End Game

Tipping Point for Planet Earth?

Professor Anthony Barnosky, Hadly

• Publisher: William Collins
• Year: 2015
• ISBN:
  9780007548163
• Topic: Sciences biologiques
• Subtopic: Science environnementale

overconsumption / population growth / dwindling resources / climate change / disease / contamination / storms / thirst / war … will the struggle to simply stay alive become humanity’s future rather than its past?

1

Past or Future?

Liz, in the Himalayas of Nepal, April 2012

It all happened pretty fast. One minute, I was sitting outside sipping my tea. The next, I was hunkered down in a cold, smoky hut, patching up a Tamang woman’s bloody scalp, which she was lucky to have at all, given the machetes that were swinging around. Like most activities around sundown in that part of the world, it was a race against time, because darkness was coming on fast, and candlelight just wasn’t going to be up to the task.

When I had boarded the plane for Nepal a few days before, that kind of adventure was the last thing on my mind. I had set out with one of my Ph.D students, Katie Solari, to meet up with my Indian colleague, Uma, and her Nepali student, Nishma Dahal, in Kathmandu. Our four-woman crew was then going to head into the Himalayas to figure out which species of pika, a fluffy but short-eared cousin of rabbits, occupied which elevations in the world’s highest mountain range. We wanted that information in order to learn how the pikas are responding to the rampant climatic warming that is now heating up that part of the world, as a kind of bellwether for predicting how global warming will change wildlife in general. Pikas, it turns out, are the perfect natural experiment in that regard, because their physiology prevents them from tolerating warm temperatures. As warming climate causes mountain environments to heat up, the pikas move upslope, taking advantage of the fact that for every hundred metres of rise in elevation, temperature falls by a little less than 1°C. Our thought was that by tracking their upslope movement over a series of years, and performing genetic tests on them to see how the animals we trapped were related to each other, we could use the pikas as the proverbial canaries in the coalmine to help forecast Earth’s ecological future.

Since we left Kathmandu, we’d been moving upslope at a much faster rate than the pikas, and we were glad of it. After hiking for two days we were above three thousand metres. The high mountain air felt fresh, if a little thin, after our time in the valley, where brick kilns and fires thickened and darkened the air with a blanket of dense smog. That was far behind and below us now, and we revelled in being in one of the world’s treasured landscapes, ascending through hillsides covered with startlingly vivid arrays of red, pink, white and purple rhododendrons. I scanned the forests for signs of the red panda, since we were in one of the last strongholds of the species. What caught my eye instead, though, was that there was no real forest understorey, and although the trees were straight and tall, all but the highest branches were gone, leaving no cover for birds, much less for red pandas.

Just before reaching the ridgetop that day we met a striking Tamang girl who invited us to stay at her family’s teahouse overlooking the slopes where the red panda was said to reside. Her smile was warm, the afternoon was cold, and we did not hesitate about taking her up on her offer. We didn’t have any better options anyway. Despite the constant signs of humanity along the trail – trash everywhere, even the steepest slopes levelled into slivers of land to grow a few meagre crops – dwellings were few and far between. Our hosts’ hut was one of only two built on the narrow ridgeline, both doing double duty as homes and as teahouses for people like us. Outside each, the family matriarch was sitting in her Tibetan garb, knitting the woollen hats that are so popular among the trekkers who pass through. I shared my binoculars and field guide with a young boy in my hut’s family; he was tan from being outside, and ready with his smile. He pointed to the birds he knew in the guide, miming the places in the forest where they lived. I scrambled around the rocks near their small cabbage garden, looking for evidence of pikas, but didn’t find any. Nishma translated that the boy had not seen any for a while, and that he thought the weasels had eaten them all in the last couple of years.

So I sipped my tea outside, reflecting on the day, waiting for the daily dinner of dal bhat (Nepali lentils and rice). That’s when the shrieks jerked me out of my reverie.

All of a sudden mothers, fathers, kids, aunts, uncles and who knows who else – all the residents of the two houses – were pouring down the hill. The boy who had been so interested in my field guide had been caught stealing wood from a pile collected by the son of the other family, who had done all the hard work shimmying up the trees, cutting off branches as he climbed. The fight was on. Both boys swung their kukris (curved machetes) at each other. Their entire families – parents and children alike – joined in the fray, beating each other with sticks, pulling at braids, grabbing at clothes, scratching and screaming. All the while, the kukris kept swinging.

At the end, all were bruised, some were bleeding, clothes were ripped and shoes were lost. While another trekker patched up the gash on the head of the matriarch from the other teahouse, the matriarch from ours asked me for medical help. Fist-sized clumps of her hair had been torn out, her face was cut, and large bumps had appeared on her head and brow. As I patched her up, the two families continued to hurl curses at each other.

