I’m back to work after a long and warm summer. Teaching has exceeded my expectations. I enjoy walking around the school, speaking to people and getting to hear about a wide variety of lives lived. I like the routine of the days and the learning.
I don’t have any posts to share this month. I have read a lot, but there’s been a lot of doomscrolling, so why share that – it’s everywhere!
I’ve joined Substack and spend my attention there. I haven’t posted and may never.
I’ve enjoyed reading this summer and lots of time with my family.
Here is a photo with a view from the hammock I shared with my grandson last week. Time with him is precious to me.
The number of people who read for fun appears to be steadily dropping. Fifty percent of UK adults say they don’t read regularly (up from 42% in 2015) and almost one in four young people aged 16-24 say they’ve never been readers, according to research by The Reading Agency.
But what are the implications? Will people’s preference for video over text affect our brains or our evolution as a species? What kind of brain structure do good readers actually have? My new study, published in Neuroimage, has found out.
I analysed open-source data from more than 1,000 participants to discover that readers of varying abilities had distinct traits in brain anatomy.
The structure of two regions in the left hemisphere, which are crucial for language, were different in people who were good at reading.
One was the anterior part of the temporal lobe. The left temporal pole helps associate and categorise different types of meaningful information. To assemble the meaning of a word such as leg, this brain region associates the visual, sensory and motor information conveying how legs look, feel and move.
The other was Heschl’s gyrus, a fold on the upper temporal lobe which hosts the auditory cortex (the cortex is the outermost layer of the brain). Better reading ability was linked to a larger anterior part of the temporal lobe in the left hemisphere compared to the right. It makes sense that having a larger brain area dedicated to meaning makes it easier to understand words and, therefore, to read.
What might seem less intuitive is that the auditory cortex would be related to reading. Isn’t reading mainly a visual skill? Not only. To pair letters with speech sounds, we first need to be aware of the sounds of the language. This phonological awareness is a well-established precursor to children’s reading development.
A thinner left Heschl’s gyrus has previously been related to dyslexia, which involves severe reading difficulties. My research shows that this variation in cortical thickness does not draw a simple dividing line between people with or without dyslexia. Instead, it spans the larger population, in which a thicker auditory cortex correlates with more adept reading.
Why size matters
Is thicker always better? When it comes to cortical structure, no, not necessarily. We know the auditory cortex has more myelin in the left hemisphere of most people. Myelin is a fatty substance that acts as an insulator for nerve fibres. It increases neural communication speed and can also insulate columns of brain cells from each other. Neural columns are believed to function as small processing units.
Their increased isolation and rapid communication in the left hemisphere can be thought to enable the fast, categorical processing necessary for language. We need to know if a speaker uses the category d or t when saying dear or tear rather than detecting the exact point where the vocal folds start vibrating.
According to the “balloon model” of cortical growth, the larger amount of myelin squeezes out left-hemispheric cortical areas, making them flatter but more extended. So while the left auditory cortex may be thicker in good readers, it is still thinner (but much more extended) than the corresponding right cortex.
This hypothesis was corroborated in the recent research. The left hemisphere had generally larger but thinner cortical areas with a higher degree of myelin.
So is thinner better, then? Again, the answer is no, not necessarily. Complex abilities that require integrating information tend to benefit from a thicker cortex. The anterior temporal lobe with its complex way of integrating information is indeed the thickest structure of all cortical areas. An underlying mechanism might be the existence of more overlapping, interacting neurons which process information more holistically.
Phonology is a highly complex skill, where different sound and motor features are integrated into speech sounds. It appears to correlate with a thicker cortex in an area near the left Heschl’s gyrus. While it is unclear to what extent phonology is processed in Heschl’s gyrus, the fact that phoneticians often have multiple left Heschl’s gyri suggests it is linked to speech sounds.
The temporal lobe is involved in reading. Shutterstock
Clearly, brain structure can tell us a lot about reading skills. Importantly, though, the brain is malleable — it changes when we learn a new skill or practice an already acquired one.
For instance, young adults who studied language intensively increased their cortical thickness in language areas. Similarly, reading is likely to shape the structure of the left Heschl’s gyrus and temporal pole. So, if you want to keep your Heschl’s thick and thriving, pick up a good book and start reading.
Finally, it’s worth considering what might happen to us as a species if skills like reading become less prioritised. Our capacity to interpret the world around us and understand the minds of others would surely diminish. In other words, that cosy moment with a book in your armchair isn’t just personal – it’s a service to humanity.
Can you see three trees from your home, school or workplace? Is there tree canopy cover shading at least 30% of the surrounding neighbourhood? Can you find a park within 300 metres of the building?
These three simple questions form the basis of the “3+30+300 rule” for greener, healthier, more heat tolerant cities. This simple measure, originally devised in Europe and now gaining traction around the world, sets the minimum standard required to experience the health benefits of nature in cities.
We put the rule to the test in eight global cities: Melbourne, Sydney, New York, Denver, Seattle, Buenos Aires, Amsterdam and Singapore.
