Above: Imgage © Firmafotografen, iStockphoto

Our planet is about one full degree warmer than it was in 1880. This might not sound like a lot. However, at a global scale, a small temperature change can have a big impact. Among other things, it causes sea levels to rise, oceans to become more acidic, and Arctic ice to melt.

Over the last couple of centuries, the planet has become warmer because of greenhouse gases released into the atmosphere. Greenhouse gases trap heat, just like in a greenhouse. But what are these gases, and how are they being released?

Did you know? Greenhouse gases are often measured in parts per million (ppm). For example, for every million gas molecules in the atmosphere, about 400 of them are currently carbon dioxide. So 400 parts per million!

Which gases influence climate change the most?

The most famous greenhouse gas is probably carbon dioxide (CO2). You often hear about it on the news. CO2 is a colourless, odourless gas released when fossil fuels, like the gas in your car, are burned. Burning the carbon-loaded molecules in fossil fuels is a big deal because it moves carbon stored under the ground into the atmosphere—where it would not otherwise be found!

For most of the past million years, the concentration of CO2 in the atmosphere has fluctuated between 172 and 300 parts per million (ppm). But since the Industrial Revolution began in the late 1700s, the concentration of CO2 in the atmosphere has rapidly risen to around 400 ppm. No wonder we hear so much about it! But did you know that CO2 only makes up between nine and 26 per cent of all the greenhouse gases in the atmosphere?

After CO2, the next most abundant greenhouse gas is methane (CH4). Methane does not survive as long in the atmosphere as CO2, but it is 20 times better at trapping heat. In 2010, more than 60 per cent of global methane emissions came from human activities. These activities include dumping garbage in landfills, drilling for oil and natural gas, and animal agriculture.

This last source one is a big one. A 2006 report by a UN agency found that 37 per cent of global methane emissions came from animal agriculture. That’s right—this powerful greenhouse gas is being produced by cows!

Ruminants: Animals that make methane

Cows are a kind of animal called a ruminant. Ruminants have four stomachs. The first stomach is called the rumen. This is where tough-to-digest food is stored so it can be regurgitated and chewed again and again to help break it down.

Bacteria that live in the rumen contribute to the process of digesting the food though enteric fermentation. That’s a process where carbon-containing material like grass gets broken down without oxygen. And it’s the biggest source of methane emissions on Canadian farms.

A cow digests its food very slowly. Because of this, about six per cent of its ingested energy gets lost as methane.

Did you know? Meat production requires 10 to 20 times more energy per edible tonne than grain production.

Can we make cows produce less methane?

The idea of cutting back on eating meat is a tough pill for many people to swallow. On average, each Canadian eats 62 kilograms of red meat and poultry every year! Clearly, we like our meat. So would it be possible to reduce the amount of methane cows produce instead? Scientists are giving it a go.

What cows eat has a big effect on how much methane they produce. Digesting certain types of food (like hay and grass) produces more methane than digesting other foods (like corn). Scientists are also studying the bacteria living in the rumens of cows. Researchers hope to understand how these bacteria can be persuaded to produce less methane.

Did you know? Methane is not only released by cows through farts, but also through burps.

Does cattle farming produce more greenhouse gas than burning fossil fuels for transportation?

In 2013, greenhouse gas emissions from agriculture made up 10 per cent of total emissions in Canada. Taken together, oil, gas, and transportation currently make up almost half.

But there are places in the world that do a lot more cattle farming than Canada. We share our home planet with 1.4 billion cows. And each of these animals produces 250 to 500 litres of methane every day!

The UN study mentioned earlier found that 18 per cent of global greenhouse gas emissions to can be linked to animal agriculture. That’s more than all cars, trains, ships, and planes combined! In fact, if you took all greenhouse gases and converted them to the same unit of measure—something called a CO2 equivalent—you would find that cattle farming produces more greenhouse gas than transportation.

So using your car less may not be the most important thing you can do to help mitigate climate change. Many experts now believe that eating less meat would actually have a bigger impact.

Learn more!

About climate change and greenhouse gases:

Climate Change (2015)
CurioCity by Let’s Talk Science

The Top Ten Greenhouse Gases (2009)
S. Fox, Popular Science

World Temperatures
M. Carlowicz, NASA Earth Observatory

About methane, cows and agriculture:

Methane Emissions (2016)
US Environmental Protection Agency

Greenhouse Gases (2015)
Agriculture and Agri-Food Canada

Methane (2014)
Agriculture and Agri-Food Canada

Cow Farts Have ‘Larger Greenhouse Gas Impact’ Than Previously Thought; Methane Pushes Climate Change (2013)
P. Ross, International Business Times

Mira Okshevsky

Mira has a Master of Science in Marine Microbiology and a PhD in Nanoscience. She is currently a postdoctoral research fellow at McGill University, where she studies how bacteria stick together is communities called biofilms. In her free time, Mira enjoys exploring the coves and beaches of her home province of Newfoundland.

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