KA MOʻOLELO O WAIHEʻE: A LOST LANDSCAPE
Beginning approximately 12,000 years ago, glacial retreat and rising sea levels brought about the emergence of our familiar island coastlines. Maui, Molokai, and Lanai once again became the three independent islands they are today, and the ecosystems that would dominate Waihee for the next 10,000 years began to evolve. The landforms we now see were taking shape even then; the dunes surrounding the wetlands and the lines of our modern-day coast were already recognizable. The most significant differences between the landscape of Waihee in the early Holocene period and that of today are found in the dramatic changes in the local flora and fauna. Of course, we can never be certain what the exact composition of this wahi pana was so many thousands of years ago, but glimpses of the past do become clearer from quality time spent on the land and in the laboratory.
Sediment cores drawn from the Kapoho wetlands in 2018 have provided scientists with one of the best of these glimpses into the ecological history of Waihee, revealing data from around 12,000 years ago through the present day. Sections of these sediment cores were sent to England for analysis at the University of Leicester’s Palaeoecology Laboratory. While many different evidentiary threads must be woven together to create a tapestry of the pre-human ecology of the Waihee refuge, pollen analysis (palynology) has given us the most complete information to date.
Waihee is not an ideal environment for sediment core analysis, for several reasons. First, the wetlands regularly dried out during the kauwela (hot season), long before the first humans arrived. While pollen can survive for tens of thousands of years (or longer) when rapidly buried under sediment, desiccation (drying-out) destroys pollen grains. Second, the distance between ocean and wetlands is very short. Since the wind blows from the ocean onto the land, we can be relatively certain that what we find in the wetlands did come from the immediate area, but not much pollen comes from the direction of the sea. Finally, pollen are incredibly tiny, and certain soil types, particularly sandy ones, do not hold pollen well at all. Because so much sand had blown in during the previous ice age (starting around 20,000 years ago), pollen did not collect easily in the wetlands. Sadly, most fell through the larger spaces between grains of sand, thereby making collection and analysis impossible.
However, all was not lost. This core analysis provided valuable insights into the ancient (paleo) ecology of Waihee. Additionally, in the summer of 2019, we developed a new method of extracting pollen from another dateable source: the interior of crab claws (more on them later). This involved extracting sediment from the abundant remains of crab claws belonging to an extinct species of land crab (Geograpsus severnsi). The process proved to be both incredibly simple and extremely effective: when a crab dies, the interior of its shell fills quickly with sediment. In short order, the entire crab is buried and preserved for long periods of time. As the thickest and most durable part of their exoskeleton, the dactyls (claws) are preserved so well that recent dating from the Waihee Refuge has found intact 1,800-year-old specimens that looked as if they’d been buried last month. It took an interested party only a few minutes with a toothpick to bore this sediment out into a bag, repeat that about fifty times, and send it off to England for analysis. Pollen collection and preservation from these dactyls gave us a remarkable quantity of pollen specimens to observe under the microscope.
While other means and strategies for uncovering the historical ecology of Waihee exist, our current understanding of the structure, composition, and biodiversity of the refuge in the millennia preceding human arrival comes primarily from this pollen analysis. As technology evolves and new scientific methods develop, we will undoubtedly be able to gain an ever better sense of the ecological history of Waihee. As I shall describe below, our knowledge of the avifauna (birds) on the refuge before people arrived remains almost entirely speculative.
What we have found, particularly about the floral history of the refuge, has both confirmed some of our previously held suspicions regarding pre-human ecology and revealed some surprises. For instance, several common species, apparently abundant millennia ago, are no longer found anywhere near the Waihee Refuge. The dominant plant species, found in greater numbers than all other species combined, was the Loulu (Pritchardia) palm. It is an unfortunate fact of pollen analysis that it cannot be reduced down to the species level, but we can easily see that the pollen of the Loulu dominated the ecosystem. Paleoecologists generally acknowledge that when one genera or species makes up more than 75% of all the pollen in a given area, a closed-canopy ecosystem is created. We can say with a high degree of confidence that Pritchardia dominated the area around the Kapoho wetlands.
