Wedged between the Hilo airport, a military shooting range and a gravel quarry is a 108-acre scrap of forest. Aggressive alien plants have invaded from top to bottom, towering over the tallest `ohi`a trees and crowding out native seedlings on the forest floor.
Yet the native `ie`ie scrambles across the rough a`a lava and climbs into the ancient `ohi`a. Shrub-sized kopiko are laden with oval coffee-like berries. Dying hapu’u, the native tree ferns, have lent their mossy trunks to support sprouts of their own kind, along with adder’s tongue and bird’s-nest ferns. Here and there in the dimness, the rosy new foliage of lama trees glows like a distant candle; it’s at once obvious why Hawaiians named the plant with their word for “light.”
The military base on which the battered forest stands is habitat for the endangered Hawaiian hoary bat, the islands’ only indigenous land mammal. Another forest denizen might be the endangered `io, or Hawaiian hawk, which is often seen in the area.
For those who want to restore the remnant Hawaiian forests, this rare lowland wet forest on the Hawai`i Army National Guard’s base at Keaukaha is either cause for despair or for determined optimism.
It’s a “ghost forest,” its native plants on the verge of being overwhelmed by invaders. Stout survivors are scattered throughout the landscape, growing and even reproducing despite being robbed of light, space and nourishment. Still, says Flint Hughes, an ecologist with the U.S. Forest Service in Hilo, they are probably incapable of sustaining themselves much longer without help.
“From the outside it looks totally trashed,” says Rebecca Ostertag, an assistant professor of biology at the University of Hawai`i-Hilo. Ostertag is heading up a joint National Guard-UH experimental restoration project on the site that started this fall. But she describes the “little pockets” of native forest that remain as “just enough to give us hope that restoration is worthwhile.”
Ostertag and Hughes are among a small but growing group of people who are attempting to restore surviving forest relics in the urgent awareness that more than 40 percent of Hawai`i’s native forests have disappeared, and with them many hundreds of the estimated 1,000 unique island plants and animals. In this, they are taking up an idea that was pioneered in the early 1970s by Hawai`i Volcanoes National Park. At that time, park workers began removing goats as the first step in what managers there call “natural restoration.” Several dozen projects, most of them five years old or less, are now underway on all the major islands and Kaho’olawe.
The National Park Service, the U.S. Fish and Wildlife Service, the Forest Service of the U.S. Department of Agriculture, and the Department of Defense have teamed up with virtually every state agency that owns forested lands, from the Department of Land and Natural Resources to the Department of Public Safety. Private landowners and non-profit groups, including Kamehameha Schools and The Nature Conservancy of Hawai`i, are involved as well. Volunteers come from schools, local grass-roots conservation organizations, and even the continental United States, where groups like the Sierra Club recruit people willing to spend their Hawaiian vacations pulling weeds and gouging planting holes in rough a`a lava.
Even with donated labor, restoration is costly. Hawai`i Volcanoes National Park has budgeted $4 million over the last four years for special restoration projects, with “almost all of it from the folks who drive through the front gate and stick out their $10 bills,” says Tim Tunison, the park’s manager of natural resources.
The Fish and Wildlife Service (FWS) is involved in 26 forest restoration projects, not including work inside its own refuges. In fiscal year 2002, these projects cost the service $1,426,212. Most are small-scale efforts to keep grazing animals from destroying the last wild specimens of an endangered plant, such as a 5-acre, $25,000 fencing, weeding and outplanting program to protect the endangered Gardenia brighamii on land owned by Castle & Cooke Resorts on Lana`i. On a much larger scale, the FWS is 14 years into an ambitious attempt to recreate thousands of acres of forest from scratch at Hakalau Forest National Wildlife Refuge on the windward slope of Mauna Kea. Here staffers and volunteers have planted more than 300,000 native trees on land virtually denuded by a century and a half of cattle grazing.
The Rules of the Game
Helping native Hawaiian forests gain ground has become a demanding game that practically every conservation-minded organization wants to play. But not everyone agrees on the rules. Some projects attempt to mesh recovery with such seemingly incompatible goals as dude ranching, “sustainable” logging of native forests, and the maintenance of private hunting reserves for pigs, sheep, and other ungulates.
The Keaukaha Military Reservation (KMR) is no exception. Here the nominal goal of the recovery work, according to one document published by the Hawai`i Army National Guard, is the creation of “tactical concealment corridors.” These are described as 25 to 50-foot-wide “realistic maneuver training lanes that minimize adverse ecological impacts” by removing only non-native understory trees and shrubs, leaving the native trees.
