How do you restore Hawai`i’s dryland forests?
The question is a hard one to answer. Because so little is left of the forest types that once blanketed the islands’ leeward slopes, any restoration is bound to involve a level of creativity that might discomfit purists. Then, too, there’s the absolute, unyielding fact that centuries of human habitation have irrevocably altered the landscape, soils, and rainfall patterns in ways that mean restoration will be, of necessity, an uphill and constant struggle.
But at the fifth annual Nahelehele dryland forest symposium, held in February, the mood was upbeat. The symposium, sponsored by Ka`ahahui `o ka Nahelehele, a non-profit established to promote protection and restoration of dryland forests in Hawai`i, featured speaker after speaker discussing approaches to bringing native vegetation back to areas ranging in size from a few dozen acres to thousands.
One of the most ambitious dryland forest restoration efforts in the state is the Pelekane Bay watershed project, part of the larger Kohala Watershed Partnership. Stretching from Kawaihae east to the summit of the Kohala mountains, the project involves protecting 6,000 acres from goats by erecting some 18 miles of goat-proof fence around fields of largely invasive grasses, installing more than 10 miles of drip irrigation line, planting 30,000-plus seedlings – trees, shrubs, groundcover – representing more than 30 different native species. Small enclosures, put up during the Works Progress Administration days of the Great Depression, have protected postage-stamp remnants of koaia-dominated native vegetation in some of the gulches. These have provided seed for many of the new plantings and serve as a vision of what used to be – and could yet be.
Plans for the project had been developed nearly 20 years ago, but no funds were available until the Kohala Watershed Partnership won a grant from the National Oceanic and Atmospheric Administration, under the American Recovery and Reinvestment Act (ARRA). With the $2.9 million award, the Pelekane Bay project was off and running, under the direction of Melora Purell, coordinator of the larger Kohala Watershed Partnership.
As Purell explained during the symposium, the entire effort was directed toward “addressing issues on the watershed that led to sediment in the bay.” Much of the bay was destroyed when Kawaihae Harbor was built. What remains has been so burdened by sediment from upslope areas that an ancient shark heiau, once under 10 feet of water, is now completely covered in silt.
While the justification for the NOAA award was to restore coastal values, Purell said, the work that the project undertook served any number of different purposes as well. “We could have had a different objective, such as restoring native forests – which we’re doing – or increasing moisture in the soil, and we would still achieve the same result from all those actions,” she told the group. In addition to fencing, planting, and irrigation, the project also installed more than 90 sediment-check dams downstream (each capable of holding back 10 tons of sediment) and treated 13 acres of bare soil with fabric seeded with native plants and grasses.
At the time the project began, in mid-2009, the area was experiencing exceptional (category D4) drought. “Our plan was to plant in the winter,” Purell said. “We put 1,200 plants in the ground and waited for rain. It never came. We ended up using backpack sprayers and the crew spent three days a week watering. So we went to Plan B, a temporary irrigation system, which then became a much larger-scale system. So now we have around 32,000 plants in the ground, and every single one of them is on irrigation.”
As for the exotic grasses that still cover the slopes, Purell said, “we decided to address this by replacing fire-prone species over time with natives.” For now, the grasses and other weedy species provide the young seedlings with some shelter from the famous Kohala winds and also hold down soil that otherwise would be contributing to the sedimentation problems of Pelekane Bay.
In February, the NOAA-funded part of the project was completed. What will happen now? Purell was asked.
“What we were able to build with the stimulus money was a large, firm foundation. We hope funders like NOAA will build, little by little,” she replied. “The Hawai`i Community Foundation got NOAA money for watershed restoration, which provided us with a small grant to continue our work, to maintain infrastructure, water plants, and check the fence.”
Over the long term, with the trees maturing, she said, “our hope is that with the trees evaporating water into the atmosphere, the area will be more humid and the cloud line will move down the Kohala Mountain. There’s an old expression, the rain follows the forest. How long that will take, how big the trees will need to be… we simply don’t know.”
Waikoloa Dry Forest
Driving down Waikoloa Road, past the golf course and condos and shops of Waikoloa Village, one might never guess that the densest wild population of the endangered uhiuhi tree is only a stone’s throw away. Just 50 uhiuhi (Caesalpinia kavaiensis) are known to exist in the wild; 10 of them are found within the 275 acres of the Waikoloa Dry Forest Recovery Project, and three more are close by.
Dave Faucette, who is the volunteer manager of the project, gave an overview of its young life at the Kona symposium.