Walking through Kapoho 10,000, or 6,000--or probably even as recently as 1,000 years ago--would have felt like walking through a dense coastal forest of Loulu fan palms, right up to the edge of the wetlands, where it would have abruptly transitioned to a sedge-covered series of spring-fed bogs. During the hooilo (wet season), it likely would have had the look and feel of a lake, while during the kauwela (hot season, or summer), a patchy series of ponds would likely have dominated the 27 acres of the wetlands. It is impossible to know which types of sedges would have dominated, some of which may now be extinct, but considering their current persistence, it is easy to envision a combination of Kaluha (Bolboschoenus maritimus) and ‘Ahu ‘Awa (Cyperus javanicus) dominating, with a diverse group of other sedges present.
The pollen record suggests that the dunes were dominated by a number of species, in particular ohe makai (Polyscias sandwicensis), probably with Kauila (Colubrina sp.) co-dominant. The mid-elevations of the dunes were very likely dominated by Aweoweo (Chenopodium sandwicencse), a popular nesting material for seabirds (more on them later), while the upper reaches of the 200-foot-high dunes were dominated by a yet-to-be-determined species of grass, but possibly Kawelu (Erograstis variablis).
There are two critical points to remember regarding these speculations. First, diversity was the order of the day. The plants noted above are those we are reasonably certain dominated this area. However, also as noted, sometimes pollen fails to preserve, and some plants produce only a small amount of pollen, rendering them invisible to analysis. Palynology (pollen analysis) can reveal the plants that were present and provide insight into dominant species, but it can also miss those that were less common or that did not produce a sufficient abundance of pollen to be visible today, such as plants that rely on insect pollinators and therefore produce substantially less pollen than wind pollinated plants. Second, while relying on the insights of experts in the field of Hawaiian ecology to paint a picture of the pre-human ecosystem, much remains speculative. I liken this to trying to bake a cake with some of the ingredients and partial fragments of the whole recipe.
Birds make up the conspicuously missing part of the Waihee Refuge today. While scientists often describe Hawai`i as the extinction capital of the world, with species continuing to decline and disappear into the present day, the historical record paints an even more grim picture of species loss. At least 77 species of Hawaiian birds have become extinct in the last 700 years, more than any other place on earth. While the reasons for this decline have been studied and documented for many years, the important role that these birds and other extinct species played in shaping Hawai`i’s terrestrial ecology could easily be overlooked. Unfortunately, this delves into further speculative ecology, but if we hope to restore our ecosystems, such speculation is necessary.
I should point out that we have found only sub-fossil (incompletely fossilized) remains of one bird species in the Waihee Dunes, and these were Uau kani (wedge-tailed shearwaters), a species that had still existed on the dunes until recently, when one careless dog owner allowed his pet to kill the last 12 individuals in a final, tragic episode for this incredible seabird. We fervently hope to see them return to their home someday. Seabirds would have dominated the landscape with their sheer numbers, especially on the dunes. Any guesses at the population size would be conjecture, but in total, they could have numbered over one hundred thousand individuals or more. Additional evidence gathered from other Maui sites suggests that the `Ua`u (Hawaiian petrel) population surpassed that of the Uau kani. Future research might help us better understand the species composition, and perhaps the size of that population, but for now we are restricted to the use of imagination and inference until further evidence surfaces.
Considering the size of the Kapoho wetlands (27 acres), it is reasonable to assume that waterbirds maintained a robust population there. These would have included `Auku`u (black crowned night heron); Aeo (Hawaiian stilt); `Alae keokeo (Hawaiian coot), still present today; Alae ulaula (Hawaiian moorhen); Koloa (Hawaiian duck); Laysan teal; and Nene. Several species of now extirpated (extinction from the local area) waterbirds would very likely have been present in substantial numbers, including the Nene Nui, or Greater Hawaiian Goose (Branta hylobadistes), and the Maui Nui Moa Nalo (Thambetochen chauliodus), descended from a more common duck species, which grew so large and robust on Maui that they lost their ability to fly. The Maui flightless Ibis (Apteribis brevis) would have done well at what is now the Waihee Refuge, with its diet likely consisting of the land snails whose shell remains are found frequently in the dune deposits.
