Joanna Kakissis

Natural calamities have plagued humanity for generations. But with the prospect of worsening climate conditions over the next few decades, experts on migration say tens of millions more people in the developing world could be on the move because of disasters.

Rather than seeking a new life elsewhere in a mass international “climate migration,” as some analysts had once predicted, many of these migrants are now expected to move to nearby megacities in their own countries.

“Environmental refugees have lost everything,” said Rabab Fatima, the South Asia representative of the International Organization for Migration. “They don’t have the money to make a big move. They move to the next village, the next town and eventually to a city.”

Such rapid and unplanned urbanization is expected to put even further strains on scarce water, energy and food resources, said Koko Warner, who works in environmental migration at the United Nations University Institute for Environment and Human Security in Bonn.

In Bangladesh, a largely flat, riverine nation where more than 140 million people live in one of the most densely populated countries in the world, past generations often moved to cities seasonally. They worked to send money home to their villages and usually returned there during planting season.

But in recent years, the moves are more likely to be permanent. More intense storms and floods, salinization damage to crops caused by the encroaching sea and especially worsening river erosion have left many people rootless, Ms. Fatima said.

Dhaka, the capital, is often the only real option in this region. It is the fastest-growing megacity in the world, according to the World Bank. At least 12 million people live in Dhaka, and there are more than 400,000 newcomers each year. The World Bank predicts that the population could grow dramatically by 2020.

Like the rest of Bangladesh, Dhaka is also extremely vulnerable to climate change: It is just a few meters above sea level and is regularly hit by cyclones and floods. The environmental group WWF recently rated it among the megacities most vulnerable to the effects of global warming, after Jakarta and Manila.

Related posts:

1. Global Urbanization
2. A climate change and development slide show
3. Postdoctoral research opportunity in Climate Change Adaptation

Pure methane, gas bubbling up from underwater vents, escaping into northern skies, adds to the global-warming gases accumulating in the atmosphere. And pure methane escaping in the massive amounts known to be locked in the Arctic permafrost and seabed would spell a climate catastrophe.

Is such an unlocking under way?

Researchers say air temperatures here in northwest Canada, in Siberia and elsewhere in the Arctic have risen more than 2.5 C (4.5 F) since 1970 — much faster than the global average. The summer thaw is reaching deeper into frozen soil, at a rate of 4 centimeters (1.5 inches) a year, and a further 7 C (13 F) temperature rise is possible this century, says the authoritative, U.N.-sponsored Intergovernmental Panel on Climate Change (IPCC).

In 2007, air monitors detected a rise in methane concentrations in the atmosphere, apparently from far northern sources. Russian researchers in Siberia expressed alarm, warning of a potential surge in the powerful greenhouse gas, additional warming of several degrees, and unpredictable consequences for Earth’s climate.

Others say massive seeps of methane might take centuries. But the Russian scenario is disturbing enough to have led six U.S. national laboratories last year to launch a joint investigation of rapid methane release. And IPCC Chairman Rajendra Pachauri in July asked his scientific network to focus on “abrupt, irreversible climate change” from thawing permafrost.

Related posts:

1. Fire, climate change, and the reorganization of Arctic ecosystems
2. A transforming Arctic
3. Chris Field says rate of climate change faster than estimated

Energy, food, and water crises; climate disruption; declining fisheries; increasing ocean acidification; emerging diseases; and increasing antibiotic resistance are examples of serious, intertwined global-scale challenges spawned by the accelerating scale of human activity. They are outpacing the development of institutions to deal with them and their many interactive effects. The core of the problem is inducing cooperation in situations where individuals and nations will collectively gain if all cooperate, but each faces the temptation to take a free ride on the cooperation of others. The nation-state achieves cooperation by the exercise of sovereign power within its boundaries. The difficulty to date is that transnational institutions provide, at best, only partial solutions, and implementation of even these solutions can be undermined by international competition and recalcitrance.

