Source: Steffen, W., Broadgate, W., Deutsch, L., Gaffney, O., and Ludwig, C., “The Trajectory of the Anthropocene: The Great Acceleration.” Anthropocene Review (vol. 2, no. 1), pp. 81–98. Copyright © 2015 by the authors. Reprinted by permission of SAGE Publications, Ltd.
The Planetary Boundaries
Once these accelerations were established, it became critical to try to quantify, as best one possibly could, the impacts they were having on Mother Nature’s most important systems, since she couldn’t tell us herself. So Rockström, Steffen, and a group of other Earth system scientists sat down in 2008 and identified the “planetary life-support systems” that are necessary for human survival, as well as the likely boundaries that we had to remain inside of in each domain to avoid causing “abrupt and irreversible environmental changes” that could essentially end the Holocene and make Earth unlivable. They published their findings in Nature in 2009 and then updated them in the journal Science on February 13, 2015.
Their argument was simple: whether we know it or not, we have organized our societies, industries, and economies on the basis of the Holocene environment, and therefore if we breach the operating levels of the key environmental systems that have sustained it all these years, we could flip the planet into a new state that could make it impossible to maintain modern life as we’ve learned to enjoy it. It was the equivalent of imagining Mother Nature as a healthy person and then identifying the optimal range of weight, cholesterol, blood sugar, fat, oxygen intake, blood pressure, and muscle mass to ensure that she stayed healthy and could still run marathons.
Just as the human body is a system of systems and organs, each of which has certain optimal operating conditions, the same is true of Mother Nature, explains Rockström. Our organs, and our body as a whole, can and do operate beyond these optimal conditions—up to a point. We don’t know in every case how far beyond the optimal we can go before the body breaks down, but in some cases we do. We know that our optimal core body temperature is 98.6 degrees Fahrenheit. We’ve learned that average humans will die—their internal systems will fail—if their body temperature gets as hot as about 108 degrees or as cold as about 70 degrees. Those are our human health tolerance boundaries, and the closer you get to either extreme, the worse your organs and internal fluids will function.
Well, Mother Nature is a system of systems and organs—oceans, forests, atmosphere, ice caps—and Earth scientists have learned over the years what are the most stable operating levels for each of these systems and organs. True, Mother Nature is not a living being—she cannot tell us how she feels—“but she is a biogeophysical rationally functioning complex unit”—like a human body, Rockström told me. “We don’t know exactly where her operating boundaries are, because we don’t understand Mother Earth as accurately as a human body, but she knows exactly where they are. And there is no give. The Greenland ice sheet melts at a hardwired tipping point. The Amazon rain forest tips at a hardwired tipping point. And just as we would never manage our bodies at the edge of the tipping point, we should not be doing that with the planet.”
So in the absence of Mother Nature being able to tell us how her most important systems are feeling, Rockström and Steffen and their planetary boundary team of scientists have attempted to make some educated estimates of where those tipping points reside, beyond which systems tip into a different state. They identified nine key planetary boundaries that we humans must make sure we do not breach (or continue to breach further, since we have already breached several). Breaching those boundaries could set in motion chain reactions that might flip the planet into a new state that could make it impossible to sustain modern civilization.
Here’s their 2015 planetary boundaries health report. Warning: It doesn’t look good.
The first boundary is climate change—and we’ve already breached it. The planetary boundary team, in line with the prevailing consensus among climate scientists, believes that we needed to stay below 350 parts per million of carbon dioxide in the Earth’s atmosphere if we wanted to stay comfortably below the 2 degrees Celsius rise in global average temperature since the Industrial Revolution—the redline beyond which most climatologists believe we will be risking unmanageable ice melt, sea level rise, extreme temperature variations, and much more severe storms and droughts. We are now at more than 400 parts per million of CO2 in the atmosphere—that blanket is now getting really thick and thickening at an accelerating rate—pushing, as noted earlier, the combined average temperature over global land and ocean surfaces to the highest levels we’ve seen since before the Industrial Revolution.
