Video Written, Produced, Filmed, and Edited by Sierra Glassman

Chickens are heavy.

Hi, I’m Sierra with Eat for the Earth and in this series we’ll learn about the relationship between animal agriculture and the environment.

There are a total of 50 billion individual wild birds on Earth. That sounds like a lot, but, each year, over 70 billion chickens are slaughtered for human consumption. Chickens don’t weigh much individually, but their population adds up to a humongous biomass–the total weight of a population measured in the element carbon, a building block of life. The biomass of chickens is 5 million tonnes of carbon, while all wild birds combined weigh a measly 2 million tonnes. So, the biomass of all the chickens alive right now is more than DOUBLE that of all wild birds.

If that comes as a surprise, consider the humble history of the domestic chicken. Chickens are descendants of the wild Red Junglefowl, native to South and Southeast Asia. In the wild, Junglefowl lay eggs only during a food abundance in the breeding season. About 8,000 years ago, chickens were first domesticated for fighting. In 800 BC Europe, Romans started to breed chickens to lay eggs earlier in the season. Now, most chicken breeds lay eggs almost every day.

Before intensive farming took off, chickens were primarily used for eggs, meat only being a luxury. That changed in 1945, when the American supermarket chain A&P partnered with the USDA to launch a breeding contest for the ultimate meat chicken — the “Chicken of Tomorrow.” They did indeed create the chicken of tomorrow, the Arbor Acres White Rocks, an entry by a family farmer. Arbor Acres is now the most common breed of meat chicken worldwide. The chickens themselves-called “broilers” by the industry-are severely obese, reaching 6 pounds by slaughter age, at about 6 weeks old. Over the past 50 years, they have experienced a 300% increase in their daily growth rate due to further breeding. Now, over 70% of the world population of chickens live their whole weeks’ long life in factory farms, never seeing sunlight. Chickens, at the will of humans, sit on the throne of bird biomass, but they’re undoubtedly not happy being at the top.

And chickens are but one species that due to humanity’s selective overbreeding, have gotten weigh out of balance. Biomass history tells a dire tale about humanity’s rapid domination of other animals.

The total biomass of livestock is 100 million tonnes of carbon, over 10 times heavier than all wild birds and mammals combined. That’s not healthy. Before human’s overhunting catalyzed the mass extinction of megafauna like mammoths and giant sloths, megafauna consisted of a large portion of wild mammal biomass, about 40 million tonnes of carbon. Now, the biomass of all wild land mammals is just 7 million tonnes of carbon. Also, fish, though outweighing all terrestrial animals, have decreased in mass. They’re down a whole 100 million tonnes of carbon due to fishing. That’s more biomass than all humans alive currently.

Humans have a history of prioritizing livestock over wildlife. 150 years ago, the native Passenger Pigeon was the most common bird in North America. Flocks of up to billions of birds would blot out the sky for days as they migrated. The impressive population came with a ravenous diet, so farmers shot them to protect their crops. They were basically viewed as feathered locusts and were all dead by 1914. More recently, in many states including Wisconsin, Montana, and Idaho, ranchers have been lobbying state governments to allow them to cull wolves. This hunting has so far disintegrated an entire pack in Yellowstone.

Humans have been discounting and persecuting wildlife for the sake of agriculture, and even more so recently with the ever-increasing demand for animal products. The disproportionate biomass of livestock is a telling demonstration of how humans have exercised our dominion over wildlife. 83% of Earth’s wild mammals and 50% of plant species have been lost already due to human activity; we are in the 6th mass extinction.

Over the last 50 years, the destruction of wild habitats for farmland has been the main cause of declining biodiversity. Since over 80% of farmland is used by animal agriculture, animal farming has been the main driver of the destruction of Earth’s biodiversity.

Biodiversity hotspots now only constitute 2% of Earth’s surface. The majority of them exist in developing tropical nations. These countries are accelerating their meat production in order to keep up with demand, and projections show that they may need to increase their animal farmland by 3 million square kilometers over the next 35 years to keep up. That’s a larger area than the size of Argentina!

It gets worse on a global scale. In order to meet food supply trends, the total area of natural lands converted to agriculture is predicted to increase to one billion additional hectares, an area larger than the whole United States. However, if we switched all current farmland to grow crops for just human consumption, we could feed an additional 4 billion people, more than the projected population growth for 2050!

Deforestation is one of the culprits of biodiversity loss. Almost all of it occurs in the tropics. In Brazil, 72% of deforestation is to make cattle pastures. And, 41% of all tropical deforestation is for the sake of pasture expansion. The worst cause of tropical deforestation after cows is oilseed, including the infamous soy bean, 75% of which is fed to livestock.

The loss of important habitat to animal agriculture has deeply affected ecosystems around the world. Over 90% of the world’s large carnivores are threatened by habitat loss and conflict with humans. Because livestock production is the biggest driver of habitat destruction, it is the main existential threat to the world’s most iconic animals. When wild carnivores decline, the whole ecosystem goes out of balance. 60% of large wild herbivores are also threatened by extinction due to resource competition with livestock. Grazing livestock can also affect river ecosystems, leading to vegetation loss and erosion, reducing the habitability and quality of waterways for wildlife and humans.

Currently, there are about 3.6 billion domestic ruminants like sheep and cows on Earth. 25 million have been added to the planet each year for the last half-decade. This population increase caused by the rise of animal farming has threatened wildlife with habitat loss, competition with livestock, and extinction. Besides animal agriculture-caused deforestation and habitat degradation, just maintaining our current level of animal agriculture is taxing.

Animal agriculture is the leading cause of biodiversity loss, water and nutrient pollution, and decreases of apex predators and herbivore populations. In order to have healthy biodiversity levels on Earth, we must eliminate or drastically reduce our meat, dairy, and egg consumption.

Animal agriculture’s disproportionate effect on biodiversity hurts people and ecosystems. But, it also offers a glimmer of hope-we can identify this threat to wild animals and start to reduce it. By rewilding farmland, we can drastically improve Earth’s biodiversity and mitigate the effects of our current mass extinction. By just rewilding 15% of the world’s farmland, we could conserve 60% of the species expected to go extinct. If 30% was rewilded, 70% of expected extinction would never occur, while half the carbon released since the Industrial Revolution would be captured by the native flora. If the world were to go plant-based, 75% of the area used for farmland wouldn’t be even needed at our current population, giving an area the size of the United States and Brazil combined to possible rewilding.

We need to escape this Extinction vortex caused by the demand for animal agriculture. By moving towards a plant-based world while healing exploited landscapes, we can create a kinder, more beautiful planet. Will you help us out?

Sierra Glassman is a recent high school graduate and Eat for the Earth summer 2022 intern. She has a passion for birds and has been accepted into UC Berkeley to study integrative biology starting Fall, 2022. She is spending her summer creating an educational video series for Eat for the Earth’s YouTube channel. During her brief time with the organization, she has researched and written three grants, had one approved (so far), created a plan for the series and an ad campaign, and is launching the second video today!

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