Restoring the Natural Landscape of Diamond Head

Diamond Head State Monument

Emily Hauck, Interpretive Technician at Diamond Head State Monument

From a biological standpoint, one of the most incredible things about Hawaii is the specific biomes that exist within the 8 main islands. The State of Hawaii has 10 of the world’s 14 climate zones. Everything from black sand beaches to arid climates and freshwater marshes to dense rainforests, Hawaii certainly has no shortage of fascinating environments. Protecting the unique areas across the islands from the threat of invasive species, wildfires, and erosion is a constant battle for land managers and scientists. Even just within the landscape of Diamond Head, State Parks struggles to reintroduce the native dryland vegetation into the crater.

The tuff (not to be confused with ‘tough’) soil that makes up Diamond Head State Monument is a hard, clay-like substance. As you may imagine, this texture is not ideal for thick, lush vegetation and most efforts to landscape the crater have suffered due to the soil and climatic factors. Dominated by low-growing, dryland plants, Diamond Head’s low rainfall (25 inches annual average), semi-arid environment are not the only circumstances influencing the native plant restoration efforts. These conditions are ideal for brush fires. A history of fires in the 20th Century and historic modifications have both shaped the vegetation pattern on the crater slopes and floor. Because of these leading factors, we have little confirmed data of the native forest that once existed within the crater walls. Three invasive species, Kiawe (Prosopis pallida), Fountain Grass (Pennisetum setaceum), and Koa Haole (Leucaena leucocephala) are the primary rulers of the modern-day crater floor and slopes, too often overshadowing what few native species are left. Ilima is one of the native species ground cover plants observed in the crater today, but some other likely plants in this environment would include ma’o (Hawaiian cotton), ‘a’ali’i (Dodonaea viscosa), naio (false sandalwood), and kokio (Hawaiian red hibiscus).

Scientists suggest that plant community restoration can help to reestablish the overall ecosystem. Meaning that, encouraging native vegetation may eventually lead to healthy populations of other native animals and plants. If you build it they will come. A study published in Nature this year found that restoring a habitat can improve its ecological functioning, giving hope to facilitators determined to see successful ecosystem restoration.

To promote native species, State Parks has planted and irrigated in the areas around the parking lot and restroom. These plantings represent a mix of native species and introduced ornamentals, including kukui (the State tree, and Hawaiian introduction), shower trees, Formosan koa, plumeria, etc. A row of kou and milo trees, and pohinahina, a native shrub, were planted along the walkway by the restroom to display native vegetation in the crater.

Sadly, not all of these native trees have survived, and the numerous factors mentioned earlier that come into play greatly influence the Park’s ability to help native plants flourish. We do, however, have a secret weapon: Volunteers! For years, State Parks’ staff has been working hand-in-hand with KUPU interns, KCC students, and other local organizations to beautify the land and restore as much of the landscape as possible. Their hard work and dedication has helped replant and repair a significant amount of land within Diamond Head crater. State Parks Staff can always use more helping hands to propagate native species, remove noxious invasives, and advocate for the restoration of Diamond Head State Monument for the next generation.

You can find more information on how to volunteer through the Hawaii State Parks volunteer website at dlnr.ivolunteer.com.

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