Tomas Pueyo Profile picture
Nov 9, 2021 29 tweets 9 min read Read on X
Why is Africa the way it is?
Why are its countries where they are?
The relationships between them
The people? The deserts?

Here are X to easily understand Africa better (politics, geography, history, demographics, climate & more)
One of the key ways to look at Africa is through this map: its river basins.

Let's start with the big one in the northeast. It's the Nile's watershed.
Here's northeast Africa at night. See that flower in the middle? That's the Nile through Egypt.
100 million Egyptians live within ~15 miles of its banks. That's ~99% of them.
More details here.


Why?
Because all the rest is just desert. The Sahara. But why is the Sahara where it is? Because of Horse Latitudes
Across the world, at that latitude—called horse latitude—there are hot deserts.
But why?
Because of winds
The equator is so hot that air goes high up in the atmosphere, where it gets cold and its water falls.
Due to the size of the earth, that air falls down at the horse latitudes. Dry air falling means no rain.
Morocco, Algeria, and Tunisia are just at the limit of Horse Latitudes, have humidity from the Mediterranean sea, and the Atlas mountains condensate the water from the wind. So there's enough water on the north of the Atlas mountain range—so ppl—but nothing south.
That sliver of green in Northwest Africa hosts 92M Africans.
But farther east it's too far south into the Horse Latitudes, so even if Libya is bigger than Morocco, Tunisia, and Egypt combined, it only has 5M ppl!
If you look at the river basins in the Sahara, you can see few of these rivers end in the sea: they dry up before they arrive.
Only the Nile manages to cross the Sahara. In fact, it's so unique, it's the longest north-south river in the world.
But where is it born? The Nile is the combination of the White Nile from Lake Victoria, in the middle of Africa, and the Blue Nile, from Ethiopia.

What ppl don't know is that ~90% of the water of the Nile comes from Ethiopia!

Why?
Again, because of rains, obviously
It makes sense that the equator has so much rain, but why Ethiopia? Because of its highlands
Ethiopia's highlands are super high, so they catch all the water from the winds blowing into it.
Here's a closeup of the Ethiopian Highlands. Very high
Why does Ethiopia have so much rain but Somalia is so dry? Because once winds pass Ethiopia, they're empty of water. It's called the rain shadow effect.
But why do winds blow in this direction in Africa, from west to east, and not the other way around? Because of the monsoon winds.
In june-sept, winds blow from the Atlantic towards Africa, bathing the continent with water.
In dec-mar, when the hottest part is farther south, they blow from the Indian Ocean.
That's why Somalia is dry: by the time the jun-sep winds reach it, all the water fell in the Ethiopian highlands.

It's also why the Kalahari (esp Namibia) and the west of South Africa are so dry: by the time eastern winds arrive in jan-mar, all their water has already fallen
Obviously, the more rain, the more food, the more ppl. That's why the map of water precipitation in Africa matches the map of population density pretty well
Except for that hole in the middle. What is that?
Around the equator, land is actually not fertile at all. It's so hot and humid that plants and animals recycle waste extremely fast, before sediments litter the floor. And then rain washes away any potential fertilizer
That's why the same thing happens at the Amazon in America: it's not fertile land, and few live there.

So although the Congo (middle green) is huge and has lots of water, it "only" has 90M ppl (to Nigeria's 200M)

But why are there so many mountains stopping rains across Africa?
Because of the Rift Valley: 2 mountain ranges with a valley in the middle that cross Africa.

These are the mountains that stop all the monsoon water that later become so many rivers, including the Nile.

