What 20 years of data reveal about heat and interpersonal violence in Latin America
Our story begins where Latin America ends.
Near Ushuaia, the southernmost city in the world, a colony of penguins lives peacefully.
Some hunt for food, others for the perfect stone to build a nest beside their partner.
Everything pointed to the beginning of another successful mating season.
But this would be no ordinary season.
Isla Martillo is warmer than it should be. The penguins are feeling it.
With their thermoregulation impaired and their breathing labored, the heat begins to breed collective irritation.
First, they start stealing each other's stones. Nests that were nearly finished have to be rebuilt from scratch.
Then, they start screaming at each other. Hot-headed, literally.
But the heat wave only intensified.
And so chaos descended upon Tierra del Fuego.
Magá, bewildered in the middle of it all, began walking farther and farther from the Beagle Channel.
Nothing made sense.
The further he strayed from the Pingüinera, the harder he tried to understand why the penguins were so aggressive.
Then, as if a sardine had fallen from the sky, he wondered:
Is exposure to unusually high temperatures associated with higher interpenguin violence?
So he did what any good researcher would: he went to the field. Magá sent messages to penguins across all of Latin America.
Magá sent messages to penguins across all of Latin America. Three voices answered. Three different cities. Three different stories about the same burning sensation.
Magá could not ignore the tingle in his flippers anymore: There had to be some pattern between those strange hot temperatures and penguins getting more violent.
But Magá knew he needed more than stories.
He needed proof.
So he looked into two massive sets of records that penguins across the world had been keeping for decades.
A collection of every extreme heatwave recorded across the globe — known to researchers as Climdex. Magá focused on TX90p: days hotter than 90% of historical averages.
A register tracking everything that can go wrong — from illnesses to violence. Known to researchers as the Global Burden of Disease (GBD) study.
He tried different mathematical equations to test the correlation between hotter than usual days and interpenguin violence.
But Magá was no amateur. He knew that a bad mood could have many roots.
Was it the heat, or was it the lack of fish in the sea?
Was it the temperature, or just the stress of living in a crowded colony?
Was it the warmth, or that the El Niño climate phenomenon was coming?
He adjusted his math to clear all that noise.
Magá ran five different tests...
Heat coefficient on interpersonal violence
...but got one same answer. The relationship was not there.
But Why?Why was the global data not showing what his hot head had experienced?
Magá decided to go straight to the source: the penguin experts.
He contacted the authors of the studies he had read.
From Martin Habets, who had been in Mexico, he learned about The Scale of the Nest.
Magá was looking at the whole colony, but the friction might be happening inside the huddles.
It maybe wasn't about massive chaos, but about the daily heat that can make a nest feel too small. A few extra degrees might not be the source of the anger, they just burn through the patience that keeps it from exploding.
Sara Moraes had a different theory. He learned about The Average Trap.
Latin America might be too big to be summed up in a single yearly number. While the planet gets hotter, some colonies are finding new ways to stay peaceful and adapt, hiding the heat's true effect.
To see the truth, she suggested to Magá to not look at the year. He must look at the day.
Instead of looking at the whole continent, Magá should just look at his neighbourhood.
He felt the tingle in his flippers return. Maybe, his math wasn't "wrong." It was just a map of the whole ocean, when he needed to see closer to the shore.
Magá looked back at his five models. His heat aggression theory needed more research...
But one factor kept showing up linked to interpenguin violence.
Magá stared at the word.
He didn't know much about "cities" but he knew Isla Martillo. He had watched the rocky coast get covered by row after row of gray, stone-like huddles.
New concrete nests had extended through the whole island after the last mating season. The nests were closer together. The air felt more trapped. The noise hardly ever stopped.
Maybe an urbanized city was just a colony that had forgotten how to breathe.
He looked at the numbers again.
For every 1% more penguins moved into the city,
an extra 26 fights broke out in a colony of 100,000.
Maybe back on Isla Martillo, the penguins weren't fighting because of heat alone.
Their stress was also spiking because there was not enough room to cool down.
Magá looked at the horizon where the stone nests were still being built.
"If the colony keeps growing like this," he thought, "the fighting won't just be a summer problem. It might turn into our new way of life."
As the colony becomes more popular, more penguins could be competing for the same limited amount of fish.
Or they could even grow envious about their neighbour's wider nest. Or the elder penguins could become unable to keep the paths clean and stop the conflicts among the younger.
Is Maga's story turning a little bit too familiar?
Well... Magá is a fictional character but the numbers are real. And they are closer to us than we might realize.
Over 20 years, across 22 Latin American countries, urbanization remained a consistent predictor of interpersonal violence.
And it is not simply about more people living in the same place.
Even after accounting for population size, the more urbanized a country, the more violence per person.
It is not the number of people. It is the conditions they are living in.
Urbanization is unstoppable. So what then?
The colony will keep growing. The question is what kind of colony it becomes.
Some cities are already trying.
At-risk young people are being offered jobs and education instead of corners and gangs.
Cable cars climbed into hillside neighborhoods the city had abandoned for decades. Libraries followed. Then parks. Then people started staying.
The city used cameras, data, and neighborhood patrols working together to catch problems before they escalated.
These cities didn't wait for a perfect solution.
They just made it a little harder for violence to take root. And it worked.
Not one solution. Many, working together.
Magá looked at his colony. He had the data. He had the research. He even had examples. But he also knew: none of this would work alone. Not without the colony.
Urban violence is not inevitable. But preventing it is not a job for one penguin.
It starts with the small things...
Knowing your neighbors, looking out for the younger ones, demanding better from those who manage the paths. The colony is only as safe as the care its members put into it.
And somewhere, in a warming world, that might matter more than the temperature ever could.