Nearly 40 years ago, a tract of pristine ʻōhiʻa forest in Kalapana on Hawaiʻi Island was cut down. The trees were reduced to wood chips for a proposed biomass energy project. Now the trees are making a comeback — and battling it out for dominance.
Environmentalists considered the event a tragedy. But for U.S. Forest Service ecologist Flint Hughes, it was the perfect natural experiment.
"The area of forest that we're looking at was logged, the trees were removed, and the area was effectively bulldozed so that it was basically barren lava strewn with dead vegetation," Hughes said.
Roughly 900 acres of ʻōhiʻa were clear-cut for wood chips. At the time, researchers were unsure if native plants would ever return. That’s the question Hughes set out to answer.
He found that ʻōhiʻa were indeed coming back — but so were invasive tree species.
"My least favorite trees would have to be albizia and strawberry guava. I can’t stand to see them because I know what they represent. They represent the elbowing out of native species across our already stressed forests," Hughes told HPR.
Like the ʻōhiʻa, the albizia tree is a pioneer species. It thrives in light gaps and can quickly choke out native plants. A bird's-eye view of the clear-cut tract shows the patchwork succession of the forest as native species battle with invasives for dominance.
"If you look at the Google images of this area 10 years ago, you’ll see these patches of albizia distinct across this clear-cut area, and that’s where they got established," he said. "Fortunately, they were hindered in their expansion because ʻōhiʻa, uluhe, other things captured the surrounding site so they really couldn’t spread as much as they can in other instances."
In the shadow of the volcanic Kīlauea, the landscape of Kalapana is constantly remaking itself — and providing ample opportunity for the forests to evolve as well.
"In some ways, a new lava flow provides a great opportunity for native forests to reestablish in areas. But, on the other hand, you’ve gotta have seed source to fly into that area and land and begin to reestablish," Hughes said.
After the clear-cut, the neighboring intact forest acted as a seed source so that ʻōhiʻa could return to the area. Hughes says this forest could serve the same purpose for surrounding areas impacted by lava flows – if we clear a path.
"ʻŌhiʻa has the capacity to regenerate and grow and persist even after severe disturbance events but it has difficulty doing so in the presence of competitive weeds. And that’s why weed management in terms of forest management is crucial for our native forests," he said.
Hughes estimates that there are roughly 290 million individual ʻōhiʻa trees on Hawaiʻi Island. Even when you tally up the combined threats of deforestation, fungal pathogens like Rapid ʻŌhiʻa Death, and climate change, Hughes doubts we’ll lose ʻōhiʻa entirely.
What’s really at stake are the ecosystems in which ʻōhiʻa can thrive, and in turn, keep the environment healthy.
A version of this interview also aired on The Conversation on July 13, 2022. The Conversation airs weekdays at 11 a.m. on HPR-1.