Lt. Col. Ronald Swafford, the guard’s environmental program manager, explains the description by noting that training is always the primary purpose of the guard’s work. Ecological research and jungle training for soldiers can take place side by side, he continues, so long as experimental plots and other sensitive areas are designated off-limits to training.
Tunison of the National Park Service says that some dual-purpose projects, such as silviculture (commercial tree plantations), “might be the best you can expect in some areas.” They provide habitat for some native birds, allow some native plants to resprout on their own, and prevent soil erosion.
“It’s better than a sugar plantation. It’s better than a cattle ranch. It’s better than a eucalyptus forest,” Tunison says. “On the gradient, I’d put it a lot closer to a native ecosystem.”
Tunison and other ecologists avoid calling the goal of these recovery efforts “restoration.” They use other terms – reconstruction, rehabilitation, re-creation, even replacement – to drive home the point that Hawai`i’s native forests can never be made whole. Too many plants, too many animals and too much knowledge have been lost forever.
And some scientists say too many land managers are unwilling to take the political heat involved when animal rights groups and pig hunters join in an unlikely coalition to fight off attempts to remove the destructive animals from land that could be restored.
“With pigs, we know what to do,” says Lloyd Loope, a research biologist at the U.S. Geological Survey’s Haleakala field station on Maui. “It’s just a matter of having the political will.”
Setting Goals
Imagine trying to restore a fresco on the wall of an ancient Roman villa with only a few small fragments to guide you, while the rest of the image lies at your feet in a heap of brightly colored dust. That is the challenge facing those who seek to restore Hawaiian forests. Plants that may have been the keystone species of forest ecosystems have gone extinct with no scientific record of their existence. The same is true of many birds that evolved along with them, pollinated them and dispersed their seeds.
“I wouldn’t say we’re doing any restoration,” says Rick Warshauer, a botanist with the USGS with a long history of involvement with such projects. “We’re stuck at the gardening scale.”
Hawai`i entomologists have discovered whole insect communities living in the water droplets collected on the leaves of a single plant. How many such small worlds once existed and now are gone, and what their importance was to the islands’ elaborate mosaic of unique ecosystems, are questions that will probably never be answered.
Meanwhile, deforestation has eroded soils created by thousands of years of weathering and plant decay, changed the basic chemistry of some remaining soils, and replaced moist landscapes with arid ones.
The dilemma is basically unchanged since 1984, when ecologist Charles H. Lamoureaux summed up the problem in the published proceedings of a symposium on “preservation and management” of Hawaiian ecosystems, held at Volcanoes National Park.
Two decades earlier, Lamoureaux noted, the National Park Service’s Leopold Committee (headed by A. Starker Leopold, the eldest son of pioneering conservationist Aldo Leopold) decreed that all parks “should be restored to or maintained at ‘the condition that prevailed when the area was first visited by the white man.’ ” Thus, Lamoureaux said, “ecosystem projects in Hawaiian national parks should aim at restoration to the state prevailing in January 1778 (if only we knew what that was).”
A more realistic goal, Lamoureaux said, was to return “semi-natural landscapes” – those that appear natural to the untrained eye, but which actually have been shaped by human activities such as cattle ranching – to “near-natural landscapes” made up primarily of native plants and animals.
Ideally, the plants and animals in these “near-natural settings” would form a community roughly similar to what existed before human involvement. The dominant plant species would use and return about the same amount of soil nutrients and water as their predecessors did, create microclimates much like what once was there, and support a similar suite of companion plants and animals.
To restore a tract of land, Lamoureaux said, conservationists would have to:
- Remove all non-native herbivores – pigs, cattle, goats, sheep and others.
- Eliminate non-native predators, including mongooses, three kinds of rats, and feral cats.
- Remove or drastically control alien plants.
- Replant the area with “rare native plants that are as genetically similar as possible to those which formerly inhabited the area.”
- Restock native animals.
- Prevent, or at least slow down, destructive changes to the landscape before, during and after restoration.
“Even when all these techniques are fully employed it will probably not be possible to reach a goal such as restoring ecosystems in national parks to late 18th century stages, simply because we don’t know what these were,” Lamoureaux wrote. “It is likely that many species then present have become extinct already anywayÉ This does not mean that such efforts should not be undertaken,” he wrote.
Promising First Steps
To date, not a single project has taken all the steps Lamoureaux recommended, and no one stands ready to claim success. But some progress has been made.
One of the longest-running and most promising efforts has been undertaken at the Hakalau Refuge, where the Fish and Wildlife Service began replanting koa in 1988. Five years ago, botanists began adding understory plants, including five critically endangered species found on the refuge whose wild populations had dwindled to 20 plants or less.
