People should cut the amount of beef, dairy and lamb they eat by a fifth to help cut the countryside's carbon emissions, said government climate advisers.
A report by the Committee on Climate Change (CCC) says major land use changes will be needed to enable the country to reach its legal target of "net zero" emissions by 2050.
It sets out a range of policy recommendations including planting up to 120 million trees each year to increase UK forestry cover from 13pc to 17pc, encouraging bioenergy crops and supporting low-carbon farming practices such as controlled-release fertilisers and slurry acidification to reduce ammonia emissions.
But it also says the nation needs to cut food waste and reduce its consumption of the most carbon-intensive foods - such as beef, lamb and dairy - by at least 20pc per person. That could mean 10pc fewer cattle and sheep grazing in the East Anglian countryside.
"These measures imply a shift towards current healthy eating guidelines and can drive sufficient release of land to support the necessary changes in tree planting and bioenergy crops," says the report.
"Alongside expected population growth, they imply around a 10pc reduction in cattle and sheep numbers by 2050 compared with 2017 levels. This compares with a reduction of around 20pc in the past two decades."
The committee's report says land uses including agriculture, forestry and peatland accounted for around 12pc of total UK greenhouse gas emissions in 2017 but says farmers and land managers can reduce these emissions by almost two thirds by 2050, with the right support.
The National Farmers' Union (NFU) welcomed the report's recognition that cutting emissions can be achieved without producing less food, or increasing imports with a higher environmental impact than goods produced in the UK.
Jake Fiennes is East Anglia's representative on the NFU Environment Forum and also general manager for conservation on the Holkham Estate, which grows large areas of arable crops as well as using cattle for both beef production and conservation grazing on the estate's National Nature Reserve (NNR).
"I think anything is achievable," he said "If the science is telling us that climate change is a threat and it is going to affect our businesses, our livelihoods and our lifestyles, then we need to have quite dramatic change. Whether through individuals or government incentives or industry action, we have to be prepared to change things that we always did before.
"But we are not all agreed as to where we start to calculate the carbon footprint. We need a unified joined-up approach that we all agree on, saying this is the matrix for carbon release and carbon sequestration - but the science is not quite there yet.
"I am of the view that we need to address our diets and eat less meat, but better quality. In England our climate is very good for growing grass and the best way to manage grass is through livestock. If we can do that in a way that captures carbon but also provides a healthy protein, then we need to keep doing that. But we may need to look at how we do that sustainably. I would need a scientist to calculate the difference between me growing feed wheat for poultry and cattle versus growing grass and having grass-fed cattle.
"We also have the opportunity to plant more trees but it has to be the right tree in the right place. We need to understand the outcomes. And I need to understand how much carbon I am capturing in my food production.
"The devil will be in the detail, but I think the principle of society as a whole needing to reduce carbon emissions is fundamentally important. I think we all agree on that."
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The NFU has produced its own plans for reaching net zero by 2040, including planting trees and hedgerows, increasing productivity, and boosting renewable energy and bioenergy production.
NFU president Minette Batters suggested plant-based foods were not necessarily more sustainable than meat production, and with an estimated 65pc of the UK's land only suitable for grazing livestock, the British public should continue to support domestic livestock production.
"A comprehensive approach across the whole UK economy is needed, and when it comes to farming we need to focus on the whole agricultural system," she said.
"When talking about changing diets, plant-based products do not always necessarily have a lower impact on the environment. It all depends on where and how the ingredients have been produced, the environmental pressures involved in its production, the environmental management associated with that country's agricultural system and the environmental resources available, as well as how far the product has travelled.
"I believe British farmers are very much part of the solution. We want to be the model for climate-friendly food production around the world - food production that continues to include nutritious beef, lamb and dairy products for the world to enjoy as part of a healthy, balanced diet."
Government agencies Natural England, the Environment Agency and the Forestry Commission responded to the report by pledging to work together to deliver "nature-based solutions to climate change".
They include delivering large-scale woodland creation, restoring peatland and developing schemes to reward farmers for cutting emissions and protecting wildlife.
Tony Juniper, chairman of Natural England, said: "Given the scale of the challenge, a joined-up approach that embraces nature's recovery is not an optional extra, but must be central to the whole plan, to both catch carbon and to help us adapt to what are now inevitable climate change impacts.
"The good news is that restoring of peatlands, the re-establishing of forest cover, and the re-naturalising of the coast will deliver multiple additional benefits for the country, including for our wildlife and collective health and wellbeing."
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