Modelling the production impacts of a widespread conversion to organic agriculture in England and Wales

•The impacts of scaling-up organic farming are assessed through land-use modelling.•Food outputs as Metabolisable Energy reached 64% of that under conventional farming.•Production losses would be greatest for cereals and monogastric livestock.•Ruminant stock increased and vegetable outputs were similar to a conventional baseline.•An organic scenario would require major increases in food imports or dietary change.