Tipping the balance
20th June, 2008
Are they environmental doom-mongering, journalistic hype or the straw that breaks the camel's back? William Laurance examines the complexities of tipping points - those small changes in a natural system that can sometimes provoke sudden and irrevocable collapse
Tipping points abound in nature – you can hardly go anywhere without tripping over them. Nature is dynamic. Nature is often nonlinear. Nature is complex and interconnected. All of these features can create tipping points.
In many cases tipping points are trivial. Warm a single ice cube by just a tiny amount, from just below freezing (say, -0.01ºC) to just above it (0.1ºC) and presto! Your ice cube becomes a little puddle. In this context the melt is inconsequential, but imagine crossing the same tiny temperature threshold in Siberia, where some 11 million square kilometres of land – an area the size of France and Germany – are locked up in permafrost.
The Siberian permafrost contains hundreds of billions of tonnes of carbon, which has slowly accumulated as frozen peat during many millennia. The peat hasn’t decomposed because there is no freestanding water, which is crucial for soil microbes.
When the permafrost melts, however, the microbes leap into action, consuming the peat and emitting as waste products methane and carbon dioxide – both potent greenhouse gases. Suddenly, many billions of tonnes of carbon emissions flood into the atmosphere. Global temperatures shoot up, causing even more permafrost to melt and spew out even more carbon emissions. All we did was nudge the temperature up a tiny fraction of a degree – but we’ve created a runaway monster.
Tipping points can arise in at least three situations. The first is a runaway chain reaction. These usually happen when elements in a system are tightly coupled to one another. Tip over that first domino and a thousand more may quickly fall in sequence. Compress enriched plutonium and you provoke nuclear fission; as each plutonium atom splits in two it shoots out a bullet-like proton that then splits another atom, which in turn fires off another atom-splitting proton, and so forth. If the reaction escalates quickly enough, you get a nuclear explosion.
In the natural world, epidemics are like runaway chain reactions. A sick person infects a few other people, each of whom infects a few others – and suddenly you have a global pandemic. This is especially so with our ultra-mobile modern society, where no pathogen on the planet is ever more than a plane ride away. New pathogens cause deadly epidemics because many people in the population lack immunity and therefore are similarly vulnerable – in effect their fates are tightly coupled, like dominoes ready to fall.
For humans, major epidemics are scary and could potentially kill millions, but epidemics can be even more devastating for wildlife, such as the hundreds of different amphibian species now being driven to extinction by a mysterious chytrid fungus. According to a prevailing theory, this virulent pathogen, which decimates healthy frog populations in just days, might have originated in Africa and humans could be inadvertently transporting its spores around the world.
A second, related cause of tipping points is an abrupt threshold. This is illustrated in the US by the disaster of Florida Bay, the triangular stretch of water enclosed by the south coast of the mainland and the Florida Keys. In the early 1990s it hit a tipping point, changing abruptly from a clear-water system that supported sea grasses and manatees to a murky dead zone overwhelmed by plankton blooms. Nobody saw this coming because nothing seemed to be changing. The bay received a steady stream of pollution from septic systems, but one day hit a critical threshold that turned everything topsy-turvy.
Oceans, too, have scary thresholds. As global temperatures rise, some scientists fear a sudden collapse of the Atlantic thermohaline circulation, a current that brings warm surface water to northern Europe and returns cold, deep-ocean water south. This climatic conveyor belt seems to be slowing (evidently because it is being diluted by freshwater from melting Arctic and Greenland ice). If it collapses altogether it could lock northern Europe into a deep freeze while destabilising the north-Atlantic climate. The last time this conveyor belt failed, some 8,200 years ago, the land temperature of Greenland fell by more than 5°C.
Still another threshold involves the acidity of the oceans. As carbon dioxide accumulates in the atmosphere, some of it dissolves in the oceans, elevating acidity and changing water chemistry. Ocean acidity has already risen by more than 25 per cent above pre-industrial levels. Greater acidity makes it harder for many marine organisms, such as corals, sea urchins, starfish and winged snails, to form their crucial skeletons or shells. In just decades, some scientists believe, the oceans will hit an acidity threshold that will kill many cold-water species, with acidic conditions spreading soon afterward into warmer waters.
The final cause of tipping points is positive feedbacks. These self-reinforcing feedbacks are reminiscent of a Russian slapping contest, where the two opponents take turns smacking each other, always hitting their foe a little harder than they were slapped. Self-amplifying situations such as this can quickly spiral out of control.
The Amazon rainforest appears vulnerable to an alarming positive feedback. The rainforest generates much of its own rainfall – which is crucial for the forest’s survival – because the dense vegetation quickly recycles moisture and returns it to the atmosphere. As deforestation proceeds, however, less water vapour is recycled, so clouds and rainfall decline. As the forest dries out, wildfires increase and destroy yet more forest, further depressing rainfall. No one knows how far the Amazon can be pushed before it collapses in a rage of droughts and forest fires.
