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  • I'm pretty sure every cuisine in the world has embraced the potato. From this simple

  • root vegetable we get latkes, gnocchi, salchipapas, poutine, potato chips, ooo! or creamy yet

  • crisp potatoes gratin with butter and cheese and a sprinkle of salt on top…[trails off

  • dreamily] I'm sorry, what were we talking about

  • The potato has many claims to fame around the world, from the devastating Irish Potato

  • Famine of the 1840s to the salty magnificence of French fries. But this humble tuber originated

  • neither in Ireland nor France

  • It was domesticatedthe process of adapting plants and animals for human useabout

  • 7,000 to 9,000 years ago near Lake Titicaca now on the border of Bolivia and Peru, in

  • the Central Andean highlands where it's known as Mama Jatha, the mother of growth.

  • So as geographers we ask, “Why were potatoes domesticated here and not anywhere else?” 

  • The story involves the ideal conditions needed for growing potatoes, how climates change

  • across space, and the ingenuity of the Andean farmers. So today we're going to go bananas

  • -- about potatoes!

  • I'm Alizé Carrère and this is Crash Course Geography.

  • [INTRO]

  • Worldwide, the potato is one of the most calorically important food crops along with corn, wheat,

  • and rice. It's the cornerstone of food security for millions of people. Like in 2019 alone,

  • we produced 371 million tons of potatoes worldwide. Which is like 96 pounds of potatoes per person.

  • Today the top producers of potatoes are China, India, Ukraine, Russia, and the US, but potatoes

  • are still integral to their South American homeland. Somewhere between 2000 and 4000

  • varieties of potatoes are grown along the length of the Andes mountain chain

  • Different crops need different temperatures, precipitation, and soil conditions to thrive,

  • which brings us to an important distinction we need to get to the root of our potato story:

  • weather and climate are not the same thing.

  • Weather is what's going on in the atmosphere at any given time and place. Today it's

  • dry and sunny but tomorrow it may be cloudy and rainy. Just like my mood can change if

  • I eat fresh, hot french fries or cold, soggy ones, weather happens in the short term and

  • is difficult to predict

  • But climate is a region's average weather over many years, which is much more predictable

  • and based on trends. So we don't know what the weather will be like in New York City

  • on January 20th, 2025, but we do know that it's usually chilly, because New York City

  • has a cold winter climate

  • It's like what former president of the American Meteorological Society Dr. J. Marshall Shepherd

  • famously (probably) said: “Weather is your mood, climate is your personality.” [And

  • my personality is a proud potato fan, even though we've all had disappointing fries before!]

  • Just like there are endless human personalities based on our DNA and how we grow up, all the

  • possible combinations of temperature, precipitation, wind, and ocean currents give us a variety

  • of global climates. And all of those processes begin with patterns of insolation, or incoming

  • solar radiation, across the globe.    For example, mountains have complex climate

  • patterns, or the somewhat predictable variation in climate

  • These mountain climate patterns come from the way insolation and temperature change

  • as we go higher in elevation, or the height of a point on Earth's surface above a reference,

  • like sea level.

  • In fact, no matter where we are on Earth, for every 1000 meters we go up in elevation,

  • the air temperature decreases by 6.5 degrees Celsius on average, which is the normal lapse

  • rate. If you've ever hiked or driven up from the base of a mountain, you've probably

  • felt the air get chilly or brought extra layers to handle the cold temperatures.

  • The normal lapse rate has big implications for Latin America's physical geography,

  • especially near the equator

  • As we climb the Andes mountains from sea level, we can define our major climate zones based

  • on elevation that have dramatic changes in plant life.   

  • At the foot of the mountains is tierra caliente or hot country, a lowland zone of broadleaf

  • evergreen tropical rainforest. The warmth and humidity here allows extensive tall trees

  • and a dense, year-round leaf canopy to develop.  

  • At about 900 m we begin to see mild temperate conditions and deciduous forests in the Tierra

  • Templada.

  • Then as we continue our climb, at about 1800 m temperate conditions get chillier. Colder

  • temperatures and coniferous forests mark the Tierra fria

  • As we move higher each zone gets smaller and at 3,600 m we reach the windswept tierra helada

  • or frost country. In the lower reaches of this zone pine forests transition to alpine

  • meadows and grasslands and markc the treeline, the upper limit of where trees grow

  • Further up around 4,600 m we see a shift from grasses to hardy lichens and mosses. And beyond

  • here we encounter the snowline or the elevation where winter snow doesn't melt in the summer.

  • This is the zone of perpetual snow that make up the snow caps on mountains. The final zone

  • has very little plant or animal life.

  • Parts of Latin America use this terminology to describe mountain climate patterns, but

  • different vertical zones and geographic terms exist around the world. Each mountain also

  • has unique attributes -- like its slope or total elevation -- which create different

  • ecosystems in these zones

  • The process of paying attention to geographic conditions, like mountain climate patterns,

  • and using them to answer questions likeWhy were potatoes domesticated in the Andes mountains

  • and not anywhere else?” is called geo-literacy

  • A geo-literate person understands that the world works as a set of physical, biological

  • and social systems, and that processes within these systems connect places to each other.

