potential impact sea level rise will have on a tidal marsh’s ability to sequester greenhouse gases.
The amount of data the Science Box generates in four minutes would take a human 3,600 minutes to collect by hand. Which is exactly what Cailene spent her summer doing in Long Marsh, a “fingerling” tidal wetland about ten miles northwest of here as the crow flies. There is no road to the marsh’s terminus; to reach the transition zones where the readings are most telling, Cailene must drop down the side of a culvert near the marsh’s mouth. Then she hikes through the waist-high grasses, hopscotching across rivulets and drainage ditches until she reaches the end. It takes her thirty-three minutes to travel from stem to stern. She can’t safely cart the Science Box all the way back there, which is why she collects her readings the old-fashioned way—with a twenty-five-milliliter syringe and an Exetainer vial. Tapping away at the calculator app on her cell phone, she says that it took her months to produce one-tenth of the data the team will collect today.
Cailene and Dana will devote much of the upcoming academic year to better understanding what separates a healthy tidal marsh from one that is not, and the rate at which each releases greenhouse gases into the atmosphere. Or, as Beverly describes it, “They are filling in the equation that describes today’s carbon cycle.”
As I drove down State Route 209 and out on the fog-struck peninsula that morning, the local NPR radio personality likened the weather to pea soup. The midday heat was bound to break records, he warned. Now, listening to Cailene, I understand that it is going to be not only the hottest day of the summer but also one of the most important, at least for these young researchers. As we prepare to walk, Dana adjusts his straw cowboy hat and tugs at his sun-bleached Cisco Brewers T-shirt, pulling it over his belt. Then he looks out across the sea of saltwater cordgrass and black needlerush, places his hands on the wheelbarrow handles, and enters the humming midmorning light. Not only will today’s work net the raw material of his yearlong thesis project, it will hopefully help illuminate how drowning tidal marsh ecosystems could inadvertently contribute to the ongoing inundation of the coast.
For much of human history we have had very little sense of the dynamic nature of life on the planet. Three hundred years ago we didn’t know that the earth has been regularly covered in massive sheets of ice that pulse in and out from the poles like a scab forming and retreating. We didn’t know that the continents were in constant motion or that animals could go extinct. We didn’t know that light traveled faster than sound or that bacteria caused disease, and we didn’t know that the universe began not with God’s word but with a big bang.
Right up through the middle of the eighteenth century, Westerners thought the earth began roughly four thousand years before Christ. But unearthing evidence of species that modern humans knew absolutely nothing about—such as a massive mastodon molar found in present-day Kentucky—hinted that there had once existed many other worlds, which had flourished and vanished over a previously unimaginable length of time. One of the earliest books to acknowledge the idea that the earth’s history might be much longer than our own was Charles Lyell’s Principles of Geology, written just over a century and a half ago. It popularized the work of William Smith and James Hutton, who spent decades comparing the appearance and disappearance of different fossilized animals in the red sandstone cliffs in Devonshire, England, in the late 1800s. As John McPhee writes in Annals of the Former World, “Some creatures … had appeared suddenly, had evolved quickly, had become both abundant and geographically widespread, and then had died out, or died down, abruptly. Geologists canonized them as ‘index fossils’ and studied them in groups” in order to get a better sense of the age of our planet. The earth scientists at Devonshire painstakingly compared these “index fossils” against each other and in doing so started to divide geologic time into different epochs. Their studies suggested that, contrary to popular belief, the earth had likely been gyrating just outside the asteroid belt for the better part of four hundred million years.
Of course this estimate of the earth’s age was not accurate either. It wasn’t until radiometric dating was pioneered by Arthur Holmes at the turn of the last century that we improved on this rough calculation—by a huge margin—and discovered that our planet actually came into existence roughly 4.5 billion years ago. Though our tools have progressed, most nongeologists, me included, are still likely to wildly misidentify different events in geologic time, often by orders of magnitude.
Four thousand, four hundred million, or 4.5 billion years—it is all the same to us. We tend to think in human lifetimes, and even there our scope is limited. We are individually preoccupied by the lives of those we know and expect to know: our grandparents, parents, children, and, if we are lucky, grandchildren. Which is why it is so fantastically difficult for us to recognize that in our frenzied attempt to keep nearly eight billion people fed, watered, clothed, sheltered, and distracted, we are fundamentally altering the geophysical composition of the planet at a pace previously caused only by cataclysmic events, like the massive asteroid that smashed into eastern Mexico, wiping out the dinosaurs, sixty-five million years ago.
Lately, Earth-minded scientific researchers and activists alike have taken to condensing the history of the planet into a single calendar year to explain just how temporally insignificant human civilization is and how profoundly we have changed the planet in the time it takes, relatively speaking, for a rufous hummingbird to beat its wings. In this version of history, the planets are formed at the very beginning of January. Sometime during the first week of the year, a giant object collides with Earth, and out pops the moon. It isn’t until late July that the first cells form. In August coral creeps across the ocean floor. Late in October multicellular organisms appear. Plants make their way onto land close to Thanksgiving. Around the first of December come the amphibians and insects. Dinosaurs arrive on December 12, and by December 26 they are gone. On the evening of December 31 the first hominoids emerge in East Africa. At ten minutes to midnight Neanderthals spread to Europe. We invent agriculture one minute before the clock strikes twelve. Shortly thereafter we start to write things down. All it takes is five short seconds for the Roman Empire to rise and fall. We enter the industrial era two seconds before midnight, the petroleum age a half a second before the year comes to a close. And in that fraction of a second we cause the end of an entire epoch.
The Holocene closes and the Anthropocene (or the Capitalocene, as environmental historian Jason W. Moore suggests calling it) begins, launching a geologic period defined by the complete and utter dominance of certain human beings and our endless accumulation of resources. In that fraction of a second, we open the earth’s veins, exhume as much energy as possible, and pump various byproducts into the air, causing the atmosphere to warm twenty times faster than normal. We cause the polar ice caps to melt, the oceans to heat, and the coastline to change its shape. We alter the very makeup of the biosphere, the twelve-mile-deep sliver of the earth that is home to all known life that has ever existed in the entire universe. “Abundant” and “geographically widespread” are two ways of describing the extent of humans’ impact on the planet. Lately I have been wondering whether the descriptor “index fossil” might also soon apply.
Global sea levels have risen about nine inches since we started keeping track in 1880. If they were to keep rising at this rate, by century’s end they would be roughly five inches above where they are today. But most scientists expect to see anywhere between an additional twenty-four to eighty-four inches of sea level rise by 2100, and every year the estimates creep higher still. Between the turn of the last century and 1990, sea levels rose, on average, 1 to 1.2 millimeters per year. Then the rate of the rise itself started to increase, rapidly. In the intervening quarter century, the per-year increase has risen to 4 millimeters, and, like so many other climate change signals, it shows little sign of slowing down.
As the rate of the rise continues to accelerate, tidal marshes are becoming inundated and, as here, they are starting to
