— Nainoa Thompson Polynesian Voyaging Society
The LHWRP crew work to target threats of the forest which include feral ungulates (hoofed animals such as cattle, pigs, goats, deer) that are capable of destroying the groundcover and small trees leaving the soils exposed, invasive weed species which have the ability to produce millions of seeds and can take over the a native forest and impact its efficacy of collecting water and deterring wildfires all of which impact overall health and functionality of the watershed.
Invasive Plant Species
Non-native species have the ability to produce millions of seeds, which can eventually take over the native plants in our watershed. Though relatively few non-native species are present on southern Haleakalā compared to wet forests, the satellite individuals have had decades to build up populations and seed banks. There are a few priority species of concern that, if left uncontrolled, could threaten the success of native forest restoration. The priority incipient invasive species include bocconia (Bocconia frutescens), silk oak (Grevillea robusta), Australian tree fern (Cyathea alsophyla cooperi), pines (Pinusspp.), gorse (Ulex europaeus), blackberry (Rubus argutus), Christmas berry (Schinus terbinethefolius),wattle (Acacia mearnsii), faya tree (Morella faya), pampas grass (Cortaderia jubata), cane tibouchina (Tibouchina herbacea), and mullein (Verbascum thapsus). LHWRP staff will continue to survey, monitor, and control priority invasive species across southern Haleakalā. We will also continue working with Maui Invasive Species Committee, Haleakalā National Park, College of Tropical Agriculture and Human Resources, Maui Plant Extinction Prevention Program, and Maui Nui Forest Bird Recovery Project, to prevent the spread of key tree invaders into the priority watershed forests. Collaborations aid in transfer of methodology and development of innovative techniques to help in tactical removal of isolated and limited populations in hopes of eliminate reproductive populations.
Ungulates that currently threaten watershed forests within the LHWRP are feral cows (Bos taurus), pigs (Sus scrofa), goats (Capra hircus), and Axis deer (Axis axis), all of which contribute to the degradation of watershed forests. The combined effect of these ungulates leads to accelerated levels of erosion, decimated vegetation and lack of canopy tree species recruitment has left many southern slopes completed denuded and potentially even void of critical soil components.
Feral cows are especially damaging and though in relatively low numbers, do a great deal of trampling and destruction of fern and shrub forest understories and are especially important in the destruction of rare plant species. Feral pigs uproot and eat native plant species, are especially damaging to native fern understories and like feral cattle rare plant species of shady, ferny gulch situations.In their removal of native plants, churning of the ground to mineral soil, and dispersal of seeds, feral pigs also facilitate invasive weed invasion (Medeiros 2004). Feral goats are extremely damaging, especially because of their locally high population densities. Though preferential in diet, the high numbers of animals tend to devour nearly all plant materials, even extremely unpalatable species such as Styphelia. Goat herbivory of koa includes foliage, young branches, bark, seedlings, and even roots (pers. obs.). Axis deer are unique in that they are wild animals, having never having been truly domesticated. As such they are extremely cryptic and nearly impossible to herd (A. Kaufman, S. Hess, pers. comm.) thus proving serious challenges for eradicate from fenced areas. Deer damage plants by browsing and grazing, bark chewing, and antler rubbing, the later sometimes resulting sometimes in the death of shrubs and small trees.
Other invasive animals include rats and mice which are widespread throughout the Hawaiian Islands. They not only devour seeds and fruits of native plants but they also prey on native snails, birds and insects many of which are crutial to the overall function of the watershed.
The conversion of forests to alien grasslands changes the soil moisture regimes, microclimate, and precipitation and cloud patterns. Pyrophytic grasses, especially Pennisetum clandestinum (Kikuyu grass), have widely invaded sub-montane and montane leeward forests on Haleakala. This thick continuous mat of non-native grass often covers bare ground and rocks that once served as natural fire breaks and slowed or stopped the spread of fire. Fire breaks in strategic locations (such as fence lines with road access) and vegetation management especially adjacent to human habitation and frequent sites of recreation are critical. Rapid response to fires through interagency planning and communication is helpful in protecting GPS mapped archeological sites, water resources, roads, and Threatened and Endangered species. The goals are to break the cycle of increasingly frequent fires while keeping humans safe and preserving biological, economic and cultural resources. The more involved long-term solutions to slowdown the fire cycle focus on returning the landscape to a less fire-prone state with native vegetation in discontinuous patches and less grass. Controlling or removing mat forming grasses and fire-dependent non-native trees (i.e. pines) would diminish the fuel loads significantly and should decrease the fire frequency and intensity. LHWRP supports the creation of an island wide seed bank and establishing seed orchards that are well supplied with regional seed to rapidly reseed areas after fires with native seeds. Fires create a window of opportunity to establish native species when grasses are not present.