Founded in 2018, 50by40 is an organisation with the mission to achieve

A 50% reduction in the global production and consumption of farmed animal products by 2040, with the remaining production systems being environmentally and socially sustainable, regenerative and humane, achieved via a Just Transition of the farming system.

This question asks specifically about global meat production. Our World In Data claims global meat production in 2018 was 342.42 million tons, a 46.68% increase since 2000. A 50% reduction from this level would result in global meat production declining to 171.21 million tons, a level last seen in 1988.

Will there be a 50% decline in global meat production by 2040?

This resolves positively if global meat production as per OurWorldInData is below 50% of its 2018 level (i.e., is 171.21 million tons or lower) in any year between 2019 and 2040 (inclusive). If OurWorldInData ceases publishing this data by this date, admins can choose a credible alternative source for resolution.

14 June 2021 edit: Cultivated meat, which is produced from in vitro cell culture of animal cells rather than from the slaughter of livestock, does not count toward the overall global meat production figure. Only meat coming from slaughtered animals will count, as is currently the case with Our World's in Data figure of 340M tons as of 2018. Since this 340M tons figure does not include fish/seafood, data from FAOSTAT as tracked by OWID — in this case, 155M tons of seafood/fish (2013 figure) — will be added to the meat figure. Again, cultivated fish/seafood does not count. This question will not resolve until 2040 data is available for both meat and fish/seafood production.