haliaeetus (related to) albicilla, the white-tailed sea eagle. These eagles were either resident in the Islands or were regular visitors in the past. (A sea eagle was spotted on Kaua'i and possibly on O'ahu late last year and earlier this year.)
Telespiza cantans, the Laysan finch, known historically only from Laysan Island.
Loxioides bailleui, the Palila, known historically only from high-elevation Big Island mamane-naio forest.

Source: Helen James, Smithsonian Institution


Oahu's Ewa Plain Karst Sinkholes And Caves Yield Extinct Bird Fossils

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Ewa Plain Karst Can Be Restored