Fourteen years after the planting began, how much of the 32,700-acre refuge can be considered restored?
“None of it,” says refuge biologist Jack Jeffrey. “We’re still working on it.”
But there are signs that the work is paying off. At the refuge’s middle elevation (between 4500 and 6000 feet), where a few 200- to 400-year-old ‘`ohi`a and koa trees survived cattle grazing, 80 percent of the young trees planted by staffers and volunteers are surviving, while native understory plants are growing on their own beneath the canopy.
Higher on the slopes of Mauna Kea, where cattle had denuded the mountainside, koa seedlings were planted five to ten years ago on the gently undulating land. The trees now show up like yards of deep green ribbon unspooling against a backdrop of tawny dry grass. Volunteers planted the trees parallel to the mountain’s stream-worn gulches, whose steep sides protected pockets of old, rare trees from trampling hooves. Now 10 to 15 feet high, the fast-growing trees cast wide bands of shade across the parched landscape.
In 1997 and 1998, volunteers planted understory trees that were grown in the refuge’s greenhouses from seeds collected from under the sheltering koa in the refuge’s gorges and kipuka (vegetative islands cut off from adjoining lands by lava flows). Among the new plantings are kolea, `ohelo, pilo, pukiawe, and naio.
Akiapola`ao, found only on the Big Island and one of eight endangered Hawaiian forest bird species found in the refuge, are regularly seen in the young koa stands. A recent USGS analysis of four endangered bird species suggests that the bird’s population on the refuge is increasing; whereas it had been seen before at a density of one bird per forested acre, the most recent surveys suggest a density of 1.5 “aki” per forested acre. (Because the populations of the other endangered birds are so low, it is impossible to come up with a statistically significant sample, Jeffrey says.)
These tiny, melodious golden birds use their bills, described by Jeffrey as all-purpose Swiss Army knives, to excavate bark and extract insect larvae. Because of that, akis had been thought to inhabit exclusively old-growth forests, Jeffrey says. “I didn’t think we would see the birds utilizing the [new] habitat in my lifetime, but yet they are. What that says to me is, son of a gun, plant it and they will come.”
Understory Revival
Hakalau, whose name means many perches, is part of an ahupua`a (Hawaiian land division) that runs from the summit of Mauna Kea down its eastern slope. Below about 4,500 feet, its dense rainforests, still largely intact, can receive 250 or more inches of rain a year. Above them, mesic, or moist, `ohi`a-koa forests stretched up to the tree line, becoming gradually drier as they climbed.
The upper reaches of Hakalau are beyond the range of mosquitos for the most part, which affords a measure of protection against avian malaria and pox to the resident birds. But here cattle had grazed for 150 years before the refuge took control of the land, converting `ohi`a forest to pasture. “When the cattle started to breed it was like a giant salad bar,” Jeffrey says of the original mesic forest. “Nothing prevented the cattle from eating all the native plants, and after that there was no regeneration.”
To the untrained eye, the loss of shrubs and ground cover may not look as dramatic as the complete absence of trees, but it is devastating, according to the USGS’ Warshauer. “The bulk of the diversity of the Hawaiian ecosystem is the bottom meter and a half, from the ground up,” he says, as opposed to other tropical ecosystems whose greatest diversity is found in their canopies. Why? “It probably takes a lot of time to evolve a rich canopy biota,” he explains, “and these [Hawaiian] islands are above the ocean for maybe five million years” – a mere blink of an eye in evolutionary history — “and then they’re gone.”
And while the refuge seems to be well on its way to toward recovering the lost understory, it may be a race against time. Jack Ewel, director of the U.S. Forest Service’s Institute of Pacific Islands Forestry, says recent research suggests climate change may allow mosquitos to breed year-round at ever higher elevations of Hawai`i’s forested slopes. This would all but eliminate native forest bird habitat on Kaua`i, dramatically reduce it on Maui, and compromise birds on all but the highest elevations on the Big Island.
Animal Control
Over the last 15 years, Hakalau staffers have managed to figure out ways to keep new seedlings protected from frost, drought, and other threats. But an additional threat to the young plants’ survival remains: wild pigs and cattle. The refuge has installed 44 miles of fencing at a cost of $1,243,627. Eight exclosures have been completed; five are considered pig-free.
