The soil's the thing
Instead of soaking up carbon dioxide from the atmosphere, growing trees will release extra CO2 from the soil because of the disturbance caused by cultivating and planting. This is the gist of your report on the findings of the CarboEurope project (26 October, p 10).
But this result presumably came from areas where trees were planted on former forest or peat soils, which are very high in organic carbon. If trees are planted in soil that has been used for arable agriculture for a long time and therefore has a low carbon content, the result is quite different.
Using surplus agricultural land for trees is a real option in the European Union, under current set-aside schemes (where land is taken out of food production, either temporarily or permanently). And the likely changes to the EU’s Common Agricultural Policy also propose taking more land permanently out of agricultural use. Here at Rothamsted we have measured the amount of carbon absorbed in soil and trees from two nearby areas of old arable land, the Broadbalk and Geescroft Wildernesses, that were set aside more than 100 years ago.
The initial soil carbon content of these areas was 37 and 26 tonnes per hectare to a depth of 23 centimetres in 1881 and 1883 respectively. Following natural woodland regeneration, this rose to 81 and 82 tonnes per hectare in 1985 鈥� an average soil carbon accumulation rate of 0.5 tonnes per hectare per year. Also, between the 1880s and 1965, Broadbalk and Geescroft gained 123 and 81 tonnes per hectare respectively in above-ground biomass, an average accumulation rate of 1.2 tonnes per hectare per year.
Establishing trees on surplus agricultural soil that has a low organic carbon content is therefore a good idea.
Menopausal falls
In reply to Debra Griffiths’s letter on people slipping and tripping, she is quite right that high-heeled shoes play a part in some accidents (19 October, p 29). Our questionnaire did ask about the type of shoes worn and I would associate high-heeled shoes both with accidents on stairs and those involving alcohol (because of women wearing fashionable shoes for a night out).
But we have evidence that suggests other major factors are at play. Our paper, reported in New 杏吧原创 (5 October, p 24), was ready for publication some time ago and we have since done further research on a larger data set published in the Quarterly Journal of Medicine (vol 94, p 699). Both papers show a rise in the number of slips and trips for women at about the age of the menopause. Comparing the age ranges 45 to 49 and 50 to 54 in women attending accident and emergency departments, we observed approximately twice as many women in the older group with fractures resulting from “underfoot” accidents, but in the same age bands there was a decline in numbers with accidents classified as “not underfoot”.
I believe that hormonal changes that lead to a reduction in muscle strength and possibly increased reaction time could be a significant factor in determining the risk of such accidents. This age factor suggests that shoes are not as significant as you might think 鈥� after all, do women abruptly change their style of footwear at the menopause? Carrying things at the time of the accident would be significant if reflex actions to prevent injury were inhibited.
On the other hand, since both high-heeled shoes and alcohol are risk factors for underfoot accidents, perhaps menopausal and post-menopausal women should reduce their risk by not wearing fashion shoes when they go out to the pub.
Glutamate and eyesight
Generally, the amount of monosodium glutamate added to food as seasoning is between 0.1 per cent and 0.8 per cent of the food (26 October, p 11). The allegations about the safety of MSG were made by a researcher in Japan who fed laboratory rats a diet that was almost 20 per cent MSG. The rats were only three weeks old, so the stress on their bodies must have been huge, and this level of MSG is equivalent to a person consuming more than 500 grams of it every day for months. So the experiment is irrelevant to human levels of consumption.
The extensive body of research on MSG as a food ingredient has been reviewed by scientists and regulatory authorities around the world, including the Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and the World Health Organization. This review included long-term, multi-generation studies, which confirmed that MSG has no adverse effect on the retina.
Cull the cats
When discussing ways of controlling the spread of Toxoplasma gondii, James Randerson neglects what must surely be the most useful method 鈥� eliminating its main vector, the cats (26 October, p 40).
Either making cat owners keep their animals under control or eliminating the creatures from our towns completely would not only prevent countless Toxoplasma infections but also the slaughter of millions of birds and small mammals, not to mention saving gardeners the unpleasant and frequent experience of coming into contact with cat faeces.
Perhaps Randerson neglected to mention this to avoid incurring the wrath of those people whose main manifestation of Toxoplasma infection appears to be an inability to understand that anyone could possibly dislike coming into contact with their pets’ waste products.