…Of special importance are rules that apply universally, such as the peremptory, or jus cogens, norms proscribing activities like genocide or torture. Failure to stop genocide in Rwanda spurred efforts to establish a new “responsibility to protect” humanitarian norm (12). As threats to sustainability increase, norms for behavior toward the global environment are also likely to become part of the jus cogens set.

The responsibility to protect rests in the first instance with the state having sovereignty over its population. Only in the event that the state is unable or unwilling to protect its people are other states obligated to intervene. The challenge is not just to declare the principle but to ensure its acceptance and enforcement. Acceptance is needed for legitimacy, and enforcement will depend on whether states are willing to make the necessary sacrifices. If the responsibility to protect is to apply to the environment as well, these same challenges will need to be overcome. We use three examples to illustrate how institutional development might proceed.

Climate change. International climate agreements must be designed to align national and global interests and curb free-riding. Borrowing from the WTO architecture, the linkage between trade and the environment could be incorporated within a new climate treaty to enforce emission limits for trade-sensitive sectors. New global standards could establish a climate-friendly framework with supporting payments, e.g., for technology transfer, to encourage developing country participation. In this context, trade restrictions applied to non-participants would be legitimate and credible, because participating parties would not want nonparties to have trade advantages.

Coevolution of institutions offers a pathway to further progress. Recently, the Montreal Protocol strengthened its controls on hydrochlorofluorocarbons (HCFCs), manufacture of which produces hydrofluorocarbons (HFCs) as a by-product. HFCs do not affect ozone and are not controlled under the Montreal Protocol. However, they are greenhouse gases (GHGs), controlled under the Kyoto Protocol. The Montreal Protocol should now either be amended to control HFCs directly or else a new agreement, styled after the Montreal Protocol, should be developed under the Framework Convention to control HFCs.

High-seas fisheries. The Code of Conduct for Responsible Fisheries, which was adopted by the U.N. Food and Agriculture Organization in 1995 was a positive step, but because adherence is voluntary, it has had little effect. Another approach would be to develop a norm, akin to the responsibility to protect (12), requiring all states responsible for managing a fishery to intercede when a state fails to fulfill its obligations. Credible enforcement is a challenge, but efforts by major powers to enforce a U.N. General Assembly ban on large-scale drift-net fishing offers hope that an emerging norm can be enforced (13).

Drug resistance. Addressing drug resistance demands global standards. The International Health Regulations (IHRs) are an international legal instrument that is binding on 194 countries, including all the member states of the World Health Organization. It currently establishes minimum standards for infectious disease surveillance, but could be amended to promote standards for drug use. For example, monotherapy treatments for malaria are cheaper but more prone to encourage resistance in mosquitoes than combination therapy drugs. Their use should be limited in favor of the more expensive combination therapy drugs. One approach to global action would be an amendment to the IHRs that obligated all member countries to collective action to promote combination therapies, supported by global subsidies, and to discourage, or even prohibit, monotherapies (14).

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1. Nature uses fiction to communicate global risks of Avian flu
2. Climate change: What to do in Bali? Avoid rearranging the deckchairs
3. Fish Piracy Feeds the Global Rich

In The Vanishing Face Of Gaia, Lovelock argues that model projections of the climate a century ahead are of little use. The models of the Intergovernmental Panel on Climate Change (IPCC) extrapolate from a smooth trend of warming, yet the real climate system, complex and fully coupled to the biology of land and ocean, is unlikely to change in this simple way. It is more likely to flip from one state to another, with non-linear tipping points that the IPCC models are too simplistic to capture. Lovelock fears that the climate will shift to a new and considerably hotter regime, and that once underway, this shift will be irreversible.

This view is not officially sanctioned ‘IPCC-speak’, but he is fully within the envelope of scientific consensus when he warns of the possibility of rapid and irreversible change. Other climate scientists — notably Wally Broecker (see Nature 328, 123–126; 1987) — have said much the same for a long time, although Lovelock uses more graphic language and his popular voice will carry further. Palaeoclimate records show that rapid flips have happened before, so this must be a strong possibility for the future if we continue to force up the levels of greenhouse gases at the current rate.

