Earth in Human Hands Read online

  Still, in some places nature is being overwhelmed. Midway Island is named for being a lone, tiny waypoint between Asia and North America, the kind of place that used to be considered the middle of nowhere. Yet it is situated in an ideal location for collecting plastic flotsam from the Great Pacific Garbage Patch. No people live on Midway Island, but our stuff is there in abundance, brought with the currents of the gyre, and birds see our colorful plastic bits, mistake them for food, and bring them to their nesting chicks. You’ve probably seen those heartbreaking images and videos of the sick and dying baby albatrosses. About one-third of the young birds die, many choking on or starving from the plastic diet. Odile and her team have examined plastic retrieved from inside those dead birds and found mostly beverage caps, but also pieces of plastic cutlery, cigarette lighters, and fishing gear.

  Odile studies what becomes of discarded plastic, how it breaks down and interacts with its environs. Contrary to the widespread myth that plastic lasts forever, it breaks down chemically and physically, reacting to radiation and agitation. It crumbles into smaller and smaller pieces, becoming minuscule and then microscopic, and then only molecular fragments of the larger polymers. These are ingested by the tiniest of marine organisms and make their way through the food chain. Perhaps appropriately, some of our plastics and their chemical products end up in our own tissue, blood, and guts.

  Plastic does take one form, recently discovered, that may in fact last if not forever then for a significant amount of geological time. Some washes up on beaches and ends up in bonfires. In 2006, a strange new kind of rock was discovered on some Hawaiian beaches containing melted plastic binding together bits of rock, sand, shell, and other materials. Some of this tough material, now called plastiglomerate, will become buried and last for many millions of years, a new rock type that has suddenly appeared in Earth’s strata, marking the time when people built things of plastic, scattered them widely, and sometimes burned them on beaches for celebration or warmth.

  The plastic flamingos are coming home to roost. Our response is characteristically human: slowly, haphazardly, and unevenly we are moving to incorporate awareness of the new reality, and taking baby steps toward mitigation. Policies and habits are shifting toward less wanton discarding of plastics, and plastics themselves are evolving to incorporate what we’ve learned about their larger role in the world. Early on in the age of plastic, scientists and engineers were concerned only with how to make materials that were useful and stable for as long as possible. Now materials scientists such as Odile Madden are learning more about the long-term global consequences of our choices of materials and manufacturing processes. They are thinking about the entire life cycle and how to design plastics with “engineered instability” so that products may disappear gracefully, becoming food instead of hazards or poisons.

  Studies are even under way to create technologies to clean up the Garbage Patch. In 2012, a Dutch teenager named Boyan Slat proposed, as part of a high school science project, an idea for a machine that could start to remove plastic from the gyre. Equipped with giant arms to pull in debris, and designed with filters to protect sea life, the solar-array-powered machine would be anchored to the seafloor and would collect plastic for recycling. The sale of the recyclable material it collected would help offset its cost. Many experts have examined Boyan’s proposal and found it potentially feasible. His machine would not clean up the microscopic fragments, but by getting rid of the larger pieces of plastic, it would cut off the source of those fragments and dissipate the gyre. I don’t know if this or some other innovative cleanup technology will be the way we rid our oceans of this unintended monstrosity, but I bet in fifty years the Garbage Patch will be smaller than today, and in one hundred years it will be gone entirely. That’s too late for generations of poor albatrosses on Midway Island, and other victims of our lack of foresight, but in the life of Gaia, the Garbage Patch will have been a momentary annoyance, here just long enough to leave some odd deposits, pressed like plastic flowers between pages in the long book of geological stratum.

  The Homogenocene

  Long before the Industrial Revolution or even the Agricultural Revolution, our species had already established a pattern of global ecological disruption. As much as we’ve altered the course of any river, we have also diverted the stream of biological evolution. It’s normal for successful species to rework their environments, forcing other species to adapt and squeezing some out entirely. We’ve been doing this for a long time, but at some point we were no longer just another species messing with all the others. We became a major new kind of evolutionary force, determining through our actions which species around the globe would flourish and which would flop.