Progress in removing the pigs has been slow. Initially, objections from hunters resulted in the agency dragging its feet on pig removal. Public hunting is still allowed in parts of the refuge, but not in areas considered prime bird habitat. In areas that have been fenced and pigs have been removed through hunting, snares have been put in place to catch what few animals remain. About 1,000 snares have been placed in the 5,000-acre Shipman Unit, says Jeffrey, but they rarely catch pigs anymore. Apart from the fenced units, “the rest of it is pig city,” in Jeffrey’s words.
Lately, budget factors have played a role in the pace of pig removal. Because of service-wide cuts, the refuge’s field staff has been cut from six to three, and those workers spend most of their time inspecting for fence breaks and controlling weeds, according to Jeffrey. About 100 more miles of fencing are needed to protect the rest of the bird habitat, he says, but no new fencing has been installed since 1997 because there’s no money for it. Still, the pig infestation at Hakalau is no longer a serious threat to native birds, Jeffrey says, because pig populations are high only in the same low-elevation areas where avian malaria is rampant.
Rats and Cats And Mongooses
Aside from the pigs, other introduced animals can harm native birds and plants. “We’re not even talking about working on the predators yet, the rats, the cats, the mongooses,” Jeffrey says.
Only a handful of Hawai`i’s land managers have comprehensive rat control problems, says Tunison of Hawai`i Volcanoes National Park. There, in an effort to target rats, staffers have set out bait boxes containing diphacinone around nene nests (rats can eat eggs and even chicks) and some rare plants (whose seeds can be eaten by the rats). Diphacinone, initially developed as a blood thinner for use in humans, causes fatal hemorrhaging in rats after repeated, low-level doses. While the bait seems to be effective, it is expensive to deploy.
Rats “have been documented to prey on everything from forest birds and seabirds to native plants,” says Katie Swift, a Fish and Wildlife Service researcher who has studied methods of rat control. Black rats and the smaller Polynesian rats are found in every sort of habitat throughout Hawai`i, Swift notes. In an experiment on Maui using laser-tripped cameras to document rats’ feeding in the bait boxes, “the rats (were) chewing on the wires of the camera,” she says. “Almost no sooner had they placed the bait than the rats were coming out and taking it.”
A more cost-effective way to kill rats would be to broadcast the diphacinone by helicopter. Late last month, the Fish and Wildlife Service was set to ask the Environmental Protection Agency to approve this method for use in Hawai`i. The state Department of Agriculture must also approve the plan.
To address concerns that diphacinone might accumulate in pigs and get passed on to humans who at them, “we picked a poison that had the lowest toxicity to humans,” Swift says. “Even if I sat down with a bowl of diphacinone and dipped it in chocolate, there’s no way I could eat enough to get sick,” Swift says. “At 50 parts per million” – ten times the concentration of diphacinone in the bait – “you wouldn’t even get as much (blood-thinning) effect as an aspirin.”
Because diphacinone only affects mammals, it will not harm native birds, Swift says. Farmers on the continental United States have been using it to control rodents for years, with no harmful effect on other animals, she says.
If the state and EPA approve spreading of the rodenticide, “we would start out very cautiously, and any state or federal lands we selected would have to go through pretty extensive public review,” Swift says. “They’re going to be really remote areas. They’re going to be areas where we have species that are very rare, that really need special protection.”
Beyond the Birds
With cattle and pigs gone, native shrubs and small trees are beginning to sprout in the mid-elevation forest of the Shipman unit of Hakalau refuge. Before replanting began, these areas looked like a cross between a forest and a veldt. Tall, stately `ohi`a and koa grew widely spaced. In between, where abundant sunlight hit the ground, alien grasses covered the hoof-pocked terrain.
The upper edges of the unit still look that way, but the canopy thickens further downslope, where old trees commingle with those of more recent vintage. In plots in the open pasture, Jeffrey has found no natural regeneration of native plants, “but further downslope, there is regeneration, and the difference is canopy,” he says.
A pair of endangered `io nests in an old `ohi`a tree. The dark-toned females’s chest feathers, the color of brown sugar, glisten in the sun as she guards her nest.
Hiking under the canopy of the old trees, Jeffrey and researcher Jeff Hatfield of the U.S. Geological Survey’s Patuxent Research Center in Maryland count five different native shrubs and a native fern sprouting at the base of a koa tree.
“Five years from now this will all be just one big fern patch,” says Jeffrey. “I’m amazed. Ten years agoÉall it was, was just the `ohi`a and koa, the tall ones, and nothing below ten feet. There was nothing other than grasses under there, and it’s all popping up now. So I’ve got pretty much faith that the forest will regenerate itself.”
