This paragraph is fantasy:

“If, however, the global population shifted to a low-meat diet – defined as 70 grams of beef and 325 grams of chicken and eggs per week – around 15 million square kilometres of farmland would be freed up. Vegetation growing on this land would mop up carbon dioxide. It could alternatively be used to grow bioenergy crops, which would displace fossil fuels”

Farming is a business. The primary interest of business is to make money. Agribusiness is not going to let itself go broke and then let the farmland be taken up with weeds. If the consumption of meat dropped significantly there would be a massive advertising campaign to get us to eat meat again, like those ads which promoted meat as the reason humans evolved.

Trying to cut meat consumption is the wrong way to look at it, we should be focussing on cutting meat production in the same way we’re campaigning to cut coal production.

If we had a planned economy these things would be possible, but in the free market we’re held back by big business. That’s the biggest barrier to real action on climate change, not the fact that most people are still eating meat.