Originally published 2021-05-25.
On 22 May 2021, the International Day for Biological Diversity, Greta Thunberg released a five-minute short film called #ForNature. Its argument was simple: the way the world produces food, especially meat and dairy, sits at the centre of three crises at once. It drives climate change, it destroys wild habitats, and it raises the risk of new diseases jumping from animals to people. Her proposed answer was a shift towards plant-based eating, with the greatest responsibility placed on governments, companies and people who have the power to choose.
Here is what the film said, who made it, which of its numbers hold up, and what the wider evidence says about food and the planet.
What the film is and who made it
Thunberg, then 18, conceived and wrote the film herself and approached the British filmmaker Tom Mustill, who has worked on wildlife projects with Sir David Attenborough. The animal-welfare charity Mercy For Animals funded the production, supplied footage and helped with research, which Thunberg acknowledged openly when she shared it.
The film was made in a deliberately low-carbon way and published on Mercy For Animals' YouTube channel. It blends archive footage of forests, farms and wildlife with Thunberg's narration, and it opens with a blunt expletive that drew headlines of its own.
”Our relationship with nature is broken. But relationships can change. When we protect nature - we are nature protecting itself.”
— Greta Thunberg (@GretaThunberg) May 22, 2021
Thank you @MercyForAnimals for sponsoring this film by @tommustill and me.#ForNature #BiodiversityDay pic.twitter.com/2tXPFaeqWq
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Its central line, posted alongside the video, was "Our relationship with nature is broken. But relationships can change."
The three harms the film links together
Climate
Farming and land use together account for roughly a quarter of the greenhouse gases humans produce. Livestock contribute through methane from cattle and sheep, emissions from manure and the clearing of forests for pasture and feed crops. Thunberg's point was that the climate debate often focuses on energy and transport while leaving food on the side.
Nature and wildlife
Agriculture is the largest driver of habitat loss on the planet. Figures widely cited from a 2018 study in Science show that animal farming uses about 83% of the world's farmland yet supplies only around 18% of the calories people eat. The film argued that this land, much of it carved out of forests and grasslands, is where biodiversity is being lost fastest.
Health and pandemics
Diseases that pass from animals to people, known as zoonoses, were a pressing topic in the second year of COVID-19. The film tied crowded, industrial animal farming to the risk of the next outbreak. The United Nations Environment Programme warned in July 2020 that intensive pig and poultry farming is expected to be a major risk factor for future spillover.
A fourth theme runs through all three: the animals themselves. Citing UN Food and Agriculture Organization data, the film said more than 60 billion land animals are slaughtered for food each year, most of them raised in factory farms.
Checking the numbers
"8 billion tonnes of CO2 a year." The film said a global move to plant-based diets could save up to 8 billion tonnes of carbon dioxide every year and cut farmland needs by about three quarters. The "up to" matters. This is the top of a range that assumes everyone changes their diet, and much of the benefit comes from letting cleared land return to forest. Real-world savings would depend on how far diets actually shift.
"60% of diseases since 1990." Some reports at the time attributed to the World Health Organization a claim that 60% of diseases emerging since 1990 came from animals. The more commonly cited figures are slightly different: about 60% of all known human infectious diseases are zoonotic, and up to 75% of emerging ones, based on a 2008 study in Nature and later WHO material. The film itself used the 75% figure. Either way, the direction of the claim is sound.
Land use. The 83% farmland and 18% calories figures are well supported. A separate 2023 study found that a vegan diet reduced land use by about 75% compared with a high-meat diet, in line with the film's estimate.
Meat without the animal?
Coverage of the film also mentioned "cultured" or "cultivated" meat, grown from animal cells in a bioreactor rather than raised on a farm. The tissue is real meat, but no animal is slaughtered to produce it.
The idea has moved quickly but unevenly. The first lab-grown burger, made by Mark Post at Maastricht University in 2013, cost more than $325,000. Singapore became the first country to approve a cultivated product for sale in December 2020, and the US approved cultivated chicken from Upside Foods and Good Meat in June 2023. At the same time, Italy banned cultured meat in November 2023, and the US states of Florida and Alabama have outlawed its sale. Price, scale and public acceptance remain open questions, so for now plant-based foods are the more practical alternative.
Thunberg's path to this film
Born in Stockholm on 3 January 2003, Thunberg began a one-person school strike outside the Swedish parliament on 20 August 2018. Her Friday protests grew into Fridays for Future, a movement that brought millions of young people onto the streets worldwide. In September 2019 she addressed the UN Climate Action Summit in New York, and Time named her Person of the Year for 2019.
She has also faced fierce criticism and personal abuse online. Then-President Donald Trump mocked her more than once, including a December 2019 tweet telling her to work on her "anger management", to which she responded by changing her social media biography. The food film marked a widening of her focus from fossil fuels to the whole relationship between people and nature.
What it means for everyday choices
The film's closing message was that those with the most power carry the most responsibility. That points first to policy: farm subsidies, land protection, procurement by schools and hospitals, and the menus of large restaurant chains. But it also leaves room for individuals who can choose what they eat.
- Small swaps add up. Replacing some beef and lamb, the most emissions-intensive meats, with beans, lentils or poultry has an outsized effect.
- Waste less. Food that is thrown away carries all the emissions and land use of producing it.
- Look at the system, not just the plate. Supporting policies that protect forests and reward lower-impact farming can matter as much as personal diet.
Anyone making a big dietary change for health reasons should talk to a doctor or dietitian first. The film is campaigning material made with an advocacy group, so it is persuasive by design, but its core message is backed by mainstream research: what we eat, and how it is produced, is one of the biggest levers we have on climate and nature.
Sources: Green Matters; VegNews; Wikipedia: Environmental impact of meat production; Wikipedia: Zoonosis; Wikipedia: Cultured meat; Wikipedia: Greta Thunberg.
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