“Around 2003, several Waikoloa residents became aware of the sale of mature wiliwili trees [Erythrina sandwicensis] for resort landscapes… They began lobbying the [Waikoloa] Village Association to stop the practice,” Faucette said. Not long afterward, Lyman Perry, a botanist with the Department of Land and Natural Resources, was invited to survey the area; to the surprise of all involved, Perry discovered the hitherto unknown population of uhiuhi as well as nearly 100 wiliwili, several of them estimated to be hundreds of years old.
The Village Association then stopped mining the area for landscape trees and allowed the Waikoloa Village Outdoor Circle “to begin to undertake stewardship of the uhiuhi trees,” Faucette continued. They hired people to remove the dry grasses from around the base of each uhiuhi, as well as from 25 wiliwili, thereby reducing the risk that grass-fueled fires would harm the trees. After applying for and receiving several grants to undertake more systematic restoration of the area with native vegetation, the Outdoor Circle recently signed a 15-year lease for the area. And with the Village Association’s permission, the group also fosters protection of the three uhiuhi just beyond the boundaries of the project area.
Fire is a constant threat, Faucette said, with a blaze in 2007 burning around 35 percent of the area. Goats, too, will kill young plants with their browsing and kill prospects of any natural regeneration. Many of the goats that once roamed the area have been taken out, but it will take completion of the perimeter fence to make sure that new plantings are protected.
Other challenges Faucette identified include the “sea of fountain grass” remaining in the areas of the project yet to be addressed and the wiliwili gall wasp. Although the parasitoid wasp released as a biocontrol agent for the gall wasp has tempered the gall wasp’s devastation, almost every tree still shows signs of ongoing gall wasp presence.
Finally, there’s the human element, Faucette noted. With uhiuhi valued for its dense, hard wood, people used to come in and cut off limbs, leaving trees scarred, disfigured, and vulnerable to disease.
The Natural Resource Conservation Service has given the project $310,500 and the state Department of Land and Natural Resources is providing $430,000 over 10 years through its Forest Stewardship Program.
Progress is slow but clearly visible. Faucette and others clear the fountain grass fr
om the `a`a clinker substrate by mowing it down and poisoning the remaining tufts. The ubiquitous kiawe (mesquite) trees are trimmed back so as to provide dappled sunlight for the new native plantings. There is no soil to speak of, so when native seedlings are planted, each is given a bed of woodchips and soil mix as it is placed into a puka of the a`a lava that covers the ground. Further protection from the goats is provided by wire cages Faucette builds around each new arrival. Watering is done with a backpack sprayer.
The loving care the plants receive is rewarded with robust growth. On the field trip to the area preceding the conference, dozens of natives were flush with new vegetation and practically bursting out of their cages. Like a proud father, Faucette rattled off their names: hibiscadelphus, alahe`e, aweoweo, hau, akia, ilima, lama, a`ali`i, hoawa… Not all are known to have grown in this area, but Faucette is hopeful that the survivors in this mix will, in the long haul, yield a healthy, self-sustaining landscape.
As part of the project, the Waikoloa Village Outdoor Circle has initiated what it calls the Waikoloa Future Foresters Program. A local teacher has developed a curriculum, and “every second Saturday,” Faucette said, “we head into the classroom, go through the lesson she’s prepared, then put it into practice in the field. We want to instill in them an environmental ethos they can carry forward. They’re all local kids, living only a mile away from the forest. They can walk there.”
Waikoloa and Pelekane Bay are just two of dozens of dryland restoration projects across the state. To name but a few: On Maui, Art Medeiros has been spearheading restoration at Auwahi, on the leeward slope of Haleakala, for years, with noteworthy results. Small areas of Pu`uwa`wa`a and Ka`upulehu on the Big Island have been fenced off for decades. At Palamanui, 55 acres in an area designated for urban development have been set aside for preservation of a remnant dry forest that is astonishingly intact. At the back of Makua Valley, on O`ahu, the U.S. Army is working to protect and restore native dry forest. Lana`i has Kanepu`u preserve.
The obstacles are daunting. Jonathan Price, a professor in the Department of Geography and Environmental Studies at the University of Hawai`i at Hilo, spoke on the topic of climate change. After describing the dramatic decline in Hawaiian flora and fauna, especially over the last century, Price noted that the “main thing to think about is … change is upon us. And it didn’t come from a tailpipe, cement factory, or powerplant. Instead, it came from a lot of the things we’re familiar with from having to deal with on a daily basis. Collectively, they’re called stressors: habitat loss, invasive plants, feral ungulates, fire, rats, mammalian predators. They all combine to create changes – fairly dramatic changes.”
