Within this loaf of delicious banana bread, there’s butter and eggs and vanilla, bananas maybe all the way from Guatemala, and a lot of sugar -- but there’s also energy.

Energy is one of those things that’s so basic and important to our lives and how the world functions it’s kind of hard to define. But at its most simple, energy is the ability to do work.

So like a few bites will (hopefully) give me the fuel to record this episode. Food energy is just one type of energy, but it’s incredibly important and necessary for humans to exist. And that can create some tricky issues.

Like as the world’s population keeps growing, we have to figure out how to provide enough food and water for everyone and still support a sustainable environment. That problem might set your geography senses tingling, because we can explore it through human-environment interactions. We might only be about halfway through our physical geography journey, but this is one of those times when the line between physical and human geography doesn’t really exist.

Some of the most critical issues we face as a society -- like climate change, eradicating diseases, or making sure everyone has food -- require knowing about Earth’s physical and human systems and the interdependency of living things and physical environments. I’m Alizé Carrère, and this is Crash Course Geography. INTRO.

People need a lot of energy throughout their lives, especially the food energy we get from the banana bread (and other stuff) we eat to power our bodies. And to understand how we get the food energy we need, we have to first understand how energy gets to the Earth. Once solar energy leaves the Sun and travels to Earth it can’t be returned, so we say energy flows in one direction.

Food energy is created when plants turn that solar energy into chemical energy. Using photosynthesis plants combine sunlight, carbon dioxide, and water to make carbohydrates -- which are little packets of food energy! A food chain describes how energy makes its way through ecosystems, or communities of living and nonliving things.

It’s basically a list of who eats who. Let’s go to the Thought Bubble. In a simple food chain, lets say a cow grazes on some grass.

Then a tiger comes along and attacks and eats the cow. When the tiger dies, bacteria breaks down its body, returning it to the soil, where it provides nutrients for plants -- like the grass. But food chains are rarely simple.

Cows like grass, but they’ll also munch on corn stalks and hay. And tigers will eat other animals too. So lots of food chains intertwine within different ecosystems and form food webs.

To organize the chaos, we can group organisms into categories called trophic levels. The first trophic level is the producers that make their own food, like the grass that uses solar energy to photosynthesize. In the second trophic level, the producers are eaten by a primary consumer, like the cow.

Then there are secondary consumers who eat the primary consumers, like a tiger who eats the cow. And there can be tertiary consumers, who eat the secondary consumers. The highest trophic level of a food web is usually the apex predator, who doesn't get eaten.

In this little food chain, it's the tiger, our secondary consumer, and we only have three trophic levels. Each time we move up a trophic level, only 10% of the energy is passed on. So the cow only gets 10% of the energy the grass absorbed from the Sun.

And the tiger only gets 10% of that 10%. That means that each trophic level gets smaller and smaller. So we might have a ton of grass, a lot of cows, but only a few apex predator tigers at the top.

And lastly, sitting at the edges are the decomposers, the clean up crew who break down dead plants and animals like our tiger into energy and nutrients that mix into the soil for plants to absorb, starting the chain all over again. Thanks, Thought Bubble! The logic of passing on less energy to higher trophic levels applies to humans and our resources too.

If we add more people or consume more food, that’s going to influence the trophic levels below us. In fact, we can predict our impact on the environment with a formula that uses population size, how affluent a society is -- which is usually measured by how much it consumes -- and how much access to technology it has, which can be both positive and negative. The world’s population has been rapidly increasing since the industrial revolution in the 18th and 19th centuries.

With new manufacturing processes and machines, we could grow and create more food, and then feed more people. And in 2020, we officially reached 7.8 billion people on the planet. As we keep adding more and more people to the world, we have to start thinking about our planet’s carrying capacity, which is the maximum population an environment can support long term with a given set of natural resources.

So there are two types of overpopulation to consider if we’re deciding if the Earth will run out of resources. People overpopulation is when there are a lot of people so a lot of resources are used. This can be how poorer countries might run out of resources, because even though consumption per person and technology’s influence is lower, the high population size means a big impact on the environment.

On the other hand, consumption overpopulation is when there are fewer people, but each individual person uses a large quantity of natural resources. This is usually how richer countries might run out of resources. In both cases, we have to take a hard look at where we’re getting our energy -- especially our food energy.

How much energy we use depends on where we are in the food chain because as we climb to higher trophic levels, it takes more total energy to generate the food that fills our stomachs. If we look across the world, some people depend on traditional practices to get food energy, and eat more grain, more seasonal foods, and larger amounts of fresh, homegrown, and unbranded foods. They eat a lot of producers, so less energy is lost between trophic levels before making it to their stomachs.

