Here's a sobering fact: over the past half-century, we've steadily marched – or perhaps sleepwalked – our planet to the brink of the "sixth mass extinction". One-fifth of all mammal species are now threatened. What led us to this crisis point? In large part, our appetite for meat.

Sound far-fetched? Consider that in 2016, an area of rainforest the size of a hundred football pitches was cut down every hour – every hour! – specifically to provide the animals who end up on our dinner plates with pastureland.

Much of the deforested land that isn't used for cattle-grazing is dedicated to growing soya beans – not for tofu or soya milk but rather to feed animals on farms around the globe. Indeed, 70 per cent of all soya crops are fed to farmed animals. Of course, not only is this large-scale deforestation devastating to the environment, it's also a death sentence for the millions of animals who are losing their habitat.

Worse, mass deforestation is occurring in the most "megadiverse" countries in the world, home to the largest number of species. Among these areas are the South American Cerrado, land of jaguars and giant armadillos; the Congo Basin, where you'll find gorillas, chimpanzees, and forest elephants; and the forests, mountains, and grasslands of the Eastern Himalayas that Bengal tigers, snow leopards, and one-horned rhinos call home.

And deforestation isn't the only threat that wild animals are facing as a result of our taste for meat. In some areas, native predators such as wolves are deliberately massacred to protect livestock, and in others, millions of wild animals have died of dehydration or starvation after finding their migratory paths blocked by fences erected to contain cattle.

How they reach your plate: live animal transport worldwide Show all 16 1 /16 How they reach your plate: live animal transport worldwide How they reach your plate: live animal transport worldwide Melbourne, Australia, 2017 A crowded transport truck Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Melbourne, Australia, 2017 A thirsty pig on transport truck is given water by a Melbourne Pig Save activist Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Toronto, Canada Pigs being transported to slaughter in freezing weather Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Toronto, Canada A volunteer gives water to thirsty pigs Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Toronto, Canada Pigs en route to an abattoir How they reach your plate: live animal transport worldwide Canada A cow looks out of transport truck just outside the slaughterhouse gates Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Spain Stacked crates of rabbits awaiting slaughter Jo-Anne McArthur / Animal Equality How they reach your plate: live animal transport worldwide Australia A pig finds some air at a sale yard Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Toronto, Canada Pigs in a transport lorry en route to an abattoir Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Melbourne, Australia, 2017 A pig in a transport truck touches noses with a man Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Melbourne, Australia, 2017 Chickens in transport crates Jo-Anne McArthur / We Animals How they reach your plate: live animal transport worldwide Spain, 2014 A rabbit's nose and feet poke out from between plastic crates Jo-Anne McArthur / Animal Equality How they reach your plate: live animal transport worldwide Spain A rabbit looks out between plastic crate slats Jo-Anne McArthur / Animal Equality How they reach your plate: live animal transport worldwide Nepal, 2017 A chicken looks out through fencing on a crowded transport truck Jo-Anne McArthur/We Animals How they reach your plate: live animal transport worldwide Spain Broiler chickens are captured and loaded into transport crates for slaughter Jo-Anne McArthur / Animal Equality How they reach your plate: live animal transport worldwide Israel, 2018 A ship carrying up to 30,000 sheep and cattle from Australia to Israel arrives at port after almost three weeks at sea Jo-Anne McArthur / Israel Against Live Shipments

Then there's the waste created by factory farms, which commonly runs off into waterways and can result in vast "dead zones," where few species can survive. Meanwhile, evidence for animal agriculture's role in climate change grows ever more damning.

Worldwide, the 20 biggest meat and dairy producers emit more greenhouse-gas emissions than all of Germany – in fact, animal agriculture is responsible for more of these emissions than any other industry. And the billions of animals who are crammed into factory farms produce enormous amounts of methane – which is 84 times as effective at trapping heat in our atmosphere as carbon dioxide.

All this spells catastrophe for many species, including polar bears, whose homes are melting, and the countless marine animals who thrive on coral reefs – the rainforests of the ocean – which are being killed off by rising sea temperatures and acidification, both linked to climate change.

The fishing industry also contributes to the carnage. In dragging billions of fish out of the depths every year – whether by trawling the seabed or combing the oceans with longlines – it kills "non-target" animals including turtles, whales, dolphins, and sharks. And although single-use plastics such as bags and straws rightly get a bad rap for causing marine pollution, it's actually abandoned or discarded fishing tackle – also known as "ghost gear" – that has been named "the most harmful form of marine debris for animals" for mutilating and killing millions of sea animals annually.

Fish farming isn't the answer, as vast quantities of wild fish are caught to feed the farmed ones, leaving penguins, puffins, and other fish-eating species to starve.

Our food choices are responsible for a colossal 60 per cent of global biodiversity loss – and as the earth's population creeps ever upwards, the increase in demand for meat is set to exacerbate the already dire situation for our treasured wildlife. But thankfully, we don't just have to sit back and let this happen. By ditching meat, fish, eggs, and dairy, we could go a long way towards easing the pressure on our planet and all the animals we share it with.

By getting our protein directly from plants rather than funnelling them through animals first, we could significantly reduce the amount of land we would need to farm – freeing up millions of hectares that could once again be populated by wild animals. Studies indicate that if everyone went vegan, worldwide food-related greenhouse-gas emissions could be reduced by as much as 70 per cent by 2050, limiting the catastrophic effects of climate change that are threatening so many beloved species.

So if we want to save the tiger, the elephant, the jaguar, and the gorilla, the best (and easiest) place to start would be to leave the chicken, the pig, the lamb, the cow – all animals – off our plates.