Long Reads: Yellowing with age
A TST Long Read
Welcome to the first TST Long Read! Long Reads is a new occasional series featuring longer articles written by guests. This is the first in the series, and I hope you find it interesting.
For this, the first Long Read, please welcome Professor John Tregoning. John is the author of the upcoming book Live Forever? The Curious Scientist’s Guide to Wellness, Disease and Ageing (out 9th January 2025). He previously published Infectious: Pathogens and how we fight them (OneWorld) which describes the history and science of infectious disease. John is currently Professor of Vaccine Immunology at Imperial College London, where he has studied the immune responses to vaccination and respiratory infection for more than 25 years. John has written 85 scientific articles and numerous articles on scientific careers. He appeared on the Royal Institution Christmas lectures, appeared on radio and has written for local and national newspapers.
I have never really left the academic system: I have worked at Imperial College London ever since I began my PhD there 25 years ago. This has shifted the start point of my year to the 1st October when the students return. Which to me is a much more impactful date than the 1st January when nothing really happens. The start of the academic year is much more visually marked, through the changing of the seasons and the autumn leaf colours. And it is seen most strikingly on the Imperial campus in the form of a ginkgo tree (Ginkgo biloba), which gradually shifts from green to yellow. The tree was planted in 1985 in memory of Dr WPK Findlay, who Wikipedia tells me was a wood scientist. His connection to Imperial was somewhat tenuous – he was an alumnus, but never worked here.
Findlay’s Gingko tree lives in front of the library, named after the physicist and Nobel prize winner Abdou Salaam. It is at the west end of the Queen’s lawn, and visible on Google maps if you squint. Its yellow shift punctuates my passage of years. Turning 45 has led to me reflecting on those passed but more forebodingly on those to come. These reflections led to my new book Live Forever? A Curious Scientist’s Guide to Wellness, Ageing and Death (Oneworld).
One of the more telling moments was walking through campus on a summer’s day, passing the shade of the ginkgo tree and noticing that the students were the same age as my children. This was coupled with the realisation that I am increasingly invisible to students – no fliers for plant sales or bops are wasted on me. It didn’t help that all of the research I had done emphasised the inevitability of my passing and how little I can do about it.
But as I researched more, one striking feature emerged. Time spent in nature improves the quality of our lives and even prolongs them. Louis Pasteur alluded to this: ‘Nature is the best doctor: she cures three out of four illnesses, and she never speaks ill on her colleagues’. One of the simplest things that trees do for our health is to reduce the damage done by air pollution. The air we breathe contains a heady cocktail of pollutants that damage our lungs; some are gases (NO2, O3, CO, SO2), some are toxic chemicals like lead and some fall into the broader category of PM2.5, a mixture of minuscule but horrible lung-damaging stuff. Whilst smoking is the main cause of COPD (chronic obstructive pulmonary disease), air pollution is a close second. COPD is characterised by an irreversible destruction of the lung. Inhaled particulates cause inflammation, confusing our immune systems into attacking ourselves, damaging the fine filigree of the lungs, reducing our ability to breathe.
The good news (for Londoners at least) is that the air we breathe is improving and has been improving since the 1950’s. Though it was at a pretty low starting point. The 1952 Great Smog killed at least four thousand, but probably closer to twelve thousand, people . As far as records go, London air is the cleanest it has ever been. The bad news is that there is actually no safe threshold for air pollution – all inhaled particulates cause damage. More needs to be done to improve it. This is where the ULEZ (Ultra Low Emission Zone) comes in. A policy that was first enacted when Boris Johnson was the Mayor of London, it has led to a 44% reduction in lead inhalation in central London. Extending it, though controversial, will increase the benefits, especially for those who live in the East of the city. This is because of prevailing wind direction – most of the crap produced by Sloane Rangers in their Chelsea Tractors gets blown over the homes and schools of the pearly kings and queens, turning them less pearly white and more sludgy grey. It is not the complete solution, braking cars generate PM2.5 from the rubber on the road, and because electric cars are heavier, they produce more of this type of material; though they do produce less of the other forms of pollutants. On balance - bicycling and public transport are best.
Which is where we return to trees. Planting trees can reduce air pollution. A recent study done by the Universities of Lancaster and Oxford explored the ability of leaves from different trees to remove particulates. Whilst the London plane tree (Platanus x hispanica) is often extolled for its air cleansing virtue, the silver birch (Betula pendula), yew (Taxus baccata) and the humble elder (Sambucus nigra) all scored higher for PM removal. The more trees the better, and those acts of cultural vandalism (such as felling the trees at Euston) don’t only harm our souls, they harm our lungs. The answer, of course, is to plant more trees. Not just in the countryside, but on streets and in gardens. Whilst I am proselytising, it wouldn’t harm matters to ban fake grass, do away with concrete drives and to legislate no-mow May throughout the land.
