Around five million years ago, a tiny California tarweed seed blew out to sea. Perhaps it was swept up by a jet stream. Maybe it clung to the feathers of a migrating plover or rode the marine currents on a sturdy bit of flotsam. Somehow, this wee speck traveled more than 2,000 miles across the Pacific Ocean to land on a fresh slab of lava: most likely the brand new island of Kaua‘i.
Rains came and watered the seed. The sun fed it, and it grew. In this wholly unfamiliar landscape, it bloomed, unfurled a scant, daisy-like flower and produced seeds of its own. With each successive generation, the tarweed’s descendants warped to their home. The mutants survived and thrived. Their genes bent in directions better able to tolerate the tropical sun, salt air, and volcanic soil. They bent until they weren’t tarweeds anymore but something new. Amazingly, they didn’t all bend in one direction. That single seed gave rise to a multitude of novel species: the 30-plus shrubs, trees, and vines known as the Silversword Alliance.
If this sounds like a superhero origin story, well, it kind of is. The pioneer species that found their ways here could endlessly perfect themselves, honing their compatibilities to the Hawaiian archipelago’s precise microclimates. Had Darwin sailed to these shores after the Galapagos, the pages of On the Origin of Species would have burst with examples of endemic Hawaiian splendor: happy-faced spiders, 50-plus types of honeycreeper birds, and 800 drosophila flies, each with an identifiable stained-glass wing pattern. Hawai‘i would’ve blown Darwin’s mind.
The Hawaiian Islands were an evolutionary utopia for two reasons: isolation and height. Once a species arrived here, it couldn’t easily mix with others of its kind a few counties over. The Pacific was too great a moat to cross for casual encounters. Each new recruit had to forge its own tribe. And the height of Hawai‘i’s volcanoes—the planet’s tallest mountains when measured from their bases at the sea floor—meant that new arrivals had a plethora of climates to inhabit: coastal dunes, lava plains, rainforests, dry forests, sub-alpine forests, and mountaintops sometimes capped in snow. The diversity of terrain signaled both opportunity and challenge. A species that flourished at sea level had to reinvent itself in order to endure the frigid, wind-blasted atmosphere found at the 13,800-foot summit of Maunakea.
Hawai‘i offered its first inhabitants just about everything, but what it lacked was equally important. Reptiles, amphibians, social insects like ants and termites—entire taxonomies couldn’t survive the type of journey the tarweed endured. There are only two endemic Hawaiian mammals: the monk seal, because it could swim here, and the hoary bat, because it could fly. Every other furred creature came later and had the help of humans.
And so, as the islands emerged one by one out of the sea, they were populated by the humbler half of the food chain: plants, insects, and birds. Free from the pressure of grazing buffalo, deer, or giraffes, plant species shed their thorns, toxins, and means of long-distance travel. Birds became fat and flightless, swelling to fill niches of missing beasts. Two caterpillars turned carnivorous—the sole examples of meat-eating moth larvae in the world. The ecosystems that emerged here over the millennia were … weird.
Which brings us back to the Silversword Alliance. That solo tarweed hit the Hawaiian Islands running. It didn’t just morph into new species, but three new genera. The most famous of its descendants is, of course, the silversword. The spiky-leafed rebel chose the archipelago’s most extreme environment as its home: the parched peaks of Haleakalā and Maunakea. The silversword is almost alone in its ability to withstand the intense solar radiation and spiking temperatures found on Hawaiian summits, though it looks a bit like a giant metallic hedgehog snuffling around the red volcanic cinders.
The silversword’s succulent leaves are covered in silver reflective hairs that keep the plant from frying in the sun or freezing at night. It can live more than 50 years. Before dying, it produces a single magnificent inflorescence that towers up to six feet tall, bearing tiny fuchsia blossoms that resemble those of its distant progenitor. The plant’s powerful perfume lures Hawaiian hylaeus bees, who bury their faces in its pollen. Native drosophila flies pay visits, as do native tephritid flies, who feed on its fruit. In an otherwise stark terrain, the flamboyant silversword is an ecosystem unto itself.
Less famous than its cousin, the greensword possesses equal superpowers. It dwells in some of the wettest spots on Earth, such as Pu‘u Kukui bog. The soil here is so saturated and acidic that tree species are dwarfed, growing only one or two feet tall. The greensword looms over this miniature canopy, dangling a chandelier of blossoms in the ever-present mist. Over on Kaua‘i, the iliau resembles a greensword on stilts, but belongs to a separate genus. Other members of the alliance include the koholāpehu (Dubautia latifolia), a ropey vine found only on Kaua‘i, and the na‘ena‘e (Dubautia reticulata), a tree in the east Maui rainforest. If it weren’t for their shared genus name, one might never know they are related.
All these idiosyncratic species sprang from a single pioneer many eons ago, and all are now imperiled by habitat loss, invasive species, and climate change. When humans finally found Hawai‘i, the fertile era of isolation ended. The laboratory was flooded with newcomers. An army of nibblers and grazers—rats, cows, pigs, goats, deer—descended on the natives, which no longer had armor with which to defend themselves. Scores of species went extinct, some disappearing before humans even laid eyes on them.
Early Hawaiians did not often travel up to the high-elevation forest, known as Wao Akua, realm of the gods. But rats did. They jumped out of Polynesian canoes and beelined up the mountain to feast on the juiciest fruits. As a result, numerous species vanished before even receiving a Hawaiian name. Some are known only from the pollen record, or their fossilized bones. Consider the po‘ouli, a forest bird first discovered and named in the 1970s. It was only by chance that biologists found this species before it, too, succumbed to extinction in 2004.
And yet Hawai‘i’s peculiar endemic paradise is not altogether lost. Successful restoration projects on each island are not only preserving what’s left but also reviving degraded habitats and bringing them back to life. Pockets of the mystery remain for us to investigate, fall in love with, and fight for.