- This three-part Mongabay mini-series examines grassroots forest restoration projects carried out within isolated island ecosystems — whether those islands are surrounded by water as on the Big Island of Hawai‘i, or cloud forest mountaintop habitat encircled by lowlands in Costa Rica, or forest patches hemmed in by human development in Brazil.
- Reforestation of degraded island habitat is a first step toward restoring biodiversity made rare by isolation, and to mitigating climate threats. Though limited in size, island habitats can be prime candidates for reforestation because extinctions are typically much higher on isolated habitat islands than in more extensive ecosystems.
- Scientists mostly agree that the larger the forest island habitat, the greater its biodiversity, and the more resilient that forest system will be against climate change. Forests also store more carbon than degraded agricultural lands, and add moisture to soils and the atmosphere as a hedge against global warming-intensified drought.
- The projects featured in this series are small in size, but if scaled up could become big forest nature-based climate solutions. In this first story, two ukulele makers strive to save Hawai‘i’s koa tree, found nowhere else in the world. In the process they restore a biodiverse tropical forest on the slopes of the Big Island’s Mauna Loa volcano.
This story is the first article of a three-part Mongabay mini-series on island habitat forest restoration projects. Read Part Two and Part Three.
It started in a very Hawaiian way: with the ukulele. Husband and wife Joe and Kristen Souza, spent decades building a successful ukulele-crafting business, known as Kanile’a ‘Ukulele, on the island of O‘ahu. Many of their instruments were carved using the native koa tree (Acacia koa), found nowhere else in the world. As Kristen told me, “It’s the most beautiful wood … and it has great tonal properties.”
For many years, the couple’s relationship with the koa was purely instrumental. Then, on a trip to the island of Kaua‘i, the Souzas noted the drastic contrast between an overgrazed cattle pasture and adjacent native tropical forest.
“We said, ‘Wouldn’t it be cool to plant a koa tree for every ukulele we built?’ We’re like, ‘Yes, that’d be really nice.’ And that was the end of that conversation,” recalls Kristen. But those words stuck with them, unacted on until 2014.
That’s when Kristen visited a degraded 39-hectare (96-acre) property on the island of Hawai‘i, situated at an elevation of 1,200 meters (4,000 feet) on the slopes of Mauna Loa, one of the Big Island’s active volcanos. Shortly after, the couple decided to buy it. Their plan: to grow koa trees and make a forest from scratch.
Their land, once cloaked in biodiverse tropical forest, had long since been denuded by grazing livestock. “The forest was trying to come back. But the koa is very, very sweet, so it’s like candy to [hungry animals]. Every time a little seedling would pop up, these cattle and horses and llamas and buffalo and … pigs would ravage the new seedlings. So, the forest wasn’t able to return.”
With property deed in hand, they launched their own NGO to help organize the restoration, optimistically dubbed Saving Hawai‘i’s Forests.
All this was easy compared to what lay ahead. Years of trial and error taught the couple just how challenging — and rewarding — rewilding a small piece of island habitat could be. They persisted, planted trees, and over time lured back threatened species, including one critically endangered tropical bird.
Extinction on steroids
The Hawaiian Islands, one the world’s most far-flung island archipelagos, have become known as the extinction capital of the world. Ninety-five of their original 142 bird species have gone extinct since humans first arrived. With 11 more species now among the missing, it’s possible three-fourths of the islands’ birds are already gone.
Scientists believe an additional 100 plants have gone extinct, with 200 plant species down to just 50 or so individuals in the wild. Invertebrates are in trouble too, but lack of baseline data makes it hard to know how many species have vanished. A recent study hints at what’s likely been lost, cataloging the survival of only 15 land snails out of 325 species.
To understand why Hawai‘i and other isolated islands have lost so much, one has to understand how island habitats work. The discipline of island biogeography, or insular biogeography, was a field greatly advanced in the 1960s by ecologist Robert H. MacArthur and biologist E.O. Wilson. An insular environment is defined as an area of habitat suitable to a particular ecosystem, but surrounded by unsuitable habitat. This can be an island isolated by ocean, a mountaintop encircled by lowland, or wildland hemmed in by human-altered landscape (forest restoration in all three of these insular habitat types are explored in this Mongabay mini-series).
