Whether human beings survive this century and the next, whether other lifeforms can live alongside us: more than anything, this depends on the way we eat. We can cut our consumption of everything else almost to zero and still we will drive living systems to collapse, unless we change our diets.

All the evidence now points in one direction: the crucial shift is from an animal- to a plant-based diet. A paper published last week in Science reveals that while some kinds of meat and dairy production are more damaging than others, all are more harmful to the living world than growing plant protein. It shows that animal farming takes up 83% of the world’s agricultural land, but delivers only 18% of our calories. A plant-based diet cuts the use of land by 76% and halves the greenhouse gases and other pollution that are caused by food production.

Part of the reason is the extreme inefficiency of feeding livestock on grain: most of its nutritional value is lost in conversion from plant protein to animal protein. This reinforces my contention that if you want to eat less soya, then you should eat soya: 93% of the soya we consume, which drives the destruction of forest, savannah and marshland, is embedded in meat, dairy, eggs and fish, and most of it is lost in conversion. When we eat it directly, much less of the crop is required to deliver the same amount of protein.

More damaging still is free-range meat: the environmental impacts of converting grass into flesh, the paper remarks, “are immense under any production method practised today”. This is because so much land is required to produce every grass-fed steak or chop. Though roughly twice as much land is used for grazing worldwide as for crop production, it provides just 1.2% of the protein we eat. While much of this pastureland cannot be used to grow crops, it can be used for rewilding: allowing the many rich ecosystems destroyed by livestock farming to recover, absorbing carbon dioxide from the atmosphere, protecting watersheds and halting the sixth great extinction in its tracks. The land that should be devoted to the preservation of human life and the rest of the living world is at the moment used to produce a tiny amount of meat.

Whenever I raise the crucial issue of yield per hectare, I receive a barrage of vituperation and abuse. But I’m not having a go at farmers, just pointing out that the figures don’t add up. We can neither feed the world’s growing population nor protect its living systems through animal farming. Meat and dairy are an extravagance we can no longer afford.

There is no way out of this. Those who claim that “regenerative” or “holistic” ranching mimics nature deceive themselves. It relies on fencing, while in nature wild herbivores roam freely, often across vast distances. It excludes or eradicates predators, which are crucial to the healthy functioning of all living systems. It tends to eliminate tree seedlings, ensuring that the complex mosaics of woody vegetation found in many natural systems – essential to support a wide range of wildlife – are absent.

The animal industry demands ever-greater assaults on the living world. Witness the badger slaughter in the UK, now spreading across the country in response to the misguided requests of dairy farmers. People ask how I would justify the return of wolves, knowing that they would kill some sheep. I ask how they justify the eradication of wolves and a vast range of other wildlife to make way for sheep. The most important environmental action we can take is to reduce the amount of land used by farming.

Facebook Twitter Pinterest ‘More damaging still is free-range meat.’ Photograph: Alamy Stock Photo

Unless you can cook well – and many people have neither the skills nor the space – a plant-based diet can be either boring or expensive. We need better and cheaper vegan ready meals and quick and easy meat substitutes. The big shift will come with the mass production of cultured meat. There are three main objections. The first is that the idea of artificial meat is disgusting. If you feel this way, I invite you to look at how your sausages, burgers and chicken nuggets are currently raised, slaughtered and processed. Having worked on an intensive pig farm, I’m more aware than most of what disgusting looks like.

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The second objection is that cultured meat undermines local food production. Perhaps those who make this claim are unaware of where animal feed comes from. Passing Argentinian soya through a nearby pig before it reaches you does not make it any more local than turning it directly into food for humans. The third objection has greater merit: cultured meat lends itself to corporate concentration. Again, the animal feed industry (and, increasingly, livestock production) has been captured by giant conglomerates. But we should fight to ensure that cultured meat does not go the same way: in this sector as in all others, we need strong anti-trust laws.

This could also be a chance to break our complete dependence on artificial nitrogen. Traditionally, animal and plant farming were integrated through the use of manure. Losses from this system led to a gradual decline in soil fertility. The development of industrial fertilisers saved us from starvation, but at a high environmental cost. Today, the link between livestock and crops has mostly been broken: crops are grown with industrial chemicals while animal slurry stacks up, unused, in stinking lagoons, wipes out rivers and creates dead zones at sea. When it is applied to the land, it threatens to accelerate antibiotic resistance.

In switching to a plant-based diet, we could make use of a neat synergy. Most protein crops – peas and beans – capture nitrogen from the air, fertilising themselves and raising nitrate levels in the soil that subsequent crops, such as cereals and oilseeds, can use. While the transition to plant protein is unlikely to eliminate the global system’s need for artificial fertiliser, the pioneering work of vegan organic growers, using only plant-based composts and importing as little fertility as possible from elsewhere, should be supported by research that governments have so far failed to fund.

Understandably, the livestock industry will resist all this, using the bucolic images and pastoral fantasies that have beguiled us for so long. But it can’t force us to eat meat. The shift is ours to make. It becomes easier every year.

• George Monbiot is a Guardian columnist