Tropical forests might be susceptible to another kind of positive feedback, according to a prominent but controversial theory. Long-term research in Costa Rica suggests that plant growth in undisturbed forests declines in warmer years. This could be because the metabolism of plants rises with higher temperature, much in the same way as cold-blooded lizards speed up in warm weather.
To increase its metabolism, a plant has to burn more energy, and so less energy is available for growth. Hence, as the Earth heats up, rainforest plants may grow ever more slowly. If these observations are correct, rainforests will actually shrink in the future, progressively becoming dominated by smaller, slower-growing trees as global temperatures rise.
Why is this important? Tropical forests store vast quantities of carbon in their dense vegetation – more than any other forest type on earth. If the rainforests are literally shrinking, they could emit billions of tons of carbon into the atmosphere. This, in turn, would accelerate global warming, which would make rainforests shrink even faster – a positive feedback. In a hotter world, even protecting a rainforest within a national park might not ensure that its carbon is safely locked away – though this is surely better than no park at all, because unprotected rainforests are often razed to the ground.
Into the unknown
As we’ve seen, at least three situations in nature can create tipping points. First, uncontrolled chain reactions can be unleashed when the elements in a system are tightly linked, like a line of falling dominoes. Second, nonlinearities can generate abrupt thresholds – the proverbial straw that breaks the camel’s back. Finally, runaway positive feedbacks, like a pair of slap-happy Russians, can easily ensue when two or more phenomena amplify each other.
But perhaps the scariest thing about tipping points is that they are devilishly hard to predict. Donald Rumsfeld, the former US Secretary of Defence, must have had tipping points in mind when he famously distinguished between ‘known unknowns’ and ‘unknown unknowns’. Known unknowns are like the impacts of global warming on cold-adapted species: we know they’re happening, even if we can’t predict their ultimate effects. Many tipping points are unknown unknowns, however; they can come at us completely out of the blue, with no warning at all.
Because of their inherent unpredictability, tipping points are a daunting challenge for decision-makers. The influential Intergovernmental Panel on Climate Change (IPCC) has downplayed the influence of some tipping points, such as the possibility that the Arctic and Greenland ice sheets might quickly collapse, or that global warming will magnify El Niños and thereby increase droughts in many parts of the world.
Some leading researchers, however, such as Tim Lenton of the University of East Anglia and his colleagues, have challenged this view, arguing that several climatic tipping points are more likely than suggested by the IPCC. Likewise, a respected team headed by Peter Cox of the British Met Office in Hadley has asserted that the Amazon is more vulnerable to future droughts than the IPCC proposes. Much blood is being spilled on the floor as IPCC scientists and governmental representatives debate how to deal with tipping points in their technical reports. But because they are subjected to multiple reviews, in which controversial issues are mercilessly axed by dissenting nations or scientists, IPCC reports are inherently conservative, especially when it comes to tipping points.
Risk-management experts and insurers are also struggling with tipping points, given that destructive storms, floods and crop-killing droughts might abruptly increase in the future. They are further worried because many different phenomena, which affect and are affected by the environment, can also have tipping points.
For example, one reason stock markets are so volatile is that stock traders have a herd mentality – buying and selling in unison. In effect, they’re like nervous wildebeest, ready to panic and stampede when bad news arrives. Under these conditions, even small disturbances, such as a spike in energy or food prices, can sometimes generate major economic shocks that reverberate across the planet. In an effort better to predict such rare, shattering events, some risk-management experts are even exploring new fields of mathematics – but the challenge is daunting.
Expect the unexpected
Despite our best efforts, there is only one real certainty with tipping points: expect the unexpected. Nevertheless, all is not hopeless. While it can be fiendishly difficult to predict specific tipping points, we now understand some key factors that make them more likely.
One key risk factor is increasing globalisation, which creates complicated economic and environmental linkages across the planet. Rising demand for furniture in the US and Europe is driving an expansion of Chinese furniture manufacturing, for example, which in turn is causing a spike in illegal logging in developing nations in Asia and Africa that export their logs to China. In a complex, interconnected world, yanking on a string in one location can cause painful jolts in far-flung and unpredictable places.
Globalisation is risky for another reason. It promotes centralisation and eliminates ‘redundancy’, because those able to produce a product or service most cheaply tend to eliminate less-efficient producers. While this has certain economic benefits, it also magnifies the chances a small disturbance will quickly snowball into a bigger crisis. In 2003, for instance, North America and Europe were slammed by major power blackouts that arose when small nodes in the electrical grids failed. Had their electrical systems been less centralised with more redundancy, they would have been far more resilient in the face of small, local disturbances.
