Meeting global net zero carbon commitments could require tree planting on land equivalent to five times the size of India, a new report has said.

More than 120 countries and hundreds more corporations have made commitments to be net zero by the middle of this century, which entails offsetting unavoidable emissions with new technologies or nature-based methods that suck up carbon.

However, relying on tree planting to meet those goals was “mathematically impossible” because there was not enough land, a new report from Oxfam said.

Achieving all global carbon removal targets through tree planting alone, rather than cutting emissions, would require an area of land five times the size of India, or the equivalent of all the farmland on the planet.

Oxfam warned that extensive tree planting to meet net zero targets could cause global food prices to rise by 80 per cent by 2050.

“Too many companies and governments are hiding behind the smokescreen of ‘net zero’ to continue dirty business-as-usual activities,” said Danny Sriskandarajah, chief executive of Oxfam GB.

Targets from just four of the biggest oil and gas producers – Shell, Eni, Total and BP – would require an area of land twice the size of the UK, Oxfam calculated.

The EU’s land-based removals targets would require nearly four times the mass of the UK if they relied on tree planting, according to Oxfam analysis.

A fifth of the world’s 2,000 largest publicly listed corporations have net zero goals that are dependent upon tree planting and other land-based initiatives.

Prof Duncan McLaren, a research fellow at Lancaster University’s Environment Centre, who was not involved in the study, said that corporate net zero targets tended to rely heavily on using tree planting to suck up their carbon.

“Oil companies, airlines and others are lining up to say they are going to be net zero but not specifying how,” he said. “They are staking a claim to offsets when actually what we need to offset is not luxury emissions from air travel, but unavoidable emissions from things like feeding the nation.”

The UK was the first leading economy to set a target to be carbon neutral by 2050, and has been followed by similar commitments from the EU, US and China.

However, it has yet to set out how it will reach the goal, and environmental groups are concerned that policy makers will ultimately rely on unproven technology and vast amounts of tree planting.

The UK’s climate change advisers say 100mtCO2 (million tons of carbon dioxide), about 25 per cent of annual emissions in 2019, will need to be offset by tree planting and other carbon removal methods by 2050.

To do this, it suggests a quarter of farmland will need to be taken out of production. But more could be needed if the UK cannot significantly cut emissions from flying, agriculture, transport and home heating.

The Government has committed to planting 30,000 hectares of trees every year by 2025, which could suck up an estimated 12mtCO2 annually.

“Land is a finite and precious resource that millions of small-scale farmers and indigenous people depend upon to feed their families,” Mr Sriskandarajah said. 

“Nature and land-based carbon removal schemes are an important part of the mix to lower emissions, but more caution is needed to ensure good stewardship that doesn’t threaten food security.”

BP said it did not intend to rely on offsets to meet its 2030 emission reduction targets. 

Shell told Oxfam that its 2050 goal did not rely on extensive reforestation.

Eni told Oxfam that nature-based solutions were “crucial” to achieve carbon neutrality, and Total said it operated on the principle that “natural carbon sinks must be connected to an agricultural or forestry value chain that is local and sustainable”.