Where there are prey species, there are predators. The guild of predators, like their waterbird and seabird relatives, was comprised of a diverse array of species. Bearing in mind that this remains highly speculative, it is reasonable to think that smaller predatory birds, such as the Maui Stilt Owl (Grallistrix erdmani), with its ability to snatch forest birds out of tree canopies with its long legs, either visited or called Waihee home. The remains of a diverse array of predators, such as harriers (Circus sp.) and hawks (Buteo sp.), have been found on other islands, although such remains have yet to be discovered on Maui.
One species that undoubtedly called Maui home was the Hawaiian Eagle (Haliaeetus albicilla), a subspecies of the Eurasian White Tailed Eagle, whose remains were first discovered in the Ulupalakua area of Maui. Recent research has demonstrated their presence in Hawai`i for at least 100,000 years, with resident populations on Maui, Molokai, and Oahu. The Hawaiian Eagle very likely subsisted on the abundance of fish (similar to its cousin, the Bald Eagle) swimming in the coastal waters of Waihee, while plentiful bird life may have offered another edible option in the flightless birds who would have made for easy prey.
Finally, the forest birds, now associated more with upper elevation forests, could have been abundant across low elevations as well, including the Waihee Refuge[1] [2] . Taken together, all of the various species of seabirds and forest birds, waterfowl, predators and prey must have been an incredible sight to witness, especially for those of us with an affinity for birds. The copious amounts of avian droppings would have fertilized the land, enriching the soil with nutrients, and encouraging life in its many variegated forms.
However, the means by which each individual species thrived, not in spite of one another, but rather because of one another remains the most poignant aspect of this story. Earlier, I mentioned the land crab, Geograpsus severnsi. With a carapace about the size of an adult human palm, this not-especially-large crab had such a large population that it dramatically shaped the entire ecosystem of Waihee. The G. severnsi, known within the trophic (food) web as a macrophages omnivore, consumed everything from dead birds and leaf litter to detritus washed ashore...and everything in between, for that matter.
In fact, their abundance at Waihee seems overwhelming. Several transects I have done on the dune revealed fragments of these land crabs every two or three feet; their role in the maintenance of the refuge was critical. Studies of land crabs elsewhere demonstrate that their constant consumption of detritus, including low hanging leaves and branches, allows birds to move about more freely and gain access to areas where they then add nutrients from their droppings to the otherwise nutritionally depauperate soil of the landscape. Seabirds in particular have an aversion to extremely dense vegetation, and so the symbiotic relationship between the G. severnsi and the seabirds was crucial. Land crabs consumed vegetation obstructing the nesting habitat of the seabirds, while they in turn fertilized the soil for new plant growth.
The extinction of these crabs seems to have occurred soon after the arrival of humans (probably due to a combination of factors, but largely that of the introduction of the Pacific Rat, or Rattus exulans). It follows that a plummet in avian populations resulted from the direct influence of the same predators that eliminated G. severnsi, as well as the indirect influence of the passing of the crabs that brought about the transformation of vast areas of open ground into dense underbrush, unusable by the seabirds.
Understanding our past and that of the formation and function of our Hawaiian ecosystems serves a much greater purpose than pure speculative enjoyment. As we face a climatically uncertain future, understanding and restoring the historical composition and activity of these ecosystems remains our most viable path to creating a healthy, sustainable, and resilient future. Ecologists have known for many years that co-evolved species are more resilient in the face of natural disturbances like storms, rises in sea level, droughts and tsunamis. Restoring our vulnerable ecosystems to whatever degree we are capable will grant us the best possible defense against such future disturbances. By looking to the past, we can better prepare ourselves to face an unknown future, together.
Geograpsus severnsi claw found at Kalaekahoomano (Waihee) Point.
— Dr. Scott Fisher