Trees don’t just extend our lives through the physical plain. The beauty of the world around us improves our lives and gives us something to live for, but don’t just take my word for it. Clinical trials demonstrate the cognitive and health benefits of proximity to nature. Walking in nature improved participants’ results in attention-testing tasks. A study from the 1980s compared the amount of self-medication used when recovering from gall bladder surgery in a group that could see trees from their room with another group that could see only a brick wall. The brick wall group used substantially more pain medication and took longer to recover! Trees can also provide therapy, in Japan the practice of shinrin-yoku or ‘forest bathing’ (basically mindfulness in a wood) leads to a range of positive psychological and physiological outcomes. Houseplants, whilst pleasing in themselves, cannot replace nature; one oft-misconceived idea is that they can increase the oxygen in a room. You would need five hundred plants to produce enough oxygen for one person – and they would only do this in the sunshine, at night they would add to the carbon dioxide. It’s simply better to get outside – at least for the sunshine and vitamin D.
As with so much else, there is inequity in people’s access to green space. Unfortunately, trees do not cover our green and pleasant land evenly. Whilst not many of Blake’s Dark Satanic Mills remain, the regions they once occupied have fewer trees. The Woodland Trust have developed an online tool to map tree inequality. This reflects a broader pattern of health inequality across the UK. Much of it along the same West to East lines as the air pollution. For example, travelling along the Jubilee Line that connects the affluent centre of London with the less affluent east end. Based on data from the London Health Observatory, over the eight stops between Westminster station (in the centre) to Canning Town (which is as East London as Peggy Mitchell, eels and The Blitz Spirit), life expectancy drops six years for men. The same happens going west to east on the train line through Glasgow, from the affluent region of Jordanhill to Bridgeton; in this case the life expectancy for men drops by two years for every station, from seventy-six to sixty-two. Access to trees is part of this, nearly a quarter of people living in Greater London do not have outdoor space of their own. By one estimate the tree coverage in my borough in Surrey is three times that of the comparator in Middlesbrough.
So the answer is appreciate nature where you can, even if that is a lone but magnificent ginkgo in a university square. One thing is for sure, trees can live for a very long time indeed. The oldest living thing is a tree. Somewhere in Eastern California towers Methuselah: a 4,855-year-old bristlecone pine tree (Pinus longaeva). This tree’s life has encompassed most of the meaningful bits of human history, certainly all the bits that involve universities. Which brings us back to the erstwhile WPK Findlay in whose memory the ginkgo was planted. Though he published various tracts on mycology during his career, for example the vital 1951 paper ‘A note on the fungi of less common occurrence in houses’, he is no longer a household name. Even his books have faded into the background, his key tome Dry Rot and Other Timber Troubles is no longer on many people’s TBR list. However, much of a fun guy he was (I feel obliged to make that joke), his main legacy is a tree planted in his name and even discovering that needed a bit of rooting around. It is quite a stark reminder of the transient nature of scientific fame (such as it is). And that we shouldn’t spend all of our efforts and stress on things that ultimately fade from memory. Rather, focus on the here and now and the connections you make with people.
Returning to Findlay’s tree, the changing of the seasons and the passing of years, all being well I probably have another 25 years of the yellowing of the ginkgo ahead of me. And it is reassuring to know that when I do eventually move on, the tree will still be there changing colours, marking the new intakes of students, some of whom will eventually become academics, worry about ageing and then pass away too.
John’s book, Live Forever? A Curious Scientist’s Guide to Wellness, Ageing and Death will be published by OneWorld on 9th January 2025. Pre-order from Bookshop.org (a small percentage of the purchase price from those using this Bookshop.org link will help fund The Street Tree.
Look out for other Long Reads in the future, and for those looking forward to a Great British or Irish tree, the next one will appear in a week’s time.
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Good to see that silver birch scores well on air cleaning, as well as its many other virtues as an urban (and rural) tree. Cheered at: “acts of cultural vandalism (such as felling the trees at Euston) don’t only harm our souls, they harm our lungs. The answer, of course, is to plant more trees. Not just in the countryside, but on streets and in gardens. Whilst I am proselytising, it wouldn’t harm matters to ban fake grass, do away with concrete drives and to legislate no-mow May”. Absolutely!