Science – Page 98 – a sibilant intake of breath

Be grateful for bees

My favourite reading snack these days is soy-covered almonds. They have lots of delicious umami flavour. Recently, I was surprised to learn that 80% of the world’s almonds are grown in a 600,000-acre section of California’s Central Valley. Since almonds need to be pollinated by honey bees (apini apis) and there is only nectar available in that area when almonds are in bloom, the bees need to be trucked in from elsewhere. Every February, more than a million hives – containing 40,000 bees – get trucked in. By 2005, it proved necessary to import a 747 full of bees from Australia for the ‘pollination event.’

The mutual exposure of those two distantly separated bee populations results in the exchange of microbes and parasites. Therein may lie the cause of the North American Colony Collapse Disorder outbreak that began in 2006. Honey bees are also used to pollinate peaches, soybeans, apples, pears, cherries, raspberries, blackberries, cranberries, watermelons, cantaloupes, cucumbers and strawberries. There are dozens of others, ranging from those that simply benefit from the availability of pollinating bees to those (such as squash and vanilla) where the bees are absolutely indispensable.

Coral reefs and climate change

While the Arctic is the most climatically vulnerable human-inhabited environment, coral reefs will probably see the most comprehensive destruction in coming decades. According to the IPCC, it is highly likely that they will succumb to a combination of heat and oceanic acidification as temperatures rise in response to greenhouse gas emissions. It is estimated that the last 25 years have seen the loss of 30% of warm-water coral cover. The worst summers so far for coral bleaching have been 1998 and 2002: in which 42% and 54% of all reefs worldwide were affected. As much as 80% of Caribbean coral may already have died.

Coral bleaching occurs when the zooxanthella algae that live in coral tissues die. The report of Working Group II of the IPCC highlights high surface temperatures as “almost certain to increase the frequency and intensity of mass coral bleaching events.” Throughout the Third and Fourth Assessment Reports, coral reefs are highlighted as being especially vulnerable to climatic change, with low adaptive capability.

Oceanic acidification reduces the calcifying ability of corals, by making it more difficult for them to extract calcium from seawater. In cases of extreme acidity, existing structures could begin to dissolve. According to the IPCC “the progressive acidification of oceans is expected to have negative impacts on marine shellforming organisms.” Studies have demonstrated that projected future ocean acidity will reduce coral calcification and weaken coral skeletons.

The Fourth Assessment Report projects that most corals will be bleached by a temperature rise of 1 to 3°C, with increasing coral mortality at higher levels of temperature increase. Between 2.5 and 3.5°C above the pre-industrial mean temperature, a summary table in the WGII report predicts simply “Corals extinct, reefs overgrown by algae.” It warns further that: “It is important to note that these impacts do not take account of ancillary stresses on species due to over-harvesting, habitat destruction, landscape fragmentation, alien species invasions… or pollution.” Given the low probability of keeping further temperature increases below 2°C – even with the advent of relatively stringent new international obligations – it is fair to say that most of the world’s coral is doomed to die. That, in turn, will undermine much of the basis of coral reef ecosystems. This is a further burden to some small island states, as coral reefs can be the habitat for important fish stocks. Reefs are also the most diverse marine ecosystems: home to about 25% of all marine species.

One way to interpret the news is this: if you have always dreamed of SCUBA diving in the natural splendour of a coral reef, make sure you do it fairly soon. Your children might not be able to do it at all. To quote the IPCC once more: “Annual or bi-annual exceedance of bleaching thresholds is projected at the majority of reefs worldwide by 2030 to 2050.”

Panda update

An article from the always-interesting Christmas issue of The Economist provides an update on the state of the panda: covering captive and wild populations, as well as new scientific thinking about what caused their endangerment. Pandas are widely cited as a truly hopeless animal. They are inept at and uninterested in reproduction, with females only fertile for 3-4 days a year anyhow. They are also only willing to eat a single food that is thoroughly lacking in calories and dies off en masse at regular intervals.

That said, captive populations seem to be on the rise thanks to better breeding techniques, while policies intended to prevent floods caused by deforestation have served indirectly to protect some wild habitat. It seems that despite their challenges – both natural and man-made – pandas will prove charismatic enough to endure.

Concrete’s climatic consequences

While aviation and ground transport get lots of well-deserved attention, in terms of their climate change impact, the concrete industry seems to get a lot less scrutiny. In a way, this is unsurprising; concrete is hardly glamorous stuff. At the same time, concrete production accounts for about 5% of all greenhouse gas emissions: mostly from the process of manufacturing clinker by heating limestone and clay. This is usually done using coal. The average tonne of concrete produced generates about 800kg of carbon dioxide: both as a result of the coal burning and the product of the chemical reaction involved (CaCO3 -> CaO and CO2, ignoring silicates). This figure does not include emissions relating to quarrying rock or transport.

