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!
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!
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.
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.
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. |
EXCELLENT post Rob!
ReplyDeleteFascinating blog entry, Sweetie!
ReplyDeleteWow, 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!
ReplyDeleteWie - I know that this comment came from YOU! What's with the anonymous posting? Or could it be that YOU are Satoshi?
Delete