What is controversial is Lovelock’s vision for humanity: rapid climate change will lead to the deaths of most people on the planet, and to mass migrations to those places that are still habitable. He does not spell out exactly how this might happen, but is convinced a hotter Earth will be able to sustain only a few per cent of the current human population. The implication is that Gaia and human society are close to a cliff-edge, and could unravel rapidly and catastrophically.

The controversy lies less in the climatology and more in the sociology. How will societies behave in the face of such change? Will we pull together with a wartime spirit, or will we fragment, fight and kill one another over Gaia’s carcass? Lovelock is on softer ground here. His only special qualification for discussing human behaviour is his longevity — having lived through the Second World War, he knows what people sometimes do to one another during evil times.

Lovelock’s vision of sudden and imminent collapse is apocalyptic, but for our long-term future and that of the planet it might be preferable to some of the alternatives. Suppose, for instance, that our profligate ways and expanding population are sustained for the rest of this century, but at a huge cost — the complete loss of all the natural ecosystems of the world. Most of us, living in cities and insulated from the natural environment, would barely notice until it was too late to do anything about it. This is what many politicians, economists and industrialists seem to want — their mantra of unceasing economic growth implies that we should take for ourselves all Gaia’s resources and squeeze from them the maximum short-term gain, leaving nothing for the future.

Following this vision, we will need to transform the entire planet into a factory farm to feed our 10 billion or 15 billion mouths. There will be no room on this giant spherical feedlot for anything but ourselves and our half-dozen species of domestic plants and animals. Gaia, the natural Earth system, will have disappeared. As for the underpinning biogeochemical cycles, the best we can hope is that we can manage them ourselves, taking over the heavy responsibility for keeping Earth habitable, which Gaia once did for us automatically.

The more likely outcome is that we would barely manage them at all. In that case, we would face a sequence of global environmental crises and a steady degradation of the planetary environment that would eventually kill just as many of us as a sudden collapse. Given that, perhaps we had better hope that Lovelock is right, and Gaia does for us — or most of us — before we do for her.

Related posts:

1. Lovelock and the Global Climate
2. Avoiding regime shifts is difficult
3. Regime shifts in the Gulf of Mexico

From ABC News

The deadly Australian bushfires appear to have been so deadly because they were unusual.  The fires caught people before they new it was coming, and unlike many fires they were too strong to fight.  What made these fires unusual?  At first look it seems to be a combination of a lack of social memory, fuel accumulation, and climate change – that together reduced community resilience to fire.

From the New Scientist’s Short sharp science blog Time for a new Australian bushfire policy?

Australia has a national fire-preparedness policy, perhaps uniquely, of encouraging people to either “stay and defend or leave early”. But as the tragedy continues to unfurl there will be increasing pressure to reexamine a policy developed for conditions that existed half a century ago.

The rationale behind the policy is that if you have a fire plan in place – that is, you have a water source, a pump that is not dependent on the power supply, you have ember-proofed your house, and so on – it is safer to stay and let the front pass over, than to leave at the last moment. And historically, it is true that most houses lost in bush fires have burnt because of defendable ember-strikes rather than direct contact with the fire, and most deaths have been due last-minute evacuations.

But conditions have changed. Southern Australia’s epic 12-year drought, higher temperatures due to climate change, and less “prescribed” burning to remove the plant life that acts as fuel, all combine to increase the risk of extreme fire. This year already, we’ve had several days in the mid-40s that have burnt leaves off trees, and squeezed the last drops of moisture out of already tinder-dry bush. One survivor described the ground underfoot prior to the fires going through as “like walking on cornflakes”.

Under those conditions, a fire plan may simply not be enough, as Victoria’s premier John Brumby told the Fairfax Radio Network today: “There is no question that there were people there who did everything right, put in place their fire plan and it wouldn’t matter, their house was just incinerated.” Brumby wants the policy rexamined.