Mother Nature knows she’s getting a fever. NASA’s Vital Signs of the Planet report on global surface temperatures noted at the end of 2015: “The 10 warmest years in the 134-year record all have occurred since 2000, with the exception of 1998. The year 2015 ranks as the warmest on record.” The climate system determines the growth environment for all living species, and that environment is heading into a zone well beyond the planetary boundary—threatening to make Earth into a hothouse the likes of which humans have never lived in before.
The second boundary, they argued, is biodiversity—which includes all the living species in the biosphere and all the nature covering the planet—that is, forests, grasslands, wetlands, coral reefs, and all the plants and animals residing within them. The planetary boundaries team determined we should maintain 90 percent of biodiversity cover from preindustrial levels. We are already down to 84 percent in parts of Africa, and going down further.
People forget, noted Rockström, that it is impossible to regulate the climate without biodiversity. If you don’t have pollinators in the air and microrganisms in the soil and birds and other animals depositing seeds for new trees through their waste, you don’t have a forest. If you don’t have a forest, you don’t have trees to soak up the carbon. If you don’t have trees to soak up the carbon, it goes into the atmosphere and intensifies global warming or into the oceans and changes their composition. The natural species loss rate is one species or less per year out of every one million species. “We set the boundary at ten,” Rockström explained, but with globalization that level is being regularly breached—we are now losing somewhere between ten and one hundred species per million species per year. That is as close a proxy as you can get for how much we are losing biodiversity.
The third planetary boundary we have breached, said Rockström, is deforestation. This concerns the minimum level of key biomes—mainly rain forests, boreal forests, and temperate forests—that we need to maintain on land to have a balanced, regulated Holocene. The scientists estimate that we must maintain around 75 percent of the Earth’s original forests. We are now down to 62 percent, and some forests are showing signs of absorbing less carbon.
The fourth boundary that has already been breached is called biogeochemical flows. “We’re now adding way too much phosphorus, nitrogen, and other elements to the world’s crop systems, poisoning the Earth” with fertilizers and pesticides, said Rockström, and then those chemicals run off into the oceans and harm plant and fish life there as well. “To develop plants and animals that eat and create protein, you need a balance of nitrogen and phosphorus,” he explained. “They determine the state of oceans and the landscape—too much nitrogen and phosphorus and you choke them—too little and they don’t grow. It is all about how much fertilizer and pesticide we can allow ourselves to use, without choking other plants in the biosphere.” Climate change can cause top-down tipping, and overuse of fertilizers and pesticides can create bottom-up tipping. Right now, said Rockström, “we have to go down to twenty-five percent of current usage.”
In four other realms, we have managed to stay just inside the levels set by the planetary boundaries team, but not with much room to spare. One is rising ocean acidification. Some of the CO2 we emit goes into the atmosphere, but a lot is actually absorbed by the oceans. This, however, is increasingly harming fish and coral reefs, which are like the tropical rain forests of the ocean.
When you mix CO2 with water you get carbonic acid, which dissolves the calcium carbonate that is the essential building block for all marine organisms, particularly those with shells, and for coral reefs. When that happens, “oceans, instead of playing host to marine organisms, break them down,” said Rockström. “We can only ruin so much calcium carbonate before the marine system turns over and cannot host fish and coral reef as it did throughout the entire Holocene epoch before now.”
Another area the planetary boundaries team says we are still managing to stay barely just inside is freshwater use—the maximum amount of water we can remove from the world’s rivers and underground reservoirs, so our wetlands and rain forests can remain in their Holocene state and we can continue to engage in agriculture at scale.
A third boundary that we haven’t quite crossed is atmospheric aerosol loading. These are the microscopic particles we put into the atmosphere with conventional pollution from factories, power plants, and vehicles. The inefficient burning of biomass (mostly by cooking stoves) and fossil fuels creates layers of smog that damage plant life by blocking sunlight; it also contributes to asthma and other lung diseases in humans.
