Here's how to help our urban trees thrive (1)
Urban trees planted in Stockholm, Sweden, have been shown to be healthy, and the methods used are now being applied in the UK with growing success. The system captures rainwater from roofs and roads, then channels it into a tree pit containing crushed granite and biochar. This allows for ingress of both water and oxygen, and the biochar ensures a resilient soil microbiome. It was created by Bj枚rn Embr茅n, Stockholm’s tree officer, and has significantly boosted the success of urban trees (21 October, p 34).
Here's how to help our urban trees thrive (2)
Fallen leaves from urban trees are often swept up and disposed of by street cleaners or residents, removing a valuable source of leaf litter, which forms the top layer of soil in forests or woodland. Returning this as a mulch, in addition to added topsoil, could help solve some of the problems you report. In addition, authorities don’t allow decaying or dead trees to remain on streets for obvious reasons, again removing a vital source of microorganisms that contribute to leaf litter.
No mention was made of earthworm populations in urban tree root systems or surrounding soil. Earthworms are known to spread fungi, both beneficial and otherwise. In general, their presence seems to increase the occurrence of beneficial mycorrhizal fungi.
Why do so many fight shy of a career in engineering?
Hayaatun Sillem is correct in her assessment of the shortage of graduates in engineering (28 October, p 21).
The lack of women in this walk of life is a problem that has consumed a forest full of research papers and focus group reports over the years, but to little effect. It isn’t simply that engineers are portrayed as either the greasy rag brigade or shown in hard hats on building sites, but that the job is viewed as low-paid grunt work needing high-level qualifications.
I once ran a course aiming to encourage women onto my institution’s engineering courses. It was a great success until the end, when I asked if they would now join us on one of our BTEC courses. Every one answered by saying that there are easier ways to earn a living.
You can cast processed foods in a positive light (2)
Why so much cynicism over “ultra-processed” foods (UPFs)? You report claims that the food industry’s goal “is to maximise profits by cajoling consumers to abandon freshly prepared food”. Why not say that the industry gives us the possibility of buying ready-to-eat food instead of having to do all the processing ourselves? And why say “they are engineered to have craving-like palatability” instead of “they are developed to be delicious”?
And after describing a key experiment, you say that “the conclusion is obvious: UPFs ‘lead people to overeat calories'”. Yes, but it doesn’t show that this was because they were ultra-processed. I would say the conclusion is obvious 鈥� people like eating hot dogs and French fries more than plain, raw fruits or vegetables (28 October, p 40).
When you say that the highest consumers of UPFs were 1.6 times more likely to die during a study, that ignores confounding factors. They surely ate more calories, so you should probably blame it on that, not the ultra-processing.
You can cast processed foods in a positive light (1)
Perhaps there is no more ultra-processed food than lab-grown meat and plant-based alternatives.
Applause for renewables, but more must be done
You rightly laud South Australia’s push to decarbonise its electricity generation, but, in common with so much reporting around net zero, the implication is that we will hit this target when all of our electricity generation is carbon-free. Global primary energy consumption in 2022 was around 179,000 terawatt-hours, of which about 137,000 TWh, or 82 per cent, came from fossil fuels. Electricity generation accounted for only about 28,500 TWh, or 17 per cent, of this global fossil fuel use (Leader, 28 October).
Older homes may never be suitable for heat pumps
S. W. Shaw calculates that around 9 million UK homes may have converted to using heat pumps in the next 15 years. However, millions of homes here are Victorian and broadly aren’t suitable for . Beyond those 9 million conversions, to really make progress towards net-zero housing, we may have to bulldoze all Victorian houses (Letters, 28 October).
Taking the carbon tax to its logical conclusion
There have been welcome ideas from readers relating to carbon taxes, but an important added ingredient is needed to make them work, to prevent “carbon leakage” via the import of goods with high embedded carbon (Letters, 21 October).
To that end, the European Union has created the Carbon Border Adjustment Mechanism (CBAM). It demands that the carbon footprints of carbon-intensive imported goods are accounted for. From 2026, these have to be paid for by purchasing CBAM certificates. This mechanism needs to be applied worldwide to ensure equitable sharing of emission reductions.
What chance is there of world trade agreements adopting this? Perhaps they will, if a critical mass of major trading partners does so.
Vape waste is a big problem too
I am concerned about the impression that discarded toys generate more e-waste than vapes. While it is true that toys make up the majority of this in landfill, I suspect vapes make up the majority outside landfill and fly-tipping sites. Some ex-smokers discard them like cigarette butts (21 October, p 14).
Could we solve the riddle of the Sphinx for good?
You raise the idea that there may be a harder core to the Great Sphinx of Giza, the shape of which was formed by wind erosion (4 November, p 13). Couldn’t this question be easily answered by the use of ground penetrating radar? If there is no hard core, then the riddle remains!