Letter
The increased risk quoted in the article and the incidence of infection surely means that the death toll from Toxoplasma must be many times that caused by variant CJD, the human form of mad cow disease, the response to which was the slaughter of thousands of cows. Why, I wonder, did James Randerson fail to reach the same conclusion regarding the feline threat?
Not by impact alone
The proposition that only asteroids that exceed a critical size are capable of causing global extinctions is intriguing (26 October, p 24). It is, however, possible that factors other than sheer size might determine whether an impact will precipitate a mass extinction.
For example, the effect of the Chicxulub impact in Mexico might have been compounded by it coinciding with a phase of extreme volcanic activity or some other large-scale, calamitous event or events. By the same token, the Chesapeake Bay and Popigai impacts might have failed to “pulverise the poor little mammals” because they did not coincide with any other calamities such as those that may have occurred at the time of the Cretaceous or Permian era extinctions.
It could also be that mammals survived the Chicxulub impact simply because they were tougher than dinosaurs.
Plenty of energy
Ian Harris sees nothing wrong in persuading people to reduce their use of resources, including energy (26 October, p 28). But there is something wrong with it 鈥� it is a waste of time. People simply don’t want to do it, especially if it means a drop in their standard of living.
It is also ineffective. Attempts to reduce energy use, paradoxically, have the opposite effect. One reason is that techniques to reduce energy consumption themselves use energy. Another is that because energy is made effectively cheaper, more gets used. Any money saved is reinvested, so boosting energy use elsewhere.
Nor is there any reason to limit energy use. There is plenty of energy available (nuclear if not fossil). Our civilisation runs on it, and will collapse without it. The raw materials for manufacturing and energy conversion are plentiful, if not always easy to extract. Resources are finite in theory but probably infinite in practice.
More than just heat
Your article about “exergy” misrepresents my work and that of my colleagues (5 October, p 30). Our view, it is said, is that “life works to degrade heat energy 鈥� generating the maximum amount of entropy”. James Kay disputes this, saying heat isn’t the only source of energy for life.
Yet our work has never referred to heat energy alone. The standard boilerplate in our papers reads: “The same principle applies to any system where any form of energy is out of equilibrium with its surrounds (such as mechanical, chemical, electrical or energy in the form of heat), a potential exists that the world acts spontaneously to minimise.”
The ideas of Kay and Eric Schneider covered in the feature are not new. Their suggestion that potentials are degraded at the fastest rate given the constraints was suggested and demonstrated more than a decade ago, and it was shown that, as a consequence, the world can be expected to produce as much order as it can.
Zero plus
As the compilers of the Chart of the Nuclides long ago recognised, the neutron is “element zero”. If your suggested “element” containing four neutrons exists (26 October, p 30), it will simply be a heavy isotope of “element zero”.
Trouble in mind
Steven Rose appears to assume that consciousness 鈥� as, presumably, distinct from other activities related to the brain 鈥� cannot be investigated scientifically without reference to philosophy (12 October, p 50). He claims that neuroscience has to confront issues such as relevance, ethics and moral responsibility if it continues to “poke its nose” into the once taboo topic of consciousness.
You could equally apply this dogma to the scientific investigation of cognition or mood, or even life itself 鈥� which, like consciousness, defies an explanation of purpose or, for that matter, a succinct definition.
In reality, we cannot expect to make progress until we ask which neurotransmitters are the targets of anaesthetic drugs, how these systems relate to changes in consciousness during the sleep-wake cycle 鈥� including dreaming 鈥� and which pathways are affected in diseases of the human brain affecting consciousness.
As for relevance, just as memory research took off after the discovery of localised brain damage associated with short-term memory loss in an epileptic patient, similar advances are likely in relation to the neuropathology of consciousness.
And as for ethics and morality, at least with respect to brain disease and anaesthetics, I am probably not alone in preferring these questions to be addressed scientifically, even if there are unresolved philosophical issues.
Protecting astronauts
Could the radiation experienced by astronauts in space be reduced by creating a magnetic field around the spacecraft (26 October, p 8)? If Earth’s magnetic field provides some protection to the Space Station in low-Earth orbit, then generating a field around the spacecraft might repel cosmic rays, perhaps by using an electromagnet powered via solar panels or some other technology.
For the record
鈥� Fentanyl is a routinely used fast-acting oral or injectable anaesthetic. Trimethyl fentanyl is a derivative of fentanyl which emerged as an opiate possibly used in the Moscow theatre siege (“Which drugs can stun a crowd in seconds”, 2 November, p 7).