The study found that almost 70 per cent of the UK's total "cropland footprint", which includes land required to grow animal feed, is now overseas. Between 1986 and 2009 the total footprint increased by 23 per cent, to nearly 11 million hectares, or nearly 1,800sq m per person per year.
While greenhouse gas emissions arising from food production remained broadly constant over a similar period, the share emitted abroad rose from 50 per cent in 1987 to 62 per cent in 2008, due in part to British farmers' higher yields.
Lead author Henri de Ruiter of JHI and the University of Aberdeen said: "Because our current food system is so globalised, it is important to consider the global effects related to our food consumption." The UK cannot reduce the environmental impact of its food production by considering only its domestic environmental consequences, he added.
The study, which was published in the Journal of the Royal Society Interface, was funded in part by the Natural Environment Research Council's Delivering Food Security on Limited Land (DEVIL) programme.
Meanwhile, a separate study has claimed that emissions from UK farming could be largely offset by 2050 through increased agricultural yields coupled with expanding the areas of natural forests and wetlands to more closely resemble those of other European countries.
The new study, by researchers from several UK institutes and published this month in the journal Nature Climate Change, argues that by raising UK woodland cover from 12 to 30 per cent - still less than the European average - and restoring 700,000ha of wet peatland, these habitats would act as a carbon sink sufficient to meet Government targets of an 80 per cent greenhouse gas reduction from farming by 2050.
Such areas would also support threatened wildlife, provide recreation and reduce flooding, they claimed. One of the authors, Professor John Pickett of Rothamsted Research, said such a "land sparing" programme "demands even greater efforts not only to intensify agriculture sustainably but to exploit the spared land more effectively for the ecosystem services that such land can potentially yield". His colleague Dr Toby Bruce added: "To allow this, productivity needs to increase on the remaining land - for example, by minimising crop losses to pests, weeds and diseases or by improving crop nutrition."
Professor Andrew Balmford of the Department of Zoology, University of Cambridge, pointed out that the research team did not allow themselves the "get-out-of-jail-free card" of increasing food imports, even though overall UK food consumption is forecast to rise by 38 per cent by 2050.
"Reducing meat consumption appears to offer greater mitigation potential than reducing food waste, but more importantly our results highlight the benefits of combining measures," he explained. "If we are serious about saving the planet for anything more than food production, then the focus has to be on increasing yields and sparing land for the climate."