  Our success as hunter-gatherers allowed us to successfully inhabit every continent. The toll was particularly heavy on the largest animals because they were either food, threat, or competition. When human beings first spread around the planet, we quickly wiped them out everywhere we went, creating a wake of extinction behind our waves of global migration. As we spread, the “charismatic megafauna” fell away from every continent we colonized: the giant kangaroos and marsupial lions of Australia; the mammoths, mastodons, and giant ground sloths of North America; the elephant birds and giant lemurs of Madagascar; and so on: when Homo sapiens showed up, the big animals soon died off.

  Even before the Agricultural Revolution, we were already remaking landscapes, setting fires to drive game from the forest. Then we started clearing fields for planting, and reengineering plants and animals to suit our needs for food, materials, labor, companionship, intoxication, and beauty.

  For millennia we’ve coevolved with our flora and fauna, manipulating some species and being manipulated by others. While we’ve driven many to extinction, to others we’ve brought absurd levels of global success. We think of eucalyptus trees as native to Australia, but they were rare there when humans showed up forty-five thousand years ago. Our use of fire to clear other species helped these fire-resistant trees eventually thrive and spread throughout that continent. When I first visited Northern California, I assumed that eucalyptuses were native there, as they so dominate the forested hills. Yet they were introduced only during the gold rush, in the 1850s, when they were thought to be a promising source of timber for railroad ties. They turned out to be lousy for that purpose, but they took well to the dry, sunny hills, where they displaced many native trees. They are now regarded as an invasive species and, ironically, given their history in Australia, have become a major fire hazard in some areas. Eucalyptuses are blamed for fueling the 1991 firestorm that destroyed thousands of homes in the Oakland Hills. If trees could dream, the eucalyptus would never have dreamed of occupying such a large territory without our help.

  Domestic cattle are now among the dominant species living on Earth—if you call that living. The combined biomass of all domesticated animals is now some twenty-five times that of all remaining wild terrestrial mammals. Some of our favored plants have become among the most widely propagated on the planet. Wheat, rice, coffee, and cannabis, to name a few, have gone worldwide by giving us what we want. You have to wonder who has been using whom, because in terms of evolutionary success, these plants have done well by us 7—others, not so much. Through our reworking of landscapes, especially for agriculture, we have destroyed and altered habitats and, often without realizing it, created new ones.

  We’ve remixed the very mechanisms of evolution and created an embarrassment of vectors for creatures to spread between distant and once-isolated locales. Life is opportunistic, and the global success of humans has presented many irresistible openings for world travel and adventure. In the cargo holds and bilgewater of ships; in the bulging microbial manifest of passenger jets; in the cool, leafy folds of produce trucks; and in the fur and guts of livestock and pets, we’ve offered transport for innumerable species. In this way, we’ve changed the geometry of the planet. Before we came along, the world was discontinuous. Oceans, deserts, and mountain ranges formed
impenetrable barriers, breaking Earth into separate regions where populations could evolve independently, and then be isolated or merged by continental drift and climate change. Now we’ve created pathways around all those borders, and to some degree the planet is one continuous habitat.

  Some species are primed to take advantage of this new human-altered geography. Many of these we consider pests, but we’ve invited them in, or at least given them a lift, a place to stay, and a way to make a living. Some have followed in our footsteps and gone global. Linepithema humile is a species of ant native to Northern Argentina that has, with our help, become a new kind of global superorganism. They first found their way from Buenos Aires to New Orleans in the 1890s, stowed away on ships, perhaps in dirt used for ballast or in bags of coffee or sugar. There they prospered, easily outcompeting all local ant species and spreading throughout the Southeastern U.S. In the early twentieth century, these eager immigrants made their way West, apparently by riding the rails, hopping trains to California. In midcentury, with the new highway system, they spread up and down the West Coast. While ruthlessly aggressive toward other species, they are also unusually cooperative with their own kind. Ants from neighboring nests don’t fight, as with other species, but welcome one another as family, forming vast, continuous networks connected by underground tunnels. Thus, in effect, they form supercolonies that can spread and grow over hundreds or even thousands of miles. By now one vast supercolony extends from Oregon down to Mexico, and there are others thriving in most southern states.