As small dabs of land isolated in a vast sea, ocean islands are colonized over millennia by floating seeds, flying birds and small animal castaways hanging onto flotsam and jetsam. After arrival, these isolated specimens continue evolving and over time radiate into new species. As a collective, they form unique ecosystems found nowhere else on Earth, made up of weird and wonderful evolutionary experiments.
But this species radiation and richness also makes island biodiversity especially vulnerable. First because the smaller the habitat, the fewer species can occupy it, and the more likely extinctions become, a dynamic defined as the “species-area relationship.” And second, because islands house species ideally evolved for where they live, but not adapted to fend off invasions by outside invaders. A third reason has only arisen recently: climate change.
When humans first reached Hawai‘i — the date is still debated, but likely occurred around 1,000 years ago — they possibly brought other animals with them, including pigs and rats. The arrival of human hunters and invasive species led to the first round of extinctions. The loss of biodiversity sped up with the arrival of European colonizers. In 1826, a ship accidentally brought disease-carrying mosquitoes to Hawai‘i. Deforestation and exploding livestock populations devastated island ecosystems through the 19th century.
Those losses continue today. From 2002 to 2021, the Hawaiian archipelago lost 1,390 hectares (3,435 acres) of its tropical primary forest, according to Global Forest Watch. Species that haven’t yet vanished, like the koa tree, are rarer than ever and at risk of becoming the next island extinction.
For Kristen and Joe Souza, their “aha!” moment came when they realized their beloved koa tree was fast becoming a very scarce commodity. “It’s being taken off of the islands to different manufacturing companies, whether it’s for furniture or guitars,” Kristen explained.
With the denuded montane property in hand, the new NGO conducted an environmental assessment and archaeological study. Then they fenced off the land to keep out roaming livestock.
Three years in, they started putting out seedlings. “We didn’t have any experience in planting or botany,” remembers Kristen, but that didn’t deter the pair: they began by planting 5,000 koa trees.
“We planted a little too close,” she recalls of the first round. “We did about 10 feet [3 m] on center, which for koa tree is way too close … Now we’ve learned … We spread them out anywhere from 25 to 40 feet [8-12 m] apart.” As a canopy tree, the koa needs more space to spread.
After their first koa experiments, the NGO set about recreating a Hawaiian rainforest, introducing other native plant species including ‘iliahi (Santalum freycinetianum), māmaki (Pipturus albidus), pilo (Kadua laxiflora), māmane (Sophora chrysophylla), hō‘awa (Pittosporum hosmeri), aʻaliʻi (Dodonaea viscosa), ‘ūlei (Osteomeles anthyllidifolia), manono (Hedyotis terminalis), and ‘ilima (Sida fallax).
The group struggled against many challenges, ranging from the difficulty of planting in volcanic rock, to keeping fences strong against hungry livestock. But the biggest struggle was intruding invasive plants. Repeated clearing “takes probably 70% of our time,” Kristen said. “As soon as it rains, they take over. They grow faster than the natives.”
Invasive species pose a major biodiversity threat around the world, but as with so many things, they are especially challenging on islands, where the ecosystem has evolved in isolation. Species living on islands often have little to no protection against invasives.
But as the years went by, and the native plantings thrived, Kristen says the NGO has grown more confident, but there’s always more to learn. “I’ll never know everything [and] whenever we have different experts come and visit, they always teach us something new, but I do believe that we have probably a 90% grasp on what we’re doing.”
Although a small project, this flourishing native forest will likely have a positive local climate impact — albeit a limited one. Research has shown that native forests composed of multiple species store more carbon and do so more reliably than either pastureland or planted forests of non-native species. Restored tropical forests also provide shade for wildlife, protecting them from rising temperatures. Forest soils also hold rainwater better than degraded land, providing a hedge against climate change-induced drought.
These climate impacts could be expanded greatly if Saving Hawai‘i’s Forests is able to achieve its future restoration goals, or if it inspires similar projects across the Hawaiian archipelago.
To date, the NGO has planted 40,000 trees on the 39-hectare property, but its ambitions are much, much bigger. Its ultimate objective: to plant 1.95 million trees — a goal of 10,000 trees for every country on Earth. But to get there the organization and its property must grow. With that in mind, the group purchased another degraded property on Mauna Loa’s slope, and is in the midst of preparing the 66-hectare (162-acre) plot for planting.
The constant challenge, as with most small reforestation projects, is finding funding.