And the fourth area where we are still just inside the boundary is known as the introduction of novel entities, namely, our invention of chemicals, compounds, plastics, nuclear wastes, and the like that are alien to nature and seep into soils and water. They do weird things we don’t fully understand, and the fear is that they could one day even change the genetic code of different species, including humans.
There is one boundary we have safely retreated from after breaching it in the past. This is the appropriate thickness of the stratospheric ozone layer that protects us against dangerous UV radiation that causes skin cancer. Without that ozone layer, large parts of the planet would be uninhabitable. After scientists discovered an ever-widening ozone hole caused by man-made chemicals—chlorofluorocarbons—the world got together and implemented the Montreal Protocol in 1989, banning CFCs, and, as a result, the ozone layer remains safely inside its planetary boundary of losses not greater than 5 percent from preindustrial levels.
The planetary boundaries team does not claim that any of the boundaries they set are hard and fast or that if they are breached we will go straight over a cliff. Their redlines are educated estimates, beyond which we enter a “zone of uncertainty”—where no one can predict what might happen, because we have just not been there before as humans.
The one thing we’ve had going for us is that up to now Mother Nature has been very good at finding ways to adapt to stress, Rockström notes. Oceans and forests absorb the extra CO2; ecosystems such as the Amazon adapt to deforestation and still provide rain and freshwater; the Arctic ice shrinks but does not disappear. Again, the Earth has a lot of buffers and adaptive capacities. But eventually, we can exhaust them. And that is exactly what we’ve been doing, particularly over the last half century.
“The planet has demonstrated an impressive capacity to maintain its balance, using every trick in its bag to stay in the current state by buffering our actions,” added Rockström. But if we keep breaching these planetary boundaries, “we might shift the planet from friend to foe.” That is a world where the Amazon becomes a savannah and the Arctic Circle a year-round ocean that absorbs the sun’s heat rather than reflecting it away from Earth. That would almost certainly create a world for humans “that would be nowhere near as benign and friendly as the Holocene—the one steady state we know has sustained the only civilization we’ve ever known.”
Already, many Earth scientists argue that it is no longer appropriate to describe our current geological epoch as the Holocene. They believe we’ve already left it behind and entered a new era that is being driven by … us. The name being given to this era is the “Anthropocene,” as in anthropo, for “man,” and cene, for “new.” It is a fancy scientific name for the power of many.
“Human activity is leaving a pervasive and persistent signature on Earth,” said Colin Waters of the British Geological Survey, coauthor of an essay in the January 8, 2016, issue of Science making the case that the Anthropocene deserves to be defined as a distinct new epoch from the Holocene.
The authors acknowledge that “any formal recognition of an Anthropocene epoch in the geological time scale hinges on whether humans have changed the Earth system sufficiently to produce a stratigraphic signature in sediments and ice that is distinct from that of the Holocene epoch,” and they go on to make the case that we have. Everything from the hundreds of millions of tons of cement we’ve poured across the Earth’s surface to radionuclides from atomic testing will be shaping the planet for years and years to come.
As the singer Joni Mitchell once put it in her song “Big Yellow Taxi,” “They paved paradise / And put up a parking lot.”
Waters and his colleagues simply put that lyric into scientific language:
Recent anthropogenic deposits contain new minerals and rock types, reflecting rapid global dissemination of novel materials including elemental aluminum, concrete, and plastics that form abundant, rapidly evolving “technofossils.” Fossil fuel combustion has disseminated black carbon, inorganic ash spheres, and spherical carbonaceous particles worldwide, with a near-synchronous global increase around 1950. Anthropogenic sedimentary fluxes have intensified, including enhanced erosion caused by deforestation and road construction. Widespread sediment retention behind dams has amplified delta subsidence.
