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UHWO Service Learning: Piliokahe Beach


Invasive koa haole with 1-foot stem and 2-foot tap root

On April 11th, the UHWO biology and botany students completed their third and final service learning of the Spring 2015 semester! Our last site is the most accessible and picturesque of the locations: Piliokahe (also called ‘Tracks’) Beach Park. The dune ecosystems of the beach park are consequently threatened by both invasive plants, and human recreational disturbance, both of which can lead to devastation of native plant communities and erosion of the dune systems.

I’m going to take a moment here to get on my soapbox about the difficulty of the work my students do. I frequently discuss the service learning component of my class with other scientists and professors – the first question is often “What exactly *is* service learning?” and after my 2-minute elevator pitch on the structure of our service learnings, I often then hear “Oh, so you just go out and pull weeds.” To be honest, I take some offense to this massive over-simplification of the work my students do, let me explain why.

The invasive plants the UHWO students remove are often full-grown, mature plants that have to be dug out by hand (usually without the aid of herbicides) to protect nearby native plants, or maintain the structural integrity of the soil. Many of the invasive plants have deep tap-roots that can be double the length of the above-ground stem (see photo). Removing them requires pick axes, ‘o’o, and weed wrenches. Bunch grasses have to be cut out individually with hand-scythes.

In addition, the sheer quantity of invasive plant material we remove can be staggering. Below is a photo of the invasive biomass removed from the Piliokahe site. Full bags weigh ~30 pounds, meaning the students remove hundreds of pounds of invasive biomass at each service learning. When Leeward Community College works at this site next weekend, they will remove another several hundred pounds of invasive biomass.

This is serious eradication of invasive organisms, not the ‘weed pulling’ you do in your flower garden.


More than just ‘pulling weeds’

As with the other locations, our first step at Piliokahe was to remove invasive buffelgrass, which was introduced to Hawaii in the early 1930s and is native to Africa and tropical Asia. This species is particularly problematic because it is fire-adapted, having a low ignition threshold and the ability to quickly reestablish after fire. Native Hawaiian plants along the dunes are not fire-adapted, so this shift in disturbance regime allows buffelgrass to rapidly dominate the habitat after being introduced. Unlike our other restorations, where we fully dug out invasive plants, we wanted to retain the buffelgrass root systems to protect the sandy soil from erosion. For this removal, then, we simply gave the buffelgrass a ‘haircut’ (as Bruce likes to say), while keeping the root system relatively intact.

As with the other sites, our restoration here involved three steps: 1) remove invasive plants, 2) prepare the ground for planting and 3) plant native plants. For this restoration, our leader Bruce Koebele gave us a wider array of plants – a total of 11 different species!


I always love the tray of plants that Bruce brings. They look so hopeful and excited for their new home!

‘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.
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.
Hinahina ku kahakai, hee-nah-hee-nah coo kah-hah-kye (Heliotropium anomalum) This endemic shrub also takes its name from silvery-gray (hinahina) hairs that protect the leaves from the sun, and its location near the ocean (kahakai).
Pa’u-o-Hi’iaka, pah-ooh-oh-hee-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. Pa’u-o-hi’iaka already spreads throughout the dune areas where our restoration was taking place, and mature plants can be seen in many of the photos below.
‘Ilima, eee-lee-mah (Sida fallax) There are two version of this native shrub on O’ahu. The first, ‘ilima ku is a taller shrub, found in the drier environments such as the Ka’ala kipuka dry forest of our first service learning. The coastal ‘ilima is ‘ilima papa, which grows prone to the ground to protect it from the ocean wind. ‘Ilima is also the island flower of O’ahu.
‘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).
‘Ohai, oh-hi (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.
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.’
Maiapilo, my-uh-pee-loh (Capparis sandwichiana) This endemic shrub is federally listed as ‘at risk.’ It takes its name from the resemblance of its fruit to banana (mai’a) which have a distinctively unpleasant fragrance (pilo).
Ma’u ‘aki’aki, mah-ooh-ah-kee-ah-kee (Fimbristylis cymosa) This native sedge is not federally listed, and due to its spiky leaves can be used as a deterrent to slugs, snails, and feral cats.
Nehe, nay-hay (Melanthera integrifolia) The name ‘nehe’ is used to refer to numerous different plants, all of which are endemic to Hawai’i. This particular nehe is found on all the main Hawaiian Islands as well as throughout the Northwest Hawaiian Islands.

Bruce had his intern David choose the locations for the plants to ensure that they were evenly dispersed. David had also come out previously and planted some large ‘ohai trees (which are marked with orange flags in the photos). We had 45 plants to plant, and only 44 students, so this time around, I got to plant a little hinahina ku kahakai myself. I’ll have to keep an eye for him when we return next semester and see how he’s doing.

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I also got a chance to revisit the dune we worked on last semester, and the plants are coming along very nicely. Dunes restored in previous years are still looking healthy, so I’m hoping the little guys we planted this semester and last will soon look as good as they do. Bruce plans to have us continue working north along the beach every semester until we run out of dune. I look forward to someday posting a panorama of all our years of restoration at this site. PilioBeforeAfter

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