This weekend, students from introductory biology and botany classes met at Piliokahe Beach on the Waianae Coast to restore native dune ecosystems! We have been working our way down the dune for several years now, and my favorite part of this site is how visible our progress is across the dune. The dune slopes that we’ve planted in past semesters are overrun with native vegetation, and each semester we work our way a bit further down the dune.
Unfortunately, this semester we had a couple little set backs. First of all, this was an extremely dry winter, and it took a bit of a toll on our previous plantings. We lost a few of the shrubs and some of the vines looked a little peaked. Still, some plants were thriving, like this ‘ohai we planted in spring 2015.
Second, we have now worked our way down the dune far enough that we are reaching a couple little plateaus on the dune that are popular camping locations, particularly for a couple of homeless folks that make their camps on the beach. When Bruce arrived at Piliokahe to get all our supplies set up, he found that someone had set up their camp directly on top of our plantings from last semester. This is frustrating and upsetting. We make a point to surround our baby plants with small rock piles to make it clear that they intentionally planted. We plant them off the main foot-trail, so unless you are traipsing all over the dune, they shouldn’t be crushed. Even so, everything from last semester that was planted on the flat ground (and not the steep dune face) was destroyed.
This brings up a question I have asked of Bruce in the past – why don’t we put up some sort of ‘ecosystem restoration in progress’ signage to inform folks using the beach that we are working here? I’m not sure who we would need permission from, or whether it would help, but it might be something to think about if this continues to happen.
This weekend, we planted more different species than we have at any other service learning – a total of 12 unique species! At Kalaeloa, we tend to stick with only a few species because that site is extremely dry and has very shallow soil depth, so only a few species can do well there without constant attendance. Remember that in habitat restoration, we need the plants to be able to survive on their own, without watering, etc. At Piliokahe, we are less limited, and can plant numerous species to rebuild a complex and health dune ecosystem. Many of the plants we choose provide erosion control (the grasses and vines) and others are rare, endangered, and/or locally extinct, so we can increase their population sizes while also rehabilitating an important ecosystem.
Plants at Piliokahe
Hinahina kū kahakai hee-nah-hee-nah koo 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). It is the official flower of Kaho’olawe and is frequently used in lei.
Hunakai hoo-nah-kye (Ipomoea imperati) This coastal vine is related to another of our Piliokahe plantings, the pohuehue. Hunakai is particularly good for erosion control as much of the vine spreads underground.
Pā’ū 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, which resemble a skirt. Pā’ū o Hi’iaka readily spreads throughout the dunes, and mature plants can be seen in many of the restored areas in the photos below.
‘Ohai oh-hye (Sesbania tomentosa) This endemic shrub is federally listed as endangered and is quite rare. 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. The ‘ohai has distinctive and pretty flowers ranging from bright pink to pale orange.
‘Aki’aki ah-kee-ah-kee (Sporobois virginicus) This indigenous grass is common along many Hawaiian coastlines. Like many grasses, ‘aki’aki forms extensive underground root and stem systems, making it also an excellent choice for erosion control and soil retention. Bruce identified this plant as the most important of our Piliokahe plantings because of its impressive erosion control abilities.
Pōhinahina, 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.
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. As a grass, kāwelu also forms large root systems, which are good for erosion control.
Aweoweo ah-vay-oh-vay-oh (Chenopodium oahuense) This endemic shrub shares its name with the aweoweo Hawaiian big-eye fish because of the distinct fishy smell of the aweoweo fruits.
Pōhuehue poh-hoo-ay-hoo-ay (Ipomoea pes-caprae subs brasiliensis) This vine also assists with erosion control, and is already well-represented throughout the dune from previous plantings, so we know it will do well at Piliokahe.
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.’
‘Ilima ee-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 previous service learnings. 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.
‘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.
As with previous service learning events, we first cleared an area of the invasive buffelgrass that covers most of the Piliokahe dunes. Buffelgrass is particularly problematic for native plants because it is fire-adapted. Road-side fires can start as easily as a discarded cigarette butt, and buffelgrass recolonizes a burned area much faster than native (non-fire-adapted) species. We cleared out quite a bit less invasive plant biomass than in previous events because we were replanting last semester’s location again (which was already cleared).
Bruce brought 50 different individuals for us to plant, which included the survivors from my botany class’s propagations, including pohuehue and ‘akulikuli. We chose a small patch on the dune front to put all the botany class propagations, so I can easily find them in future semesters. I also got to plant my little ‘akulikuli in the mix! Shayna’s one surviving pā’ū o Hi’iaka got mixed up with some of Bruce’s other propagations and planted as part of another service learning project with some local high school students, so it’s off on its own adventure.
We surrounded each plant with a large ring of rocks to make it clear that these are intentional plantings that should not be walked or camped upon. Hopefully, this will be sufficient to keep the plants protected from human activity. If it’s not, we may have to think about something a little more obvious – small chicken-wire fences, or planting flags, or signage that indicates work going on the area.
We also gave each plant ~8 gallons of water (half poured into the hole prior to planting, and half over the plant after it was planted). Bruce’s restoration experience indicates that 8-10 gallons of water per plant is sufficient to support the plant until it is fully established without additional waterings. Unlike landscaping or gardening, our plants must be able to support themselves without additional care from humans. Pouring half the water into the planting hole prior to the actual planting allows the water to sink further down into the sand, which not only keeps it from evaporating right away, but also encourages the plant to develop deeper roots, which will serve it well in the long term.