Mauna Loa forests, natural area reserves dodged lava bullet

When Mauna Loa began erupting late at night on Nov. 27 for the first time in 38 years, officials with the Hawai‘i Department of Land and Natural Resources anxiously watched to see where the spewing lava would go.

In the potential path of the destructive lava were several state forest reserves and natural area reserves filled with endangered species, their native habitat and years and millions of dollars spent on restoration work.

Less than 24 hours after the eruption started, the behavior of the fountaining lava — which was being propelled hundreds of feet into the air, sending flows down the slopes of the volcano’s Northeast Rift Zone and spewing volcanic gases and ash into the atmosphere — caused concern for Steve Bergfeld, the Hawai‘i Island Branch Chief for the state Division of Forestry and Wildlife.

He said in a news release that he was most worried about the Pu‘u Maka‘ala Natural Area Reserve on the mauna’s southeast side in the Puna and South Hilo districts.

If lava flowed into the 18,730-acre Pu‘u Maka‘ala reserve, years of restoration work and control of hoofed animals to create habitat for numerous endangered Hawaiian forest birds and re-establish native vegetation could have been erased.

Yes, the agency’s top priority is the safety and protection of life, property and public resources, but: “One of the areas we were most concerned about is the [natural area reserve]. There’s a lot of endangered species and really good forest habitat in Pu‘u Maka‘ala that we’d hate to see lost,” Bergfeld said.

Fortunately, the Department of Land and Natural Resources dodged a lava bullet — at least this time — as the eruption and its flows became focused on Mauna Loa’s northeast flank, where they would stay for about two weeks until Dec. 10 when the lava supplying fissure 3, the main vent, ceased.

Lava never reached Pu‘u Maka‘ala. It was a huge relief, said Nick Agorastos, Natural Area Reserve Program manager for Hawai‘i Island. Bergfeld agreed, saying most — if not all Big Island residents — were relieved for many reasons that the eruption paused.

The concern was valid. Previous Mauna Loa eruptions in 1942 and 1984 surrounded the reserve with vast expanses of hardened lava right outside the fencing surrounding the area meant to keep ungulates (hoofed animals) out. Agorastos was concerned right away when the 2022 eruption began.

“Many of the resources found in Pu‘u Maka‘ala are irreplaceable, even if they are covered over by a natural process like Hawaiian volcanism that has shaped these lands for millennia,” he said after the lava flows ceased. “The natural processes that created these marvels of nature are either disrupted and missing for a whole laundry list of reasons, so once these treasures are gone, they are likely gone for good and not likely to return.”

The diversity found in the state’s natural area reserves range from marine and coastal environments to lava flows, tropical rain forests and even an alpine desert. Within these areas rare endemic plants and animals, many of which are on the edge of extinction.

Pu‘u Maka‘ala is home to the endangered ʻAkiapolaʻau, ‘Ākepa, ‘Alawī and Nēnē as well as other native Hawai‘i bird species including the ʻIʻiwi, ʻApapane, ‘Amakihi, ‘Elepaio, ʻŌmaʻo, ‘Io and Pueo. Kōlea also can be found in the reserve.

Native vegetation growing there includes Koa/ʻŌhiʻa montane wet forest, ʻŌhiʻa/Hāpuʻu m­­­­­­­­­­ontane wet forest, montane west grassland and Carex alligata, or the Hawaiian sedge.

The statewide Natural Area Reserves System was established to preserve in perpetuity specific land and water areas that are as unchanged as possible and support natural flora and fauna as well as Hawai‘i geological sites. There are reserves on five islands, all of which encompass the state’s most unique ecosystems.

In a nutshell, the natural reserves are Department of Land and Natural Resources-managed lands with significant native ecosystems in place, Bergfeld said.