“All this makes us think about climate change in a particular way,” he continued, “but this” – climate change – “is 100 years from now. I’m tempted to say that I’m not worried about that now. We have more burning issues today.” To illustrate his point, Price pulled up a cartoon of a burning house, with one fireman saying to another, “we need to sit down and figure out what to do about this termite problem.”
Still, Price would be the last to say that the “termite problem” – climate change – is too far off to worry about. Indeed, he and colleagues in the UH system and government agencies are trying to figure out, on a fine scale, just how climate change models will play out regionally. The models can then be compared with current climate patterns, and management efforts can be integrated with those predictions.
Already the research is showing an increasing slope in average temperatures over the last 30 years as compared to the slope over the last century, Price noted. What’s more, the rise in temperatures is more pronounced at high-elevation sites than low-elevation ones.
In what are now the driest areas of the state, Price said, the models predict a decrease in rainfall during the wet season (winter). The frontal systems that bring winter storms are expected to come down less often in the future, he noted, and “this means drought, especially for leeward sites.”
Dry-season precipitation is expected to increase “just very slightly,” Price said, but with current precipitation being “close to nothing,” the overall impact will be a net decrease in annual rainfall.
Hawai`i will also lose climates at high elevations, where the cool climate that now exists will disappear. With a rise of 3 degrees Celsius predicted at the summit of Mauna Kea, Price said, “the coldest area won’t exist.” Elsewhere, too, changing patterns of precipitation and temperature mean existing combinations of these elements may disappear as well, he said.
At the lowest elevations, “we will have a new climate … a climate that hasn’t existed for millions of years,” he said.
For some plants, the change could be a boon. Drawing a lesson from past warming trends, Price noted that in eastern North America, after the last glacial period, certain tree species expanded their habitat rapidly, arriving in northern areas thousands of years ahead of species that shifted at much slower rates. As a result, he said, “we have forest types today with a mix of species that didn’t exist before.”
How those species were able to respond depended on their unique characteristics. Oaks could disperse rapidly, with their acorns being easily transported by squirrels and birds. “Species like oak are on the A train,” Price said, “moving north at a very fast pace.” Hemlock, on the other hand, responded much more slowly.
In Hawai`i, the same behavior may be expected in the response of different species to changing temperatures and weather patterns. “Look at lama and Christmasberry,” Price said, referring to a native dry forest tree and an invasive shrub, respectively. Both occupy the same habitat now, but Christmasberry produces many more fruits per tree than lama. And while the dispersability is high for Christmasberry, with thousands of small seeds, it is only moderate for lama – and, with the birds that used to disperse the large lama seeds now extinct in the wild (the `alala, most importantly), functional dispersability is actually very low.
Furthermore, even without an overall change in annual rainfall, variability in the seasonality of rain could also be a problem, Price said. “We have some species very attuned to seasonality,” he said. “Wiliwili, for example, leafs out in winter. If rains come in the summer, it could put wiliwili at a disadvantage.”
Later, Price emphasized the uncertainty that inevitably accompanies any discussion of the impacts of climate change. “Many of the projections are fairly uncertain,” he wrote in an email to Environment Hawai`i, “although in some cases, we are seeing these changes occurring even now.”
Regardless of the lack of certainty, the best way to deal with future challenges, Price suggested, was with protection, pre-emption, and positivity.
Those areas most in need of protection, he said, were the “gradients,” areas where different climates are very close together. Examples he cited were Waimea Canyon (in Kaua`i); Kanaio, Auwahi, and Lihau mountain (Maui); and Pu`uwa`awa`a (Big Island). In each of these cases, the dry forest is adjacent to mesic areas that may dry out: “dry forest areas have the seeds of the future,” Price said.
Pre-emption, Price went on to say, “is the idea that we need to detect invasives and remove incipient populations, control future source populations, and reduce alien sources of dispersal and disturbance (especially feral ungulates).” Pre-emptive restoration of native species is also required. For example, Price said, “if `alala are not here, we need to replace them.”
Finally, positivity is essential. “We are N
OT doomed,” Price said. “Hawaiian dry forest climates will continue to exist, and even expand in some cases. Proper management can ensure these forests persist.”
— Patricia Tummons
Volume 21, Number 9 April 2011