The violence in this spectacular, top-of-the-world setting was jarring – the wood they were fighting over was for our evening’s cook fire. For me, the pieces fell into place. Every day, young Tamang boys travel from higher, barren elevations down to the upper treeline to collect wood. That’s why we noticed as we climbed higher that all the low branches were gone. The trees were being stripped bare where they stood, leaving no cover for the red pandas, which ironically are a major lure for the trekkers, the profits from whom the Tamang rely on for the few things they have that they don’t take from the land – like mobile phones, and the small solar panels to charge them.

The problem is, the land is starting to let them down. Or maybe it’s vice versa. For the days we worked in the Himalayas, we, through our Tamang hosts’ cooking, depended on the wood collected from those trees that were being stripped bare, the water that was syphoned from the melting glaciers above, the cabbage and potatoes grown in small family gardens, and the rice and lentils carried up the mountain on their backs. I had climbed above five thousand metres, and thought I had escaped the smog and chaos of the ‘modern world’. But what became all too apparent was that there is now no place clear of humanity’s impact. And that the farther you get from our creature comforts, the closer you live to the land, and the more apparent is our dependence on Earth’s natural resources.

Even more of a wake-up call was seeing that where those human impacts get to be too much, you end up in the middle of a machete fight, the result of tensions that boil over as an inevitable byproduct of depleting what you need to stay alive. I was left with an uncomfortable question in my mind. Had I seen civilisation’s past in those mountains of Nepal, or had I caught a glimpse of the future?

Judging by the trends of the last few decades, that machete fight, and what led to it, is all too plausibly the world of the future. What is now normal – not only in places we usually think of as economically underprivileged like Nepal, India and Africa, but in fact through most of the world – is a landscape and seascape that has been so changed by humanity that our life-support systems are teetering precariously on the brink of collapse. And in systems as complex as those that keep society ticking along in the way we’re now used to, collapse has a habit of sneaking up so stealthily that you’re blindsided. Suddenly you’re in the middle of a new normal, and suffering devastating consequences that are happening too fast to do anything about.

In popular parlance, that’s known as hitting a tipping point. Things may seem to be changing gradually, or at face value even not at all, until you reach some critical threshold, and everything becomes different. Think, for example, of water heating up on the stove. The reason it seems a watched pot never boils is because you don’t observe any major changes until the water reaches a critical temperature, which (depending on the heat of the flame) can take a long time to happen. When the temperature does hit the boiling point (about 100°C, or 212°F, at sea level), however, instantly everything changes. Bubbles roil, and the water changes its state, turning into steam. Boiling water exemplifies what scientists mean when they talk about tipping points: a rapid change from an ‘old’ state of being to a new, very different state, caused by pushing the system past some important threshold value. The actual change from the old state to the new one is called a ‘critical transition’.

Tipping points (or, if you want to sound like a scientist, critical transitions) are not confined to boiling water. At just about any scale and in any system you care to name, you can think of one. The egg gradually rolls towards the edge of the counter, until it drops over it and reaches its new state of being broken on the floor. A butterfly metamorphoses from a caterpillar, or a frog from a tadpole. The canoe rocks, then all of a sudden tips over and is upside down. Your car runs perfectly well, then one day it won’t start. Property values build up over decades, then crash in a year.

For people too, tipping points are the rule rather than the exception. In fact, if you think about what happens to you and your loved ones, tipping points are the defining moments. A woman is pregnant for nine months, then in the space of minutes a baby is nursing at her breast. Tipping point. The baby grows, gradually learns to talk, walk, play, reason, and then all of a sudden hits puberty. Big tipping point. More gradual change through the teen years, young adulthood, and then that special someone comes along and two previously separate lives join together in marriage – once again, a tipping point. Gradually the two grow old together, accumulating their respective aches and pains as middle age gives way to the retirement years, then a fall breaks a hip. Another tipping point. And finally, of course, the biggest state-change of all, from life to death.

The ubiquity of tipping points has prompted a great deal of research among theoreticians of late, which has made it very clear why living things tend to experience major changes in such fits and starts. Basically, it has to do with how many parts something is built of, and how those parts are connected to one another. The more parts there are, and the more intricate their connections, the greater the likelihood that the resulting system will remain stable for long periods of time. But by the same token in such systems, the greater the likelihood that when change does come, either by tweaking lots of parts simultaneously, or by damaging just one super-critical part, it will come fast, and it will hit hard, flipping the system from its ‘old normal’ to a ‘new normal’. These sorts of systems – with many intricately connected parts that influence each other – are called, not surprisingly, ‘complex systems’ in the jargon of science.

