Cattle farming, shown here in northern Brazil, is emission-intensive and often accompanies large-scale deforestation.Credit: Yasuyoshi Chiba/AFP/Getty

Efforts to curb greenhouse-gas emissions and the impacts of global warming will fall significantly short without drastic changes in global land use, agriculture and human diets, leading researchers warn in a high-level report commissioned by the United Nations.

The special report on climate change and land by the Intergovernmental Panel on Climate Change (IPCC) describes plant-based diets as a major opportunity for mitigating and adapting to climate change ― and includes a policy recommendation to reduce meat consumption.

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On 8 August, the IPCC released a summary of the report, which is designed to inform upcoming climate negotiations amid the worsening global climate crisis. More than 100 experts, around half of whom hail from developing countries, worked to compile the report in recent months.

“We don’t want to tell people what to eat,” says Hans-Otto Pörtner, an ecologist who co-chairs the IPCC’s working group on impacts, adaptation and vulnerability. “But it would indeed be beneficial, for both climate and human health, if people in many rich countries consumed less meat, and if politics would create appropriate incentives to that effect.”

Deforestation concerns

Researchers also note the relevance of the report to tropical rainforests, with concerns mounting about accelerating rates of deforestation. The Amazon rainforest is a huge carbon sink that acts to cool global temperature, but rates of deforestation are rising, in part because of the policies and actions of the government of Brazilian President Jair Bolsonaro.

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Unless stopped, deforestation could turn much of the remaining Amazon forests into a degraded type of desert, and could release more than 50 billion tonnes of carbon into the atmosphere in 30 to 50 years, says Carlos Nobre, a climate scientist at the University of São Paolo in Brazil. “That’s very worrying,” he says.

“Unfortunately, some countries don’t seem to understand the dire need of stopping deforestation in the tropics,” says Pörtner. “We cannot force any government to interfere. But we hope that our report will sufficiently influence public opinion to that effect.”

Paris goals

Although the burning of fossil fuels for energy and transport garners the most attention, activities relating to land management, including agriculture and forestry, produce almost one-quarter of heat-trapping gases resulting from human activities. The race to limit global warming to 1.5°C above pre-industrial levels ― the goal of the international Paris climate agreement made in 2015 ― might be a lost cause unless land is used in a more sustainable and climate-friendly way, the latest IPCC report says.

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The report highlights the need to preserve and restore forests, which soak up carbon from the air, and peatlands, which release carbon if dug up. Cattle raised on pastures created by clearing woodland are particularly emission-intensive. This practice often comes with large-scale deforestation, as seen in Brazil and Colombia. Cows also produce large amounts of methane, a potent greenhouse gas, as they digest their food.

The report states with high confidence that balanced diets featuring plant-based and sustainably produced animal-sourced food “present major opportunities for adaptation and mitigation while generating significant co-benefits in terms of human health”.

By 2050, dietary changes could free up several million square kilometres of land, and reduce global CO 2 emissions by up to eight billion tonnes per year, relative to business as usual, the scientists estimate (see 'What if people ate less meat?').

“It’s really exciting that the IPCC is getting such a strong message across,” says Ruth Richardson in Toronto, Canada, the executive director at the Global Alliance for the Future of Food, a strategic coalition of philanthropic foundations. “We need a radical transformation, not incremental shifts, towards a global land-use and food system that serves our climate needs.”

Careful management

The report cautions that land must remain productive to feed a growing world population. Warming enhances plant growth in some regions, but in others ― including northern Eurasia, parts of North America, Central Asia and tropical Africa ― increasing water stress seems to reduce vegetation. So the use of biofuel crops and the creation of new forests ― seen as measures with the potential to mitigate global warming ― must be carefully managed to avoid the risk of food shortages and biodiversity loss, the report says.

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Farmers and communities around the world must also grapple with more intense rainfall, floods and droughts resulting from climate change, warns the IPCC. Land degradation and expanding deserts threaten to affect food security, increase poverty and drive migration.

About one-quarter of Earth’s ice-free land area seems to be suffering from human-induced soil degradation already ― and climate change is expected to make thing worse, particularly in low-lying coastal areas, river deltas, drylands and permafrost areas. Sea-level rise is also adding to coastal erosion in some regions, the report says.

Industrialized farming practices are responsible for much of the observed soil erosion, and for soil pollution, says André Laperrière, the executive director of Global Open Data for Agriculture and Nutrition in Wallingford, UK, an initiative that aims to make relevant scientific information accessible worldwide.

The report might provide a much-needed, authoritative call to action, he says. “The biggest hurdle we face is to try and teach about half a billion farmers globally to re-work their agricultural model to be carbon sensitive.”

Nobre also hopes that the IPCC’s voice will give greater prominence to land-use issues in upcoming climate talks. “I think that the policy implications of the report will be positive in terms of pushing all tropical countries to aim at reducing deforestation rates,” he says.

Regular assessments

Since 1990, the IPCC has regularly assessed the scientific literature, producing comprehensive reports every six years or so, and special reports ― such as today’s ― on specific aspects of climate change, at irregular intervals.

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A special report released last year concluded that global greenhouse-gas emissions, which hit an all-time high of more than 37 billion tonnes in 2018, must decline sharply in the very near future to limit global warming to within 1.5°C of pre-industrial levels ― and that this will require drastic action without further delay. The IPCC’s next special report, about the ocean and ice sheets in a changing climate, is due next month.

Governments from around the world will consider the IPCC’s latest findings at a UN climate summit next month in New York. The next round of climate talks of parties to the Paris agreement will then take place in December in Santiago.

António Guterres, the UN secretary-general, said last week that it is “absolutely essential” to implement that landmark agreement ― and “to do so with an enhanced ambition”.

“We need to mainstream climate-change risks across all decisions,” he said. “That is why I am telling leaders don’t come to the summit with beautiful speeches.”