Monday, October 17, 2016

Meet the Natives

In an earlier post (Floral Inflation), I described how Midway Atoll went from having just a dozen or so species of plants to over 200 over the course of about 100 years (the botanical equivalent to the acceleration of a Lamborghini). And although I included the names and photos of a few native plant species, I didn’t really do them justice. I thought I should revisit to topic and introduce you to some of the beautiful and interesting native plants we have out here and so I began the task of researching the plants and taking some photos. Little did I know that I would be pulled, in an ironically-metaphorical sense, “into the weeds”. What once seemed like a neatly circumscribed topic became muddied with complications. What is native to this place? And how do we know?  What to do about the fact that the very physical environment of Midway has changed so radically over the decades? It has taken me some time to extract myself from the thicket but I hope that you will find what I have to share with you worth the wait.

Every ecologist is well-versed in concepts of “native” versus “exotic” and uses this as a way to separate the “good species” from the troublesome. Back in New Mexico and Oregon it was a pretty straightforward task to take the list of plants found at a site and split them into these two categories. Generally speaking, if a plant existed in the area prior to the arrival of white people it was considered native and if it wasn’t it was exotic (the exact word used changed over time as folks struggled to find something politically acceptable and included “non-native”, “alien”, and “invasive”). It wasn’t that the indigenous peoples of North America didn’t move plants around (for example, bringing corn from Mexico to the Mississippi basin), but the changes that ensued after Columbus’ “discovery” were so profound in comparison that dividing things into “pre-“ and “post-Columbus” has typically proven very useful (check out this book by Charles C. Mann for more on that topic). Ecosystems that still retained their native species were judged to be more pristine while those dominated by exotics were thought of as degraded.

So my original plan was to do a little research into the dozen or so plants I had been told were native to Midway and write about them. Early on I had noticed a few things that seemed really cool. Even though there weren’t many native species, they seemed diverse in terms of their growth forms – which included bunchgrasses, sedges, sprawling vines with showy flowers, big shrubs that enable the formation of dunes, and delicate wildflowers – as well as in their life histories – a mix of opportunistic short-lived plants that produced a lot of seed and long-lived plants with more complicated ecological relationships. One thing most of them had in common was the ability to grow from cuttings or to produce large, durable, seeds worthy of sea voyages – traits essential for establishing themselves remote islands far from their source populations.

As I was putting together that post though I also took on the task – as part of my work responsibilities – of compiling a list of plant species for the atoll. In doing so I relied heavily on the work of Forest and Kim Starr, botanists based out of Maui who have for decades catalogued and researched Midway’s flora. They listed not a dozen but 39 native species encountered here over the years. Digging deeper, I found that while the term native could be applied to species discovered here during the very first botanical surveys, it might also include those found on nearby islands or even on one of the main Hawaiian islands (Oahu, the Big Island, Maui, etc.) but encountered here at a later date. And what about species that might have been missed on those earlier surveys or those that were native to the region but only showed up once the island had extensively modified during “military occupation” or where purposefully introduced? What did it really mean to be a native plant species on Midway? This was a question without a simple answer and required that I examine each species individually using whatever evidence I could acquire which included research into published journal articles and unpublished works (the “gray literature”) as well as herbarium records and online databases.

In the end I reckoned 22 of the 39 species to be truly native to Midway atoll, meaning, they were had a very good chance of being here before the Pacific Commercial Cable Company set up operations here in 1903.  The remaining 17 species were those that were native to somewhere in Hawaiian archipelago but probably had made it to Midway with the help of people – either by them acting as their couriers or by the changes wrought by them as a consequence of their presence here. My research also revealed what had been lost. Of the 22 native species, about half had their entire populations eliminated from Midway as a consequence of the environmental perturbations that resulted from the island’s occupation (one of these was subsequently reintroduced and still struggles to survive). Three are now extinct – that is, vanished entirely from the planet.  The 12 survivors are clearly a hardy bunch and play important roles in the US Fish and Wildlife Service’s efforts to restore the islands ecosystems.

The first botanical surveys of Midway Atoll were conducted by ornithologist William A. Bryan who visited these remote islands for just a few hours in 1902 (a side trip taken while en route from Marcus Island back to Honolulu). Until that time, Midway had been visited primarily by bird hunters and a few unfortunates who found themselves shipwrecked here.  Little had been done to modify the environment at the time and Bryan described Sand Island as a “barren, blinding, heap of sand” noting also that nearby Eastern Island was much greener, covered in low shrubs, and more hospitable despite its smaller size and simpler topography. In his very short time at Midway, Bryan recorded a mere 13 species of plants consisting of three shrubs, four wildflowers, four grasses, and two vines but admitted that that he would likely have encountered more species if he’d been there longer. Eight of these plants are still present on the atoll and are critical players in restoration efforts here, including alena (Boerhavia repens), emaloa (Eragrostis variabilis), koali awa (Ipomoea indica), and popolo (Solanum nelsonii). Unlike some of the northwestern Hawaiian Islands, there are no plant species endemic to Midway (that is species that occur here but nowhere else in the world). Of the 13 true natives, five no longer occur on Midway and of these, two are extinct. One of these is the grass Kamanomano (Cenchrus agrimonioides var. laysanensis) which was once abundant on several of the Northwestern Hawaiian Islands but was last seen in 1961 on nearby Kure Island.  The other, ʻahinahina (Achyranthes atollensis) was a shrub in the amaranth family with hairy leaves that grew up to four feet high on sand mounds and was never seen again on Midway after 1902!