Pu‘u Maka‘ala was designated and established in 1981. Active management of the reserve began about 1990, with the first of many ungulate-free fenced units completed in 1995 and expanded since. Roughly 12,500 acres are now free of ungulates. The primary ungulates of concern at Pu‘u Maka‘ala are feral pigs; although feral goats, feral sheep and mouflon sheep are found in adjacent lands and could potentially become a threat in the future, Agorastos said.

Feral pigs destroy native vegetation and prevent its regeneration by eating, trampling and digging up plants. The animals also can accelerate the invasion of weed species by disturbing native ground cover and dispersing seeds on their coats and in their droppings. In addition, pig wallows and Hāpu’u trunks that have been hollowed out by the animals provide mosquito-breeding sites that can promote the spread of avian diseases such as avian malaria and pox — the two most deadly diseases for Hawai’i’s native forest birds.

The continued presence of feral pigs in the reserve contributes to loss of native plants and loss of ground cover that even adversely affects groundwater retention.

“Over three decades of active management have been invested in Pu‘u Maka‘ala [Natural Area Reserve],” Agorastos said, adding that a complete cost estimate of the stewardship, preservation and protection efforts in that 30 years since the establishment of the reserve would be difficult. “However, there has been roughly $11.2 million in fencing done since the 1990s, with a comparable and combined amount in weed control, predator control, rare plant and bird management, fire and infrastructure maintenance and other watershed protection measures.”

Forests take many decades to mature, so any loss of critical watershed forests such as Pu‘u Maka‘ala is essentially permanent. Agorastos started making calls shortly after the most recent Mauna Loa eruption started to find out where the lava was headed, knowing that if push came to shove, many of the irreplaceable resources the state has in the reserve could have been saved if they were in jeopardy.

He said plans were being made for collecting seeds and propagules of known rare plants in Pu‘u Maka‘ala and the removal of infrastructure that could be physically and appropriately moved, such as water tanks and fire equipment, rodent traps, stored supplies and other scientific monitoring equipment.

“We’ve spent a lot of years working with Three Mountain Alliance and its watershed-protection predecessor fencing and removing ungulates from the area,” Bergfeld said, adding the state Land Department also has done a great deal of plant and endangered species restoration work and monitoring in the reserve. “It’s been free of ungulates for many years and the forest is recovering well.”

“After all this work, we didn’t want to start over,” Agorastos said in the same release.

Early in the week of Dec. 8, field teams with the Department of Land and Natural Resources Division of Forestry and Wildlife were running mist net lines to capture native forest birds in Pu‘u Maka‘ala, including ʻŌmaʻo. The birds are found there and in the adjoining 50,000-acre Mauna Loa Forest Reserve on the northeast side of the mountain, where the recent eruption was centered, in the Hāmākua and North Hilo districts.

Bret Nainoa Mossman, avian ecologist for the Hawai‘i Island Natural Area Reserve Program, said ‘Ōmaʻo are exciting birds because they’re one of the few remaining native species that primarily eat fruit.

“So they’re really important for spreading native plant seeds around the forest,” Mossman said in the news release, adding that becomes doubly important as the birds spread seeds across lava fields. Much of the Mauna Loa Forest Reserve is covered in lava from previous eruptions.

The field teams discovered the ‘Ōmaʻo population on the volcano was still hopping around near fissure 3 during the eruption.

“They’re just living their best life up in that high-elevation zone,” Mossman said.

While they were likely moving away from the active flows, vog was having some effect. Mossman said field cameras were seeing the birds near burrows of the endangered ‘U‘au, so he speculated they could have been going into burrows to shelter from the worst of the volcanic fog.

Several state Land Department areas were shuttered during the eruption, with only the Mauna Loa Forest Reserve continuing to be closed. Bergfeld said it will be reopened once lava cools down, which could take several months.

And while the Pu‘u Maka‘ala reserve was untouched by Madam Pele this time around, how she impacted the Mauna Loa Forest Reserve will need to be evaluated. Fortunately, it looks like most of the impacted land in that reserve was former lava flows.