In the greenhouse, horticulturist Baron Horiuchi has been developing propagation techniques for most of the 19 endangered plants known to grow at Hakalau. Among them are Cyanea shipmanii, whose lower trunk is armored with fat green thorns – a rarity among Hawaiian plants – and Phyllostegia brevidens. The Phyllostegia is a scentless mint last seen in the wild in the 1870s and had been thought extinct until 1999, when a Bishop Museum expert identified it from a sample Jeffrey collected in 1990. Jeffrey and deputy refuge manager Jim Glynn found the plant, collected a branch that had been broken off by a pig, and brought it to the greenhouse.
“There was a whole bunch of old jive seeds, fungus-ridden seeds,” Horiuchi says. “I made up a ten percent bleach solution, put the seeds in there to get rid of the fungus, planted it on tree fern substrate Éand presently we’ve outplanted 206 of them.”
Saving endangered plants “was like a dessert, it was fun to do,” Horiuchi says. “Then we started finding a lot of them.” Horiuchi, a 44-year-old former fisherman and carpenter, supervises the volunteers who come in batches of 10 to 20 to plant and weed about 45 weekends each year.
“I’m from the Big Island, yeah? I’m a small town Hilo guy, and having this job is like a dream come true,” Horiuchi says. “It’s so worthwhile to help the `aina [land]. We have over 600 volunteers a year É and all these people feel the same way I do. We love the forest, we love the trees, we love the wildlife, and we want to protect it.”
Giving Respect Where It’s Due
At the Keaukaha forest, success may lie simply in learning more about an ecosystem even less well understood than that of Hakalau. Lowland wet forests like the one on the 509-acre KMR base are the Rodney Dangerfields of Hawaiian forests – not respected and therefore not studied.
“People just gave up on them,” says the Forest Service’s Hughes, who studies lowland wet forests. “They thought that everything was trashed, that it wasn’t worth saving, there were no birds left in the forest, there were very few viable remnants left. And so most of the conservation work has been focused at 2,000 feet and above.”
In July, geographer Jonathan P. Price of the University of California at Davis and Warshauer of the USGS informed colleagues at the Hawai`i Conservation Conference that lowland and coastal forests are biologically rich and “surprisingly resilient.”
The two scientists tallied 263 plant species that have been reported in lowland forests set back from the coasts, including just over one-fourth of all the islands’ flowering plants. Nearly four out of five were endemic, they reported. In coastal forests, where ocean spray limits the flora to salt-tolerant species, the two found 136 species, more than half of them endemic, including 13 percent of all the known flowering plants.
These estimates may be low because biologists haven’t done much sampling in these forests, Price and Warshauer reported. They surveyed several coastal and lowland wet forest tracts and catalogued nine native species that had previously not been thought to grow at elevations below 200 meters. The wetter the site, the greater the plant variety, they reported.
“The growing list of relict sites represents all that is left of an originally rich portion of the Hawaiian flora,” they wrote in a conference abstract. “Analysis of these communities É may help guide the identification, protection and potential restoration of some of the better sites.”
That’s part of what Ostertag of UHH and her colleague Mike Wysong, a biologist with the Guard’s environmental services division, hope to achieve at Keaukaha. “We want to work on preserving an ecosystem that we don’t know much about,” says Ostertag. “It’s already pretty degraded and it’s going to be a little bit harder and our success rate may not be as high É but if we design our experiments carefully, we’ll at least learn something that can help in other places.”
Their work is part of a five-year, $2.4 million study, sponsored by the National Science Foundation. Under the grant, made to UHH, students from Ostertag’s classes and from the Hawai`i Community College in Hilo participate in the fieldwork.
The first step – a site survey and design of experimental treatments — began in August when a group of eight scientists, students and Guard biologists met to explore the triangular tract. It had just been fenced and contained about half a dozen wild pigs, which were to be shot by troops in training.
“What we’re looking at here is highly degraded lowland forest,” Wysong says. “Of course, lowland forest is not intact anywhere on the islands anymore, but there are remnants, and some parts of this area look really good.”
The dirt road that borders the triangle’s longest side was once part of the old Hawaiian Puna Trail, linking Hilo to settlements southeast of town. Along the roadside grow alien trees that are commonly considered pests: cecropia (trumpet tree), schefflera (umbrella or octopus tree), and the macaranga (also known as bingabing), with its enormous limp leaves.
A pair of towering old mango trees was probably planted to mark the trail, but otherwise the land has been left alone for more than a century, says Wendy Tolleson, an archaeologist who served for several years as the Guard’s cultural resources manager. The only known archaeological site is a platform that housed a roadworkers’ shed in the 1880s when the Puna Trail was widened.