It’s weird to think of future geologists hitting our layer of sediment and trying to figure out iPods, Cadillacs with fins, and selfie sticks. Even if geologists one day can agree on this new era, there remains a dispute as to when it started. Some say it should be the dawn of agriculture—thousands of years ago; others argue it started with the onset of transoceanic Western colonialism in the early seventeenth century. “Of all the candidates for a start date for the Anthropocene,” wrote Steffen and the Great Acceleration team, “the beginning of the Great Acceleration is by far the most convincing from an Earth System science perspective. It is only beyond the mid-twentieth century that there is clear evidence for fundamental shifts in the state and functioning of the Earth System that are (1) beyond the range of variability of the Holocene, and (2) driven by human activities and not by natural variability.”
Because of this dispute, the International Commission on Stratigraphy, which is in charge of naming geological epochs, still has us in the Holocene. But for the purpose of this book we’re in the Anthropocene, an epoch where the power of many—that be us—is now the dominant factor shaping and reshaping Earth systems and pushing out planetary boundaries.
But whatever era we are in, insists Rockström, “we have a responsibility to leave the planet in a state as close to the Holocene as possible.” That is not going to be easy, though, because the “many” in the power of many is also in acceleration more than people realize in many places.
The Power of Many, Many, Many
In April 2016, when I visited Niger to do a documentary on the impact of climate change on African migration patterns, our first stop was the northern town of Dirkou, in the middle of the Sahara. It was 107 degrees Fahrenheit in April; I was interviewing African migrants, many from Niger, who had traveled to Libya in search of work and, for a lucky few, a leaky boat ride to Europe. As I mentioned earlier, however, most found no work and no boat, only abuse from Libyans who did not want them in their country, which was experiencing its own economic and political meltdown.
So what we found in Dirkou were hundreds of men from Niger and other countries of West Africa who were marooned in a twilight zone of no jobs and no more money and unable to get north for work or south to go back home. They were being cared for by the International Organization for Migration. I interviewed several of these men under a burning hot sun next to a semitrailer overflowing with goods heading south. Most had been gone from their home villages for more than a year, so I asked one of them, Mati Almaniq, from Niger, how his family was faring.
He told me had left his three wives and seventeen children back in his village to search for work in Libya or Europe and returned deeply disillusioned. Almaniq said he left them with a store of food but knew that by now they must have eaten through it all. “They are in the hands of God now,” he said. Such is life on the edge. One of his traveling companions standing next to him told me he left twelve kids back home. This was not unusual—mothers in Niger have an average of seven kids each.
I wrote all this into my New York Times column, and the next day I got an e-mail from my friend Robert Walker, president of the Population Institute, pointing out that “Niger’s population in 1950 was just 2.5 million. Today its population is 19 million, and the U.N.’s latest population projection indicates that its population, even with declining fertility rates, will reach 72 million by 2050. Factor in climate change, along with regional conflict and instability, and you have a demonstrably unsustainable country. Making matters even more untenable is the child marriage prevalence rate in Niger: the highest in the world.”
Niger is one of many countries, not all in Africa, where the other acceleration that I would include under the banner of “Mother Nature”—population growth—is still occurring. This growth will lead to more and more consumption of “natural capital,” harming rivers, lakes, soils, and forests in their countries and beyond. Even though in many other parts of the world, population growth has flattened out or even reversed, the planet’s total population will rise from about 7.2 billion today to about 9.7 billion by 2050, according to the latest United Nations report. That means in just over thirty years there will be another two billion people on the planet.
Pause for a moment and think about that number: two billion more people.
And still even more important is the fact that the impact on the planet’s natural systems and climate will become exponentially more devastating, because more and more of those 9.7 billion are moving to large urban areas and up the socioeconomic ladder into their respective middle classes—where they will drive more cars, live in more and bigger homes, consume more water and electricity, and eat more protein. Their per capita impact on the planet will be much greater. Today, roughly 86 percent of Americans have air-conditioning in their homes and apartments. Only 7 percent do in Brazil and less than that in India. But once their basic needs are covered, they will want air-conditioning, too, and they are entitled to demand it as much as anyone living in Japan, Europe, or America.
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