Tomatoes from Spain, olive oil from Italy, plums from Chile, salmon from Alaska and green beans from Kenya – how often might some of these ingredients end up in your basket? In the UK most people's shopping trolleys contain a significant proportion of imported foods. But could these foods be grown and produced at home? Which countries are capable of food self-sufficiency? A new series of maps shows which countries could feed their entire population, and which countries are limited by lack of land or water.

Marianela Fader from the Potsdam Institute for Climate Impact Research, Germany, and colleagues, calculated the growing capacity of every country in the world, and compared it with food requirements, both now and projected forward to 2050. Their model employed climate data, soil type and land-use patterns for each country, in order to simulate yields for a variety of types of crop. Using current data on population, and food and water consumption in each nation, they were able to assess what proportion of its food a country could produce.

Although many countries choose to import food right now, the model showed that there are surprisingly few that could not maintain the same diet and still be food self-sufficient. "Today, 66 countries are not able to be self-sufficient due to water and/or land constraints," said Fader. This equates to 16% of the world's population depending on food imported from other countries.

The countries with the most reliance on imports were found in North Africa, the Middle East and Central America, with over half the population depending on imported food in many of these locations. Outside those locations many countries could become food self-sufficient if they chose to.

But roll the clock forward to 2050 and population pressure paints a very different picture. Vast swathes of the global map are coloured red and orange, highlighting those countries that would have to maximize food production – by improving agricultural productivity, and expanding cropland, for example – in order to feed their population. The figures suggest that over half the world's population could depend on imported food by 2050.

"Assuming that all low-income economies achieve full potential productivity by 2050 in addition to full cropland expansion – which would be a huge societal and technological challenge and thus a very optimistic assumption – the food self-sufficiency gap will still be equivalent to about 55–123 million people, with over 20 million in Niger and Somalia alone," explained Fader, whose findings are published in Environmental Research Letters. Add on the impact of climate change – not included in this study – and the problem could be even more severe.

A number of developed countries, including the UK, the Netherlands and Japan, are already unable to meet the food requirements of their populations. This reliance on imports looks set to become worse as population levels rise. However, unlike the developing countries, these nations will probably be able to buy their way out of the problem.

Food security is going to be a big issue over the coming decades. The study indicates that improving agricultural productivity can play a key role in maintaining food security. Meanwhile, a change in diet, such as towards more seasonal and vegetarian food, could also have a significant impact, although this is not explored in the current work.