The forest and surrounding land passed from the territory to the National Guard in 1914, the Army Corps of Engineers in the 1920s, the U.S. Navy in the 1930s, and back to the Guard in 1947. Over the years the Keaukaha base has housed a prison camp, a hospital, and a fuel depot for adjacent Lyman Field. It’s “just a fluke” that the forest, tucked into the corner farthest from the airfield, was never bulldozed, Tolleson says.
Roughly four-fifths of the tract has been invaded by members of the aggressive melastome family, from tree-sized specimens to creeping ground cover. The remainder is dominated by strawberry guava, one of Hawai`i’s most ubiquitous, intractable invaders. “There are alien overstory trees, understory trees, shrubs and herbs,” says Hughes. “In terms of restoration, you’ve got to deal with every one of those, which makes it a challenge.”
Towering over all the invaders are large, old `ohi`a trees, spaced several yards apart. These give an edge to restoration efforts at Keaukaha over other lowland forest sites where fast-growing alien trees have outgrown `ohi`a. “Anywhere the `ohi`a gets overtopped,” he says, the chance of restoration “is gone.”
As members of the group follow a transect line laid through the dense growth by Hawai`i Community College students Beth Barwise and Cynthia Thurkins, they come across small patches that resemble the lowland wet `ohi`a-lama forest of botany textbooks. Here large kolea trees have seedlings at their feet, some of which have become shoulder-high shrubs. Below the lama and kolea grow large hala, valued for their leathery leaves used in weaving mats and dozens of other essentials; mamaki, another useful Hawaiian plant; and kopiko, the native coffee, whose leaves are stippled on the underside with rows of tiny holes that resemble piko (belly buttons). The Hawaiian tree ferns, hapu`u, are here too, though few of them are taller than head-high and many are dead. Some now serve as nurse logs for `ohi`a seedlings.
Preliminary surveys suggest that the seedlings of all the native species except lama are surviving at least to shrub stage. The scientists aren’t sure whether the more detailed survey will confirm that finding and if so, why the lama seedlings are dying off. In experimental plots, they will try to determine the conditions in which lama and other native forest plants best reproduce. The experiments will involve removing aliens from different forest layers – the canopy, the understory, ground level, all levels, and none – to see what the effect is on native seedlings’ growth. In some areas, Wysong says, half to three-quarters of the forest canopy would go if all the aliens were removed. That poses the question of what effect the additional light would have on the remaining natives – would it favor them or the competing aliens?
Other plots may test the site’s suitability for native plants that are found in similar habitats, but not at Keaukaha. Among them are the pritchardia, the native palms, says Ostertag. A Crystal Ball
What will the restored forest look like?
“The truth is we don’t know for sure,” Ostertag says. “We just have guesses. We have a few examples (but) we don’t know the degree of diversity or homogeneity or even all the species.”
To get a better idea of what their work might yield, the KMR team troops down to a patch of forest in the state’s Keauohana Forest Reserve in Puna. There, Hughes has been studying the ecological effects of albizia, an introduced tree favored initially for its ability to fix nitrogen in Hawai`i’s nitrogen-poor soils.
The albizia invaded a swath of lava laid down in 1955, and have overtopped `ohi`a, the flow’s first colonizers. At about ten years old, the albizia are now 30 to 50 feet tall. On an adjacent 200- to 400-year-old flow, some albizia have become so massive that it would take four adults to encircle them with their arms.
But a bit deeper into the forest, at the base of a natural staircase of lava, the hikers enter a stand of nearly pristine native forest so lovely that they all fall silent. Tall, thin `ohi`a, clothed in shaggy gray bark, thrust their heads and narrow shoulders into the blue sky. At 30 to 50 feet tall, they are about 300 years old, according to Hughes’ estimate.
The outspread arms of lama trees are filled with birds’- nest ferns up to ten feet across. Healthy kopiko grow alongside and underneath the lamas. `Ie`ie vines embrace the `ohi`a, while native peperomia and thousands of other native plants carpet the forest floor. The only jarring note in the scene is off to one corner, where a handful of slender reddish-brown trunks – the vanguard of an invading force of strawberry guava. The invaders are not well established yet and still relatively easy to remove, say the botanists.
“This is what we would like KMR to look like,” says Wysong. “This is what we’re shooting for.”
Whether or not the Keaukaha forest ever resembles that at Keauohana, it needs to be self-sustaining, with only occasional weeding and other help from its caretakers, the scientists agree.
“What you want is the natives functioning,” Hughes says. “Otherwise what you have is a botanical garden, and that’s not what we’re after.”
