In developed countries, it's double that.

Or about the same weight as an adult dolphin.

But experts now advise cutting down the amount of meat we eat, to help reduce climate change.

So, here's a thought experiment.

[What if the whole world turned vegan?]

Around 15 percent of all greenhouse gasses emitted by humans are from livestock production.

If we all became vegan, these emissions would be slashed.

Eating meat takes up space, a lot of it.

Around 80 percent of all farmland is dedicated to meat and dairy production.

That's about the size of Europe, the U.S., China, and Australia combined.

Meat and dairy typically provide 18 percent of our calories, but account for 60 percent of greenhouse gas emissions from agriculture.

A report by the UN's climate body, the IPCC, recommends we all reduce the amount of meat we eat.

And also how much we waste.

The report found 8 to 10 percent of all global emissions are down to food loss and food waste.

But not all meat is the same.

Large-scale farming of beef has a particularly high impact, and has been a big factor in the loss of the Amazon rainforest.

When cows digest their food, they produce methane, a powerful greenhouse gas that's about 28 times more powerful than carbon dioxide over 100 years.

And when cows burp, this methane is emitted.

One cow releases between 70 and 100 kilograms of methane every year, and there are around 1.5 billion cattle in the world today.

But it's not that simple.

A lot depends on how the meat is produced.

Most meat is mass-produced by large-scale industry, and this can come with a heavy environmental impact.

But small-scale farming of animals can have a lower environmental footprint.

And sometimes, for example in the case of traditional grazing, it can be beneficial in terms of biodiversity.

Vegan alternatives can also come with their own problems.

For example, large-scale production of soya can lead to deforestation, and almond production requires huge amounts of water.

But if everyone switched to a plant-based diet, it could bring several positive health benefits.

One study estimated that if everyone ate a vegan diet, with lots of fresh fruit and veg, around eight million deaths could be avoided around the world by 2050.

There are no simple answers.

But if everyone were to change how they look at food, cultivate it, and eat it in a sustainable way, we could, potentially, change the world.

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