Living things are extremely complex systems, composed as they are of millions of mutually interacting parts that are connected to each other in spaghetti-tangle ways. The scale of the complexity begins to boggle your mind when you realise that anything alive is actually built of many smaller-scale complex systems, separate entities in themselves, but connected together to form ever-larger and even more complex systems. Starting at the molecular level, for instance, DNA replication itself is a complex system that we are just barely beginning to get a working knowledge of. That, of course, is intimately dependent on the workings of, and at the same time influences, the slightly larger-scale complex systems that we call cells. And so it goes, with connections between cells, organs, individuals, groups of individuals, species, communities, and entire ecosystems. The human body has more cells of microbes than human cells; the complexity of our own body’s ecosystem is not remotely well understood. The most complex system of all is the global ecosystem, which is composed of all life on Earth, and the myriad ways that life forms interact with each other and with the inanimate environment around them (like air, water, soil, and so on).

Which means that humans, being life forms ourselves, are not at all separate from the rest of the global ecosystem; on the contrary, we’re intimately embedded in it, just like every other animal (and plant, and microbe – it’s a long list). We count on it for such essentials as a place to live, air to breathe, food to eat, water to drink, and for comfort and solace. But there is no denying that, unlike other animals, our place in the global ecosystem has taken on an unusual role – because we now dominate it. So much so that, just like the flame heating that pot of water towards a boil, we have been inexorably pushing key pieces of our planetary life-support systems towards a tipping point. The tipping point we are pushing towards, however, differs from the boiling of water in an important respect. Once you cool steam, it returns to its previous state, liquid. By contrast, there is no going back once we cross the sort of threshold we’re marching towards, which is more like the one an egg crosses when it tips off the edge of the counter.

People who study tipping points for a living have a name for crossing those thresholds of no return – the system is said to exhibit ‘hysteresis’. The resulting irreversible kinds of state-changes become more and more likely as the complex system gets, well, more and more complex. Intuitively, that makes a certain amount of sense. The more parts to a system, and the more interdependencies between those parts, the harder it is to get all the pieces back in the same order if it happens to fall apart – say because a critical part wears out, or because you inadvertently broke it. Think of the watch you took apart as a kid, or the cars we drive today.

At the huge scale of the global ecosystem, the number of parts, their diversity of function, and the number of connections between them are so enormous that it is little wonder that hitting a tipping point means big, irreversible changes. That isn’t just theory: the geological and palaeontological record is replete with evidence of past threshold crossings that changed the planet forever. One of the most famous is dinosaur extinction, which happened about sixty-six million years ago. In that case, the global ecosystem was almost literally pushed past a critical threshold by an asteroid slamming into it, with cascading impacts throughout the planet. For tens of millions of years prior to that, the Earth had maintained a supersized version of the food chain, where Tyrannosaurus rex and its cousins hunted prey that in some cases stood as high as a two-storey house and weighed thirteen tons or so. In the course of what may have amounted to a bad weekend, all that was over, and the new state of the world was one where puny mammals, and eventually us, began to rule the Earth.

Not all planetary-scale tipping points are caused by something as dramatic as an asteroid strike, but even so, they still show up unmistakably in the geological record. The most recent global state-shift was when the last ice age gave way to the interglacial warm time in which we still live. The glacial state featured ice, miles thick, covering much of the northern hemisphere and mountain glaciers throughout the world, a condition that had prevailed for about a hundred thousand years. Then, over the course of a few millennia, beginning about fourteen thousand years ago, the climate gradually got warmer, without much overall effect, until suddenly, with a last flicker from cold to warm between eleven and thirteen thousand years ago, the new interglacial state arrived, and it was a whole new world, one without massive continental glaciers.

That was an important global tipping point for humanity, because it set the stage for our domination of the planet. The cause was a complex interplay between three features of the Earth’s orbit around the sun that vary regularly, but at different paces: how elliptical the orbit is, how much the Earth’s axis tilts, and how the Earth wobbles as it rotates. As those three orbital features came into alignment over thousands of years, not much happened to the glaciers, until finally the Earth was in just the right position to maximise the amount of sunlight striking at critical seasons. With that, a warming threshold was crossed for the planet, the glaciers disappeared rapidly, and new ecosystems assembled virtually everywhere, as plants and animals formerly separated by ice came together. At the same time, humans finally arrived on every continent (except Antarctica), and began to grow dramatically in number, while other large animals died out rapidly. Then, around eleven thousand years ago, the global ecosystem stabilised into its interglacial new normal, where it has been right up until the last couple of centuries. This new normal caused formerly continuous landmasses to become separated by high sea-level stands, and their plants and animals set off on new independent ecological and evolutionary journeys. Now, though, the world has once again begun to change in a way, and at a speed, that signals a new planetary tipping point is just ahead.

