This weekend, UH West O’ahu biology students met at Piliokahe (Tracks) Beach to restore dune ecosystems, including removing invasive species, and planting native and endemic plants. This service learning is part of an ongoing project at Piliokahe which also includes volunteers from Malama Learning Center.
As always, our first step was to remove invasive plants from the area. The dunes at Piliokahe are primarily overrun with buffel grass (Cenchrus ciliaris) which is native to Africa and was introduced to Hawai’i as fodder for cattle in the 1800s. Buffel grass overtakes native plants by altering the fire regime of the ecosystem. Following a fire, buffel grass is able to more quickly repopulate the area as opposed to the native plants which are not well-adapted to fire. The dunes also have many kiawe trees – while we do not have the tools to remove full-grown trees, we did remove any fallen branches. And, as is common for any public beach, there is a frustrating amount of human trash, which we also cleared from our area.
After we cleared the area, Bruce introduced us to the plants we would use to restore the dune.
Pau o’hi’iaka pah-ooh-oh-hye-eee-ah-ka (Jacquemontia ovalifolia subsp sandwicensis) The Hawaiian name of this endemic vine translates as ‘the skirt of Hi’iaka’ – the vine is said to have protected Hi’iaka, the infant sister of the volcano goddess Pele, from the harsh Hawaiian sun as she lay on the beach while Pele was fishing. The vine produces rather pretty thick green leaves and small bluish purple flowers, which resemble a skirt. Pa’u-o-hi’iaka readily spreads throughout the dunes, and mature plants can be seen in many of the restored areas in the photos below.
Pohinahina, poh-hee-nah-hee-nah (Vitex rotundifolia) This native shrub gets its name from its tendency to fall over (pohina) as it grows taller and from the silvery-gray (hinahina) hairs that protect it from the sun. It is native to Hawai’i, but also found in Japan, India and many other Pacific islands.
‘Akulikuli, ah-coo-lee-coo-lee (Sesuvium portulacastrum) This native shrub is common in coastal areas, marshes, lagoons, and rocky shorelines and can grow directly out of exposed coral beds. It is so well-adapted to shore life that it can take up moisture directly from sea-spray off the ocean, despite the salt content of this water source. ‘Akulikuli bears a strong physical resemblance to the invasive pickleweed, and the two are sometimes confused.This plant is also edible – the small, succulent leaves can be eaten raw or cooked.
Mau’u aki aki, mah-ooh-ah-kee-ah-kee (Fimbristylis cymosa) Aki aki is the Hawaiian name for grass, although this native plant is actually a sedge. While native to Hawai’i, mau’u aki aki is also found throughout the Pacific islands. The spiky leaves of the plant can make it a deterrent to invasive pests such as slugs, snails, and feral cats.
Dwarf Naupaka, noh-pah-kah (Scaevola coriacea) This endemic shrub is federally listed as endangered. It’s close full-size relative naupaka kahakai (Scaevola taccada) is commonly seen along Hawaiian beaches, however, we do not use this species because it’s large size allows people to hide trash underneath the branches. The dwarf naupaka makes an excellent smaller ground-cover, while also being well-adapted to coastal conditions.
Naio, nye-oh (Myoporum stellatum) This rare shrub is found only in Kalaeloa and Nanakuli. Our site today is found between these two current populations of naio, and so was a likely habitat for this plant in the past. Despite being quite rare, naio is not listed as endangered, but only as ‘at risk’. It was sometimes substituted for ‘iliahi during the sandalwood trade, giving it the unfortunate nickname of ‘bastard sandalwood.’
Nohu, noh-hoo (Tribulus cistoides) This native shrub shares its name with the scorpion fish because of the spines found on the nohu seedpods.
‘Ohai, oh-hai (Sesbania tomentosa) This endemic shrub is federally listed as endangered. As a member of the pea family (also called legumes) ‘ohai is a nitrogen-fixing plant, which also provides nitrogen for other plants growing in the area. ‘ohai has distinctive and pretty flowers ranging from bright pink to pale orange. Unfortunately for the ‘ohai, introduced rats particularly enjoy its seeds, making it difficult for the plant to reproduce in some areas. Predator fences, such as the one protecting Ka’ena Point, help ‘ohai populations to thrive.
‘Ohelo kai oh-hello-kye (Lycium carolinianum var. sandwicense) In Hawai’ian, kai means water or sea, and ‘ohelo kai has berries that are similar to the ‘ohelo plant that grows on Big Island, hence the name ‘ohelo kai (‘ohelo by the sea).
Ma’o mah-oh (Gossypium tomentosum) Known as Hawaiian cotton, this shrub is federally listed as vulnerable and is a close relative of commercial cotton (Gossypium hirsutum). Ma’o is much more resistant to herbivory by insects than G. hirsutum, and the two have been bred in order to confer insect resistance into G. hirsutum. There is a wild population of ma’o currently growing across the road from the Piliokahe dunes, so our restoration efforts will help keep the current population healthy.
Ewa ‘hinahina, ay-vuh hee-nuh hee-nuh (Achyranthes splendens var. rotundata) This shrub is federally listed as endangered and is found in only three places on O’ahu island. The Hawaiian name for this plant was lost, so we know little of its use or importance in Hawaiian culture. It’s modern name comes from it’s habitat of the ‘Ewa plains, and hinahina which means grayish or silver. The leaves of this plant have small ‘hairs’ which give the plant a grayish or silver appearance and protect the plant from the heat of the sun.
Kāwelu, kah-weh-loo (Eragrostis variabilis) This endemic grass is found throughout the Hawaiian islands. The swaying of the grass in the wind was the inspiration for the kāwelu hula step.
We found a couple of other interesting organisms, too! Our overturned rocks startled a little gecko, and Sabrina managed to capture a little sand crab! We named the gecko Billy and the sand crab Herbert. Here’s hoping they enjoy their new plant friends!
As always, I also stopped by the previous sections of dunes that we have restored in past semesters. I’m always impressed at how well the plants from are doing. The dune we planted last fall is now almost entirely covered by plants!