Tipping points also become far more likely when a system is stressed, and the Earth today is a poster-child for stress. With our burgeoning population and escalating demands for food, energy and goods, and with seismic changes in our increasingly globalised economy, we are stressing our planet in countless alarming ways.
Environmental and economic shocks are not just a possibility in the next few decades – they are practically guaranteed.
Though hard to predict, new catastrophes are certainly coming, so we must plan and save accordingly. If we wish to survive future tipping points we need to prepare seriously for them, by keeping some of our resources in reserve. We also need to reign in globalisation, especially with the environment potentially at risk. A far broader public debate is needed on globalisation, because so few economists are trained to understand its real perils. Finally, we must take our foot off the economic accelerator, to reduce the intense and varied stresses on our global environment.
With tipping points we really are in fearsome, uncharted waters. Let’s be careful that we don’t sink.
William Laurance is a senior scientist at the Smithsonian Tropical Research Institute in Panama, and former president of the Association for Tropical Biology and Conservation. He is the author of several books as well as nearly 300 scientific articles
This article first appeared in the Ecologist August 2008
Naturalmente in Germania, negli ambienti più affezionati alle ricette austereVann Mollyvann, an architect who headed an independent Cambodian agency to manage Angkor, fought for the zoning and other measures to prevent what he called an "Angkor Disneyland." He eventually was fired for being obstructive, and the agency, Apsara, was put under the direct control of Deputy Prime Minister Sok An. エアマックス狩り Not everyone can afford an original art piece, he says, "but art derivatives provide easy access to art, with a charming touch." アバクロ 公式 Americans have memorialized World War II, but the China-Burma-India Theater is generally less known, except for the Flying Tigers and the feats of the multinational special forces unit known as Merrill's Marauders in Burma, which became a book, film and TV series. ルイヴィトン ショルダーバッグ Q: You also managed to get "Matrix" directors, the Wachowskis. That was quite a coup as they haven't done an interview in over a decade. Asked about avoiding potentially harmful additives and ingredients, Ma recommends a diverse diet to achieve nutritional balance. "No matter how delicious it is, dietary bias is not wise," Ma advises.
Brazilians abroad share the spirit, too. Sampio has been posted in Shanghai for more than two years and celebrated two Carnivals with other Brazilians who partied away. The Latina Brazilian Restaurant has a long history in town and there's a Brazilian band in the Xujiahui branch. シャネル グロス Taking a walk on the rooftop of the three-story museum is a relaxing experience before or after viewing the exhibits inside its walls. エアジョーダン11 Durian pastry (liulian gao ??????) When many people first see this pastry, they think it pretty much like cream puffs that have durian filling inside. But hand-made durian pastry is made of durian-flavored dough with the distinctive fragrance of durian cream inside. Durian is mixed with flour, which makes the dough an attractive yellow color. Durian cream oozes out with every bite. ニューバランス 1400 I just want to keep it a pure place for welfare without other involvements, Sun says. モンクレール ダウン They visited so frequently, legend has it, that Emperor Shunzhi (1638-1661), father of Kangxi, had fled his palaces in Beijing to become a monk in one of the temples on Wutai Mountain.
Winslet starred in the HBO miniseries "Mildred Pierce," based on the 1941 James M. Cain novel, which grabbed a top 21 Emmy nominations. グッチ キーケース What's appealing to everyone is she looks so nice and normal, Lela Rose said. "We are so used to all this Hollywood hysteria that her normalcy is in itself refreshing." ルブタン パンプス Geng works in different media. Besides canvas, he experiments extensively in the darkroom but he doesn't "take" and "develop" photos. プラダ リュック Surveying the scene, it was easy to understand why this valley between the Longmen and Xiangshan mountains was once known as "Yique" - literally "the gate of the Yihe River." Without going through China, it's not going around the world. We need to feel it, enjoy it and meet the people of China, said Zapp.
State of Origin: Player ratingsLess than a minute into the second period, Pahlsson deflected a Duncan Keith long shot to make it 3-0 to the Blackhawks. chaussure tn pas cher At Oklahoma City, Baron Davis scored 24 points, including a key 3-pointer in the final minute, to help Los Angeles end a three-game losing streak. abercrombie pas cher Said graduating senior Zack Heystek: "It definitely helps to hear that message, especially from the person who said it. It was very inspiring. And it was awesome to meet him. The blood was just flowing and it was just crazy." chaussure louboutin pas cher RUSSIA'S space chief said yesterday his agency will consider sending a spacecraft to a large asteroid to knock it off its path and prevent a possible collision with Earth. A Democrat, Obama has been promoting a retooled strategy since an election in Massachusetts last month deprived his party of a "super majority" in the US Senate and forced him to work more closely with rival Republicans.
