The rate and extent of global land exploitation by humans is unsustainable and undermines attempts to stop global warming, according to a leaked report by United Nations scientists.
Sky News has seen a final draft of the report, being discussed by the Intergovernmental Panel on Climate Change (IPCC) in Geneva this week.
Climate Change and Land warns that humans now exploit 72% of the planet’s ice-free surface to feed, clothe and support the growing population.
Agriculture, forestry and other land use accounts for almost a quarter of all greenhouse gas emissions caused by human activity.
Since 1961 more than two million square miles, an area equivalent to the size of Australia, has been brought into agricultural use.
A doubling of meat consumption over that time has resulted in a 70% increase in methane emissions from cattle and sheep.
Agriculture is also becoming ever more intensive as farmers attempt to extract the maximum yield from their land.
Emissions of nitrous oxide – another potent greenhouse gas – have doubled as farmers use more artificial fertilisers.
Richard George, Head of Forests at Greenpeace UK, said: “The way we’re consuming is a disaster for the planet.
“All over the world huge areas of forests are being destroyed to grow palm oil, to raise cattle and to produce animal feed and it absolutely has to stop.
“We cannot protect our climate, and we cannot prevent species extinction, if we don’t reform how the food system works and how we’re using land, both in the UK and abroad.”
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Intensive agriculture also compacts the soil, increases erosion and reduces the amount of organic material in the ground.
According to the Sustainable Food Trust, Britain has just 100 harvests left because fertile soil is being depleted so quickly. Around three million tonnes of fertile soil is being lost each year.
The report warns that growing crops for energy – for example aircraft fuel – is not a quick fix for climate change.
A global area of just 772,000 to 2.3 million square miles of bioenergy production could put food security at risk, particularly in sub-Sahara Africa, as crops grown for human consumption are displaced to less productive regions.
Mr George said biofuel was a “false solution.”
“Roughly an area bigger than Bedford in the UK is currently being grown to produce biofuels to go in the tanks of people’s cars,” he said.
“That’s a disaster when we need to be using the land we have to grow food for people or restoring forests.”
The IPCC report says land should be managed more sustainably so it can store more carbon.
Between 2008 and 2017, 30% of all carbon dioxide from human activity was absorbed by plants and trees and then locked away as organic material in the soil.
But far more carbon could be drawn out of the atmosphere.
Peatlands could be restored by stopping land drainage and the countryside could be rewilded to interlink agriculture and nature, so more carbon makes its way into the soil.
Cutting meat consumption and reducing food waste would also reduce the land used to sustain the human population.
The UK’s Committee on Climate Change recently published a report setting out a transition to a net-zero emissions target.
It advocated a 20% reduction in consumption of beef, lamb and dairy to release more land for forests and peatland restoration.
Afforestation of 30,000 hectares a year, increasing woodland cover in the UK from 13% to 17%, would result in 22 million tonnes of carbon dioxide being stored in trees.
Speaking ahead of publication of the finalised report next week – but before the draft was leaked to Business Standard – Dr Stephen Cornelius, WWF’s chief adviser on climate change, said: “We need to see an urgent transformation in how we use land in the future.
“This includes the type of farming we do, our food system and diets, and the conservation of areas such as forests and other natural ecosystems.
“All of which can either help or hinder the reduction of greenhouse gas emissions.
“This new report should bring this home to us.”
The IPCC said it doesn’t comment on leaked reports, adding: “Drafts of the report are collective works in progress that do not necessarily represent the IPCC’s final assessment of the state of knowledge.
“According to the IPCC procedures, reports are made available to the public after their Summary for Policymakers has been approved and the underlying report accepted.”