People are not fruit flies. Marcos del Mazo/LightRocket/Getty Images

April 11, 2024   7 mins

There’s a thing in movie franchises called a crossover, where a character from one franchise appears in another. You know the sort of thing: Alien vs. Predator; Batman v Superman: Dawn of Justice. The entire and seemingly interminable Marvel Cinematic Universe series, the total runtime of which is now officially longer than some small wars.

For studios, the financial appeal is pretty obvious. Each character has its devoted fanbase; if you put two characters in one movie, you can get both of them along to the cinema at once. And because the draw is the characters, not the quality of the movie itself, you can skimp on a decent script or convincing effects.

I was thinking about this as I read The Weight of Nature: How a Changing Climate Changes Our Minds, Brains and Bodies, by Clayton Page Aldern. At the risk of sounding cynical, it struck me as a cinematic crossover event. What are people worried about? Climate change. What else are people worried about? Modern life and mental health! What if we got someone to write a book about
 how climate change is damaging our mental health? Then we’d get the climate worriers and the mental healthers buying the same book!

Aldern is not the first person to think of this, and to be fair, climate anxiety is a real problem. Every few weeks a newspaper will run an article by someone saying they won’t have children out of fear that the world won’t be fit to live in, and a global 2021 survey found that more than half of the 10,000 young people surveyed agreed with the phrase “humanity is doomed”. For what it’s worth, I think they’re entirely wrong about that — climate change will have a lot of negative effects on the world, and it’s reasonable to be worried about it, but it’s not going to kill everyone.

“Climate change will have a lot of negative effects — but it’s not going to kill everyone.”

On the whole, though, he wants to say something both more subtle and more ambitious than “people are worried about the future”. He wants to say that climate change itself is damaging our brains. He wants to say it’s doing this in obvious ways — we get grumpier and stupider when it’s hot — and in more insidious ones, with the spread of unpleasant diseases and neurotoxins, and, most poignantly, by causing us grief and displacement and loss of identity and all these things which then have various impacts on our brain.

He does this with the weight of academic authority behind him: he is a “neuroscientist turned environmental journalist”, according to the blurb. (Although he does only have a master’s degree in neuroscience. I did a philosophy MA in 2005 but I would feel a bit of a fraud calling myself a “philosopher”.) This makes the book’s flaws all the more baffling, until you remember that it’s a crossover event.

There’s a certain kind of pop-science book that relies on a particular format: story, study, lesson. Christopher Chabris, a psychologist, first noted it in the work of the disgraced science writer Jonah Lehrer. But it’s a staple — you’ll notice it in Malcolm Gladwell books, for instance. You tell some moving, heartwarming or inspiring story; you recount the results of some study which apparently explains what’s going on in people’s brains in those situations; and then you draw them together to give the reader some pat little take-home message.

I rather thought that we had progressed beyond those books, at least in the upper-mid-market pop science titles that might get reviewed in The Times and New York Times, or excerpted in The Guardian. The “this study on 17 undergraduates at Ohio State University shows that actually creativity stems from our right anterior superior temporal gyrus” stuff so rarely withstood the scrutiny of the replication crisis in science that almost all of them turned out to be essentially content-free.

But Aldern follows the formula to the letter. Each chapter starts with a desperate anecdote: a child dying from an amoebic brain disease caught from a swimming pond; a father whose family burned to death in a wildfire. Then there’s a study, usually in zebrafish or fruit flies, showing us how changes to our environment make us forget, or how living near mountaintop-removal mines is associated with higher rates of depression. Then there’s a flowery lesson presented in conclusion: “The weight of nature presses, but we get to press back. A depression is a state, but it is also a refuge, a place from which to come forth.” OK then.

But what people want from these books isn’t science per se, with its nagging uncertainty and its boring on-the-one-hand-on-the-others. What people want, I think, is vibes: a thrilling sense of fear and sadness, like watching a horror movie or a weepy. (A crossover event between Nightmare on Elm Street and The Bridges of Madison County, perhaps.) That’s my theory, anyway, which would explain why this book can contain claims that are not only under-evidenced but obviously, screamingly false, and still have E. Annie Proulx call it an “important watershed book”.

For instance, Aldern cites one study which looked at the children of mothers who were caught up in Superstorm Sandy in New York and New Jersey in 2012. It found, he said, that among other things, boys who were exposed in utero to the stress of climate change saw a 60-fold increase in ADHD. Think about that for five seconds. What is wrong with that picture? This study found that the prevalence of ADHD in US children and adolescents in 2022 was about 10%. A 60-fold increase in that prevalence would mean that 600% of boys exposed to storms while in utero get ADHD!

