A Trip to the Islands

Years ago, I participated in the design of the Visitor Center at the Red Rock Canyon National Conservation Area in the Mojave Desert just west of Las Vegas. A land of extremes, subtle variations in wind, heat, humidity, and soil mark the line between life and death at Red Rock. Aztec Sandstone towers above the desert floor, making the area a world-class rock-climbing destination. The cliffs are sheer and treacherous. In the higher elevations, naturalists find “sky islands”—isolated ecosystems where conditions diverge from those on the desert floor, enabling unique niches of plants and animals to survive, but also effectively fencing them in.

Some sky island inhabitants are immigrants, brought in by blowing winds, animal droppings, and the boots and pant legs of tourists. Others have been there for thousands of years, since the last Ice Age when the Southwest was much cooler and wetter than it is today. Back then, even lands barely above sea level could host woodland communities of spruce, fir, pinyon, juniper, and even Ponderosa pine. But when the climate warmed, the desert dried out the flats and steadily climbed into the hills until the mountain holdouts became marooned, surrounded by inhospitable lands that would quickly roast them if they dared to venture from their elevated retreats. Over time, each of these secluded niches followed their own evolutionary paths, driven by local topography and their haphazard makeup. Did you know that there are still jaguars and ocelots living in Arizona?

Sky islands exist in many places along the mountain ridges of the American Southwest, where deserts surround and confine them as effectively as the Pacific Ocean surrounds the many mountaintops that occasionally pierce its surface. Most Pacific islands were formed by the movement of tectonic plates, generating uplift and, occasionally, lava erupting from cone-shaped volcanoes. In 2014, NASA satellites were lucky enough to capture the birth of one such island, Hunga Tonga-Hunga Ha’apai (a name I love, by the way) in the Kingdom of Tonga, which sits in the middle of the South Pacific east of Australia.

It’ll be some time before the coconuts, iguanas and sea gulls move in. For a while, it’ll just be a steaming pile of rock. But they’re all coming, and I’m fascinated by how they get there. Some get blown in by cyclones. It’s a hazardous ride, but over thousands of storms, someone’s bound to win the lottery. Some fly in—think birds, bats, and lightweight spiders with fancy parachutes and the ability to withstand high altitudes without pressurization or pretzels. Others get floated in by debris. Palm fronds make magical life rafts for common geckos and any number of invertebrates and tree frog tadpoles. Some arrive in the slurry of plankton conveyed by oceanic currents. Somehow, these infant sea creatures know to head for land at just the right time. Pacific islands are often surrounded by coral reefs which, it turns out, make ideal nurseries.

Still others get flown or floated in as seeds. They arrive stuck to the feathers of migrating birds, swallowed and later expelled in feces, or they float all by themselves, in hardened shells that can withstand the long saltwater cruise until the tide rolls them up on some sandy beach, where the sun warms and dries and triggers them to sprout. They face long odds, each of these castaways. But given enough time and happenstance, they populate one island after another. And yet because each is miles and miles apart, and may be inhabited by a different set of flown, floated, and/or pooped out creatures, their neighborhoods evolve in their own random directions. One island has salt water crocodiles or drooling dragons at the top of its food chain. Another is heavily trod by flightless birds. One island has huge invertebrates but no land mammals. Another has no coconuts but huge tree ferns.

When I think of such islands, my mind wants to leap to modern cities, urban islands where local geography and historical circumstances conspire to allow them to host millions of diverse creatures, sharing various evolutionary traits with their distant cousins, and yet each very much a unique mega-organism. Chicago, Indianapolis, St. Louis, Kansas City—all feel to me like great, urban islands surrounded by the ocean of prairie. Who was flown, floated, or dumped there seems just as random as the future inhabitants of Hunga Tonga-Hunga Ha’apai. Once they each achieved some mysterious threshold they became magnetic, self-sustaining ecosystems, drawing more and more species and resources into their orb, donning their own cultural doodads, and expelling those that couldn’t make the cut. What makes the naked city go? Who puts it on the map? Who crafts poetic stanzas about its grand avenues, bustling streets, and back-alley hangouts? Who can’t afford to live there? Who is put off by the weather, the traffic, the noise, the pollution, the crime, the schools? Such considerations are no less daunting than the searing Mojave sun or the pounding Pacific surf. That very process of natural selection suggests to me that these urban islanders can feel just as confined as the residents of Red Rock. At some point, you’ve commuted so far from the Loop that it no longer feels like you live in Chicago. I don’t know what that distance is, but when you start rooting for the Packers, Chiefs, Colts or Lions, you’re off the island!

All this island talk leads me to wonder about SETI (the Search for Extra-terrestrial yada yada) and whether the Earth isn’t just another kind of island, the ultimate sky island, surrounded by a vast desert/ocean of space that confines and separates us from our galactic cousins. Just like the Red Rock residents likely have no awareness of their cousins in Mexico or California, I wonder about our ignorance about potential life in far-off galaxies. Perhaps, long ago, we were among those who were dropped here aboard a rogue asteroid, flown in with some random stardust, or even excreted by some ancient space traveler making use of our blue planet as a convenient porta potty. Over eons of time, we’ve evolved in our own Earthling ways, so much so that we might not even recognize life elsewhere as life. Hmmm? “I am a rock, I am an island.” Kind of gives that old tune a different spin!