We need to consume meat and animal-sourced foods in line with what the planet can sustainably produce, or risk the future of life on Earth.
As a global population, what we’re eating and how we’re producing it right now is good for neither us nor the planet. While over 800 million people are going hungry, over two billion of those who do have enough food are obese or overweight.
An unhealthy diet is the biggest cause of non-communicable disease. And the way we produce food is rapidly degrading the planet - causing 70% of biodiversity loss on land and 50% in fresh water, and being responsible for around 30% of greenhouse gas emissions.
Some foods are, however, worse for the planet than others.
While animal-sourced foods generally have a bigger impact on nature than plants and crops, the production of meat, dairy and seafood can be particularly harmful.
Meat tends to have the highest environmental impact, partially because livestock produce methane emissions through their digestive process - something called enteric fermentation - but also because most meat comes from livestock fed with crops.
This means the environmental footprint is not just the resources used for the livestock, but also those that go into producing the feed.
Of particular concern are livestock intensively raised in small spaces. They live on diets of soy and grain, the production of which is driving conversion of nature in places like the North American Great Plains and the Brazilian Cerrado, and leading to biodiversity loss and increased greenhouse gas emissions.
Rows of soy bean growing. Cerrado, Brazil. © Peter Caton / WWF-UK
So do we need to change our eating habits?
The science certainly shows that the overconsumption of meat, as well as heavily processed foods and refined sugars, can increase the risk of heart disease, cancer and diabetes, while eating fruit, vegetables and other plant foods leads to positive health outcomes for people.
But it is important to recognize that moderate consumption of animal-based foods can be part of a healthy and balanced diet, while there are many parts of the world in which meat provides a vital source of nutrients not available in other accessible foods.
Environmental health too depends on us preventing overconsumption: it’s simply not possible to produce the volume of meat currently being consumed without harming the planet.
However, it is also true to say that certain methods of livestock production — sustainably grazing cattle, for example — can positively impact the environment. Research shows that cattle raised on well-managed, naturally occurring grasslands (as opposed to forests that have been cut down to make way for cows) can increase the amount of carbon stored in the ground and contribute to a biologically rich grassland ecosystem.
Livestock integrated into crop lands naturally fertilize the land, reducing the need for the application of synthetic fertilizers.
And food produced in harmony with a healthy ecosystem is a real win-win. For example, some ranchers and herders are contributing to food security and improving local livelihoods by rearing livestock on natural grasslands, while also playing a vital role in stewarding environmentally valuable land.
When considering our dietary future, it is also worth bearing in mind that feeding billions of people will always use a significant amount of natural resources.
For example, even if we became an entirely vegan planet, the reality is we would still use approximately the same amount of cropland as needed to feed humans and animals today.
Food production can become nature positive, supporting regenerative ecosystems, but many different types of food and food production are part of the solution.
Centenary Farmer's Market, Thimpu, Bhutan. © James Morgan/ WWF-US
The way forward
Globally, we need to consume meat and animal-sourced foods in line with what the planet can sustainably produce.
That means globally reducing the amount of meat and animal-sourced food currently consumed. But there is no one-size-fits-all solution.
The contribution made by each of us will be in line with our unique culture, culinary traditions, environmental footprint and health profile.
In some places, the amount currently consumed is far beyond what is healthy for people or planet. In others, meat consumption should actually be increased to help achieve health and nutrition goals.
The science is clear that we can continue to enjoy some meat as part of a healthy and sustainable diet but we must learn to balance meat consumption with the environmental limits that the Earth places upon us.
If we fail to do so it will be impossible to safeguard human health and the health of our one shared planet.