  Unfortunately, the Linepithema humile don’t play well with others. They have severely disrupted many ecosystems, decimating animals and birds and trees that depend on the local ants for food or seed dispersal. For example, the horned lizard of coastal California has been dying off, as its normal diet of local ants has succumbed to the aggressive colonists. The result is a dramatic decrease in biodiversity in many of the occupied landscapes. The invasive Argentine ants are also farmers. They breed aphids—milking them for a sugary secretion. These ant farmers sometimes successfully compete against human farmers when their aphids destroy our crops.

  What will stop them? Perhaps nothing we do, at least not on purpose. In parts of the southern United States they seems to have met their match in another invasive species we’ve brought to our shores, the Asian needle ant, or Pachycondyla chinensis, who may be even better adapted for invading “our” territory.8 Also, in California, as of this writing, the drought seems to be holding the Argentine supercolony in check for now, as it thrives only around moisture.

  The combination of extreme aggression toward outsiders and extreme cooperation with their own kind, combined with their facility at co-opting human transport and industry to spread around the planet, has made them a globalized success story. These adaptable stowaways have spread to every continent except Antarctica, forming supercolonies in Europe, South Africa, Japan, Australia, and many Pacific islands. The largest of these extends from southern Italy through western Spain, a distance of more than twelve hundred miles. When placed together in close quarters, ants from the European and Californian supercolonies, or any of the others dispersed around the globe, recognize each other as family. Thus, with our unsuspecting help, they have perhaps formed the world’s first global megacolony, a planet-enshrouding superorganism enabled by this newfangled human-connected evolutionary topology.

  The Argentinian ant is just one dramatic example of how human transport, travel, and migration have provided opportunities for some species to thrive in new ways, usually at the expense of others. Historian Charles Mann has suggested that this mashed-up new biological phase we’ve induced be called the Homogenocene, as we have blended so many evolving populations, once geographically dispersed and isolated, into one homogenized genetic broth. In the 1970s Carl Sagan used to zip around Ithaca, New York, with a bumper sticker on his orange Porsche reading, “Reunite Gondwanaland!” referring to the time when all Earth’s continents were merged into one supercontinent. I guess, biologically, this is what we’ve now done. We’ve seriously rearranged the evolutionary geometry of the world—and all this biological meddling I’ve described doesn’t even include the intentional manipulation of genomes, the engineering of new organisms, or even the potential resurrection of old ones.

  New World

  This is not your grandmother’s Earth. In 2011, a collection of scientific papers was published in a specially themed issue of the Philosophical Transactions of the Royal Society entitled The Anthropocene: A New Epoch of Geological Time? Several groups of scientists and other scholars laid out the evidence for, and discussed the implications of, the new era we have entered, one characterized by human activity as a geological force. One of these papers, entitled “The Anthropocene: Conceptual and Historical Perspectives,” by Will Steffen, Jacques Grinevald, Paul Crutzen, and John McNeill, included a two-part figure that masterfully made the case in graphic form. The two parts could almost be labeled “Cause” and “Effect.” The first set of graphs here shows the changes, since the start of the Industrial Revolution in the mid-eighteenth century, in multifarious measures of human activities that have caused changes to Earth systems.

  Whatever you choose to measure, be it global population, the damming of rivers, increases in communication or transport technology, or the relentless spread of McDonald’s restaurants, the pattern is similar: a gradual but accelerating influence until about 1950. After that point, everything starts shooting exponentially off the charts, in the phenomenon known to scholars of the Anthropocene as “the Great Acceleration.”

