Haleakala National Park
This half-mile trail will lead you on a 30 minute walk through one of the biological battlegrounds of the Park. The trail begins in the shade of a 20th century alien forest and ends in native Hawaiian shrubland that looks as it did centuries ago. Numbered posts and plaques are found along the trail.
Haleakala National Park was established in 1916 to preserve the original Hawaiian habitat. Alien plants and animals that have been introduced by man make it a difficult challenge. Today the park's resource managers are reclaiming remnants of the native shrubland around Hosmer Grove by removing thousands of invasive alien eucalyptus and pines. Without the removal of adult seed-bearing plants and their rapidly spreading seedlings, an alien forest would soon overrun the native shrubland between here and the crater, thereby erasing a fragile Hawaiian ecosystem that has taken millions of years to develop.
Plants native to Hawaii got here via the three W's: wind, bird wings or waves. The Hawaiian Islands emerged from the sea millions of years ago and a colonizing plant managed to become established once every 100,000 years. Plants evolved to take advantage of a variety of new habitats. Most plants differ from their ancestors, and 86% are "endemic" to Hawaii, found nowhere else on earth.
Plants and animals that were brought to Hawaii by people are called "alien". The trees of Hosmer Grove include pine, spruce, cedar and eucalyptus imported from all over the world. They were planted around 1910 by Hawaii's first territorial forester, Ralph Hosmer, as part of a forestry experiment. Most of the grasses seen in this area are also aliens that became established when cattle were grazed here.
Sights Along the Trail
Forestry - Years of clearing the land for cultivation and ranching have taken their toll. By the early 1900's removal of native forests had led to erosion and drought. Ralph Hosmer established forest reserves throughout the islands. He experimented with 86 species of trees on Maui, like these eucalyptus, hoping to improve the watershed, and provide building lumber and fuel for the sugarcane mills.
Fencing - Near the trail is a fence which was built to keep goats and pigs out of the Park. Because Hawaii is over 2000 miles from the nearest continent, all land mammals found in Hawaii today, except the winged Hawaiian Hoary Bat, have been introduced by people. These alien animals destroy fragile native plants which evolved without the presence of browsing mammals.
Results of the Experiment - Hosmer's plan for timber farming in Hawaii never worked out. Only 20 of the 86 species introduced here survived. Of these, some with shallow roots are blown down in storms. Some found the soil chemistry or fungi unsuitable for growth or reproduction. But others have thrived.
Gentle thorns - Beneath the alien trees are 'akala, or Hawaiian raspberry. In the summer you may find deep-red fruit among the broad leaves. The branches have only small hair - like thorns, having lost the need for defensive thorns, until grazing mammals were brought in.
Native Seeds - You may see berries and seed pods on many of the shrubs along the trail. Although these berries are eaten by the native and alien birds, many of them can make people quite ill. Seeds from these shrubs have trouble sprouting amid the thick alien grasses.
Overlook - As you sit amid the Haleakala sandalwood or 'iliahi, and other native shrubs, notice how each has evolved ways of withstanding the often intense conditions on the mountain. The large gnarled trees growing up from the gulch are the native 'ohia, you may see red bottle-brush shaped flowers on them. Honeycreepers, like those pictured on the panel in front of you, dip their curved beaks into these flowers for nectar, and in doing so pollinate the flowers. This active interdependence highlights the need for preserving all elements of a forest, and not just the tree.
This trail continues on a l/4 mile loop into the native shrubland; turning right will take you back to the parking lot. Looking across the gulch you see a mixture of native trees, shrubs and ferns. The larger 'ohi'a, koa, and olapa are still found in remote gulches, but covered much of the lower mountainside just a century ago. The native forests are a vital part of the watershed, drawing clouds and rain to the mountain, and controlling erosion.
Some trees have escaped from Hosmer's experimental forest. The Mexican Weeping pine, Monterey pine, and eucalyptus are aggressively seeding and must be constantly tended to prevent them from overrunning the natives.
Germination - Some seeds from native shrubs have tough outer hulls and botanists were unable to make them germinate. But a researcher found that from the dropping of the chukar partridge and the Chinese ring-neck pheasant seedlings emerge. These alien birds appear to be benefiting the native plants by breaking down the seed hull, and taking the place of a native seed eating bird which is probably now extinct. However, chukar and pheasant can adversely impact native bird populations by serving as disease reservoirs.
Adaptation - Look at the native plants around you and try to see them as a pig or goat would. Except for the heath-like pukiawe, most of these plants are easy food for grazing animals. When the ancestors of these plants arrived in Hawaii millennia ago, there were no grazing animals. As plants adapted to their surroundings, they lost defenses they no longer needed, such as poison, thorns, and scent. Fencing protects native plants from grazing pigs and goats.
The Silver Geranium - With its silvery tridentate leaves and small whitish flowers, is endemic to Haleakala. It is found nowhere else on earth. Over 86 % of Hawaii's native flowering plants are endemic to the islands. A single colonizing ancestor usually changed or developed into many new species; this is known as adaptive radiation. There are more than 10,000 species of plants, birds and insects that are endemic to Hawai'i. But sadly, with this great diversity comes great loss. Nearly 75 % of our nation's documented plant and bird extinctions were endemic Hawaiian species.
Back to the Future? - From here the trail leaves the shrubland and returns through Hosmer Grove to the parking area. As you walk among the trees, try to picture what the mountain looked like before the native forest was removed. Nearly two-thirds of Hawaii's original forest cover has already been lost. When forests disappear, so do the birds, snails, and insects that depend on them. About 70% of our native birds are already extinct because of deforestation, overhunting and diseases carried by alien birds.
Biodiversity - The native shrublands support a large diversity of life, unlike the understory of this pine and eucalyptus forest. Notice as you walk under the Norway spruce ahead that there are few other plants which can survive being deprived of sunlight and inhibited by plant chemicals.
We humans brought this struggle to Hawaii's native life; we bear the responsibility for preserving the unique ecosystems remaining within our National Parks. With deforestation of the world's rainforests continuing at one acre per minute, we hold a vital piece of earth's natural heritage.
Details mentioned in this article were accurate at the time of publication