“We do need a lot of support. That’s for sure,” Kristen says, adding, “We want to have a staff. We would like to [hire people] to run the greenhouse full time, and … do invasive removal and planting, and help different landowners.” At present, everything is done primarily by volunteers.
The NGO has turned to creative ways to raise money. It has partnered with local companies and invited donors to sponsor a tree. In October, the group will hold a sweepstakes: For each $10 gift, donors get a chance to win a custom guitar or ukulele.
The money, Kristen half-jokes, could go toward dealing decisively with fast-spreading invasive species. “I don’t ask for much, just a chipper with a truck and a trailer!”
The group’s volunteer base continues to grow. The oldest is 96 years old. The youngest are of school age. The NGO also partners with a local addiction treatment center called Habilitat. Chosen residents travel to the forest to work six days at a stretch.
“We teach them any job that needs doing, whether it’s invasive removal, working in the greenhouse, planting, seed-gathering, weed-whacking, pruning. Everything!” Kristen says. “It’s all workforce development.”
Addiction center residents also benefit from their close connections with the land. “They have that time away … in a forest where there’s nobody for miles,” Kristen says. During their six days of work, they also do other self-healing practices, such as meditation and healthy food preparation.
The return of life
Those visiting and working in the restored forest are often rewarded with wildlife sightings. “We’ve seen the birds return,” Kristen says. “We’ve seen the ʻio, which is the native hawk [Buteo solitarius] and the palila [Loxioides bailleui], all the native birds [come back]. You used to just see them sporadically here and there, but now, because of all of the trees, [they’re] returning.”
The ‘io, or Hawaiian hawk, is listed as near threatened on the IUCN Red List, while the palila, one of the famed Hawaiian honeycreepers, is critically endangered. It’s believed fewer than 2,000 palila survive today.
Three other honeycreepers are found in the new forest: the ʻapapane (Himatione sanguinea), the Hawaiʻi ʻamakihi (Chlorodrepanis virens), and the ʻiʻiwi (Drepanis coccinea); the last is considered vulnerable. The restored forest has also become home to the pueo (Asio flammeus sandwichensis), a native owl, and the Hawaiʻi ʻelepaio (Chasiempis sandwichensis), a flycatcher listed as vulnerable.
And it’s not only birds. Kristen has seen a native spider species return, known as the nanana makakiʻi (Theridion grallator), a species made truly distinct by what looks like a smiley-face emoji on its back. And there’s also the pulelehua (Vanessa tameamea), one of only two native butterfly species found in Hawai’i, currently listed as vulnerable. That’s a remarkable density of threatened species occurring in just 39 hectares.
More changes may be coming to this part of the Big Island: Kristen says the state government has increasingly shown interest in forest restoration on Manua Loa’s slopes as well.
“[The forest] just sings,” she says, an appropriate observation considering this project began with the ukulele. “It’s unbelievable!”
Banner image: The vulnerable ʻiʻiwi (Drepanis coccinea), a honeycreeper found in the new forest. Image by Gregory “Slobirdr” Smith via Flickr (CC BY-SA 2.0).
Read Part Two:
Mountain islands: Restoring a transitional cloud forest in Costa Rica
Régnier, C., Bouchet, P., Hayes, K. A., Yeung, N. W., Christensen, C. C., Chung, D. J., … & Cowie, R. H. (2015). Extinction in a hyperdiverse endemic Hawaiian land snail family and implications for the underestimation of invertebrate extinction. Conservation Biology, 29(6), 1715-1723. doi:10.1111/cobi.12565
Hanski, I., Zurita, G. A., Bellocq, M. I., & Rybicki, J. (2013). Species–fragmented area relationship. Proceedings of the National Academy of Sciences, 110(31), 12715-12720. doi:10.1073/pnas.1311491110
Lewis, S. L., Wheeler, C. E., Mitchard, E. T., & Koch, A. (2019). Restoring natural forests is the best way to remove atmospheric carbon. Nature, 568(7750), 25-28. doi:10.1038/d41586-019-01026-8
Osuri, A. M., Gopal, A., Raman, T. S., DeFries, R., Cook-Patton, S. C., & Naeem, S. (2020). Greater stability of carbon capture in species-rich natural forests compared to species-poor plantations. Environmental Research Letters, 15(3), 034011. doi:10.1088/1748-9326/ab5f75
FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.