Meat can be a touchy subject. Strict vegans and unrepentant carnivores rarely find any common ground. But whatever your view on the ethics of eating meat, there are some hard facts that should inform any debate.

Billions of animals are slaughtered every year

Humans are easily outnumbered by our farm animals. The combined total of chickens (19 billion), cows (1.5 billion), sheep (1 billion) and pigs (1 billion) living at any one time is three times higher than the number of people, according to the Economist.

But those figures are dwarfed by the number of animals we eat.

An estimated 50 billion chickens are slaughtered for food every year – a figure that excludes male chicks and unproductive hens killed in egg production.

The number of larger livestock, particularly pigs, slaughtered is also growing, as the chart below shows.

Nearly 1.5 billion pigs are killed to feed the growing appetite for pork, bacon, ham and sausages – a number that has tripled in the last 50 years.

Half a billion sheep are taken to the abattoir every year. The number of goats slaughtered overtook the number of cows eaten during the 1990s, although the figure for cattle excludes the dairy industry.

When it comes to seafood, the number of individual fish and shellfish is almost impossible to calculate. One hundred and fifty million tonnes of seafood were produced for human consumption in 2016 – nearly half from aquaculture (for example trout or shrimp farms) rather than caught in fisheries.

We eat more meat per person than ever

In the last 50 years the number of people on the planet has doubled. But the amount of meat we eat has tripled.

Most of this growing demand has come from middle income countries, and particularly China, which became the world’s biggest consumer of meat as its economy boomed.

In contrast, the appetite for meat in Europe and North America has stabilized, and even declined.

India, despite rapidly catching up with China in terms of population, still consumes a tiny fraction of the world’s meat.

Pork has long been the most popular choice at the dinner table. But poultry has now caught up, and is likely to overtake it. In 1961 just 12% of global meat production came from chicken, duck, goose, turkey and fowl. Now poultry makes up a third of all the meat eaten worldwide.

In contrast, the most popular red meat, beef, has seen its global share nearly halve in the last 50 years, to 22%. But it still remains nearly five times more popular than lamb.

Meat production costs the Earth

The environmental cost of our growing appetite for meat is alarming. Agriculture is responsible for 10-12% of greenhouse gas emissions, with meat, poultry and dairy farming producing nearly three quarters of that.

Meat farming produces much higher emissions per calorie than vegetables. Beef is by far the worst culprit – four times higher than chicken or pork.

But it is not just the greenhouse gases produced by livestock that damage the environment. Cattle farming, in particular, requires much more land than other forms of agriculture, which drives deforestation. The largest population of cattle in the world is in Brazil, where numbers have quadrupled in 50 years, a trend that has led to the destruction of vast areas of the Amazon rainforest.

Much of this land is used to grow crops for animal feed – one third of the world’s grain goes towards feeding livestock.

Meat production is also a thirsty business, at a time when the availability and abundance of fresh water supplies are becoming a major concern.

Too much meat is bad for our health

For many people, meat is an important source of protein, vitamins and minerals. But some meats are high in saturated fats that can raise cholesterol, and eating too much red and processed meat has been linked to bowel cancer. The burgers, steaks and sausages served up in most wealthier countries tend to be a lot bigger than the recommended 70g a day.

It’s been estimated that swapping some of the beef we eat for beans, peas and mycoprotein (derived from fungi) could reduce mortality by 5-7%.

Livestock provide livelihoods

Meat, dairy, fish and eggs provide 40% of protein consumed globally, and in many parts of the world there is not yet a secure alternative.

It’s estimated 1 billion people are involved in the rearing, processing, distribution and sale of livestock, with half of those reliant on livestock for their livelihood. Agriculture as a whole makes up approximately 3% of global GDP, with livestock contributing 40% of that. The livestock economy is particularly important for poor rural populations in low- and middle-income countries.

The meat substitute market is growing

The search is on for alternatives which satisfy consumers’ taste for meat. Some of these involve the cultivation of animal cells in labs – growing real meat in a petri dish rather than using an animal. Another approach is the engineering of plant- or fungi-based meat substitutes, to give them the taste and texture of beef, pork or chicken. And there are attempts to make insects – already eaten in parts of Asia and Africa – a more popular choice on menus worldwide.

For millions of people, eating animals is a way of life – one of the cultural cornerstones of their domestic and social lives. For others, like Yuval Noah Harari, the way modern agriculture treats animals is one of the “worst crimes in history”.

Whatever your view, as the World Economic Forum’s Meat: The Future series makes clear, as the world’s population heads towards 10 billion, the current trends in meat consumption and production cannot be sustained.