The World Without Us

It is an archive containing more than 160 years of human efforts to harness plants. The specimens, sealed in thousands of five-liter bottles, are of virtually everything. From each experimental strip, Gilbert and Lawes took samples of harvested grains, their stalks and leaves, and the soil where they grew. They saved each year’s fertilizers, including manure. Later, their successors even bottled the municipal sewage sludge spread on Rothamsted test plots.

The bottles, stacked chronologically on 16-foot metal shelves, date back to the first wheat field in 1843. When mold developed in early samples, after 1865 they were stoppered with corks, then paraffin, and finally lead. During war years, when bottle supplies grew scarce, samples were sealed in tins that once held coffee, powdered milk, or syrup.

Thousands of researchers have mounted ladders to peruse the calligraphy on time-yellowed bottle labels—to extract, say, soil collected in Rothamsted’s Geesecroft Field at a depth of nine inches in April 1871. Yet many bottles have never been opened: along with organic matter, they preserve the very air of their era. Were we to go suddenly, assuming no unprecedented seismic event dashes thousands of glass vessels to the floor, it’s fair to surmise that this singular heritage would survive intact long beyond us. Within a century, of course, the durable slate-shingled roof would begin to yield to rain and vermin, and the smartest mice might learn that certain jars, when pushed to the concrete and shattered, contain still-edible food.

Supposing, however, that before such entropic vandalism occurs, the collection is discovered by visiting alien scientists who happen upon our now-quiet planet, bereft of voracious, but colorful, human life. Suppose they find the Rothamsted archive, its repository of more than 300,000 specimens still sealed in thick glass and tins. Clever enough to find their way to Earth, they would doubtless soon figure out that the graceful loops and symbols penned on the labels were a numbering system. Recognizing soil and preserved plant matter, they might realize that they had the equivalent of a time-lapse record of the final century-and-a-half of human history.

Rothamsted Research Archive.

PHOTO BY ALAN WEISMAN.

If they began in the oldest jars, they would find relatively neutral soils that didn’t stay that way for long as British industry redoubled. They would find the pH dropping farther into the acid end by the early 20th century, as the advent of electricity led to coal-fired power stations, which spread pollution beyond factory cities to the countryside. There would also be steadily increasing nitrogen and sulfur dioxide until the early 1980s, when improved smokestacks cut sulfur emissions so dramatically that the aliens might be puzzled to find samples spiked with powdered sulfur, which farmers had to start adding as fertilizer.

They might not recognize something that first appeared in Rothamsted’s grassland plots in the early-1950s: traces of plutonium, a mineral that barely occurs in nature, let alone in Hertfordshire. Like grape vintages embodying annual weather, the fallout from tests in the Nevada desert, and later in Russia, marked Rothamsted’s distant soils with their radioactive signature.

Uncorking the late 20th century, they would find that the bottles held other novel substances never before known on Earth (and, if they were lucky, not on their planet, either), such as polychlorinated biphenyls— PCBs—from the manufacture of plastics. To naked human eyes, the samples appear as innocent as comparable handfuls of dirt in specimen bottles from 100 years earlier. Alien vision, however, might discern menaces we only see with devices like gas chromatographs and laser spectrometers.

If so, they might glimpse the sharp fluorescent signature of polyaro-matic hydrocarbons (PAHs). They might be astonished at how PAHs and dioxins, two substances emitted naturally by volcanoes and forest fires, suddenly leaped from background levels into center-stage chemical prominence in soil and crops as the decades advanced.

If they were carbon-based life-forms like us, they might leap themselves, or at least back away, because both PAHs and dioxins can be lethal to nervous systems and other organs. PAHs were buoyed into the 20th century aboard clouds of exhaust from automobiles and coal-fired power plants; they’re also in the pungent odor of fresh asphalt. At Rothamsted, as at farms everywhere, they were introduced deliberately, in herbicides and pesticides.