Cement manufacture can be incrementally improved in three ways: by reducing the ratio of clinker to other additives, by making kilns more efficient, and by using fuels other than coal for the heating. All of these can make contributions, to a certain degree, but only a complete shift to biomass heating could have a terribly significant effect on greenhouse gas emissions (and that effect could be moderated by the emissions from transporting the biomass).

Demand for cement is growing at about 5% a year, and is partially driven by the construction of new hydroelectric dams and nuclear power plants. At present, the rate of demand increase exceeds the rate of efficiency improvements. As such, greenhouse gas emissions associated with concrete are increasing every year. The average North American home uses about 25 tonnes of concrete, mostly in the foundation.

George Monbiot discusses concrete in his book, focusing on geopolymeric cements as a solution. Carbon capture and storage (CCS) is theoretically possible, but with an added problem. Concrete plants must be sited near limestone quarries. These are not necessarily near the salt domes or aquifers where CCS can probably be most effectively deployed. Geopolymeric cements are similar to the pozzolan cement used by the Romans to build the roof of the Pantheon. They are made from clay, certain kinds of sedimentary rock, and industrial wastes. Producing them generates 80-90% less carbon dioxide. This is because they require a lot less heating and the chemical reaction that produces them does not generate CO2 directly.

The modern version of this material was only developed in the 1970s and has yet to be widely adopted. Partly, that is because of the cost of refitting existing cement works or building new ones. Partly, it reflects the hesitation of the construction industry to use new materials. Such objections can probably be most efficiently addressed through carbon pricing. If the concrete and construction industries were paying for those 800kg of CO2, the incentives they face would probably change decisively and fast.

Copper indium gallium selenide solar cells

Nanosolar, a company supported by Larry Page and Sergey Brin (the founders of Google), has announced that it will be selling thin-film solar cells profitably for $1 a watt. Apparently, the cells are printed with copper indium gallium selenide – an alternative to silicon. Cells based on the material can convert solar radiation to electricity with 19.5% efficiency. In theory, this material can applied to foil, plastic, glass or cement – producing electricity generating surfaces. It can also be made into more conventional panels of the sort Nanosolar is starting to sell.

In the 1950s, solar cells cost about $200 per watt. By 2004 they were down to $2.70. Further reductions could make solar power cost competitive with fossil fuels, potentially even in the absence of carbon pricing. Combined with either better storage (to moderate light/dark and sunny/cloudy cycles locally) or better inter-regional transmission (the sun is always shining somewhere), such cells could eventually make a big difference in the overall energy balance. Solar has been discussed here previously.

Grass ( Fungus ( Virus ) Fungus ) Grass

There is increasing scientific awareness of the intricate and essential ways in which different organisms depend on one another biochemeically. Termites could not eat wood without bacteria in their digestive tracts. Humans are likewise dependent upon the huge variety of microorganisms that comprise our microbiome.

Dichanthelium lanuginosum takes such intricacy a step further. It is a grass that lives in very hot soils – such as those in Yellowstone Park. ot only does it depend upon a fungus for its heat resistance, that fungus depends in turn upon a virus. Remove either the fungus or the virus and the grass can no longer live in its ordinary niche. Apparently, something similar has been observed in some tomato plants.

The example demonstrates just how shockingly complex the combination of biochemistry, ecology, and evolutionary biology really is.

Source: Márquez et al. “A Virus in a Fungus in a Plant: Three-Way Symbiosis Required for Thermal Tolerance.” Science 26 January 2007: Vol. 315. no. 5811, pp. 513 – 515.

Reasons for vegetarianism

During the last few days, a number of people have asked about the reasons for which I am a vegetarian. As shown in the Venn diagram above, my reasons fall into three major clusters:

Hygienic concerns
Animal rights concerns
Ecological concerns

Basically, the first category applies if you only think about your own immediate well being. If you are willing to consider the possibility that it is wrong to treat some animals in some ways, considerations in the orange circle start to apply. If you accept that we have general duties to preserve nature (or recognize that our long term survival depends on acting that way), issues in the yellow circle are of concern.

The specific issues listed are just examples. They are not exhaustive representations of all the problems in each area. Possible reasons for being vegetarian also exist outside these areas: for example, you can think it is wrong to eat meat when the grain used to fatten the animals could have alleviated the hunger of other humans.

A few issues are unambiguously in one area – for instance, the de-beaking of chickens is almost exclusively an ethical problem. The fact that no experimental laboratory could get ethical approval to treat their test subject animals in the way factory farmed animals are treated as a matter of course is telling. Some overlaps are ambiguous. Overfishing destroys the habitats of species I consider us to bear moral duties towards (such as whales and dolphins), even if the fish themselves can be legitimately used as means to whatever ends we have.

Naturally, different kinds of meat and processes of meat production do more or less well in each area. For my own sake, I think each of the three areas is sufficient in itself to justify vegetarianism. It is possible to imagine meat production that doesn’t have any of these problems, but it is an extreme rarity today and my appreciation for meat is not strong enough to justify the cost and effort of seeking it out. That said, I would be much happier if people who were going to consume meat made such choices, instead of helping to perpetuate the machinery of modern industrial farming.

