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A growing body of research is making clear the fact that the way we eat is unsustainable, for human health and for the environment. With our food system responsible for at least 15% of greenhouse gas emissions, and an increasing burden of ill health related to consumption of red and processed meat, there is an urgent need to find answers to the question of how to feed the world's population – projected to reach 10 billion by 2050 – in a healthy and sustainable way.

How we transport our food, store it, cook it, and how much is lost or wasted (an estimated 30% worldwide) are also key considerations in the sustainability of our food system as a whole. And widely varying scenarios across the globe mean there can be no one-size-fits-all solution: while in affluent societies excessive calorie intake has contributed to a rapid rise in rates of obesity, in the developing world more than 3 billion people are classed as malnourished.

Meat: a key contributor to global warming

The world's total global meat consumption currently stands at more than 300 million metric tonnes per year, having risen from seven million in 1960, and could rise by as much as 76% by the middle of this century (including a doubling in the consumption of poultry, a 69% increase in beef, and a 42% increase in pork). The rearing of livestock for meat, eggs and dairy products generates some 15% of total global greenhouse gas emissions and uses 70% of agricultural land.

A 2014 paper by Oxford researchers was the first to provide quantitative evidence that going meat-free can dramatically reduce the impact of our diets on the environment. Since then, further Oxford studies have demonstrated that adopting more plant-based, 'flexitarian' diets globally could reduce the greenhouse gas emissions of the food system by more than half. Indeed, researchers argue that we will fail to sufficiently mitigate climate change if we don't change the way we eat.

A dramatic difference for human and environmental health

Research by Professor Charles Godfray, Director of the Oxford Martin School and the Future of Food programme at Oxford University, set out the health and environmental benefits of changing the protein sources in our diets from meat to alternatives such as mycoprotein, algae, peas, insects and lab-grown meat. It showed that these protein sources could reduce the overall global burden of diet-related deaths by 2.4%, with that number climbing to 5% in high- and upper- middle-income countries. The findings also laid bare the striking difference in CO2-equivalent emissions between beef (23.9kg emissions per 200kcal) and alternative protein sources such as beans, insects, wheat and nuts (1kg per 200kcal). Chicken and other protein sources such as tofu, pork and algae produce only 3–6kg CO2 equivalent.

While different protein sources may not yet be as attractive to consumers, innovative alternative protein products are beginning to make their way on to supermarket shelves and restaurant menus, accompanied by considerable hype and interest. Lab-grown meat has yet to reach commercial production but has already been extensively marketed and written about in the media. One of the heralded promises of lab- grown meat is its potential for radically reducing the greenhouse gas emissions involved in meat production.

Future of Food programme researchers Dr John Lynch and Professor Raymond Pierrehumbert, of Oxford's Department of Physics, found that some projections for the uptake of particular forms of cultured meat could indeed be better for the climate, but others could actually lead to higher global temperatures in the long run.

With current uncertainties around how cultured meat would be produced at scale, they concluded that the availability of low-carbon energy sources to fuel production will be key if lab-grown meat is to help in the drive to reduce carbon emissions.

The environmental cost of 'business as usual'

While changing our eating habits can dramatically decrease carbon emissions, transitioning away from meat-based diets may be a difficult public health problem. One proposed method for encouraging change in the UK's eating habits has been a tax on red and processed meat. The research, led by Dr Marco Springmann of the Oxford Martin School and Nuffield Department of Population Health, calculated that optimal taxation to account for health costs in high-income countries would mean a 20% tax on red meat and more than 100% on processed meat like bacon, sausages and jerky. Such measures could prevent 220,000 deaths globally and save over US$40 billion in healthcare costs every year, he found.

Professor Godfray believes a dialogue would be needed for a successful, large-scale transition to sustainable protein sources: 'For the foreseeable future, the meat and alternative protein industries will coexist and have the opportunity to complement one another. Both incumbents and new players, and the various stakeholders who are involved throughout the protein supply chains, will gain from a nuanced debate about how to evolve and reshape regional and ultimately global food systems to provide healthy and sustainable diets.

'Only through dialogue and structured collaboration will society be able to transform the protein system, to create a future where safe, sustainable, affordable and healthy protein is provided to all.'

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