Native Plants in Decline along the The Mānoa Cliff Trail
The Mānoa Cliff Trail is an easily accessible hike that is still great for observing native plants. The vegetation along the Mānoa Cliff Trail ranges from Lowland Mesic Shrub land to Lowland Mesic Forest.
Sadly, native vegetation along the trail has been observed to be in rapid decline:
- Recent surveys and our own observations have documented approximately 110 native plant species (as well as at least 115 non-native species) present along the trail or in the vicinity (Mt. Tantalus area), but based on numerous historical records dating back to the late 1800s (Bishop and Smithsonian museum records), 94 other native species are now missing from the area.
- Evidence for rapid decline has also been observed in the population of 'oha wai (Clermontia kakeana), a native shrub in the Lobelia family. In 1980-1983 Coleen Cory, a biology graduate student at California State University, located 104 'oha wai (Clermontia kakeana) plants along the trail as part of her study in pollination biology. When we started this project in 2005 we were only able to locate 16 'oha wai plants in the area.
The current decline has at least two major causes:
- Competition for light and space by quick growing alien plants (weeds)
- The disturbance and destruction of native seedlings and groundcover species by pigs rooting for worms (for example, māmaki (Pipturus albidus) seedlings and a patch of 'ala 'ala wai nui (Peperomia leptostachya) were eliminated by pig rooting in one section of the restoration area cleared of weeds)
Our restoration work aims to protect and promote native plant growth
In 2005, with the assistance of the Conservation Council of Hawai'i, we received a permit from the Na Ala Hele program to restore a section of the Mānoa Cliff Trail between its junctions with the Pu'u 'Ōhi'a and Pauoa Flats Trails. The land is owned by the State of Hawai'i.
Our effort involves manually controlling alien weeds. We have good success such as:
- Koa and mamaki natural regeneration after opening the canopy
- Clermontia kakeana and Bidens asymmetrica from spread seed
- Olona (Touchardia latifolia) and papala (Charpentiera ovata) propagation and outplanting
A fence to keep out feral pigs was constructed in late 2009 by DLNR around 6 acres of the site. We have achieved great success with our work to date
- Poster presented at the 2010 Hawaii Conservation Conference that describes the restoration site and progress (pdf 5mb)
In addition to this website, see articles about the Manoa Cliff forest restoration on Nathan Yeun’s photography and Hawaiian natural history website:
Hawaiian native plant descriptions:
Images of Hawaiian plants: