BBC: Cattle are the biggest source of greenhouse gases, accounting for more than three-quarters of all emissions from global livestock, a survey shows.
The assessment, described as the most detailed of its kind, identified Europe and the Americas as the world's epicentres of beef production.
Annually, the world produces 586m tonnes of milk, 124m tonnes of poultry and 59m tonnes of beef.
The findings appear in the Proceedings of the National Academy of Sciences.
The assessment, funded by the...