A few thoughts on climate justice

A couple of articles at Slate.com address the issue of ‘climate justice.’ This is, in essence, the question of how much mitigation different states are obliged to undertake, as well as what sort of other international transfers should take place in response to climate change. The issue is a tricky one for many reasons – most importantly because anthropogenic greenhouse gas emissions constitute a unique experiment that can only be conducted once. If we choose the wrong collection of policies, all future generations may face a profoundly different world from the one we inherited.

If we accept Stern’s estimate of a five gigatonne level for sustainable global emissions, that works out to about 760kg of carbon dioxide equivalent per person on Earth. Releasing just 36kg of methane would use up an entire year’s allotment, as would just 2.5kg of nitrous oxide. One cow produces about 150kg of methane per year. Right now, Canada’s per-capita emissions are about 24,300kg, when you take into account land use change. American emissions are about 22,900kg while those of India and China are about 1,800kg and 3,900 respectively. Because of deforestation, Belize emits a startling 93,900kg of CO2e per person.

The questions of fairness raised by the situation are profound:

Should states with shrinking populations be rewarded with higher per capita emissions allowances?
Should states with rising populations likewise be punished?
Should developing states be allowed to temporarily overshoot their fair present allotment, as developed states did in the past?
To what extent should rich states pay for emissions reductions in poor ones?
To what extent should rich states pay for climate change adaptation in the developing world?

It may well be that such questions are presently unanswerable, by virtue of the fact that answers that conform with basic notions of ethics clash fundamentally with the realities of economic and political power. We can only hope that those realities will shift before irreversible harmful change occurs. Remember, cutting from 24,600kg to 760kg per person just halts the increase in the atmospheric concentration of CO2. The level of change that will arise from any particular concentration remains uncertain.

Another vital consideration is how any system of international cooperation requires a relatively stable international system. While it is sometimes difficult to imagine countries like China and the United States voluntarily reducing emissions to the levels climatic stability requires on the basis of a negotiated international agreement, it is virtually impossible to imagine it in a world dominated by conflict or mass disruption. It is tragically plausible that the effects of climate change could destroy any chance of addressing it cooperatively, over the span of the next thirty to seventy years.

Salmon farming and sea lice

Recent work by Martin Krkosek of the University of Alberta has demonstrated strong links between the practice of salmon aquaculture and the incidence of sea lice infestations that threaten wild populations. One study used mathematically coupled datasets on the transmission of sea lice (Lepeophtheirus salmonis) on migratory pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. They concluded that:

Farm-origin lice induced 9–95% mortality in several sympatric wild juvenile pink and chum salmon populations. The epizootics arise through a mechanism that is new to our understanding of emerging infectious diseases: fish farms undermine a functional role of host migration in protecting juvenile hosts from parasites associated with adult hosts. Although the migratory life cycles of Pacific salmon naturally separate adults from juveniles, fish farms provide L. salmonis novel access to juvenile hosts, in this case raising infection rates for at least the first 2.5 months of the salmon’s marine life (80 km of the migration route).

Packing fish together in pens that are open to the sea is an almost ideal mechanism for breeding and distributing parasites and disease. In nature, you would never find salmon packed 25,000 to an acre. Keeping them in such conditions – and making them grow as quickly as possible – generally requires chemical manipulation. The earlier discussion here about antibiotic use and its role in the emergence of resistant bacteria is relevant.

These concerns also exist in addition to the fundamental reason for which fish farming cannot be sustainable: it relies on catching smaller and less tasty fish to feed to the tastier carnivorous fish that people enjoy. It thus lets us strip the sea bare of salmon or cod or trout and compensate for some period of time by using cheaper fish as a factor for their intensive production. Given that those cheaper fish are caught unsustainably, however, fish farming simply delays the emergence of truly empty oceans. And the industry is trying to have farmed salmon labelled ‘organic.’ Ludicrous.

Source: Krkosek, Martin et al. “Epizootics of wild fish induced by farm fish.” Proceedings of the National Association of Sciences. October 17, 2006, vol. 103, no. 42, 15506-15510.

P.S. Shifting Baselines also has some commentary on sea lice and salmon farming.

Entertaining physics demonstrations

His name is Julius Sumner Miller and physics is his business.

For those who lacked my good fortune in seeing most of these demonstrations a number of times at Vancouver’s Science World, the videos should give a sense of how physics can be made universally comprehensible and exciting. The facts that Mr. Miller looks like a mad scientist and that he has a penchant for hyperbole may well contribute to his ability to hold one’s attention.

My involvement as a camper and leader at SFU’s Science Alive daycamp also impressed upon me the effectiveness of physical demonstrations in sparking children’s interest in science. That is especially true when the demonstrations involve rapid projectile motion, strong magnets, cryogenic materials, aggressive combustion, and explosions.