Metrosideros polymorpha (and Volcanoes!)

Well, I got back from Hawaii on Saturday and am now squarely within my last days as a full time New Yorker. I'll most likely work Monday - Wednesday for the next three weeks then finish up at my job (save a few hourly tasks to wrap up my Hawaii project).

Hawaii was wonderful, and thank goodness I scheduled three days on the Big Island. Otherwise, I'm afraid I would have spent far too much time "on call" for work, even if I officially had the day off. I highly HIGHLY (HIGHLY!) recommend the Big Island to any Hawaii-bound individual that is even a casual naturalist. The variety of ecosystems and the rugged beauty of this - the youngest of the Hawaiian islands - place is stunning.

I flew into Kona last Monday morning and immediately set off for Volcanoes National Park. "Why, it's only 90 miles!" I thought to myself, "I'll be there well within 2 hours."



Not so much. The winding roads through the big island - and their ever-changing elevations - definitely slows down the works and driving 90 miles really requires at least 2.5 hours of driving. Of course, as soon as I got to Volcanoes National Park and saw the Kīlauea Crater spewing sulfurous fumes, all that driving was worth it.


Large parts of the park were closed on my recent visit, since the volcano has been acting a bit differently lately. A few weeks ago it began spewing lava in a new location and as a result, the gases have been considered too dangerous to inhale in certain areas. If I had stayed 'til dark, I would have been able to see the red glow of lava further along the edges of the park (at the crater itself it primarily flows underground), but I wasn't up for a long, winding drive at night.



Now then. Let's get to the plants. It's pretty amazing to see a shrub with such a lovely flower on it blooming with an active volcano so nearby. This plant is Metrosideros polymorpha or ōhiʻa lehua. If it looks familiar, you could (maybe, possibly) remember a post I wrote that had some shots of Callistemon citrinus. These plants are both in the Myrtaceae or myrtle family and their flowers (with diminutive petals and brightly-colored, showy stamens) are quite similar.



This species of Metrosideros is endemic to Hawaii, meaning that it can only be found in the Hawaiian islands. Though it does have relatives in New Zealand that are quite similar. The species itself is highly variable and over the years varieties of Metrosideros polymorpha have been further categorized into new species, all equally endemic to Hawaii. Some of the variations we find among the Hawaiian species include the hairiness of the leaves (hairier in drier climates, as the hairs trap ambient moisture) and the color of the leaves (changing from green to greenish-gray to gray).


The species itself is highly adaptable. It can maintain itself as a small shrub or tower to 20+ meters. The incredibly light seeds can blow for miles in the wind and this is partly why the plant is often the first colonizer of post-volcanic, lava-laden landscapes. As it colonizes a lava field, it begins to degrade the rock into soil and provides perching locations for birds. Ultimately, the landscape succeeds into a fern forest, as can be found just a mile away from the Kīlauea crater itself (more on the ferns this week).




I was all too excited to pick up a book at the Volcanoes National Park visitor's center - Hawaii's Plants and Animals: Biological Sketches of Hawaii Volcanoes National Park - and it's a terrific read so far. When I was reading about Metrosideros the authors noted a curious phenomena with this plant: at times, massive swaths of ōhiʻa will die out. When biologists at the park first documented this, they immediately investigated whether a foreign pest or disease was the cause of such dieback, but no culprit was found. Instead, they can only determine that a heavy rain or drought can trigger this mass death. It seems to be part of the evolutionary hardwiring of the plant. Today that is problematic because, given the pervasiveness of the alien plant Pennisetum, the former ōhiʻa forests can be quickly invaded by this weed and prohibit young ōhiʻa to take root. Forecasting ōhiʻa dieback and managing the re-population of young ōhiʻa is a chief concern for land managers on the big island today.