Most buildings in these cities failed to meet the 3+30+300 rule. We found canopy cover in desperately short supply, even in some of the most affluent, iconic cities on the planet. Better canopy cover is urgently needed to cool our cities in the face of climate change. https://rmituniversity.maps.arcgis.com/apps/instant/portfolio/index.html?appid=7bbb6fa639d34eb38d2ff6fb035feffd
Explore all three interactive maps, zoom in or out and search by address or place, hit the “i” button for more detail. Source: Cobra Groeninzicht
Shady trees are good for health and wellbeing
People are more likely to suffer from depression, anxiety, obesity and heatstroke in places with fewer trees, or limited access to parks. But how much “green infrastructure” do we need to stay healthy and happy?
Dutch urban forestry expert Professor Cecil Konijnendijk set the standard when he introduced the 3+30+300 rule in 2022. This benchmark is based on his wide-ranging review of the evidence linking urban nature to human health and wellbeing.
While the rule is still relatively new to Australia, it is gaining momentum internationally. Cities in Europe, the United States and Canada are using the measure, formally or informally, in their urban forestry strategies and plans. These cities include Haarlem in the Netherlands, Malmö in Sweden, Saanich in Canada, and Zürich in Switzerland.
Achieving 100% canopy cover is possible over streets, even in built-up areas. Thami Croeser
Putting the rule to the test
We applied the 3+30+300 rule to a global inventory of city trees that collates open source data from local governments. We selected cities with the most detailed data for our research, aiming for at least one city on every continent. Unfortunately no suitable data could be identified for cities in Africa, mainland Asia or the Middle East.
Our final selection of eight cities features several regarded as leaders in urban forestry and green space development. The City of Melbourne is renowned for its ambitious Urban Forest Strategy. New York is home to successful projects such as MillionTreesNYC and The Highline. Singapore is known for lush tropical greenery including standout sites such as Gardens by the Bay and Bishan-Ang Mo Kio Park.
Analysis of Melbourne and Sydney was restricted to central areas only, based on limitations in the data, while the other six analyses covered whole cities.
Most buildings across the eight cities met the three trees requirement but fell short on canopy cover. In contrast, three in four (75%) buildings passed the 30% canopy benchmark in Singapore and almost one in two (45%) passed in Seattle.
Just 3% of buildings in Melbourne had adequate neighbourhood canopy cover, despite 44% having views of at least three trees.
Central Sydney fared better, although only 17% of city buildings were shaded enough despite 84% having views of at least three trees.
Access to parks was also patchy. Cities such as Singapore and Amsterdam scored well on parks, while Buenos Aires and New York City scored poorly.
Since completing this study, we partnered with Dutch geospatial firm, Cobra Groeninzicht to map ten extra cities in Europe, the US and Canada. We found similar results in these cities.
Singapore was the only city to receive a pass mark on all three components of the 3+30+300 rule. Croeser et al., 2024.
Too small and spaced out
We were surprised to discover so many buildings around the world had views to at least three trees but still had inadequate neighbourhood canopy cover. This seemed contradictory – are there enough trees, or not?
The issue comes up in other studies too. For example, the city of Nice in France recently revealed 92% of residents have views to three trees, but only 45% had adequate neighbourhood canopy.
When we looked into this issue, we found those three trees, visible as they may be, are often too small to create decent shade.
Planting density was an issue too. When a city did have large trees, they tended to be very spaced out.
Explore all three interactive maps, zoom in or out and search by address or place, hit the “i” button for more detail. Source: Cobra Groeninzicht
City living is tough for trees
Many of our roads and footpaths sit on a base of compacted crushed rock, topped by impermeable asphalt or paving. This means very little water reaches tree roots, and there isn’t much space for the roots to grow. As a result, street trees grow slowly, die young, and are more susceptible to pests, disease and heat stress.
Above ground, trees face further challenges. Power companies have legal powers to demand sometimes excessive amounts of pruning. Residents and developers frequently request tree removals, often successfully.
This trifecta of high removal rates, heavy pruning and tough growing conditions mean large, healthy canopy trees are rare.
Planting new trees is surprisingly difficult too. Engineering standards often act against tree planting by requiring large clearances from driveways, underground pipes, or even parking spaces.
Instead of managing potential conflicts, trees are often simply deleted from streetscape plans. Sparse planting is the result.
Conservative powerline clearance rules requiring intense pruning of street trees are being challenged by urban forestry experts. Thami Croeser
Finding solutions to nurture tree canopy
Fortunately, there are solutions to all of these issues.
Legal reforms to put trees on equal footing with other infrastructure would be a great place to start. Trees do come with risks as well as benefits, but we need to manage those risks rather than settling for hot, desolate streets.
Better planting standards will be important too. Technology already exists to create larger soil volumes under footpaths and roads. Clever asphalt-like materials (often called “permeable paving”) allow rain to infiltrate soils. These approaches cost more, but they work very well. Not only do they potentially double tree growth rates trees, but they also help reduce flood risks and minimise issues such as roots blocking drains or causing bumpy footpaths.
Our study is a clear call to action for cities to expand, maintain and protect their urban forests and parks to prepare for climate change. With another record-breaking summer predicted, hot on the heels of the world’s hottest year, growing tree canopy has never been more urgent. We must push forward with these reforms and ensure our urban populations have all the green infrastructure they need to protect them into the future.
Trees planted in specialised soil volume systems grow much faster, as do trees with proper access to water. In this trial, the tree on the right was planted in a soil vault, while the tree on the left (planted at the same time) was not. CityGreen