People have changed too. Small towns like devastated Marysville – 90 minutes’ drive northeast of Melbourne – as well as the ever-expanding fire-prone city fringes, are as likely to be home to retirees and “treechangers” (city people who move to the country for a life change) as they are to families with generations of bushfire experience.

One of the commonest reasons for people who intend to stay and defend their properties to change their mind and leave at the last moment is that with no direct experience of fire they are not prepared psychologically.

According to Robert Heath, a psychologist at the University of South Australia in Adelaide, they don’t bank on the overwhelming heat, the lack of contact with the outside world, the darkness, or the noise: loud and like a huge blowtorch, apparently. Perhaps it’s not surprising then, that many people who lost their lives are thought to have done so while fleeing in their cars.

For more details see:

• The Melbourne Age videos
• The Australian – “spot-on forecast – why was no one ready?”
• Leader’s rethink survival strategies from Sydney Morning Herald.
• Australian Broadcasting Company’s full coverage of the bushfires.

Thanks to Arijit Guha for pointers.

Related posts:

1. Stephen Pyne on the Australian fires
2. Tim Flannery on Australian bushfires
3. Slow variables that shape bushfire resilience

Both of Taleb’s books are highly entertaining. But he over-reaches. There are some odd mistakes. For example, he makes much of a supposed kink in the integral of the Student-t distribution, (where tail probability declines linearly with deviation from the mean) but if you compute the integral using R software there is no kink — so Taleb evidently made a mistake.

Based on web sites, Taleb made his fortune using a kind of option trade. He purchases only options to buy securities at a certain price during a specified time window in the future. So if the security is trading above Taleb’s price, he buys it and then immediately sells at the market price, thereby making a profit. He says that his life involves long periods of time watching while nothing happens and his options to buy expire. But once in a great while he makes a killing. This is exactly like predators who specialize on very large prey, or fishing for big game fish, or hunting for rare but big game animals.

His writings have done a lot to publicize the importance of huge rare events. I think this is a good thing. But also he over-reaches. In some recent interviews he seems to be gloating over the current economic collapse. And (according to economist colleagues) some economists see his ideas as rather routine. Yet he is a provocative and entertaining writer; if sales measure impact he has made a difference.

To me, the most novel feature of the current ongoing collapse is the coincidence of huge shocks with apparently different triggers. Who would have thought that an epidemic of bad loans in America, steep ramp of energy prices, and biofuels tightening the link of energy to food prices would coincide, against a backdrop of lower economic firewalls between countries and increasingly intense food limitation of the human population, with almost no scope for growth of the food supply. It’s a wonderland for testing resilience ideas and a global tragedy, all at the same time.

For a recent talk I re-analyzed a bunch of information from the Millennium Assessment, to try to figure out if humanity had any chance at all for making it through the next few decades.

If everyone shifts trophic status to roughly herbivore level, and we educate all the world’s women to secondary level, we have a chance.

The difference between 12 billion and 9 billion people in 2050 is one child per woman. If all the world’s women were educated to secondary level, fertility would drop by about 1.7 children per woman. And we can probably feed 9 billion herbivorous people, if we can maintain the crop diversity of the major grain crops high enough to avoid catastrophic disease outbreaks.

Energy needs for agriculture and climate change could make it pretty hard to achieve the rosy scenario; climate heating, more variable precipitation and sea level rise have bad implications for agriculture. So the rosy scenario itself may be way out on the tail of the distribution. And what will happen to relations among people as the going gets rough? Human conflict can wreck agriculture. What are the chances that no one will use nuclear weapons? Even a few nukes would take out huge areas of arable land for millennia. And, as Will Rogers said about land, they ain’t makin’ any more of it. A Taleb-like fat tail breakdown seems not so implausible.

Related posts:

1. Black Swans: expecting the unexpected
2. Gelman’s notes on Black Swans
3. Tom Peters, Black Swans, and Resilience

All along the B.C. Coast, wilderness tourism operators who run bear-viewing, whale-watching and sport-fishing resorts are reporting tough times because of declining salmon runs.

