Five of the UK's biggest supermarkets have promised to halve the environmental impact of a weekly food shop by the end of the decade.
Tesco, Sainsbury's, Waitrose, Co-op and M&S said they would reduce carbon emissions, deforestation and the food waste and packaging they produce.
Their efforts will be monitored by the WWF conservation group.
"Food production is one of the biggest threats to our planet," said WWF chief executive Tanya Steele said.
The chief executives of the supermarkets, which together serve more than half of UK food shoppers, said in a joint statement: "We recognise that a future without nature is a future without food. By 2030 we need to halt the loss of nature."
Before the end of next year, they also promised to set science-based targets for how they would help to limit global warming to 1.5C above pre-industrial temperatures.
This is a key target for world leaders at the COP26 climate summit in Glasgow, with scientists saying it must be met to avoid the worst effects of climate change.
Currently, the world is now about 1.2C warmer than it was in the 19th Century - and extreme weather events like heatwaves, floods and forest fires are already becoming more intense. Unless more is done, the planet is already on track to warm by more than 2C by the end of this century.
The food industry is responsible for more than a quarter of total greenhouse gas emissions and almost 60% of the global damage to biodiversity, so minimising its impact could make a significant contribution to reducing climate change.
Each year, the industry emits 17.3bn tonnes of carbon dioxide - about 19 times more than commercial planes.
About a quarter of the world's greenhouse gas emissions come from agriculture, forestry and other land use - and experts say the way food is grown and consumed needs reforming.
Ms Steele from the WWF said the world could only tackle the "climate and nature emergency" if food retailers played their part.
"The promises these CEOs have made are game-changing and we hope other food retailers will follow in their footsteps, so that every shopper can be confident that the products they buy aren't fuelling the climate crisis and pushing precious wildlife closer to the brink," she said.
Later, as the COP26 summit continues, it is expected that 45 governments, including the UK, will pledge urgent action and investment to protect nature and shift to more sustainable ways of farming.
And, in a separate development, another 20 countries joined a global forum aimed at reducing deforestation from the production of commodities such as palm oil, cocoa and soya - the Forest, Agriculture and Commodity Trade (FACT) dialogue forum.
Matt Williams, an expert from the Energy and Climate Intelligence Unit think tank, said "food and farming have largely been missing from this summit so far" but this "plants the seeds" for it to make a serious contribution to reaching net-zero emissions.
Another 27 countries also signed up to a sustainable agriculture pledge to help them meet their climate goals, and will use funding earmarked for agriculture subsidies to reduce emissions.
And the UK government has announced a £500m programme which it said would help to protect over five million hectares of rainforests from deforestation - an area almost 20% of the size of the UK itself.
But Anna Jones at Greenpeace UK said the attempts to address the supply chains of the food industry were "little more than a talking shop".
She said "there's nothing on the need to reduce demand for products like meat and dairy that are driving deforestation".
Large-scale demonstrations are taking place in Glasgow, where the summit is being held, as well as in London and other cities in the UK and around the world.
The marches come after thousands of young activists, including Greta Thunberg and Vanessa Nakate marched through Glasgow on Friday protesting against investment in fossil fuels and the failure to tackle the climate crisis.