“We don’t have the manpower to keep on tending it constantly,” Ostertag adds. “We just can’t do that. No one in Hawai’i can.”
Improving Nature’s Chances At Volcanoes Park
On some parts of the archipelago, the forces unleashed by the landscape’s transformation from native- to alien-dominated are so powerful that even the most expert and well-funded land managers, blessed with the clearest mandate to place conservation above all other goals, cannot keep up with the changes. That is the situation at Hawai`i Volcanoes National Park, where in the 1960s an invasion of North and South American grasses created a ceaseless cycle of fire in the dry `ohi`a woodlands of Mauna Loa.
Lava-sparked fire is one of the forces that created the isolated kipuka where many unique Hawaiian plants evolved. But fire was never a constant in the forests as it is in some parts of the American continent, where plants that re-seeded vigorously after a fire had a competitive advantage.
Tawny broomsedge and shaggy, red-tasseled beardgrass seedlings can sprout within three days of a fire that kills the native `ohi`a and pukiawe. And when the natives seeds do sprout, they grow but slowly. After a year they may be only two inches tall, dwarfed by grasses that can shoot up to a height of six feet.
The grasses create fuel loads of six tons an acre or more, encouraging more and hotter fires, says Park Service biologist Rhonda Loh. “With each successive fire you lose more and more native trees, and eventually you end up with a savannah dominated by non-native grasses.”
Instead of continually replanting fire-sensitive species only to watch them continually burn, park biologists are trying to use fire-tolerant native species to crowd the grasses into insignificance. The scientists have identified about 20 native species that grow well after fires. Just above the summit of Kilauea, they are planting 2.5 million seeds and 20,000 nursery-grown seedlings of these species in a 1,000-acre `ohi`a woodland decimated by a wildfire on June 30, 2000. It is the most extensive “active rehabilitation” project the park has ever undertaken, says Tunison, the park’s natural resource manager. The intention is not to restore what has been lost, but to replace it with something that, so far as the scientists know, never existed in Hawai`i until now: “A native plant community that can coexist with fire,” in Loh’s words.
The strategy is a sort of ecological jujitsu: acknowledging the inevitability of fire and of continued invasion by grasses, it uses the power of those alien elements to benefit native species rather than to conquer them. “We have to accept that the grasses are going to be part of this `ohi`a woodland ecosystem,” says project manager Loh, “but we don’t have to let them replace it.”
The work is based on research conducted in the 1990s by Stanford University ecologist Peter Vitousek and others that shows some Hawaiian plants reseed well after fires. Among them are koa, mamane, iliahi or sandalwood, ko`oko`olau, ilima and ohelo. These plants were present, but sparse in the dry `ohi`a forests, perhaps because of 100 years of goat grazing in the park, Loh says.
Park scientists decided they could use these plants to create a community that, like the grasses, would grow back more abundantly after fire. “The strategy is that once you get these plants established, they’ll mature and reproduce and create a seed bank in the soil much larger than we could ever hope to create,” she adds. “Maybe another 20 or 25 years later another fire will come through and they’ll top kill our individuals, but they’ll sprout at the base, and the seeds will be able to germinate after the grasses are gone. With each successive wildland fire you will get more and more of the native fire tolerant plants.
“It’s hard to say what ecosystem functions you’re going to retain, because I don’t think they’ve been well defined, but the hope is that we retain some elements of the native forest that was there.”
Rather than trying to blanket such a large area with new plantings, the researchers are creating 851 “nodes” of fire-tolerant natives. Each node is about a meter in diameter and is placed along one of a dozen different transects. The hope is that when the plants reproduce, they will radiate outward from these nodes.
Researchers have also been planting two dense firebreaks, each the length of four football fields, to protect the precious kipuka and a nearby golf course. Made up of mostly koa, with native shrubs and ferns planted beneath it, the firebreaks are intended to create shady, moist environments less susceptible to fire.
In late summer, the effects of the fire and of the restoration were obvious from the Mauna Loa Strip Road. From an `ohi`a forest where the trees were more or less intact, their trunks thrusting up through a thick carpet of tall red and ocher grasses, the landscape changed. Suddenly it became a ghost forest of leafless, dead `ohi`a, their lanky skeletons weathered to a pale silver. Resprouting grasses grew in scattered clumps about two feet tall. But just as tall, and vividly green amid the bleached-out tones of the burned zone, were young koa trees – some resprouting on their own, others sprouting from human-broadcast seeds.