But the biggest impact may be occurring in the Broughton Archipelago, where Mr. MacKay operates, and where pink salmon runs have all but vanished, sending a shock wave through the region’s ecosystem.

“Some of the northern pods are just not here,” Mr. MacKay said yesterday. “And we’ve had three occasions [this summer] when we did not see any orcas at all. That’s pretty weird.”

He said northern killer whales visit the area during the summer months, collecting in big social gatherings where breeding takes place.

“When they get together like that it’s called Super Pod Day, and we will see over 100 dorsal fins out there at a time,” Mr. MacKay said. “That didn’t happen this year, for the first time since we’ve been collecting data, which is almost 30 years.”

Mr. MacKay said it’s not coincidental that the whales have vanished along with the salmon.

“It’s pretty simple. …What do you think these orcas eat?” he said.

Surveys by the Department of Fisheries and Oceans indicate pink salmon stocks have fallen to extremely low levels in the Broughton Archipelago. In Glendale Creek, a key indicator stream, there have been only 19,000 spawners counted this year, compared with 264,000 last year.

Pink salmon, which usually spawn in prodigious numbers, are a keystone species on the West Coast. Chinook salmon, the mainstay of the orca diet, feed on young pinks, while grizzly and black bears depend on spawning adult pink salmon to bulk up for hibernation.

…

Brian Gunn, president of the Wilderness Tourism Association, said the collapse of salmon stocks is threatening the survival of ecotourism businesses.

“The bear-viewing businesses, the whale-watching operations, they built up a lot of equity showing people these wild animals. Now the fish aren’t there and they are seeing their equity drain away. …If the salmon go, so does the wildlife, and so does the business.”

Mr. Gunn blamed the fish-farming business, saying a heavy concentration of net pens in the Broughton Archipelago has created sea-lice epidemics which kill young salmon.

Related posts:

1. How Salmon Farming Endangers Salmon
2. A surprising decline of pollination services in USA
3. Enhancing ecosystem services in agricultural lands

Large blooms of blooms of blue-green algae are clogging parts of the sailing course at one of China’s Olympic sites in Quindoa. Algae are being manually removed by a thousand boats and thousands of people at (AFP, AP, Guardian, NYT, and photos from Xinmin). Bloomberg news writes:

Warmer waters, increased rainfall and high levels of nutrients in the ocean brought about the algae explosion along vast stretches of the 800-kilometer (500-mile) coastline, according to the Qingdao Weather Bureau.

Qingdao, located 830 kilometers from Beijing, is mobilizing more than 1,000 fishing boats to scoop up the algae and contain the outbreak, Wang said.

“We can only haul the blue-green algae manually and we’re doing all we can with our arms full and by the boat-load,” said Wang, a sailing spokesman for the Beijing Games organizing committee. “All you can see is fishing boats along the coast.”

via Great Beyond

update: BBC video of army algae removal

Related posts:

1. Algal Bloom along the Coast of China
2. Mapping global flows of virtual green and blue water
3. Green Lands, Blue Waters

Huge investment funds have already poured hundreds of billions of dollars into booming financial markets for commodities like wheat, corn and soybeans. But a few big private investors are starting to make bolder and longer-term bets that the world’s need for food will greatly increase — by buying farmland, fertilizer, grain elevators and shipping equipment.

Part of the article is reminiscent of the TechnoGarden scenario of the MA, in which rich companies invest in the underdeveloped African agriculture infrastructure. The article states:

Emergent is raising $450 million to $750 million to invest in farmland in sub-Saharan Africa, where it plans to consolidate small plots into more productive holdings and introduce better equipment. Emergent also plans to provide clinics and schools for local labor.

One crop and a source of fuel for farming operations will be jatropha, an oil-seed plant useful for biofuels that is grown in sandy soil unsuitable for food production, Ms. Payne said.

“We are getting strong response from institutional investors — pensions, insurance companies, endowments, some sovereign wealth funds,” she said.