  • We can use these observations to interact with our environment and create particular

  • outcomes

  • And even though geo-literacy might be a modern term, engaging with the world with a geo-literate

  • lens is something people have been doing for 1000s of years

  • Like 7 to 9 thousand years ago Andean farmers observed how a mountain was made of spaces

  • with different climates and ecological niches, which is where certain plants thrive but not

  • others. And they passed down this knowledge over generations, using their geographical

  • understanding to select plots of land

  • Even today, farmers all over the world need to think through all theingredients

  • for weather and climate to plant crops, and we have all sorts of technology to help them

  • track air pressure, precipitation levels, and more. But ancient Andean farmers didn't

  • have these same tools. Let's go to the Thought Bubble

  • The Andean foothills and mountains are used to grow lots of crops, like tomatoes, beans,

  • and maize

  • But the diversity of potatoes is a source of pride and a cultural symbol of traditional

  • Andean agriculture, food systems, history, community, and identity

  • Historically, we think one way time was measured here was by how long it took to cook a pot

  • of potatoes

  • Even today potato seeds can be gifted to young couples setting up a household.

  • And farmers in the high Andes measure land based on the area a family needs to grow their

  • supply of potatoes.

  • Over the years, farmers realized that when they plant their crops could make the difference

  • between a good harvest and a poor one

  • For example, areas in what's now southern Peru are prone to periods of drought.  

  • As modern geographers, we know that typically there are cold water currents along the Peruvian

  • coast, which help bring rain to the Andean highlands

  • But some years, there's a pooling of warm water along the Peruvian coast, which can

  • bring drought until the ocean currents change again

  • Without the aid of satellites or an understanding of ocean currentsAndean farmers began

  • to notice that if the stars -- especially the Pleiades stars in the Taurus constellation

  • -- were hidden by water vapor in the atmosphere and hard to see around the Winter solstice in

  • late June

  • It indicated an El Niño year which is linked to reduced rainfall several months later.  

  • So they'd plant their potatoes earlier to take advantage of whatever rain that fell.

  • If they could see the stars clearly, they knew they'd get enough water to plant the

  • potatoes a little later

  • Basically, Andean farmers were geographers who observed the relationship between clouds

  • in the atmosphere and rainfall patterns later in the seasonwhich in turn helped people

  • survive in the Andes for centuries.

  • Thanks, Thought Bubble. Any way that people observe atmospheric conditions, find patterns,

  • and make decisions based on those patterns is geography in action

  • Nowadays, scientists can observe and predict climate phenomena on a global scale, from

  • ocean current patterns like El Niño and the Southern Oscillation to what latitudes different

  • plants (like potatoes) can grow at.

  • We can categorize climate patterns in a lot of different ways, like using temperature

  • and wind patterns. But those can be hard to see, and something like vegetation growth

  • is much more obvious

  • In general, natural vegetation starts with a tropical rainforest at the equator and transitions

  • into ice and snow and sparse vegetation as we get to the poles -- sort of mirroring the

  • mountain climate pattern we talked about before. This visible connection between vegetation

  • and climate helped climatologist and botanist Wladimirppen devise a classification system

  • in the early 1900s called theppen system

  • It's still widely used today with many improvements by many people and with many terms that reference

  • a type of climate and a type of natural vegetation, like the tundra or the rainforest!

  • Specifically, theppen system divides the world into six major climate categories. Using

  • the visible vegetation as a guide, Koppen came up with precise definitions for each

  • climate region based on average monthly temperature, average monthly precipitation and total annual

  • rainfall

  • The first four categories are based on moisture and temperature characteristics, and they're

  • usually labeled with capital letters. Like (A) represents tropical climates which are

  • known for having high temperatures and receiving a lot of rain. And (E) represents polar climates

  • which tend to be cold and dry

  • Then the last two categories are based on moisture and elevation instead of temperature.

  • Like (H) represents the highland climates in the world's mountainous regions. Like

  • where our original Andean farmers grew potatoes.

  • Then within each of these big categories there are subcategories marked with additional letters

  • to break climates up into even more precise groups.  

  • So let's use potatoes as our example. They thrive in cold weather, so if we look at a

  • ppen climate classification map of South America, it makes sense that they thrive in

  • the Andes

  • In the west along the Andes, there are bands of (H) which means highlands and BWk -- which

  • says the area is arid, desert, and cold. The transition out of those desert highlands is

  • a BSk -- which says the area is arid, has a steppe climate, and is cold. Those are some

  • ideal potato growing conditions

  • If we overlay a fullppen climate classification map with a map of everywhere potatoes are

  • grown, we see that potatoes are really hardy because there's a lot of overlap with a

  • lot of different climates

  • We know that many species of potato were domesticated by Andean farmers, but we also know that plants

  • are adaptable. Those farmers used their geo-literacy to grow more plentiful crops, but also to

  • begin breeding plants to tolerate different temperatures

  • The Andean empires flourished because of food security from crops like potatoes. And thanks

  • to global trade and the hardiness of potato species, today potatoes are grown in over

  • 100 countries -- from India in the tropics to Finland close to the Arctic Circle

  • From hot and cold regions to dry and wet regions, and all climate combinations in between, humans

  • have adapted to the natural environments around us and used our growing geo-literacy to thrive.

  • But increasingly, the Earth's environments are also impacted by our choices