Half-concealed by the grasses, the seedlings and saplings of mamane, koloa, na`ena`e, alani and other understory plants grew in circular patches. Native ferns, many with new fronds still tightly furled, filled the gaps. Young, tiny-leaved pukiawe lay close to the ground, the pale, delicately tapered tips of each branch flaring upward like miniature flames.
The three-year project is now in its final year, says Matthew Schwartz, in charge of propagation for the project. Costs are approaching $400,000 – not including the research on which the work is based or the many hundreds of volunteer days invested in it.
With more than 20,000 nursery-grown plants in the ground, survivorship is between 80 to 90 percent, except for sandalwood, which has about 40 percent survivorship. To compensate, project managers intend to plant sandalwood seeds directly into the ground.
Results so far are good enough to declare the project an initial success, Loh says, but adds: “the real rest will not be until the next wildfire comes.”
“If we can keep fire out of that area for 15 years then we’ll probably be successful in rehabilitating that site,” says Tunison. With the risk of fire minimized, the once-dominant `ohi`a may return, he adds, “but it’ll take a while.”
Park managers are so encouraged by the initial success that last month, they began trying the same strategy, using slightly different species, on about 500 of the 3,800 acres of mesic forest burned by lava in July and August.
This approach – which might be called ecosystem shifting rather than ecosystem restoration – is a departure from conventional notions of how restoration should be done. “If they knew what we were doing on the mainland, they’d probably be horrified,” Tunison says. Still, in his view, Hawai`i’s most damaged ecosystems can be healed only by working around alien plant species, rather than spending money and energy in a pitched, and wholly uncertain, battle against them.
In nearly intact areas, he says, land managers can rely on so-called “natural restoration,” which removes grazers, controls weeds and lets the native seed bank do the rest of the work. That strategy has been used on about 38,000 acres in the park and seems effective, “but we’ve taken it about as far as we can go,” he says.
Measuring Progress, Meter by Meter
“In the more altered ecosystems I think this rehabilitation approach is the only thing that’s going to work,” Tunison says. “We’ll have to figure out how to do it in a more dilute fashion over larger areas.”
Jack Ewel of the Forest Service agrees. “Right now we’re proceeding with forest restoration as an exercise in intensive horticulture, a square meter at a time,” he says. “But when we scale that up in Hawai`i and look at the thousands and tens of thousands and hundreds of thousands of acres” that have been gravely damaged, well, “it’s clear we’re going to need some new techniques, less expensive and less labor-intensive, that can be used on a broader scale.”
Some key questions need to be answered before landscape-scale restoration becomes practical. Ewel lists some of them: “Where are the weak spots in the life cycle of the invaders so we can attack them at an opportune time? What does it take to catalyze reproduction in native species? It’s clear they don’t do it every year.” Other problems, such as 150 years’ worth of soil loss caused by deforestation, “are engineering problems that we’re not going to solve overnight,” he adds.
Complicating matters in Ewel’s view is the fact that two of the major goals of restoration – conserving native plants in all their diversity, and ensuring that the restored areas can support a complete community of living things over decades, even centuries – are sometimes in conflict. To resolve that, he says, ecologists may have to compromise by making use of some non-native plants.
“If we were to remove invasive plant species from Hawai`i the islands would turn brown,” Ewel says. “A lot of these things are here to stay. I think we’re going to pay a very serious price if we don’t take advantage of the opportunity to plant some species that add nitrogen to the soil and prevent further erosion,” regardless of their origin.
To some, such talk is an echo of the philosophy espoused by state foresters at the turn of the 20th century, who, in an urgent effort to protect denuded watersheds, planted eucalyptus, albizia and other trees by the millions – many of them now regarded as pests.
Still, few would deny that extinctions have left some ecological niches vacant, that those vacancies have created serious gaps in many natural communities, and that the gaps aren’t likely to be filled through some miraculous re-creation of plants and animals that are gone.
For example, says Warshauer, “we need to get birds back as a dispersal agent, and the alien birds serve a function there, tooÉ Maybe selected alien birds might function in roles that were previously filled by natives, and maybe we ought to be thinking of them as surrogates.”
Because of the devastating losses the islands have suffered, Warshauer says, restoration “success” is a goal that, like enlightenment, must always be pursued but can never be attained.
“I will not live that long,” he says. “There’s no end point. We just aim for it. The essential thing is, whoever owns it, wherever it is, try to do whatever it takes to preserve as much as you can now.”
— Heather Dewar
Heather Dewar, environmental reporter for The Baltimore Sun, was this year’s visiting journalist with Environment Hawai`i.
Volume 13, Number 6 December 2002