The fund chose Africa because “land values are very, very inexpensive, compared to other agriculture-based economies,” she said. “Its microclimates are enticing, allowing a range of different crops. There’s accessible labor. And there’s good logistics — wide open roads, good truck transport, sea transport.”

However, unlike the TechnoGarden scenario, this investment seems focussed on increasing yields of food and fuel, rather than producing multiple ecosystem services. Consequently, such investments attempts to increase yields by practicing intensive agriculture are likely to lead to negative impacts on other people and ecosystems using water, and potentially leading to local or regional ecological regime shifts (see our paper Gordon et al 2008).

Also, many of these investments are not aimed at increasing agricultural yield on the ground, but hedging against inflation risk, and providing market power for large funds to leverage investments in other financial instruments, such as options, derivatives and other more complicated packages. This coupling of financial markets, to the already coupled food, fuel, and climate systems means that the systemic consequences of these investments are likely to be unexpected and novel.

Related posts:

1. Interaction of agriculture and climate change: opportunties of synergistic policies
2. Ecological Economics of the Global Food Trade
3. Jon Foley argues for resilient integration of industrial and organic agriculture

Nonetheless, people need answers to complex questions. In a recent global survey, respondents were asked to identify the questions that were most important to them. Questions were then ranked in order of the number of respondents who identified them as important. All of the top-ranking questions were deeply complex. What does sustainability look like? How must humans adapt to survive the changes of this century? What economic structures best support a shift to sustainability? How can we re-invent politics so people feel that they have a voice? What kind of leadership does the world need now?

Complex questions can be addressed by scenarios – sets of stories about the future, derived from collaborative processes and models, designed to integrate diverse perspectives. The scenarios of the Millennium Ecosystem Assessment are a recent example.

Scenarios are a way of building resilience – the capacity to maintain useful features of nature and society, while inventing and implementing transformations to new ways of living. In a recent talk at Resilience 2008 I discussed some of the connections between scenarios and resilience. To break out of traps, people need positive stories of what the future could be, and blunt warnings of dangerous paths. Scenarios provide such motivating visions. Moreover, the process of scenario-building itself may create connections that enable transformation. Scenario projects form networks of people in settings that promote playful, inventive thinking at the margin of formal politics. The scenarios, the insights, the people, or the networks themselves are capable of infiltrating wider thinking, and thereby contributing to change when the conditions are right.

What could expand the use of scenarios to build resilience? We need more people trained in relevant skills such as collaboration, rapid prototyping, flexible fast modeling, synthesis, and use of art, music, science and stories together. Courses exist and a sizeable literature is available. Yet the best way to learn scenarios is by doing. Why not try scenario thinking the next time you face a complex problem with long-term consequences?

Related posts:

1. New New Orleans Pt 2 – Issues, Leverage Points, Scenarios
2. The how and why of linking future scenarios across scales
3. Re-Orient: world economic production in MA scenarios

Stern’s optimistic view that CO2 emissions could be greatly reduced without a corresponding reduction in living standards is rejected by critics beginning from two diametrically opposed positions. Although deeply hostile to each other, the two groups find some surprising common ground.

The first group are ‘Deep Green’ pessimists who see the end of consumer capitalism as both inevitable and desirable. At least since the reports of the Club of Rome in the 1970s, members of this group have argued that continued economic growth is inherently unsustainable. …

The mirror image of Deep Green pessimism is that of the ‘Dark Brown’ pessimists who say that we should do nothing to stabilise the climate because to do so will wreck our standards of living. Dark Brown commentators from thinktanks like the Competitive Enterprise Institute warn of ruinous economic consequences even from modest first steps such as the implementation of the Kyoto Protocol. …

Both groups engage in a fair bit of wishful thinking about their position, the Greens arguing that we’ll all be happier in the long run and the Browns claiming that the environmental problems will solve themselves if we ignore them. But these opposing claims are secondary to the shared presumption that economic growth depends on increasing exploitation of the natural environment and, in particular, on the burning of fossil fuels.