This time it’s not something from outer space or Earth’s orbit that’s pushing the planet towards a point of no return. It’s us, pushing relentlessly towards thresholds on several different interconnected fronts: population growth, overconsumption of natural resources, climate disruption, pollution, disease, and killing anything that gets in our way. Some scientists think that going too far in any one of those arenas could push Earth past a planetary boundary that would have devastating consequences. Think, then, what would happen if we exceeded critical thresholds in more than one of them at once. Again, both intuition and data predict some very bad effects. Intuitively, two bad things hitting at the same time is clearly going to have much more impact than only one. We can again turn to the past to see that this is indeed the case when it comes to global tipping points. The kind of climatic shift that eleven thousand years ago turned an ice-age Earth into the warmer planet we’re used to had in fact happened many times over the past couple of million years. But evidence about the last ice-age-to-warm critical transition suggests that it was different from any of the others in a very important respect. That last big climate change was also accompanied by the extinction of half of the big-bodied species on Earth – instead of the full complement of about 350 such species, the last global tipping point left us with only about 180.

The reason? It wasn’t just hitting a critical threshold in the climate system. It was hitting that climate threshold at the same time that Homo sapiens expanded their populations, colonised the world, and began to hunt and to compete with other large-bodied species. Where climate change hit in places where humans had not arrived there were sometimes a few extinctions, but nothing too major. Where humans arrived on a continent before climate change hit – for example in Australia fifty thousand years ago – they caused more extinctions than happened with climate change alone, but those extinctions were spread out over several thousand years. But where human arrival and climate change hit at the same time – as in the Americas – the number of extinctions was multiplied many times over what you’d expect by simply adding up the anticipated effects of a few extinctions by climate change, plus a few more by human impacts. It is this multiplying effect that may be the big issue if we exceed several thresholds simultaneously, or if exceeding a threshold in one part of the global ecosystem causes a domino effect of exceeding thresholds in other interacting parts of the system. Unfortunately, those simultaneous threshold crossings are all too plausible from a complex systems point of view, because the individual systems of our world – human population growth and consumption, climate change, environmental contamination, and so on – are so interconnected.

Just how close are we to hitting those thresholds on the various fronts? Very close indeed. It’s already happening in certain regions of the world – that machete fight in Nepal, and the lack of basic natural resources that caused it, is just one tiny indication. Substitute guns for machetes, and all of a sudden you have a world that is not too different from that portrayed in 1981’s The Road Warrior, the second of the Mad Max movies, in which a leather-clad Mel Gibson defends one of the last remaining supplies of oil in the outback of Australia with his mute sidekick, the perpetually dirt-smudged ‘Feral Kid’. In March 2013 in Egypt, at least briefly, that became reality, as reported by David Kirkpatrick in the New York Times: ‘Qalyubeya, Egypt – A fuel shortage has helped send food prices soaring. Electricity is blacking out even before the summer. And gas-line gunfights have killed at least five people and wounded dozens over the past two weeks’ (30 March 2013). And in developed nations like the United States and the United Kingdom, there are people who are so worried about something similar happening that they have been laying in stockpiles of guns, ammunition, food, and whatever else they think it will take to ensure the survival of themselves and their families if the worst should come to pass. A perusing of survivalist (or ‘prepper’) websites shows just how seriously these people take the threat of disaster, spending millions of dollars on be-prepared merchandise, setting up specialist dating websites and developing products like filters that can make urine taste like bottled water and the $449 ‘Centurian children’s tactical vest’.

What the preppers are worried about are the things we are all reading in the news, realities that are pointing in the direction of crossing dangerous environmental thresholds, which would lead to huge societal problems, if not outright collapse. Climate change has already begun to ramp up storms so much that in 2005 the sea swallowed New Orleans. Waterfalls poured into the tunnels of New York City’s subway system in 2012. Massive droughts sparked crop losses and wildfires over huge areas of the United States and Australia in 2012 and 2013. Shortages of things we once took for granted are now becoming commonplace, to the extent that even big business is getting worried. Coca-Cola, for example, cited water availability as one of the key challenges to its continued success in its 2010 report to the Securities and Exchange Commission. Environmental contaminants are so rampant that fish are growing two heads in some places, and that’s just from the obvious pollutants. Sneaking in under the radar are things like hormones (such as endocrine disruptors), which we have unwittingly been spreading everywhere, recently implicated in causing such things as children hitting puberty earlier, increased heart disease, obesity and type II diabetes. Even small-scale oil ...