In Aldern’s defence, and to my surprise, the study really does claim a 62-fold increased risk specifically for ADHD in boys. But it’s obviously nonsense, a product of small sample sizes made even smaller by chopping them up into bits — boys, girls, boys with ADHD, girls with depression — and picking the most dramatic results. It is the sort of number that should make your eyebrows shoot up immediately. (And in fairness, the study itself only mentions that clearly implausible number down in the results section, and leads on somewhat more credible, though still pretty mad, ones.) Nomura’s study “almost beggars belief”, Aldern says, coming close to, but not quite reaching, an insight.

Aldern also, hilariously, says that a local brewery “saw a gap of 25 degrees Fahrenheit (-3°C)” between indoor and outdoor temperatures at one point. How, you might wonder, can a difference in temperature be positive in Fahrenheit but negative in Celsius? Easy: if you’ve put 25°F into an online temperature calculator and just copied-and-pasted the result. Yes, if the temperature outside is 25°F, that means it’s -3.9°C and pretty nippy. But if the temperature goes up by 25°F, then it can’t go down in Celsius. Again: this stuff should be obvious to anyone who’s paying attention, and that makes me think that no one involved in the book was paying attention.

But this book isn’t a serious effort to find stuff out. Maybe I, as a crashingly literal bore who wants to know how much we know, am the wrong audience. This is a book for fans of the climate crisis and the mental health epidemic, and anything that can bring the two heroes into the picture at the same time is fine.

For instance, Aldern says that “climate change causes amnesia”, because a changing environment triggers forgetting to aid learning. He backs this up with a study in fruit flies and then extrapolates from it to say that people who live near a vanishing glacier in Iceland are therefore
 developing amnesia? Except he doesn’t quite say that: he slips into flowery gesturing language. (He often does, usually when it seems like he doesn’t know exactly what point he’s making: “History can be an act of elegy, but perhaps it can be an act of evolution, too.” Righto.) But I’m left baffled. Is the claim that people who live near this glacier will remember things less well, or not?

To be clear, climate change certainly is changing our brains, because our brains change with every new experience we have. That’s what learning and memory is: the subtle rewiring of our brains to store new information. But for most people, climate change — at least so far, in most of the world — is subtle; bad, but subtle. The changes it has wrought in most of our lives so far are minor. The Covid pandemic or the war in Ukraine driving up petrol prices will have changed our environment far more in recent years.

Or, to be honest, much more quotidian things than that. If you’ve moved house or changed jobs, had a child, started a new relationship or ended an old one, you will have felt the world around you change much more dramatically than anything that climate change has (so far, for most of us) done. And maybe these events do cause us to forget more, or cause our identities to “slip”, as Aldern claims climate change does. But we don’t tend to think of them as fundamentally eating away at who we are. No one’s going to write a book called The Weight of Moving House about the neuroscience of having to remember which box you packed the duvets in.

Climate change is real and will cause real problems. And some of those problems will be psychological: no doubt a lot of people have suffered and will suffer trauma, as changing weather patterns mean their crops die or their houses flood or burn. But this isn’t mystical or subtle, it’s just bog-standard “horrible events are unpleasant to live through”. You don’t need studies about transient forgetting in fruit flies to explain it.

What would be more interesting to examine, perhaps, is the nature of climate anxiety itself. It makes sense to worry about it — as mentioned, it’s big and unsettling, and full of unknowns. But in the West, I think, there’s also a nagging sense of guilt: we drove the cars and built the factories, we polluted the atmosphere, and we got rich doing so. I do wonder if books like this are a manifestation of that guilt: we buy them to show that we’re the good guys, we worry, the climate plagues our thoughts.

The irony is that — precisely because, for most Western people, climate change is still a relatively distant concept — the real impacts of climate change on mental health come via the media, including books such as Aldern’s. But the case that climate change is “changing our minds and bodies” in some subtle, insidious way — any more than all the other changes in our environment — is, to put it mildly, not convincingly made.

But it’s not there to convince us, any more than Godzilla x Kong: The New Empire is meant to convince me that King Kong is really on the loose. It’s just a crossover. Love climate change? Love mental health? Then you’ll love The Weight of Nature!

Tom Chivers is a science writer. His second book, How to Read Numbers, is out now.