Many people feel the corruption first-hand. Among them is Samantha Wang, who has an 11-year-old son studying in a leading primary school in Shanghais Pudong New Area. louboutin pas cher homme An earthquake with a preliminary magnitude of 7.2 on the Richter Scale hit Japan's northeastern region this morning, said the Japan Meteorological Agency, which issued a tsunami warning. woolrich oulet online I hope it will be a beautiful book, as well, something that everyone can take something away from, Obama said. "Maybe if you're a local gardener yourself, you'll be drawn by the pictures of the ... garden in its various stages throughout the seasons. If you're a kid, maybe you'll pick up the book and read along with your -teachers, and look at how we've -incorporated young people in our garden." mulberry outlet RUMORS have abounded for years that Britain's Prince William will get engaged to his long-term girlfriend but one retailer is now so sure an announcement is imminent it has prepared a range of commemorative mugs. air max femme pas cher But the agency said nearly three-quarters of the costs resulted from binge drinking - four or more drinks per occasion for women and five or more for men.
Australia ended qualifying atop the group with 20 points, five clear of second-place Japan, and conceded only one goal in eight matches. air max pas cher The utility faces massive compensation payouts to tens of thousands of people who had to flee their homes and saw their livelihoods destroyed by the world's worst nuclear disaster since Chernobyl 25 years ago. doudoune moncler pas cher We need 10 to 15 nuclear plants to generate electricity in our country, Mottaki said. Iran, the world's fifth-largest crude exporter, currently has one nuclear power plant, under construction by Russia. doudoune moncler pas cher United States-based marketing firm Zeta Interactive scanned comments on more than 100 million blogs and Websites to determine which celebrities received the best, and worst, "buzz" in 2009 to produce a snapshot of public opinion. As with the initial quake, yesterday's aftershock sent boulders on the city's Port Hills tumbling towards houses. Parts of the eastern city which suffered the most damage in February's tremor suffered from flooding and liquefaction - where solid ground is turned into liquid by the force of the quake.
In questi anni, sotto la pressione di una crisi senza precedenti e di inaudita complessitàAccording to a survey by the news Web portal Sina.com, 53 percent of the 3,148 respondents said the introduction of a demerit point system was reasonable. The survey also found that 44 percent of respondents thought that the policy may lead to discrimination. tiffany outlet The jail's former warden is being investigated for allegedly taking bribes, linked to another corruption case involving the province's top jail management officer, today's China Youth Daily reported, citing Wang Yuanrong, office dean of the Deshan Prison in Hunan Province's Changde City. Tiffany Outlets Scenic spots such as Xintiandi and Lujiazui plunged into darkness to join Earth Hour on Saturday. Shanghai's three tallest buildings, Shanghai World Financial Center, Oriental Pearl TV Tower and Jin Mao Tower, all turned off landscape lights from 8:30pm to 9:30pm. air max Professional models from African countries paraded the catwalk wearing the traditional clothes with a modern touch backed by African music at the "African Fabrics: Fashion Forever" show. The imminent World Expo is a key driver of the new regulations that also cover dogs and the issue of crowd safety.
Fire fighters with gas masks, working in shifts because of the fumes, sprayed water to dilute the acid. mulberry handbags His colleagues said Liu was a decent and easy-going person and his death came as a shock, Xinhua said. parajumpers pas In photographer Zhao Lei's studio hang wedding pictures telling the story of how lovers met each other and fell in love. Some show couples cooking, doing the laundry and watching TV, showcasing marital bliss. hollister femme I believe the bilateral collaborations that have been established during the World Expo will extend continuously, and our friendship will spread to every corner of China just like seeds of the 'dandelion' - the nickname Chinese visitors have given to our pavilion. abercrombie and Statistics show that in the first six months of this year, departments of the central Party and government sections saved a total of 597 million yuan (US$87.3 million) from reining in overseas trips, vehicle purchase and business reception.
The supplier was diagnosed with life-threatening illnesses but left hospital the next day, the newspaper said. Pandora Jewelry The first country to issue a production license for H1N1 vaccines, China had inoculated more than 3.78 million people as of October 31, with no reports of serious adverse reaction, according to the Health Ministry. mocnler pas Xu Xinjian, an officer of a police station in Xinxian County, turned himself in on September 6 after he fled the scene the night before, the newspaper said. abercrombie and Last October the rules on safety standards in public places were overhauled by the city government, making it mandatory for markets and shopping malls to install surveillance cameras. The movie's rich elements of suspense and black humor, as well as its star-studded cast, will make it a box office sensation during this festive season, said Wu Hehu, the chain's deputy general manager.
Post a Comment
Using this website means you agree to us using simple cookies.