Restoring Habitat Through Effective Management
Hakalau Forest National Wildlife Refuge’s goals are to aid in the recovery of endangered forest birds and plants, and restore their habitat. Current efforts are focused in three areas.
Restoring the native forest - Since 1989, almost 400,000 native plants have been out-planted at the Hakalau Forest Unit. These include common but important rainforest community elements such as koa and ‘ōhi‘a, and understory species such as ‘ākala, kōlea, ‘ōhelo, ‘ōlapa, pilo, and pūkeawe, as well as the endangered haha and ‘ōhā wai. Each year over 20,000 plants are grown at the on-site refuge greenhouse. Seeds are collected on site, germinated, propagated and transplanted by hardworking volunteers supervised by the refuge horticulturist.
The refuge has been concentrating on reforesting the upper elevation open pastures areas to increase available habitat for native birds and plants. With the looming threat of global climate change, many native forest birds and plants are at risk of extinction. As alien mosquitoes (disease vectors for avian malaria and pox) become acclimated to higher elevations due to warmer climates, forest bird extinctions may occur as native birds run out of disease free habitat at the higher elevations. Endangered plants are incapable of rapidly changing their genetically programmed environmental limiting factors in response to climate change. By elevationally expanding the forest upward, and increasing forest habitat area, the refuge hopes to prevent future extinctions and aid in the recovery of endangered species.
To accomplish this daunting task, the refuge has been reforesting the upper pastures since 1989. For koa planting, the refuge staff uses a D-5 bulldozer, with a mini-blade attachment about 1 meter wide, to create 1 meter square grass free plots in rows about 4 meters apart throughout the area to be planted. Young koa trees about 1 foot tall, grown in plastic dibble tubes at the refuge greenhouse, are then planted by volunteers. Each plant is fertilized with a high phosphorus complete fertilizer. At the highest elevations, because of the heightened frost damage to koa less than 1 meter tall during the winter months, frost deterrent devices, 1 meter square shade cloth stretched between two pieces of lath for support, are placed on the east side of the seedlings to reduce mortality. The koa grows rapidly, reaching about 5 meters, with canopy closure, within about 6-8 years. At this time, understory species are planted to create a diversity in the understory. Koa alone will not eliminate the exotic grass ground cover as shade tolerant Kikuyu and Ehrharta continue to grow under canopy. To reduce competition for understory plantings, 1 meter scrapes, by hand with a pick-mattocks are made before planting. A power auger is used to drill the planting hole, as the understory plants are grown in 4 inch pots to maximize size.
Documenting the status of biological resources - The health of native plant and animal populations and their responses to management efforts are constantly being monitored. Forest bird surveys, feral ungulate surveys, endangered plant monitoring, vegetation recruitment plots, invertebrate surveys, and weed surveys are methods used to assess the status of plants and animals and their habitat. Research is also underway to identify the factors responsible for the decline of particular native plants and animals and to determine how to reverse the downtrends.
In koa plots planted in the early 1990’s and planted with understory plants in the late 1990’s, we currently see a reduction of grasses and an accumulation of leaf litter. Many of the understory plants are now 3 or more meters tall and are flowering and fruiting. Ferns have begun to grow in the leaf litter, further reducing the grass cover. The forest habitat is coming back, and the “proof in the pudding” is the return of the native forest birds to an area that was open pasture just 20 years ago. Many of the common species, ‘apapane, ‘i‘iwi, ‘elepaio, and ‘amakihi are seen regularly within the replanted areas. Two of the refuges three endangered forest birds, the Hawai‘i creeper and ‘akiapōlā‘au, are regularly seen foraging in the planted koa groves, several kilometers above the old growth forest. Twenty years ago we thought that it would take a lifetime or two to get to this point. Seeing this change far surpasses our wildest dreams and the next 20 years are going to be even more exciting.
Goals for the Kona Forest Unit are to rehabilitate degraded forest habitat through control of feral ungulates and invasive nonnative plants, reforestation and supplementing endangered plant populations. Ultimately, the Kona Forest Unit may provide opportunities for public nature interpretation and education, and will complement the State of Hawai‘i’s natural resource management programs at the South Kona Forest Reserve and the Kipahoehoe and Manukā Natural Area Reserves, as well as nearby land management efforts by the National Park Service at Kahuku and The Nature Conservancy at Kona Hema.