Short answers, pulled from the story.
Agriculture, forestry, and land use contribute between 13% and 21% of all global greenhouse gas emissions. When the broader food system is included, covering processing, transport, and waste, the share rises to 37% of total global emissions.
In 2010, enteric fermentation in ruminants accounted for 43% of all agricultural greenhouse gas emissions globally. Livestock occupies 70% of all agricultural land and demands around 30% of agricultural freshwater while supplying only 18% of global calories. Manure management contributes another 7-10% to global agricultural greenhouse gas emissions.
Agriculture produces carbon dioxide, methane, and nitrous oxide. Nitrous oxide and methane together account for more than half of direct agricultural greenhouse gas emissions. Nitrous oxide is 300 times more effective at trapping heat per pound than carbon dioxide and persists in the atmosphere for around 120 years.
Traditional rice cultivation is the second largest agricultural source of methane, after livestock. Flooded paddies allow organic matter to decompose without oxygen, releasing methane as a byproduct. The near-term warming impact of global rice cultivation is equivalent to all carbon dioxide emissions from aviation worldwide.
A 2023 study found that a fully vegan diet reduced individual greenhouse gas emissions by 75%. The IPCC Sixth Assessment Report, published in 2022, stated that diets high in plant protein and low in meat and dairy are associated with lower greenhouse gas emissions.
Researchers are investigating genetic selection, introduction of methanotrophic bacteria into the rumen, vaccines, and feed modifications to reduce methane from livestock. The seaweed species Asparegopsis armata is under study as a feed additive that reduces methane production inside ruminant stomachs. Grazing management is another farm-level approach under investigation.