And why is the Rift Valley there? Because of plate tectonics.
Africa is splitting in two in the Rift Valley. The plates are separating at that level. Central African lakes Victoria, Tanganyka, Malawi, and others are just the central Rift valley trapping water from the 2 mountain ranges on the sides
So there you are: the earth's plate tectonics and size cause Africa's mountains and winds, which cause the continent's geography, and create all these climates where humans thrive—or not:
- Egypt's Nile feeds 100M ppl
- Morocco, Algeria, Tunisia are the Med coast above the Atlas
- Libya is nothing because it has no water. Same as most Saharan countries
- The few Saharan countries that survive live around internal lakes: eg Chad / Niger around Lake Chad
- Ethiopia's highlands catch wind's water, which supports 120M ppl
- But Somalia has none left, so it's desert
- The Rift Valley creates rivers and lakes that can feed populations: Uganda, Rwanda, Burundi, Malawi, Zimbabwe..
- Tanzania, Kenya, Mozambique, and South Africa get enough water from eastern monsoon winds that they can support big pops
- Namibia doesn't, so it's desertic. Southern Angola isn't great either. But the north could have a bigger population
- Congo: too hot and humid to be fertile, so its population is limited.
- But the West Africa pop is huge: it has humidity + heat w/o too much as the Congo. That's all the countries btw Senegal & Nigeria

I go into more detail on all of this in this week’s article
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More from @tomaspueyo

Sep 8
Never bet against the US:
Ppl think its biggest strength is its institutions, the dollar, entrepreneurship... But one of its biggest assets is its geography 🧵
1. Size
The US is the 4th largest country. It spans an entire continent, reaches two oceans, and is big enough to be a geographic heavyweight in the world Image
2. The Mississippi Basin
It's the 4th largest drainage basin in the world and occupies 40% of the contiguous 48 US states, touching 32 of the US’s 50 states. 11 US states directly take their name from it. Image
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Sep 4
Climate caused the US Civil War, because:
1. Slavery was the main cause of the war
2. Different crops were the main cause of slavery
3. Climate caused different crops in the North vs South

This is terribly important to understand the US today and how to heal it
🧵
1. Slavery was the main cause of the war: the Abolitionist North & the Slavery South were competing to expand westward to increase their political influence

But the North grew & expanded faster, to a point where it could force abolition on the South, which then seceded
In 1790, the Free & Slave states had the same population, and there were many more Slave States (8 vs 5), so Slave States controlled the Senate.

By the eve of the war in 1860, the North had 50% more population and 4 more states, giving them control of both the House & Senate Image
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Aug 14
Moscow is one of the weirdest capitals:
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How did it create the biggest country on Earth?

It involves horse archers, human harvesting & tiny animals 🧵
The first shocking fact is that Russia is so far north it's at the edge of arable land. How can you create a capital with so little food? Why not in the middle of the most fertile area on Earth? Image
This far north is extremely cold
Moscow is the 3rd coldest capital in the world and by far the biggest: with 20M ppl, its metro population is 8x bigger than the 2nd biggest cold capital, Stockholm!Image
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Jul 28
This map tells you how a seemingly innocent difference, like wheat vs rice eating, can have dramatic political, economic, and cultural ramifications:
🧵 Image
The areas that harvest wheat vs rice are different. Why?
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Rice needs heat and lots of water. Ideally, flooding the fields to also kill weeds. Rice dies with frost.

Wheat resists it well, prefers cooler temperatures, but dies when it's flooded Image
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Jul 7
Did you know the West's trade deficits to China are not recent, but started 2000 years ago? This is the story of how silk, porcelain, tea, opium, and silver have determined the history of the world 🧵
The Romans already complained about deficits to China! Mainly because of silk Image
Back then the Chinese already preferred manufacturing and selling products than consuming foreign products. Chronicler Solinus ~200 AD: The Chinese "prefer only to sell their products, but do not like to buy our goods."Image
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Jun 25
Why did 🇮🇱Israel strike 🇮🇷Iran now, and not months or years ago or in the future?

A unique combination of a dozen factors converged to make the moment unique for 🇮🇱Israel: 🧵
1. No Hamas to its southwest
2. No Hezbollah to its north
3. No Assad threat to the northeast
4... Image
4. No more Syrian army to attack 🇮🇱Israel's planes: As the new forces of HTS took over Syria, Israel bombed all the existing Syrian military. No more fighter jets or surface-to-air missiles to threaten 🇮🇱Israel Image
5. Ability to fly over Syria to refuel
This is critical, because 🇮🇷Iran is ~600-1000 miles away from 🇮🇱Israel, so 1200-2000 miles round trip

The range of Israel’s stealth F35 is only about 1,350 mi
To operate inside 🇮🇷Iran, 🇮🇱Israel needed refueling over Syria Image
Image
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