As incomes rise, though, people generally go through a nutrition transition, or a change in food habits and culture because they have more wealth. In richer countries, food is generally more homogenized, highly processed, and tends to be meat-heavy. They're eating more primary and secondary consumers, and it takes more energy to feed all those trophic levels.

Like as China has risen economically, the people have moved away from a traditional rice based diet to eating more meat, particularly beef. But every person doesn't live their life exactly the same way, so we're going to use average numbers to discuss energy consumption here. Some people are eating more meat and some people are eating less!

In 2018, each person ate an average of just under 80 kilograms of meat in a year, and with 1.35 billion people in China, that’s more than 108 billion kilograms of meat per year. Many other countries out-eat China per person, like an average American eats 120 kilograms of meat per year. That's like one person needing 1350 kilos of grain a year to survive, because that's how much it takes to feed that amount of meat.

But if we hop down to a lower level on the food chain and ate grain instead of meat, those 1350 kilos of grain could feed 22 people for a year. This is why you might've heard about vegetarian and vegan diets being more environmentally friendly. They take fewer resources and less energy to feed you.

So to put it all into perspective: eating a hamburger or something processed like banana bread takes more energy than just eating a banana. And that's only part of the picture… we also have to think about how that food is grown and gets to us. For example, since I live in the United States and we import bananas, a more energy-saving choice might be to eat cornbread from corn grown in Iowa -- or just eat the oranges grown in my backyard!

Urbanization and industrialization change how we produce our food, and how much energy that takes. We can't just look at food chains, because most of our food energy comes from a combination of solar energy to help plants grow plus whatever work and fuel we put into agriculture practices. For example, animal husbandry is a branch of agriculture focused on raising livestock, and requires land for grazing and fresh water.

For thousands of years, we’ve raised animals like llamas in the Andes, yaks, goats, and sheep in the Himalayas, reindeer in the Arctic Circle, and camels in Mongolia and in the Sahara. And humans met those animal husbandry requirements through transhumance, or moving herds between pastures with the change of seasons to help ecosystems stay productive. Indigenous communities especially have farmed in ways that have left plenty of energy for local ecosystems.

But as our societies have industrialized, farms have become large users of fossil fuel -- from using equipment to plant and harvest crops, to transportation to deliver the food to urban areas. This is one spot where that technology piece of the formula can factor in. As demand for meat has increased, we've also created factory farms dedicated to producing meat, which require even more energy because all those animals need food to eat and water to drink.

So there are farms that grow crops just to feed animals on other farms, like in the Corn. Belt in the middle of the US. Instead of using the solar energy captured by these crops to directly feed people, it goes to the next trophic level to fatten up cattle and hogs.

The Corn Belt is also a Pork Belt and a Beef Belt. So we’re devoting a ton of land, jobs, and industrial processes to keep our spot high up on the food chain. And as the world population keeps growing, managing the amount of resources we have -- especially food energy -- is an increasingly urgent problem.

With 7.8 billion people on Earth we are changing the flow of energy through our ecosystems, and those changes are tied to a cascade of environmental and social problems. To find solutions, as geographers we examine how local choices intersect with larger scale outcomes. On the population side, we can help feed growing populations by understanding where food is produced and how it’s distributed.

Locally, strong distribution networks, with access to affordable healthy foods, are critical to making sure everyone has enough food. Regionally and globally, we can study the economic incentives that allow food to easily flow to some places and not others, or systems that break down local food networks to create global ones -- like how affluence is tied to eating more meat. To reduce our consumption impact, knowing our foodshed, or the area that feeds us, is critical.

We can limit how much meat we eat or try to eat locally grown foods. And these local actions can impact ecosystems and food economies around the world as demands change. Maintaining energy flows and finding a way to feed everyone on the planet is not going to have a quick solution.

But as we all work together to keep moving forward, thinking carefully about what we eat, how it gets to us, and how to create food sustainably are some of the ways we can each have the greatest impact. And creating a sustainable planet is something we’ll keep exploring spatially including next episode when we look down beneath our feet -- to the soils. Many maps and borders represent modern geopolitical divisions that have often been decided without the consultation, permission, or recognition of the land's original inhabitants.

Many geographical place names also don't reflect the Indigenous or Aboriginal peoples languages. So we at Crash Course want to acknowledge these peoples’ traditional and ongoing relationship with that land and all the physical and human geographical elements of it. We encourage you to learn about the history of the place you call home through resources like native-land.ca and by engaging with your local Indigenous and Aboriginal nations through the websites and resources they provide.

Thanks for watching this episode of Crash Course Geography which is filmed at the Team. Sandoval Pierce Studio and was made with the help of all these nice people. If you want to help keep all Crash Course free for everyone, forever, you can join our community on Patreon.