Underlying both Deep Green and Dark Brown positions is a fundamental misunderstanding of the nature of economic progress and of economic activity in a modern society. The concept of economic growth is so firmly embedded in our thinking that we forget it is just a metaphor. The idea of growth implies physical expansion, and any process of physical expansion has limits. …

The public-good nature of information explains how economic progress can continue without additional resources. Most obviously, improvements in information technology allow more and faster communication which in turn allows for yet more technological improvements. There is no apparent indication of diminishing marginal returns in this field; if anything the opposite. …

Despite the claims of Dark Browns and Deep Greens, we can, if we choose, have both a stable climate and steadily improving standards of living throughout the world. But the fact that we can achieve these things does not mean we will. At this stage, failure seems all too possible, as does a half-hearted response that will imply the need for much more costly action in the future.

While I am relatively optimistic about the ability of human society to successfully adapt and mitigate climate change I am worried that:

1. Economic growth is not being decoupled from its use of global ecosystems, and
2. Estimates of the costs of climate change fails to consider that we are substantially reducing the ability of the biosphere to adapt to climate change, which will have unknown but likely substantial negative impacts on human wellbeing.

Related posts:

1. Poor People Living in Rich Neighborhoods Die Sooner
2. Community-mapping projects for sustainability
3. Ranking University Sustainability

Nutrient overenrichment of waters by urban, agricultural, and industrial development has promoted the growth of cyanobacteria as harmful algal blooms (1, 2). These blooms increase the turbidity of aquatic ecosystems, smothering aquatic plants and thereby suppressing important invertebrate and fish habitats. Die-off of blooms may deplete oxygen, killing fish. Some cyanobacteria produce toxins, which can cause serious and occasionally fatal human liver, digestive, neurological, and skin diseases (1-4). Cyanobacterial blooms thus threaten many aquatic ecosystems, including Lake Victoria in Africa, Lake Erie in North America, Lake Taihu in China, and the Baltic Sea in Europe (3-6). Climate change is a potent catalyst for the further expansion of these blooms.

Rising temperatures favor cyanobacteria in several ways. Cyanobacteria generally grow better at higher temperatures (often above 25°C) than do other phytoplankton species such as diatoms and green algae (7, 8). This gives cyanobacteria a competitive advantage at elevated temperatures (8, 9). Warming of surface waters also strengthens the vertical stratification of lakes, reducing vertical mixing. Furthermore, global warming causes lakes to stratify earlier in spring and destratify later in autumn, which lengthens optimal growth periods. Many cyanobacteria exploit these stratified conditions by forming intracellular gas vesicles, which make the cells buoyant. Buoyant cyanobacteria float upward when mixing is weak and accumulate in dense surface blooms (1, 2, 7) (see the figure). These surface blooms shade underlying nonbuoyant phytoplankton, thus suppressing their opponents through competition for light (8). Cyanobacterial blooms may even locally increase water temperatures through the intense absorption of light. The temperatures of surface blooms in the Baltic Sea and in Lake IJsselmeer, Netherlands, can be at least 1.5°C above those of ambient waters (10, 11). This positive feedback provides additional competitive dominance of buoyant cyanobacteria over nonbuoyant phytoplankton.

Global warming also affects patterns of precipitation and drought. These changes in the hydrological cycle could further enhance cyanobacterial dominance. For example, more intense precipitation will increase surface and groundwater nutrient discharge into water bodies. In the short term, freshwater discharge may prevent blooms by flushing. However, as the discharge subsides and water residence time increases as a result of drought, nutrient loads will be captured, eventually promoting blooms. This scenario takes place when elevated winter-spring rainfall and flushing events are followed by protracted periods of summer drought. This sequence of events has triggered massive algal blooms in aquatic ecosystems serving critical drinking water, fishery, and recreational needs. Attempts to control fluctuations in the discharge of rivers and lakes by means of dams and sluices may increase residence time, further aggravating cyanobacteria-related ecological and human health problems.

Related posts:

1. Nitrogen deposition making lakes more regulated by phosphorus
2. Eutrophication creates deformed frogs
3. Mapping Coastal Eutrophication