Undisputed natives. Boerhavia repens (top) and Lepturus repens (bottom) were
noted during the very first botanical explorations of Midway. Both of these species have widespread distributions across the tropics and subtropics.
Erling Christophersen and Edward Caum, travelling with the Tanager Expedition in 1923-4, were the next to document the flora of Midway and turned up four additional native plant species. These included the beautiful morning-glory vine Pohuehue (Ipomoea pes-caprae ssp. brasiliensis), and the spectacular yellow-flowered ilima (Sida fallax). Ilima, which also occurs on the main Hawaiian Islands has great cultural significance and is the most desired flower when creating the traditional lei or flower wreath. Two of the four species are, however, now gone from Midway. Phyllostegia variabilis, appears to have disappeared from the planet so quickly that there is no common name for it and virtually no information about it (try finding anything about this species using Google and you will surely be disappointed!). Moa (Psilotum nudum), is a rootless fernlike plant that no longer occurs on the atoll but persists across a wide swath of sub-tropical and tropical areas of the globe and was used by native Hawaiian people to prevent chafing incurred in the wearing of loincloths!

Botanists travelling with the Tanager Expedition (1923-4) were able to make a more complete list of Midway's flora adding Sida fallax (top)  and Ipomoea pes-caprae ssp. brasiliensis (bottom) to the list of native species.
The 1930s and ‘40s were periods of profound change at Midway as the islands became a tourist destination with the establishment of a Pan American Airways Clipper station (which included a hotel and restaurant) and then, shortly after, drew the attention of the US military as global tensions rose and the atoll was recognized as a place of strategic significance. Buildings were erected, roads constructed, and runways paved. Occasional visits by botanists documented the effects that these changes had on Midway’s flora. Johnson Neff and Philip Du Mont spent a month on the atoll in 1954 to “study bird problems” but also found time to document the plant life as it existed at that time. Two native species, mau'u 'aki'aki (Fimbristylis cymosa) and ena'ena (Pseudognaphalium sandwicensium var. sandwicensium) were recorded for the first time. These are species that, though native to the Hawaiian islands, had never before had a place to grow on Midway but were now found to be growing along paved surfaces. Ena’ena, interestingly, mostly finds its home on lava flows on the Big Island but was thriving in this novel ecosystem. In 1980 Derryl Herbst added kaʻa, puʻukaʻa (Cyperus polystachyos) to the list of sort-of-native Midway plants. This widespread and hardy sedge found a niche at the end of a runway where water pooled during the wet-season and decades later became a foundational species in creating wetland habitat for the endangered Laysan duck. The discovery of the succulent akulikuli (Sesuvium portulacastrum) in 1995 by Marie Bruegmann is a bit of a mystery as habitat for this plant – areas close to the beach that receive salt spray and are occasionally washed over by storm-driven waves – would seem to have been some of the least disturbed areas on the atoll.

Extensive modification of Midway's environment created suitable habitat for "new native species"
such as Fimbristylis cymosa (top) which grows in cracks in the runways; Although it is likely that the hardy,
salt-tolerant mat-forming Sesuvium portulacastrum (bottom) existed on Midway for many centuries it was not discovered until the 1990s.
When management of Midway was turned over to the US Fish and Wildlife Service in 1996 (see Trading Guns for Goonies) restoration of native plants became a priority. Ten species of plants native to the Hawaiian islands were either introduced or just showed up in the years that followed. These included species that were in trouble elsewhere and needed new homes. Aweoweo (Chenopodium oahuense), a robust shrub in the goosefoot family, and and Bryan’s flatsedge (Cyperus pennatiformis var. bryanii) were brought to Midway from Laysan Island, the former becoming an important species used for restoration while the latter failed to establish. Efforts to secure the critically endangered loulu lelo (Pritchardia remota) compelled Fish and Wildlife Service staff to collect several hundred seeds from their source population on Nihoa island and grow them out in the nursery on Midway. Today, five of these plants survive adding a some security to the original population.

Though not native to Midway, the Nihoa fan palm (Pritchardia remota), originall found only on the
island of Nihoa in the Northwestern Hawaiian Islands is currently being grown on the atoll as
part of efforts to secure its global population.
Efforts to re-establish the native plants of Midway Atoll and to provide habitat for endangered plants native to other parts of the Hawaiian archipelago are more concerted now than ever. The US Fish and Wildlife Service has stepped up its efforts to restore degraded habitat on Midway atoll which now includes a native seed library, a greenhouse, and a brand-new, 6,600 sq ft shadehouse. Through its native plant propagation program Midway has become an important site for conservation of the popolo at a time when populations elsewhere continue to decline. Exact definitions of what is native or not no longer seem so important in a world of changing climate and rising seas. What seems imperative now is to do the most we can with this 2 square miles of sand and coral out here in the Pacific Ocean with respect to both the wildlife and the plant life. This will require boldness, creativity, but also humility. Of the 22 “original” native species, half had their entire populations eliminated from Midway as a consequence of the environmental changes wrought upon the island during the early part of the 20th century and only one of these, akiaki (Sporobolus virginicus) has been successfully reestablished. We need to do better than that in the future and doing so will require utilizing sound science in guiding future actions. That and maybe a little luck!


Currently, 20 species of "native" plants are being propagated by the
US Fish and Wildlife Service at Midway Atoll.

5 comments:

  1. Fascinating blog entry, Sweetie!

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  2. Wow, this is a fantastic and fascinating post! Definitely sums up the complexity of plants out on Midway Atoll--and how valuable your work is! And I have to say, I am quite impressed with your use of plant puns!

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    1. Wie - I know that this comment came from YOU! What's with the anonymous posting? Or could it be that YOU are Satoshi?

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