  The next set of graphs here, from the same paper, shows different measures of the global-scale effect of all that increased human activity on various natural systems.

  Many of the modifications graphed here, such as changes in atmospheric gases, losses in biodiversity, exploitation of fisheries, and loss of rainforests, also show the Great Acceleration in human impacts over the last sixty-five years.

  Environmental historian John McNeill, another member of our local Washington Anthropocene Group, is a coauthor of the just-mentioned study compiling measures demonstrating the existence of the Great Acceleration. He has been a prime mover in the collaboration between history and geology that is needed to study the Anthropocene. He’s also in possession of a dry, self-deprecating wit. After one of our Anthropocene gatherings at the Library of Congress, he joked to me, “Well, of course you know we cherry-picked that data. We only included things that fit this pattern.” This led to some enjoyable speculating on possible measures of human activity they could have included that would not have fit the pattern so well: the number of dirigibles made per year has not increased according to this pattern. The average number of cats per household has not increased exponentially. This made, briefly, for a fun game. It’s not too hard to come up with metrics that have not kept pace with the Great Acceleration. Yet, in the end, this exercise in contrarian thinking only reinforces the point: any set of meaningful measures will reveal the same pattern.

  Venus and the Ozone

  An instructive example of inadvertent global change is the near-destruction of Earth’s protective ozone layer. Had it unfolded slightly differently, this could very easily have been a frightening story of epidemic cancer deaths and crop failures. It is now a story of a close call, a tragedy narrowly averted. Everyone’s heard of it, but most people don’t know that the problem was discovered in time because we were exploring the planet Venus.

  Pages of our missing planetary operation manual are scattered around the solar system. Sometimes in our wanderings, poking around out of pure curiosity, we stumble upon fragments of priceless practical knowledge directly applicable to understanding our influence on the home world. Many such insights have come from studying “Earth’s twin.” Venus sometimes seems uncannily constructed as a convenient foil for our discovery of the Anthropocene Earth. Our nearest neighbor is a place where aspects of many of our self-made problems, our planetary changes of the third kind, exist n
aturally, in exaggerated form. There is, of course, greenhouse warming gone off the rails, which I describe in chapter 1. We also find in the clouds of Venus the most extreme case of acid rain you could imagine, with sulfuric clouds so acidic that their pH is less than zero.

  In the 1970s we also discovered that something very strange, involving chlorine and oxygen compounds, was going on in Venus’s upper atmosphere. Early spacecraft investigations revealed that ultraviolet light is not affecting the gases there the way we thought it should. According to seemingly obvious chemistry, the ubiquitous CO2 drifting up from the lower atmosphere wouldn’t stand a chance at higher altitudes. It should be continually broken up by energetic ultraviolet rays from the Sun, which should be splitting off oxygen atoms and reassembling them into other compounds, such as ozone (O3). Yet, for some reason, that’s not happening. The level of CO2 we measured in the high atmosphere was much higher than in our models, and all the predicted ozone and other oxygen compounds were nearly absent. Some unknown process was, it seemed, protecting CO2 from the anticipated destruction. This unexpected and strange stability presented a puzzle, which was solved by Michael McElroy at Harvard and Ron Prinn9 at MIT, two atmospheric scientists whose careers have straddled earth and planetary science. The answer, they found, lay in the highly reactive element chlorine. Even minuscule amounts of chlorine in such an environment wreak outsize havoc on oxygen compounds, catalyzing their destruction and reconstituting CO2. Modeling Venus in the early 1970s, McElroy and Prinn showed that you would not expect ozone to survive in an environment where stray chlorine atoms were running wild. Right around the same time, Jim Lovelock was making the first observations showing that chemicals called chlorofluorocarbons (CFCs) leaking from old fridges and sprayed from aerosol cans were accumulating in Earth’s atmosphere, and likely seeping up into the stratosphere.