If we want to cut the environmental impact of livestock, switching to insects and imitation meat products is our best bet, according to a new report.

The inevitability of turning to insects to feed the world's growing population has been looming for a while. And now we finally have some data on how much this shift would actually help the planet.

As more people move to live in cities and have higher incomes, meat consumption is steadily growing, which sucks up an enormous amount of resources. Livestock takes up 60 percent of all agricultural land, and on top of that a third of all crops we grow are livestock feed.

For now, projections are based on the assumption that this current trend will continue. But what if our preferences for meat changed - how would that impact sustainability?

With this question in mind, a team led by scientists from the University of Edinburgh in the UK analysed various alternatives to conventional animal products, looking specifically at their impact on agricultural land use.

The researchers examined what would happen if we swapped half of our current animal products to one of these alternatives: edible insects; lab-made meat; imitation meat and soy-based products; or aquaculture.

Rather than trying to predict our future, their goal was to simply provide new data on potential scenarios of cutting back rampant meat production.

"The approach is explorative, rather than predictive, and assumes half of existing animal products are substituted by each alternative food, to provide at least equal energy and protein," they write.

"The 50 percent replacement assumption is largely arbitrary, but is simply used as a reference point against which to compare alternative diets."

These alternative diets also included several unlikely scenarios, such as calculating what would happen if people around the world all shifted to the average Indian diet (low in animal products), or the average US diet (high in animal products).  

After standardising and comparing the options, the researchers arrived at the most sustainable ones.

They found that if we replaced half of all animal product use with either soybean curd (tofu) or mealworm larvae products, we'd save a third of the land currently used for the world's agriculture.

And that would reduce knock-on effects such as greenhouse gas emissions and deforestation.

As the team point out, this is just a benchmark. Replace more or less, and the land savings will scale accordingly.

But that doesn't mean they're advocating that we all shift exclusively from steak to mealworms.

Instead, you can view this report as a tool for assessing our future options. If helpful scenarios include growing more worms and fewer sheep, then perhaps it's time to start seriously considering it.

"The efficiency of insects and their ability to convert agricultural by-products and food waste into food, suggests further research into insect production is warranted," the team writes.

Besides, the idea of crunching on crickets is stomach-churning for a relatively small minority of western cultures, while people elsewhere have already been eating bugs for millennia.

"It is very widespread, especially in Asia, and not seen as unusual in those cultures," lead researcher Peter Alexander told Damian Carrington at The Guardian.

"We are not trying to mandate or even suggest some policy that you eat insects every day [but] our work indicates the potential benefits that are there."

And if you're one of those people holding out for lab-grown meat, the news is not so good - according to the report, there are still too many unknowns with this technology, which makes it difficult to assess its potential sustainability. For now, cow-less burgers are still not very cost-efficient or nutritious.

If you care about increasing the sustainability of our land so that we can keep feeding future generations, looks like the best answer right now is to actively work for a new balance between livestock and its substitutes.

"A mix of small changes in consumer behaviour, such as replacing beef with chicken, reducing food waste and potentially introducing insects more commonly into diets, would help achieve land savings and a more sustainable food system," says Alexander.

The report was published in Global Food Security.